87 RM250 rebuild ?s

[tracetrimble]

87 RM250 rebuild ?s - updated w/ bore pics

the piston skirt shattered on my 87 RM250 last weekend, and i have a couple questions. keep in mind i only paid $300 for this thing, and it's an 18 yr old dirtbike, so i'm not looking for perfection or anything...

i'm planning to flush the crankcase with gas to get the bits of piston out, instead of splitting the cases. when i got the bike, the tranny oil looked like it had never been changed. should i go ahead and flush the tranny too while i'm at it, or might that damage the clutch?

the cylinder is still stock bore (67mm), but has some scratches around the intake ports. will .25 mm over take out most all scratches, or should i go more?

also, i was under the impression this is a sleeved cylinder, but i can't see the sleeve. if this is nikasil, i'm parting the bike out...

anyone know where i can find a service manual for this bike?

thanks.

 

[Chili]

My 86 125 is a steel cylinder no sleeve and pistons can be found easily for boring it up to 80 over. About the only manual of any use you are likely to find at this point is a clymers generic one covering a broad spread of Suzuki RM's years and cc's. As for flushing the tranny you can do it it but use oil not gas, just flush several litres of cheap oil through until it starts to come out clean.

 

[tracetrimble]

ah, steel cylinder - that makes sense.

i found a rebuild kit for $99 that comes with a Wiseco piston, ring, wrist pin with circlips & bearing, and gaskets. seemed like a good deal. :-?

we have a nice machine shop here at work, and i'm planning on having them bore it. is there anything special about boring it out that'd require taking it to a bike shop? what's the tolerance on the bore diameter?

 

[tracetrimble]

the exhaust valves also seemed a little sticky. researching this, i find that they are not really even necessary for the bike to run, and just add a little top end? also read some complaints about them damaging other parts by hanging up or something. should i just tack weld them in a benign position, and forget about it?

 

[QKENUF4U]

take it to a bike shop and have them bore it correctly.
exhaust valve ??? you mean power valve (old old old style) leave it alone if it works
99$ is a good price for a complete top end kit, get it and take the cylinder/piston with you to the bike shop to have it bored (they will send it out more than likely to a person in your town that is equiped to do bore jobs on motorcycles and knows how to do it correclty)
a cylmers manual will do ya fine for torque specs etc..

 

[tracetrimble]

i can't find a Clymer manual. yes this bike is OLD school.

whatever the exhaust / power valves are called, they're on the exhaust side. they don't really seem to do much, only move a small distance, but one of them seems stuck. that's why i'm asking.

our machine shop at work is very capable, a couple of the operators machine car engines on the side & such. i really just need the bore tolerance unless there's something magical that bike shops know.

thanks for the replies.

 

[Chili]

You should be able to find the Clymer's manual for it still, I have one that would cover that bike but it is in the shed which is pretty much unaccessible without a days worth of shovelling a path to the door or I would get it for you. Keep in mind if you increase the bore size the head should be modified to match the increased bore size. Our two best race mechanics locally here are real cheap for the bore and head mod so I've never bothered to try to get it done at a local machine shop.

I found the Clymer's manual on that big auction site searching for rm manual. I won't post a link because the anti spam software will *** out the URL. It is item #4599678772.

 

[tracetrimble]

thanks!

 

[tracetrimble]

well, come to find out, 87 was the first year of non-borable cylinders. >:\ the local shop said about $400 OTD to sleeve and rebore it.

anyone know if an 88 cylinder will work on an 87? found one on big auction site, and the guy "thinks it will." the part numbers on bikebandit are different for those two years, FWIW.

thanks again.

 

[nickyd]

yeah, that's right - son of a - just checked my books and it says its a boron composite - resleeving is an option....not the greatest - but still an option.

 

[tracetrimble]

what are the chances of reusing what i have? the bore looks pretty good, except down by the ports there looks to be aluminum deposits from the piston. i've heard of removing that stuff with acid? maybe hone it, throw a topend kit on it, play with it for a few hours and sell it.

it's kind of a tough decision for me to part it out because the rest of the bike is in good shape. i've been stripping it down and cleaning it along the way, so it's already kinda parted out anyway, but the wheels are true, bearings & bushings all seem in good shape, rear subframe is straight, doesn't leak anything... then again, older 2-strokes seem to be a dime a dozen these days, and i could pick something up with a lot better parts availability.

 

[nickyd]

its done like that more often than you think........you paid $300 for the bike - a sleeve installed will run you close to that. shop the internet then make your decision. a used cylinder might be in worse shape however...

