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XT225 Serow Riders Technical Website V1.16.00 Last update 01/26/06

A resource for riders of the Yamaha XT225/250 Serow. This site is for information only and we do not sell anything.

News Flash: IT'S IN !!!!!, Ms Chika Ando, has translated the Builders Talk section of the Yamaha Japan Serow website. Follow our link and find out what the designers of our Serow have to say over a glass of fine wine.

It appears the XT225 has been replaced in Japan for 2006 with the new Serow250. There is even a 20th Anniversary version. What does this spell for the XT which is exported to the US ? Will Yamaha USA pull the XT from the lineup ? Will the US get the Serow250 ? Please see the Japanese links below to get a look at the new Serow

If this is useful why not subscribe to our email list at xt225serow on Yahoo. Once you've subscribed you can search the archives of the discussions and access the pictures in the Files area. Thanks to Adrian, the original author and builder of this site and to everyone who has sent the information contained here and granted permission to reproduce their messages & expertise. You're far too numerous to credit individually. Please feel free to send in updates or suggestions and we will try and keep the site current. Please email us here.

Links inside this page
Importers, Retailers and prices
Information & Magazines
Known Weaknesses
Tyre Choices
Upgrades & Add ons
Hard Starting
Suspension set-up
It won't start...
Places to ride or compete
Packing things
Selected spares list

Links on this server but outside this page
Diagram of head assembly
Diagram of clutch assembly
Diagram of carburetor assembly
Diagram of starter motor
Adjust gear shift lever
US parts fiche
Make a chainwheel guard
Circuit diagrams
Models and years

The natural serow is a family of small stocky mountain deer found in Asia and Japan. The Yamaha model has similar aptitudes and habitat, although it can be found in the US and many have migrated to the UK. Note that US and Japanese specification bikes are subtly different from each other.

The Serow is one of the lowest dual purpose bikes around, which is why it is popular with newcomers to dirt. It is listed as suitable for a small beginner which can be seen by when you see the scale of the machine next to a Japanese rider. Of course good riders can ride any size of bike.

The 2006 US model can be seen here and the Japanese Yamaha site is here with links to a 360 degree viewer.

Japanese riders' pages:

Selected English language (mostly US) XT225 Serow links:

Key UK/USA links

Places to ride or compete

Clubs and people who organise things UK RoW Information: Selected books:

Importers and Retailers in the UK (and prices)

These dealers aren't being endorsed or criticised. For those where myself or other Serow riders have personal knowledge of their service I've written how we've found them. I'm not affiliated with any of them.

Prices are clearly very variable and specific to your region and time of year. In mid-1990s Serows were rare in UK and prices high to reflect this. Now there are lots of used examples and so they have dropped in value, new prices following behind. Here are some guides (January 2002):

In Chains


Suppliers of JT sprockets for the Serow. A very helpful small company who really know their stuff, Ive been using them for years.
Unit 9
Hightown Industrial Estate
Crow Arch Lane
BH24 1NZ
Tel: 01425 474800
Fax: 01425 461962

The Container Company Ltd

Have ceased trading, but I believe same people at:

Dirt World

Their spares line staff know Serows and their faults and can advise accordingly. Rapid delivery of parts with realistic P&P charges, although in many cases it's probably best to order direct from Fowlers.
Tel: 01226 2447700

Concept Motorcycles

Stockists of Serow, speak to Ian Clarke
Unit B
571 Stanningley Rd
LS13 4EL
Tel: 0113 2909878

Ellastone Off Road

Have the occasional Serow to break. Send what they say they will.
Ashbourne Road
ST14 5LF
Tel: 01889 590186

West Coast Imports

Importers of used trail bikes from Japan
Unit 4
Hawksworth Road
TA24 5BZ
Tel: 01643 702511


Importers of bikes and parts. Also organise offroad days and corporate entertainment.

Bogbusters International Imports Ltd
Yew Tree Farm, Newcastle Rd Betchton
CW11 4TD
Tel: 01477 500777


Service Exchange Parts


This firm of engineers specialise in specialised motorcycle and car engine work. Not cheap, not fast, but they do seem to have plentiful equipment and skilled staff to use it. Call to discuss your work, their carrier will collect and then they'll give a quote when they've inspected your parts.
39 Sideley Road
DE74 2FJ
Tel: 01509 673295
Fax: 01509 673244

The Off Road Centre (formerly Notts Trail Bikes)

Alasdair sells a variety of grey imports, UK spec bikes and accessories.
Oakwood Road
Oaktree Business Park
NG18 3HQ
Tel: 01623 428777
Fax: 01623 626884

Motorcycle Centre

Importers of used trail bikes from Japan
Lambs Business Park
South Godstone
Tel: 01342 892768

K&M Motorcycles Ltd.

