RM250C2 rebuild questions

[vlxk]

Hello everyone, recent rescue of a C2, mostly complete with the exception of salvageable plastic. I have a list of questions a mile long but I will not be overbearing as a noob and ask them all at once

I have the bike torn down and in several sub-assemblies. The cylinder is on std bore as close as I can tell. I heard the bike run when I bought it. Upon teardown, the crank nut (rh side) was 4-5 turns from coming off, all three of the bearing retainer screws were broken off. It had a new gasket on the clutch side. Here are the first questions...

1) the main bearing on the right side is standing proud about 1.3mm from being flush with the case bore, shouldn't the new bearing I install be flush? The retainer plate is missing so I'm going to make three separate retainers to go under the screws. I have a Clymer manual but it was made with a 125 as the focus as far as reference pictures go, a lot of the pictures are not really what I am looking at.

2) While the cases are split, of course the trans shift dogs dropped out. Going by the Clymer manual the shift drum is supposed to be in the neutral position to line everything up. I have been able to get the trans in neutral, but I'm not sure it is shifting correctly. I can turn the input shaft and hold the counter shaft so I assume that is neutral. How do I determine all is well? It is difficult to hold the shift shaft in place and shift up/down on the bench. Seems like it takes a lot of effort to change gears and I'm not positive it shifts through the entire range.

3) What have you guys used for airboxes? Every one I find has the back side broken out like the one I have.

I have looked at every page on the Suzuki specific page and the Tech page...lots of really good info there!

Thanks for your help, and I'm super pumped to be a part of this great group! More questions to follow I'm sure.

Kenny

[shelpi]

1st of all get a real good manual,  Ive built a few differant model RM's and PE's and they dont like to bench gear change, knock up a engine stand I used to wrestle and build on the bench (no time for a engine stand) , whats the main bearings part number and the seal used?
Use LH drill bit to get out broken bolts as they may wind out the bolt, make sure you are dead centre of the bolt ( if you havnt got a drill bench perhaps take it to someone that does it) cos if it wont come out (easy out) then drill to the inner pitch ie 6mm x 1mm = 5mm then if dead centre the helix left should pull out with the help of a pointy scribe with undamaged thread left behind even if loctite was used, this is a start others will be great helps Im sure
all the best

[vlxk]

Thanks Shelpi, I have the broken screws removed and the holes cleaned up. I'll start looking for a good manual.

The bearings cross over to #6305 but I think I will go back w/Suzuki this time, there isn't much price difference and I want to make sure of correct fit. The "tabs" I made to act as the retainer ring don't sit flush with the case when the bearing was still in the bore. Like I said it was about 1.3mm outboard of the case. Logic tells me it should be flush but I have been wrong before!

Taking measurements it appears there is plenty of room in the bore to seat the bearing flush and the seal behind will be well down in the bore on the opposite side. I just want to be sure when it goes back together.

Thanks again!

[80-85 husky]

common sense dictates the bearing should be flush. someone experienced in rebuilding zooks will be a long soon im sure.

[SUZUKI311]

Because the bearing is "outside" the  crank seal, ensure the correct seal has been fitted, and isn't too wide, thus preventing the bearing from sitting flush. I have rebuilt the 250C2 motor before, but I cant recall any dramas like this before.

[shelpi]

Because the bearing is "outside" the  crank seal, ensure the correct seal has been fitted, and isn't too wide, thus preventing the bearing from sitting flush. I have rebuilt the 250C2 motor before, but I cant recall any dramas like this before.

thats why I asked for the part numbers of both as the stock oem seal has locating tabs and yes there are other after market seals and bearings
Im not sure what you mean husky, Ive been building suzuki's since the late 70's to now and worked for a suzuki dealership and still raceing them now oops did I just react to a shit stirer

[Doc]

To test the shifting you really need to have the cases bolted together 'with' the centre gasket installed. Fit the nylon/teflon chain buffer on the gearshaft before fitting the lever. Without the buffer the shaft can push out toward the clutch side causing interference and poor shifting. Rotate the shafts whilst trying to select all gears. Any tightness in any shaft says there is an issue.

[oldfart]

Exactly what Doc Has stated ..... and to add make sure you have the primary side seal in correct way round.

[alexbrown64]

Not sure if you have the Suzuki owners manual for the 78C 1/2  but it has some great engine rebuild pics which might help you out if you dont have it.
https://onedrive.live.com/view.aspx?cid=407D7EF0965D3991&resid=407D7EF0965D3991!4938&app=WordPdf
Cheers,
Alex

[vlxk]

I'm really concerned with the shifting question. There are several videos on youtube about transmissions but it seems they are mostly newer bikes that have a different shift mechanism. They are able to select all gears with just a click of the shift drum. On mine it takes a very deliberate yank on the lever to get any movement in the transmission.

I am confident the trans is assembled correctly, just concerned with the effort required to change gears on the bench. I am hoping it will be better once the engine is back together and the internals are spinning around and getting good lubrication.

Thanks so much for the owners manual link, that will help a bunch in combo with the Clymer manual I have.

This forum is great!

[oldfart]

You have answered your own Question ... Its all about the gears rotating along with the lubricant.

[evo550]

Yep, once it's full of oil and things are spinning all will be as it should.

[pmc57]

It's been a while since I did one of these, but if I remember rightly the OEM (Suzuki) R/H seal should have a series of lugs around the outboard side. These are there to ensure the seal when installed stays the correct distance from the bearing. If a generic seal is fitted or the OEM is fitted wrong way around and is pushed too close to the bearing, the inner race will rub on the seal lip causing seal failure.

My way to install seal and bearing is to mount the retaining plate to the R/H case first. Next install (slightly heat the case) the bearing so it buts up against the retainer plate. Next install the seal with lugs toward the bearing so the lugs just touch the outer race of the bearing.

Tip. When installing the crank (R/H side first), if the shaft is a neat or tight fit in the bearing, make up a puller to pull the shaft into the bearing inner race so no thrust is applied to the outer race is the way to go. The books sometimes show a plastic hammer being used on the mag end of the crank to drive the crank shaft home.. I don't think this is the ideal approach.

Ensure you have all the correct spacers and lock washers and all should be good.