Rebuilding 2 bangers

[Scorpion82]

Ok did a quick search and couldn't find anything relevant.

Is it hard to do a full rebuild on one ?(2-stroke) or is it something that shouldn't be attempted by beginners.

[Semi]

from what i gather, its a lot easier than on a 4 stroke, you dont have messy complicated cams and valves to worry about

[Satan1]

Much easier than a four stroke, what model in particular?

[Scorpion82]

1991 Cr 250.

[Satan1]

Easy as mate, are we talking top end and bottom end?

I think you will find a few threads on;
www.dirtbikeworld.net - What planet are you on?

From what i have heard there is no easier engine to work on, Im sure desmo can help you get your parts and there is tons of people on here that will walk you through.

[Scorpion82]

I think i need to do the bottom end as well, if i'm holding the piston up (without the head on obviously) the bottom of the piston just scrapes the crank

Thanks for the info Shane.

[Mr M00se]

2t top end rebuilds are peice of piss, does get abit more coplicated when you need to split the cases but there are allot of guys on here with a hell of allot of knowledge

[taint]

with a 2-stroke rebuild, if you pay to get it done the labour alone will cost a fair bit more than the OEM parts do

[Scorpion82]

Yeh I wasn't really worried about rebuilding the head, there isn't much to those and i have someone that can hone so that's fine. More the bottom end, i also think the head has been modified on it as well

[RICO]

2 strokes are a piece of piss mate, you should be able to get a workshop manual for that bike anyhow, aslong as you follow that, You shouldn't go wrong, if you get stuck someone on here (me included) will be able to help you out!

Oh and you'll learn a bit as you go, pretty usefull as the engine is not that complicated, great to learn on, get a manual and give it a go!

[Scorpion82]

Yeh i've got a workshop manual for it and had a read last night, doesn't seem as complicated as i first thought. I've had a bit of a look around on the net but not sure where to look in Australia, can you get aftermarket cranks etc. for most of these engines in Aus? I can't bring myself to pay the $920 Honda want

[ritza]

get on the web lookup "hotrod" cranks see if they do one, then ring hamish engineering in welshpool to get one for you ...then glue it in and your good to go

[Scorpion82]

Heh they only do the model the year after mine. Someone at work suggested getting it rebuilt, has anyone had any experience with getting them done like that?

[sathid]

Pretty sure that the 91 CR250 would have had a nicasil bore, so if it is damaged, you will need to have it re-plated.
There are no good re-platers in Australia that I have heard of.

Bottom end rebuild as well?

Might be worth investing in a workshop manual if you can find one. And I'd look around for a cr forum if you can find one.

[Mr M00se]

What getting the crank rebuilt?. You realy need to take it out and get all the tollerances checked on it, then if in spec get it re ballanced, new bottom end bearings gaskets piston. Hopefully the cylinder in in spec too and theres no probs with the niksil or ovaling