Importers of used trail bikes from Japan
10 Dalestorth Road
NG17 3AA,
United Kingdom
Tel: 01623 460700
Fax: 01623 460700

Penrith Motorcycles

Importers of used trail bikes from Japan
Unit 9
Cowper Road
Gilwilly Industrial Estate
Penrith Cumbria
CA11 9BN
Tel/Fax: 01768 891300

Moto-X Motors

Importers of used trail bikes from Japan
29-31 Ashton Road
Tel: 0161 652 7393 (Sales)
Tel: 0161 624 2313 (Spares)

Northern Trail Bikes

Importers of used trail bikes from Japan
Tel: 01904 673080

Worlds End Motorcycles

Importers of used trail bikes from Japan
Tel: 01273 726678

Leisure Trail UK

Specialises in import and sales of Honda CRM
250 Oakleys Yard
Beech Avenue
Long Eaton
Tel: 0115 973 2466

Bill Smith

Often has new machines in stock at very reasonable prices.
Bill Smith Motors Ltd
30 - 36 Tarvin Road,
Tel : 01244 323845 / 320685 / 320699
Stores and Clothing : 01244 348515
Fax : 01244 350118
Email :

Japan Integral Solutions Int'l Ltd. (Japan)

EXPORTERS of used trail bikes
Tel: 00 81 3 3928 0935
Fax: 00 81 3 5991 7062

RaceSpec Direct

A large Off-Road Mail Order Company but rather biased towards MX and XR400s.
Yauncos Cottage
Tillers Green
GL18 2AP
Tel: 01531 890639
Fax: 01531 890250

Fowlers Motorcycles


10% discount for TRF members

The largest stockist of spares for imported Japanese Bikes including the Serow. The Yamaha parts line are happy to identify items on their Japanese-spec fiches and P&P is reasonable and rapid (i.e. often next day) for small orders. Have your frame number (the first 3 figure code in particular define model eg 4JG) ready but be prepared to find that your bike doesn't quite match the fiche! Be very careful with parts for rear wheel on rear disc models and front disc for twin-pot models. Don't bother requesting their catalogue though, it's not a great asset.

2-12 Bath Road
Tel: 0117 977 0466

Moto-Ward Ltd.

Yamaha motorcycle parts and accessories
117 Brighton Road
Tel: 0208 399 0630
Fax: 0208 296 0704

Riders of Yeovil


Can get you any part for this bike. It is based on the XT125 frame, and many parts are the same apparently. They seem nice enough people to deal with and are often recommended by list members.
Tel: 01935 421681

Earl's Performance Parts Direct


Rapid construction and delivery of braided oil and brake hoses.
4D Brent Mill Industrial Estate
South Brent
TQ10 9YT
Tel: 01364 73956
Fax: 01364 73957


Are the UK distributor of a range of great-looking, non-slip, lightweight loading ramps.
Wilfs Motorcycles
Tel: 01730 269817
Fax: 01730 260775

Off Road Only


Excellent telephone sales and mediocre WWW site for a wide range of gear at sensible prices.
Llandrindod Wells
United Kingdom
Tel: 01597 851811
Fax: 01597 851962


Mailorder suppliers of a wide range of bits and pieces for scooters, including a very nifty LED tail light (The fit has not been tested on a Serow yet).
109/111 Corporation Road
Tel: 08700 660 393
Fax No: 08707 586 586


Technical information sources and magazines


After every dirty trip

After washing the bike:

Routine maintenance chart

This was first based on a sheet from the Container Company, but now includes many extra details. Please keep sending them in.
Service interval 6000km
1 year
2 years
3 years
4 years
Battery The OEM battery is maintenance free. Check case for damage and that terminals are clean and coated with vaseline, maintenance charging is recommended.
Cylinder head and exhaust pipe nuts check & tighten
Air cleaner element clean replace clean replace
Valve clearance
inlet 0.05-0.09mm
exhaust 0.15-0.19mm
Check and adjust when engine is cold and clean.
Remove spark plug, rocker covers and flywheel case plugs and then turn crank to TDC (some engines have a 'T' on the flywheel) mark in the crankcase window by turning anticlockwise, both valves are closed every alternate rotation. Check gap with feeler gauge. If adjustment ios required loosen lock nut and then turn central square adjuster. Tighten locknut and recheck. To be safe, turn engine 2 complere rotations and observe correct functioning nd recheck.
Replace O-rings on rocker covers if they are compressed into square sections
Spark plug
0.6 to 0.7mm
clean replace clean replace
The two NGK plugs are very similar. DR8EA is recommended in the US manual, DR8ES-L in the Japanese. An NGK rep. explained to me that the DR8ES-L is a little 'hotter' and might, in theory, give better combustion without a risk of engine damage. Their relative merits are likely to depend on the precise carburation of your bike.
SPLITFIRE plug for Serow is SF-413B
Fuel line inspect frequently for cracks replace
Engine oil and filter
Yamaha suggest:
1100ml of 20W40
10W30 in cold climates
but 10W40 seems fine
Replace, hot if possible. Some riders change as often as every 500 miles, using 'plain' oil as insurance against lubrication failure.
Mobil 1 has been recommended. It may cost a fortune, but the Serow's sump is tiny. Runs a treat and never seems to get dirty or lose lubricity. Probably better to use specific M/C oil as Mobil 1 has been reported to cause clutch slippage.
The filter is made of metal gauze and can be washed out with petrol if an emergency oil change is required.
The O-rings on filter housing and sump do perish and get squashed and for total cost of 3 I recommend occasional replacement. The screws don't need to be as tight if the O-ring is good.
Brake fluid replace replace
Steering stem check for smooth, notch-free operation with no fouling of cables
strip and re-grease annually
Lever free play Ensure that all controls have a spot of free play at all times.
Front brake 1mm at adjuster
Rear drum brake 20-30mm at pedal - don't forget stop light adjustment
Rear disc brake
Clutch lever 10-15mm at end of lever
Throttle 3mm at actuator, few degrees at twist
Cam chain tensioner This is automatic but on occasion you may wish to check it. Remove the plug bolt and insert a flat blade screwdriver. Rotate clockwise, and then release spring.
Chassis bolts check & tighten
Fork oil
10W 344-355ml per leg
vent air pressure replace vent air pressure replace

Cleaning and oiling an air filter (tips)

The Serow utilises a flat double density foam filter. It must be correctly oiled for proper functioning. Remove the filter on its plastic frame from the left side of the airbox and gently pull the frame out of the filter. Clean the filter either with petrol (dangerous), proper kerosene-based cleaner (read the instructions) or paraffin (cheap) followed by detergent and water (takes a long time to dry properly). Squeeze the filter, don't wring it. Make sure it is clean and dry. Check for damage and replace if it is torn.

The filter needs to be moist but not wet otherwise the oil gets sucked into the carb. Engine oil can be used but filter oil is better as it has a volatile solvent which aids penetration and it is 'sticky' when dry. Some are coloured so you can check for uniform oiling. Put the dry filter in a zip-seal poly bag and pour around 30ml oil onto it. Massage the oil into the filter, add a bit more oil if it is soaked up. Excess oil should be removed by repeatedly squeezing the filter between sheets of clean newspaper; this stage is critcial as excess oil strangles the engine. Remove the filter from the bag and leave 10 minutes to dry. The instructions on some product say to repeat the process but once is often enough. Slide the filter back onto its frame.

Clean inside the airbox with an oiled cloth. Lightly grease the periphery of the filter and airbox lid and replace them. The bike may be difficult to start as the pores of the foam may be blocked. Once it's running take it on a trip and it'll be OK then.

New OEM Yamaha filters are delivered in a few drops of light oil. I don't know if this is supposed to be adequate but I wouldn't chance it.

If you're doing a lot of riding I suggest you get a spare filter and keep it oiled in a bag so you can slot it in while the other one is being prepared. Some people recommend re-oiling a filter after every use - I suppose it depends on where and how you ride. After 1000km of Derbyshire trail riding, the drain was clear and the filter was still slightly moist and not dirty to the touch. After 2000km it had a few bits of foliage on it but the bike ran quite roughly in midrange. Cleaning and re-oiling the filter cured it so they need to be really clean.