 

[tracetrimble]

check out item # 4601871631 on big auction site. if that will indeed work on my 87, and i'm working on verifying that now, i can throw that and a new topend in it for about $150. worth it? i think i could get at least $500 selling it if it runs well & doesn't smoke...

 

[nickyd]

that looks pretty from the outside.....but we need to see the inside....or trust them. you will pay minimum $75 for that. you could get a sleeve for about that much and pay probably 2hrs or so labor to have it installed at a machine shop....

 

[tracetrimble]

hmm... that wasn't really the impression the shop gave me, i'll call a couple other places. thanks.

 

[nickyd]

I have paid $275 for a sleeve install (including the sleeve). the machine shop has to bore out your cylinder, press in the sleeve (heat, press, let cool, etc), then bore the sleeve to match the piston (even if its stock, the sleeves are undersized), then champfer the ports and hone. I'm sure other places will do it cheaper but the guy I go to is well known and does insanely perfect work....so I don't mind paying him - plus he's a small shop so I like to keep the little guy going.

 

[tracetrimble]

called LA Sleeve, they said $495 including new piston & topend gaskets... i think i'm just gonna clean up the bore, throw a new piston kit in it, and get rid of the bike pretty soon. got my eye on an 01 CR250. :) thanks for all the responses.

 

[nickyd]

yeah sounds reasonable.....$275 for sleeve, $100 for piston, plus gaskets is what I'd expect....certainly not cheap.

 

[tracetrimble]

here are a couple pics of the bore, does that look like aluminum deposits, or worn thru the coating?

<img src="http://img.photobucket.com/albums/v280/tracetrimble/IMG_4070.jpg" alt="Image hosted by Photobucket.com">

<img src="http://img.photobucket.com/albums/v280/tracetrimble/IMG_4069.jpg" alt="Image hosted by Photobucket.com">

<img src="http://img.photobucket.com/albums/v280/tracetrimble/IMG_4073.jpg" alt="Image hosted by Photobucket.com">

 

[nickyd]

looks like the plating is gone

 

[tracetrimble]

bummer. the only thing that was making me think it might not be worn thru is the borders / frames around the ports. seems like it would wear more in those areas, and it looks like there's still plating there.

 

[tracetrimble]

well, it's definitely worn thru. using muriatic acid, it was apparent that the borders / frames around the ports are the edges of the coating inside the ports. should I bother honing / deglazing the bore if i'm just going to throw a new piston in it?

also, that 88 cylinder didn't sell on bigauctionsite. i talked to the guy some more, and he said he had a shop inspect it and they said it measured 66.95 mm, and looked like it had been replated and would need a finish hone before is it used. he also uploaded more pics to the site, and they all look identical to what i have... anyone know if my power valves are pressed in? can they be easily swapped over? i may offer him like $50 for it and take a shot. thoughts?

 

[darringer]

I used to have an '87 rm125. If I remember correctly, the cylinders are the same between '87-'88 for both the 125 and 250. The powervalves are easily removed. I believe everything is a direct swap, as they changed again in '89 or '90. When re-assembling, make sure the powervalves don't hang down into the cylinder, where they will catch a ring.

 

[tracetrimble]

:bang: one more question... looking at the pic on page 2 of this thread, is that an exhaust bridge? (meaning I need to drill the piston) thanks. :cool:

 

[tracetrimble]

ancient thread revival!

i finally got my bike back together and broke it in this weekend. thanks to everyone here who helped me. it started on the third kick, and this thing is running GREAT! i ended up tearing it all the way down after noticing the crank seal had failed on the clutch side.

even though i flushed the bottom end VERY thoroughly (i have a parts washer), and quite a few chunks of aluminum came out, i found 3 more big pieces down in the main bearing ball cages when i opened it up. it wouldn't have gone too far with those in there. one local shop i talked to early on said not splitting the cases after a piston failure would be like pissing into the wind, and they were right.

i ended up getting a great buy on a sleeved cylinder that had been freshly bored 1 mm over with a matching piston off the big auction site, new wrist pin bearing, and full gasket & seal kit. these motors were also assembled with all phillips head screws (!), 70% of which i destroyed while disassembling it, so now it has all stainless allen head screws. the crank bearings felt smooth & tight (they were getting plenty of tranny oil!), and the clutch must've been replaced right before i got it because the thickness mic'd as new, so i didn't replace those.

i collected all this junk over the last 6 mos, and finally got motivated to reassemble it last week. it really only took me about 5 hrs to put it all back together. i also totally stripped the frame, sanded the fenders, cleaned everything, straightened a couple bent things, and did some touch-up painting. all it needs now is a new rear tire. bad news is i'll probably have more money in it than it's worth, but it's still a lot of fun!

thanks again!