After only a couple of outings to RJs Motorsports track in Midhurst near Barrie on the old RM125, I was hooked again. On the second outing I had tuned the suspension and was doing much better but it felt very sensitive to throttle input, like the power band was very narrow. After riding my kid’s KX100 that had a much smoother power delivery, I started playing with the power-valve setting, however, since the kids now had a bike to ride and I was keen on riding more often, I decided it would be a good idea to get something a bit newer. Started looking on Kijiji for a newer 125 but people seemed to want a lot of money for them. I really didn’t want a 4 stroke but most of the bikes at the track were YZ250Fs and I found 3 for sale under $2500 on Kijiji. My research only turned up glowing reviews of the YZ250F and some people were suggesting they were better than 2 stroke 125s in virtually every way.
Decided to go for it and picked up this 2001, a couple of minor issues but pulls nice and strong and seems to be in good condition.
After tinkering …
YZ250Fn parts list and exploded diagrams
To Do List
- Can be hard to hot start – lowered the idle and then had a tough hot start, opened up pilot fuel screw about 1/16 turn. I read that these bikes are supposed to idle at around 1800 rpm because with a low idle the cam chain not consistently loaded making them run very rough – new plan, raise the idle back up. Had a bit of a wandering idle and backfire on shutdown, closed pilot screw 1/8 turn so now is 1/16 turn in from original setting
- Left side radiator guard is missing
- Repair bolt in upper fork yoke, winter?
- Replace main bearings
- Repair exhaust stud in cylinder head – investigate thread inserts to repair stud in cylinder head, I assumed there were supposed to be two exhaust studs but checking the parts list and exploded diagram there is only one – check threads in the exhaust bolt hole – got new 2003 head
- Install new head, valves, cams, cam chain, piston and rings
- Tiny bit of play in swing arm – replaced linkage bearings, still some play – traced to a clearance between lower rear shock bolt and ID of bearing inner race, shimmed with coke can. Similar issue with a clearance between the bolt that connects the linkage to the swing arm and the collars, put old collars back in. Are these linkage bearing kits not made to tight tolerances???New (used) rear brake lever – made new clevis to replace bolt
- Replaced bolt in upper fork yoke with longer bolt with nut on the end because threads are trashed (not by me!)
- Install new front wheel bearings
- Install new lower shock bearing
- Kick start lever (aluminum) worn – welded blob on steel hub
- New muffler bracket – made one from exhaust hanger band and tool drawer liner
- Repack muffler with FMF standard packing
- Repair huge dent in muffler
- New shouldered bolt for front brake lever
- New rear brake fluid reservoir
- Check valve clearances
- New handlebars (from RMX250) – a touch wide so cut 1/2″ off each end
- Add spacer to spring in kick start lock so it doesn’t vibrate out while riding
- Solder loose wires on pick-up coil
- Remove numbers from side panels
5 thoughts on “2001 Yamaha YZ250F – Traded”
After installing a brand new lower shock bearing and then a brand new linkage kit (that also has a lower shock bearing in it!), there was still a crap load of play! I managed to trace it to large clearances between,
1. the bolt that holds the linkage to the swing-arm and the ID of the collars
2. the lower shock mount bolt and the ID of the bushing
I found the old collars, cleaned them up and fitted them but the old lower shock bushing was corroded and still had a bit of clearance over the bolt anyway. A buddy recommended making a shim out of a coke can, this worked a treat. Now there is next to no play at all, sweet!
All the bearings used are Moose brand, I don’t know if these issues are just due to low quality bearings or what? Clearly it is not right to have enough radial clearance to fit a bit of coke tin in or to have to re-use old collars.
Went out to the track on Saturday with one of my boys and got 6 laps in before there was a nasty rattling/knocking coming from the engine and it felt like someone jammed the brakes on! At first I thought something had got caught in the front wheel but it turned out to be a valve that had broken!!! The piston and cylinder head are trashed along with the valves. The cylinder looks fine and I cannot feel any play at all in the piston and crank. A month or two back, a guy was selling a 2003 head with (auto decompression) cams and valves for about $250, I thought about picking it up at the time so I could delete the decompression lever but decided to save my money, ugh. Doesn’t look good for me to get any more rides in this season, ugh.
The piston is toast but the cylinder looks fine. Do I rebuild and ride or is it time to part it out and switch back to 2 stroke?
Through Kijiji I found a guy in Ottawa with a 2003 cylinder head from a bike that broke its con rod?!?! The valves were bent but he has a set of valves from another head. It’s going to be about $650 with tax and shipping and then I will just need a piston and I should probably put in a new cam chain. A new piston kit with piston, rings and gaskets is $340 and for some reason a Wiseco or Athena cam chain is about $100 and a genuine Yamaha chain is listed at $38 + tax??
Right now the plan is to rebuild and ride, but I have also seen a nice looking 2002 KX125 so if I can work out some money somehow, I’ll get a 2 stroke as well!
The new head assembly arrived yesterday, woohoo! Only $595 with tax and shipping from Capital Powersports in Ottawa – very impressed with their service! Since the head is from a 2003 bike it has the auto-decompression cam and I can delete the decompression lever from mine. Ordered a new piston and rings, gasket set and Yamaha cam chain from local bike shop TSR, hopefully it should arrive this week. A couple of guys at work were scaring me saying that the con rod is likely bent but my good friend in the UK, Andy had a great idea, check that the piston travels to the top of the cylinder, if the con rod was bent it would not reach the top – put the cylinder and old piston on yesterday and it all looks good – sweet! Maybe I’ll get another ride in this season after all.
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