Spokes and rim

Check for loose spokes and corroroded rims. Tighten loose rattles with a PROPER spoke wrench (One reader broke a spoke trying to bodge with an adjustable spanner). Be careful not to pull the rims out of true. If the spokes or rim are in a bad way get it rebuilt properly. Try Hagon, Central Wheel Services or Talon Engineering. A rebuild with Excel rim and stainless spokes onto your hub will cost around 170.

Spare parts list

Not an all inclusive list, but a range of items which have been used by me or submitted to me. Naturally I can't accept responsibility for errors! Please let me know details such as cost or part numbers especially for hard-to-find parts.

Many parts of the Serow are standard to other Yamaha Trail bike models, in particular DT125R, XT125/250/350 and even the SR125. This is one reason that Fowlers can supply many parts from stock. If you take the part to a local dealer it's quite likely you'll find a suitable fitment.

In addition, the engine was first fitted to the "Forrester" Quad from the 1990s and many parts are much cheaper from the agricultural agents.

Item Rough Cost
UK retail July 1999
Part number
Yamaha and/or pattern
Please note that this list is not be guaranteed to be accurate.
Front brake discs EBC MD6066D is 245mm diameter for XT225W (also DT200)
EBC MD6067D is 220mm for 4JG frames Mk1&2 (also DT125LC)
Front brake pads (for single piston calipers)
(almost rectangular with a lug at each short end)
15 EBC101, Ferodo FDB383, Dunlop DP406, SBS596, Brembo YA14
Sintered pads for XT350 fit and may be better than OE
Front brake pads (for double piston calipers) as fitted to latest Japanese spec bikes 12 EBC FA275, Dunlopad DP420, SBS 728
fit rear of Yamaha YZF600 R "R6" 1999-02 and Yamaha YZF 1000 R1 2002
Rear brake shoes 13 EBC Y503(possibly G suffix for grooved MX type), Ferodo VB229, SBS2028
Rear brake pads
(basically rectangular with a single large, pierced lug on long side, little tangs pointing from pad to lug)
22 3XP-W0046-00

Pattern part catalogues sometimes list the wrong part, so be careful. However pads fit many UK import bikes including certain models of YZ125&250, RM125&250, DR350&650, KX125&250, KLX250&650
Vesrah VD-432, EBC FA152, Ferodo FDB659, Armstrong A152

Front brake lever 9 3FY-83922-00
WR200 or TTR 250 parts fit and are readily available
Dogleg type: 55Y-83922-00
Front brake master cylinder service kit 18
Complete front master cylinder 45
25 used
5CG-2583T-10 or 2KF-25850-00
Is there a difference between these?
Brake discs Take care with pattern parts as some are too thick and bind.
Always melt Loctite on the retaining screws before attempting to loosen them. This will need between 30s and a minute of gentle, carefully aimed use of a blow torch. An impact driver may save heads on fasteners. Whilst the screw is hot undo it a few turns.
Clutch cable 9
Clutch lever 7
Clutch lever rubber boot 2-50 Yamaha 1E6-26372-00
Clutch plate set (5+1) 36
Clutch spring set (4) 5 Minimum length for old springs is 35.3mm, nominal new length of 37mm.
Chain etc.
Gearbox sprocket is somewhat "special" with Yamaha splines and Honda two bolt fixing, but is same as Yamaha RD/DT/GS fitment. Don't try to fit a Honda one as the splines will chatter and wear away. 6 pattern 263-15 for RD-DT

In Chains sell JT brand front sprockets:
15 (JTF1263-15) is slightly too high for bike to pull in 6th
14 (JTF1263-14) offers extra torque, maybe better top speed
13 (JTF1263-13) causes chain wear

