250-500cc Picked up another stray...

Drove out out to NY on Saturday to pick this up.

1994 wxc 250 by bmcg419, on Flickr

1994 WXC250. I ended up trading a 1996 Polaris Indy XCR600 that needed some engine work and a bunch of polaris indy parts + $150 for it. Probably have about $600 into including all the parts I gave him.

Motor was recently gone through (supposedly) with a new stator and top end. Has revalved forks and rear shock, FMF Pipe, and fairly recent/decent plastics. Needs seat cover, carb work and has some broken bolts on the frame, but all in all not a bad bike.

Only issue is the guy painted the frame at one point, so the VIN sticker is completely missing... Thinking about selling the plastics, subframe, tank, airbox, radiators, etc. and finding a 98-00 frame that I can swap the suspension and motor onto. I've got leftover plastics/subframe from my 1999 WR125 when I converted to the 00-04 plastics, so that may be the ticket...

I think I would just fix that bike, it doesn't look to bad.

the 92 to 94 is different than 95 on, you can't put that tank on it
the rear fender is a later style and does not line up with the side plastics
all 92 to 99 rear fenders work
i like my 93 about the easiest bike to ride

I like the bike for sure, but the lack of a VIN and/or no paperwork makes it near impossible to legally ride around here.

I'd be willing to find a 93-94 frame with a VIN and transfer everything over too, but since I have a 1999 subframe, tank, tank plastics and radiators it would be a good place to start if I wanted to find a 98-99 frame. Plus, I heard a rumor that DC plastics was going to start reproducing plastics for the 95-99 bikes. Another reason to maybe try and find a newer frame.

i ve got a similar 1993 WR 125- there is a VIN sticker AND the VIN Hammerd into the Frame- maybe its worth getting some sand paper and searching for the VIN number? sometimes the colour is just covering it up...

Still not seeing any VIN. Took some paint thinner and sandpaper to it and still can't find a hint of it. Shouldn't it be stamped on the flat portion of the steering head?

Untitled by bmcg419, on Flickr

by bmcg419, on Flickr

stray?

Ok, now the real fun begins. Got it fired up and idling pretty well this weekend. Went to rip it around the shop parking lot and it had no low-mid range power. Checked compression first and the best I could get was 90psi. WTF?

So I ended up pulling the top end to check everything. Here's what I found:

Untitled by bmcg419, on Flickr

Untitled by bmcg419, on Flickr

by bmcg419, on Flickr

by bmcg419, on Flickr


The scoring on the intake side is more than fingernail deep and will take a lot of polishing to remove. Also, 2 small marks/gouges between the exhaust bridge.
The bore was relatively round and measured at 2.638" (67.005mm).

Here is the big problem I found. The motor is using a ProX Rod kit for a 99+ CR/WR250 which is a 125mm Rod. The 92-98 Engine is supposed to use a 129mm Rod (with the 70.8mm stroke crank & 35mm piston compression height). Thought someone might have also swapped a 99+ 72mm stroke crank in there as well, but was proven wrong by a few things:

The distance from the top of the jug to the piston @ TDC = .174"
The distance from the top of the jug to the piston @ BDC = 2.960"
Difference between the two = 2.786 x 25.4 =70.76mm

I'm not sure what the stock compression ratio, deck height, or trapped volume is on the 92-98 WXC/WXE250 engine, but the deck height seems wayyyyyy too low. Even if the deck height is only supposed to be .020", a volume calculation of that extra 0.154" would give it an additional trapped volume of 13-14cc. And that would reduce the compression ratio by quite a bit.

So the shorter rod (by 4mm) is effectively reducing the compression compression ratio and deck height, increasing the CC volume and messing up the port timing.

I have the jug off and down at work and could machine approx .156" off bottom (and re-chamfer it) to correct the 4mm difference instead of splitting the cases and putting the correct rod in.

