cb250rs splitting the crank cases

[guest1017]

Hi All
is it possible to remove the lower crank case from a Honda cb250rs without stipping the head and barrel off.
rgds Ian 

[steveD]

Not possible at all. I do have an RS 250 and a Haynes manual which I have just consulted. Unfortunately you will have to remove the engine from the frame and then remove the top end. Remove the side cases and then the two crank cases will spilt horizontally to expose all of the gears etc. It might be best to have a look on ebay as manuals are usually for sale quite cheap.
Hope this helps.

Cheers Steve.

[guest1017]

Hi Steve
the engine is already out, there is a crack in the lower engine case about three inches long where someone has tried to hammer out the bolt from the front engine mounting plate , I think the top end mounting studs may pass through to the bottom case, hence the need to strip the top end which has just been rebuilt !!! , figure i'll weld the crack up, if it distorts the case i'll have to strip it and fit another lower case .
rgds Ian

[steveD]

Blimey sounds a bit of a mess. I'd seriously consider another bottom end, bite the bullet and trash yours. There seem to be plenty on evilbay at the moment.

Steve.

[chris22]

I have taken the bottom crankcase of one of these several times without disturbing the top end.
The only thing you have to be careful with is ensuring the locating hole in the gearbox bearing lines up with the locating pin. If you dont, when tightening the bolts on the lower case the pin pops out of the cover and the bearing is free to float causing problems with gear selection.
Hope this helps.

[Steve H]

Yep I would agree the bottom case will come off without stripping the bottom end. I replaced a broken fork selector on mine.

[Propellor]

With regard to possibly swapping cases, I'm guessing the main cases are machined as a pair?

[Steve H]

From memory my cases had split on the front mount because of corrosion, the lower bolt had expanded due to rust and the alloy had also expanded, the pressure had caused a crack. Since there were two mounts and one was still good, I put it back together without trying to remove the bolt.

[guest1017]

hi
thanks for the replies, it seems a seized lower engine mounting bolt is a common problem on the rs,luckily you don't need to undo that one to remove the engine, the guy who had this rs before me wacked the crap out of the bolt and that's what has cracked the case, the crack is ground out ready to weld I figure it will distort the case, I have nothing to lose by welding it, the sheared off bolt is still in the lower lug, half drilled out, that's an easy job with a good drill bit.
rgds Ian