Rear chain wheel
Note that drum brake models have a dished chainwheel whereas rear disc models have a flat one.
13 pattern 842-45 for DT125F & XT350
Chain 50 120 links 428V O-ring
For larger tyres the rear wheel can be slid back, use a 122 link chain
Chain and sprocket set 90 Kits are available to convert to the more common 520 size. In this case 102 links used with 41/13 ratio.
Genuine cylinder head (incomplete) 380 So you don't want to damage that!
Wire mesh oil filter 7 5HO-13440-09 Make sure you get the right one. The box says it suits XT350and SR125. Filter for TT250 looks VERY similar but isn't! Check for 4 small holes around pressure relief valve.
Oil filter cover O-ring 1-80 Yamaha 93210-54175
Oil filter drain screw O-ring 0-60 Yamaha 93210-07135
Sump plug O-ring 1 Yamaha 93210-35389
Copper washer for oil check screw 0-50 Yamaha 90430-06014
Air filter element 7
Throttle cable 12
Inlet manifold (carb to engine) 22
Petcock O rings 5 for the set 3AJ-24534-00-00 is the O-ring
3AJ-24523-00-00 is the 3 hole packing washer
4X8-24512-00-00 is the O-ring between tap and tank - it'll be obvious if this is leaking. May need replacing if you remove the tap.
The parts above can be replaced by taking off knob (very small lock screw) and then undoing the screw-retained plate underneath. Be ready for spring spacer!
Clutch cover gasket 7 The clutch cover is often hard to remove as the rear dowel gets rusty. The kickstart oil seal will withdraw from shaft with care but ensure you keep it in housing by tapping it back in if it starts to come out. A new gasket is very likely to be needed as you will damage it. Note also that the gasket has a 'bead' of sealant along the top edge where bolts are sparse so you may wish to use sealant along that length if you are attempting to reuse a gasket..
Retrofit kick start kit 150 - 300 Grey importers can supply kits but delivery is long. Is it worth it?
Starter solenoid 25 4KD-81940-00
Battery 12V 6AH no-spill, no maintenance 64 Yuasa from Yamaha
52 Yuasa from dealer
30 No-name from dealer
17 Quad
Yuasa YTX7L-BS have proven long life and reliability. Note that MF type batteries cannot be charged with conventional fixed-voltage chargers.
Headlight bulb 2 upwards OEM 35/35 halogen is difficult to source. Fit either 30/30 non-halogen or even more common H4 standard car fitment 55/60 halogen (housing doesn't seem to melt).
US model higher wattage bulb 55/60W Sylvania 9003 or equivalent fits perfectly in the Serow but you may want to disconnect your front turn signal *running lights* to preserve wattage.
Alternator rotor assembly 150 to 170 Several riders have suffered from disintegrating rotors that rattle and then sieze engine as lumps fall off.
Master fuse carrier 1-25 including 2 fuses Pattern part from good bike shop specialising in Jap bikes. Fit heatshrink tubing to bullet connectors to bring upto O.E. specification and improve on this by adding heatshrink tubing at fuse end also.
Wheels and Bearings
Front wheel identical to DT125LC mark III
XT350 similar but disc of different diameter
Rear drum brake wheel one model (which?) of DT125R
Rear disc brake wheel DT125 mark III
Wheel bearings 3 to 5 each 6202-2RS
6202-DDU (these are supposedly better sealed)
2 at front, 3 at rear
Steering stem top cup & cone 40 Yamaha 22F-23411-01 & 22F-23412-01
also needs 22 of 3/16" ball bearings
Steering stem bottom taper roller NTN part number 4T-32006X
Bottom taper seal is part of the Yamaha bearing kit at a high 45. However a seal D.U.204/112 DSL can be made to fit with modification: Remove the inner lip completely so it is flush with the bottom of the inside of the seal (careful work with the scapel or whatever) so you open it up enough for it to just slip over nicely. Then you will find the outside lip fouls the cage on the bearing when fitted together. Again, a simple job to cut a little off the seal depth until it fits right. Not as good as OE but a lot cheaper.
Available from Mervin on 0116 251 4379
Taper bearing set 30 Moore International of Poole (UK) +44(0) 1202 462214 have had one of their suppliers make a taper bearing in the right dimensions (43 X 25 X 11) - ask them for Item Code 324305 and they will charge you 12.50 + VAT. The bottom bearing is a standard engineering type 32006, however this normally requires a separate seal. Better still, the motocross enthusiasts at Moore International can supply a sealed taper bearing - ask them for Item Code 32006RS, cost 11.00 + VAT.
Odds and Ends, Chassis and 'Bodywork'
Mirrors 15 Who needs them?
Rear shock 230 Hagon
70-100 used
Speedo cable 8 1KH-83550-04 inner and outer set
Model 1 rear light lens 4 1Y1-84521-30 fits DTR125R & FS1EDX
Japanese model indicator lens 2
Japanese model indicator body 5 used
8 new
3RW-83340-00 (note front and rear are different by virtue of lead length)
TTR250 Brushguards to fit Serow $24-$35 Yamaha parts list
1 3BN-26141-20-00 GUARD, BRUSH 1 (PWS1)
1 3BN-26142-20-00 GUARD, BRUSH 2 (PWS1)
1 95027-06035-00 SCREW, PAN HEAD
2 92907-06600-00 WASHER, PLATE
1 90387-06500-00 COLLAR
1 90109-062A8-00 BOLT

Tyre choices

A few suggestions and comments. Tyre choice on dual use bikes is always a compromise between off-road traction and wear on the tarmac. If you trailer the bike to boggy sites then ED04 may be best. If you commute along gravel roads something like the Enduro 3 would offer lots of life. The low weight and power of the Serow will help more knobbly tyres to last a decent time. There are riders who prefer trials tyres, claiming that they provide better traction on firm surfaces and no less in deep mud, where almost nothing bites.