Any experts care to weigh in on machining the jug? Anyone know the stock CR, trapped volume or deck height of the 92-98 250 engines?

the deck height squish area is set with gasket combos but it assumes a reasonably close tolerance
moving the cylinder down? can't remember the 92-98 stroke, if its correct you will be fine
but if its not then the port size and timing will be ineffective
sorry to see the cylinder damage in an otherwise cool find

Thanks man. Its no big deal, just trying to get it correct. Basically the rod is 4mm too short, so the piston @ TDC & BDC is 4mm lower than it should be. I'm thinking I can take 5/32" off the jug to correct the reduced rod length and bring the port timing, CR and deck height squish area back in tolerance.

I've compiled some data from the repair manuals, wiseco and wossner websites and by measuring a few spare parts I have.



92-98 WXE/WXC250
Bore 67mm
Stroke 70.8mm
Rod Length 129mm
Compression Ratio (closed ports) ?
Compression Height 35mm



99+ WR/CR250
Bore 66.4mm
Stroke 72mm
Rod Length 125mm
Compression Ratio (closed ports) 8.4:1
Compression Height 38mm

Don't forget to adjust the power valves as well.

Hows the rod? I would be tempted to cut cylinder, keep an eye out for another and correct rod too, you never know you may need to do rod swap in future then you will have stuffed it up proper have loads of base gaskets to make up 4mm.

The rod is near perfect. It was definitely done pretty recently and is tight with very little side to side play.

Also worried about the clearance from the intake manifold boot to case if I take that much off the cylinder...

Sent a few emails out to inquire about putting the ProX 03.6320 Kit w/ the modified big end pin. Best I found was $180 for labor, parts and shipping so that's probably the route I'll go. Split the cases, put some new crank bearings and seals and it should be good to go.

So this just happened...


Wxc 250 by bmcg419, on Flickr

Wxc 250 by bmcg419, on Flickr

And my WR360 sandwiched between the KTM and BMW.

Wxc 250 by bmcg419, on Flickr

Some people should just not be allowed to pick up a wrench.

Clutch cable route hole is broken, along with the hole for the cover next to it. Not hard to fix, just one more thing I have to get done. After going through everything on the engine, it seems the entire engine was put back together with epoxy and multiple gaskets over each other. No one even cleaned off the old gaskets. Looks like the crank bearings had failed at somepoint too as the inside of the case was marked up.

The only good thing I can say is the crank is in good shape. Checked the ends on V-blocks and they are within .001", but probably closer to .0006-.0008".

The cylinder is at Powerseal for plating and will probably be done this week. Just sent the crank out which should be done late next week. Still waiting on the Wiseco piston kit, but should be a ways out since I need to order gaskets, etc.

When I put the cases back together, should I use the Husqvarna gasket or will yamabond, threebond, etc. be ok?

94 wxc250 engine by bmcg419, on Flickr

94 wxc250 engine by bmcg419, on Flickr

If the center cases come from the factory with a gasket use one when rebuilding the motor or there is a good chance the crank or gearbox may bind up as it will be shimmed for a gasket

Yup yup yup the gear sets are shimmed so not putting the center gasket in may cause issues, buut its a dirt bike and the tolerances cant be that tight., can they?
I use threebond on the gasket faces as i can never sleep too easy.

i like to use gasket adhesive on one side of the gasket and a thin film of grease on the other side. that way when something is pulled back apart the gasket can be reused. you need to use an actual gasket everywhere there was one, or it is very likely thing s wont work right as previously stated.

Alright, thanks for the replies guys. I like that trick on grease for the gasket, should work nicely if I have to split the cases again.

Also, I just pulled the transmission out and some of the gears were binding up. After disassembling, I found some of the rollers inside the case.

Is there any good way to get them back in and stay put w/out them binding up? I tried inserting them after the gear was in place and they just ended up falling down and getting in each others way. Maybe some tacky assembly lube?

Get the rollers in with a bit of grease then slip gear on the shaft, rinse off with wd40 to get grease out.
Hold the gear sets in the left hand with the counter shaft pointing up anf lower the right hand case over them.
Once home turn over and stuff gear drum in and slip selector forks in position then i put the bars that hold the forks in in.
Dont forget shims on selector drum and gearsets.
Be patient an go slow.