Please send me your experience with these or other fitments.What terrain do you use them on, how long do they last. how easy are they to fit, number of punctures, best air pressure to use etc?

The Serow has limited clearance at swing arm and some widths need to be checked before assuming any of these fit. One reader has fitted a 140/80 rear tyre by using a lengthened arm (I'm hoping to get details of this), longer chain and brake rod to move wheel back in swing arm. This might be beneficial for mud clearance and lengthened wheelbase even if standard tyre retained.

Tyres marked TESTED are known to fit as I've a reliable report.

Front Wheel size is 21x1.60

Rear Wheel Size is 18x2.15

Comments and opinions from diverse sources

Michelin Moose 90/90-21 Michelin Moose 120/80-18 TESTED Steve writes: Mooses fitted front and back are excellent once fitted, they last quite a few years but are very difficult to fit, it usually takes two people, sometimes three if its a tough make of tyre. Michelins are one of the more pliable/easier makes to fit, but still difficult. I have a friend who fits his own mooses but I wouldn't, I think they are far too difficult. But I do help fit them, mainly out of guilt.
There is a lot of bad press flying around about mooses but a number of us have used them for quite a few years without any problems. They obviously wear out, but can last about 3-5 years in the UK. The mooses are made to an equivalent of about 14 psi.
Michelin Baja 90/90-21 140/80-18 (Will it fit?) Michelin say: Street-legal, desert-proven
Baja tyres cost more than any other off-road,or semi-offroad tyre, but they last SO LONG, it is well worth it. I rate them very highly. I have used a number of sets on DR 350, DT200, WR,XTZ 660, and I will put a set on my Serow just as soon as I can get out and wear out the motocross tyres it came on.They are fully road legal, therefore OK for Cambrian Rally etc, but they look just as knobbly as any enduro tyre. They are radials, and because the side wall is so flexible, they can run a much harder compound than would be possible on a cross-ply. Hence the high mileage,even on the road.
2.75x21 45P
Bridgestone TW-302 4.10x18 TESTED Quite tarmac orientated. The prototype non-trials tyre tyre for MCC long distance trials since 6/2000. At 20psi they roll quite nicely on the road. For trials use I dropped to around 8psi. Initially they felt very loose and insecure but over a few hours I got used to them both on and off tarmac. At low pressures they seemed equal to MT21s until I encountered muddy grass and may have the edge on the road. The closer black pattern appears to give a longer road life. Sidewalls are soft and the tyres are easy to fit but front doesn't seat centrally on bead very easily.
Bridgestone ED661 Bridgestone ED660
(aka Gritty)
I think these are the ones used by Norwest Trails in Skye where ground is very wet and soft. Very knobbly, squirmy on the road, and they will wear rapidly on tarmac. Possibly not legal in US?
Bridgestone ED04
Cheng Shin C858 'Cats Paw'
275x21 or 300x21
Cheng Shin C858 'Cats Paw' 4.10x18 Made in Taiwan, the price is good. Don't look knobbly enough for use in the winter! Is the 300 too big?
Cheng Shin C6006 The OEM tyre on the 2000 U.S. model Serow.
Continental TKC80
Continental TKC80
400R18 gives plenty of swingarm clearance
TESTED Fairly open block design with history of good use on bigger bikes such as BMW R1100GS.
They are in a separate category inbetween the knobblies and the OE "trail" tyre. Reasonably good off-road, and amazingly good on-road for such a knobbly tyre. They give a good mileage on-road as well.You can ride to Spain, trail ride and get home,on a set of TKC80's, which you certainly can't on MT21's. In that respect I think they are in a class of one!
Michelin Enduro Comp II
Enduro Comp IV
TESTED A pair of these tyres fitted front and back are really pleasing due to the off road grip, so that the Serow now goes where it's pointed and climbs up all sorts of hills. They are excellent for trail riding on a mixture of terrain, including, mud, chalk and sand, but do tend to wear out rather quickly on the roads. You also have to treat them with caution on the road, due to the agressive tread pattern. The recommended/standard tyre size fits perfectly on the rim. The chain adjuster is set at about number 6, this clears the swinging arm ok, with still a lot of adjustment to go.
Pirelli MT-21
80/90 P21 or 90/90 R21
Pirelli MT-21 Enduro
110/80P 18 or 120/80P 18

TESTED The 120/80 rear is a much bigger and knobblier tyre than the 110/80 - far more than the slight size difference would suggest (check them out side by side). The smaller one is better on the road. Fitting a 120 section MT21 gives great grip, but it effectively raises the gearing quite a lot (much larger diameter than a 110). Most noticable effect is that it makes sixth gear on the road a bit breathless, necessitating a change down for hills and headwinds, where the smaller tyre would not have needed one. However the 120 is much better in serious mud, so it's my choice for the Welsh winter, even though it's also a tight fit in swing arm.

Considered by many to be the ultimate dual-purpose tyre. Knobs can be broken off by big bikes at high speeds - so no problem here then.... A review.

20psi is a suggested pressure to compromise between grip and puncture resistance although they feel more secure on rocks at 12psi.

MT21s are excellent on the dirt (except in deep mud, loose stones, slippery tree roots), fair on the road. On tarmac they howl a bit and wear fairly quickly, but they handle OK. As to life, the 110/80 rear I fitted for my Picos trip lasted about 2000 miles (still plenty road legal but losing its bite on mud).
Compared with full knobblies I have used in the past, wear rate is very good.

worn rear MT21

Rear Pirelli MT21 120 section shown here has lasted very well: about 2000 miles so far, including Iceland crossing and a mix of road and dirt. Initial wear is quite rapid, then slows down. The tyre is no longer much good in deep mud, however, but OK for hacking around.

Pirelli MT43
2.75 21
4.00 18 TESTED The standard road-legal trials tyre. Used by almost everyone on long-distance trials. Square blocked, soft compound with offset blocks at edge. Use at around 8psi off road and 20psi on tarmac. The rear tyre needs the wheel to be near the back of the swing arm, so try a combination of a longer chain or smaller front sprocket - the tyre has a large rolling circumference anyway.
Maxxis M6001
M6001 4.10-18 Rarely seen in UK. An inconclusive review.
Maxxis M6006
2.75-21 or 90/90-21
M6006 120/80-18 A street-biased tyre, available mail order in UK. Intended for big bikes, but small sizes available.
Maxxis M7000
M7000 120/100-18 DualSport tyre, with not a lot of mud clearance.
Dunlop D604 90/90-21 D604 120/90-18 Trailmax is too wide for the rim. These are basically road tyres.
Dunlop D905 (are these road legal?)
or K139 3.0-21
Dunlop D606
This looks to be Dunlop's clone of the well known MT21 on the rear with choice of front fitment.
Dunlop D903 3.00-21 D903 120/80-18 A widely spaced, street legal (in US) enduro tyre. I can't imagine a long life if used on road although the Dunlop chart suggests more road-worthy than D606.
Avon AM24 80/90S21 Avon AM24 80/120S18 Street orientated. The tyre of choice for BMW GS machines that do miles of unpaved roads. Will these last forever on a Serow?
Enduro 3 90/90-21S
Metzeler Enduro 3
110/80-18 or 120/80-18
Fitted OEM to BMW G/S and big KTMs, this is a soft-compound street-worthy tyre which offers fair traction on unpaved tracks.

TESTED For the summer you might fit a 90/90 front and 80/120 set of Enduro 3 Saharas. They are superb on the road - grippy, stable, quiet, amazing lean angles. They make the bike quite a little scratcher. Very little wear in a couple of thousand miles. They belie their name too, as they put up a surprisingly good show in mud. A very good choice for someone who only occasionally ventures into boggy ground.

Metzeler Enduro 1 TESTED Enduro 1 is similar in properties to the Sahara but is specifically intended for lighter motorcycles and has somewhat softer compound, to allow for proper warmup. My impression so far is that it is an excellent choice for both street and (dry Greek terrain) dirt usage.
Metzeler MCE 2 Front 90/90-21 Metzeler Six Day Enduro 120/90-18R
and Six Days 2
TESTED Very highly recommended. Rear only just clears the shock (higher profile) but it does fit. too - just over 100 for the pair. They give enough grip for tarmac (they're road legal), and they really give good traction in the mud. We went through some nasty bogs last year, and they've never clogged up. Ten times better than the usual MT21 style option. Life may be only 1000 miles.

Known weakpoints

Fuel system

Hard starting






A few of us have exposed Serows to rather too much water. They are remarkably good at staying running in water but here's some tips:

Suspension Setup

The Serow's suspension is not state-of-the-art but is quite adequate for the likely use of the bike. There are at least two variations at both front and rear.

It won't start...

This check list is adapted from the January 1998 issue of US magazine Dirt Bike.and gives a sequence to get a troublesome bike running - if it normally runs of course!
  1. Make sure there's some petrol in the tank, enough to get to the outlet.
  2. Don't let anyone pull the carb apart until you've exhausted all other simpler options. Note however that US bikes do benefit from attention to the carb, but this is a one off job.
  3. Ensure the fuel valve is open - horizontal is OFF on a Serow.
  4. Don't forget to switch on the ignition and have the kill switch in the run position. The electric starter will only run when the bike is in neutral or in gear with the clutch pulled in. US models have a similar cutout on the sidestand.
  5. A flat battery will not stop an electric start Serow from being kick or pushstarted but they do start more easily with a good battery (don't know why).
  6. Don't jump start from a car or truck. Charge the battery with a proper charger for sealed cells.
  7. A properly set-up Serow needs choke and no throttle for cold starts and no choke but a quick throttle for hot starts.
  8. Rather than blaming the bike or its manufacturer think "What have I done to this bike?" You may have disconnected a wire to fit an accessory or service another part, or even not refitted the spark plug after a valve job.
  9. Old (more than 6 months) or wet fuel do not work too well. Drain the float chamber, tank and refil and try again. If nothing drains from the float chamber then either the fuel is still off (see point 3) or the float valve is stuck. Some of these seems to stick until jolted, in bad cases it may just need a strip down. If the drained fuel is full of bits then the carb jets are likely to be blocked (see point 14).
  10. Maybe there really is a problem? By now the spark plug and cylinder could be fouled by petrol. Remove the spark plug, reconnect the HT lead and place the plug on the engine. Turn it over and check for a blue spark. If there's no spark try a new plug.
  11. Ignition problems on Serows are rarely due to failed CDI units, so don't panic, try to find the cheap, but not always easy-to-find problem.
  12. Check resistance of HT lead and plug cap with engine off. It should be around 15kOhms. A higher resistance shows that something, probably the cap, is open circuit. Work back through orange lead to coil under the tank. Check connectors behind right side panel and under seat. Check the circuits of the kill switch. Listen carefully for the clutch relay activating as the lever is moved with the engine in gear.
  13. The Serow ignition timing is fixed and unlikely to be disturbed unless you've been heavy handed in the crankcase cover.
  14. If you've fuel and a spark maybe it is a carb problem after all, especially if the machine has not run for 6 months or more. The choke circuit can be cleaned with the carb in the bike. Remove the nylon choke 'nut' carefully, making sure you retain the spring loaded needle valve. Look for dirt and blast a jet of carb cleaner in. You could try strating again or carry on and remove the carb for cleaning.
  15. Most bikes should be running by now so the remaining causes are more serious. Rarely there may be a compression failure, but as the most common cause for a lack of compression in a four stroke is insufficient valve clearance it's time to check them.
  16. It's also possible that the cylinder, rings, valve stems or valve seats are worn but this doesn't occur overnight. If it ran a while back it's unlikely to be due to one of these. Such wear and tear problems are often shown by oil buring, in particular in cold or highly revved engines. Have you noticed this? Diagnosis begins by measuring compression with a meter of dry and oiled cylinders...

Popular Upgrades, Modifications & Accessories

Other Accessories

Dirt Bike Packing

For days on dirt

What is optimal toolpack for a Serow? Stock box items are rather cheesy and the lid doesn't inspire confidence. Don't forget that cheap tools are bad at any time, when you're tired and cold they are useless. This is my current tool-roll, and is under review. Anything to add or discard?

Spares to take along


Little dirt bikes don't offer much load carrying potential, nor do you want to pick it all up - either through spillage or bike get-offs. Think hiking rather than touring.

We've tried to make this information accurate but we cannot accept responsibility for errors. Check with a trained mechanic if unsure. Please let me know if you find a mistake or want to add your knowledge to the pages.

Last updated 04th January 2006 by Rob