Honda GB250/CBX250rs engine

[ZK-Awesome]

I'm after a new (used) engine for my GB250 MC10. The current one has a collapsed big end bearing, it's a write-off.

I'm after one without massive K's and doesn't burn too much oil. It is the twin carb model (I think they changed to single carb later on), and has the RFVC head.

I've sent out heaps of emails to wreckers, still waiting to hear back.

Help me out!

Brock

[FROSTY:Me]

Not trying to teach gramma how to suck eggs but have you priced a kits and a bore for your engine?
I'll stand corrected but I think the xr2520 engine is the same as mine

[ZK-Awesome]

Hi Frosty,
my understanding is that because the big end bearing has lunched itself, there are lots of bits of metal now running around in the bottom end, probably making holes in stuff, making the engine a write-off. Would that be correct?

Also I think there are differences with the XR/XL engines, some have twin carbs some don't, some are rfvc some aren't, bore & stroke slightly different, mounting to frame slightly different (from a bit of research on thumpertalk).

Thanks for your help anyway mate

[FROSTY:Me]

I dunno dude-sight unseen yasee. Ill try that again cos I phrased it badly.
Yours is a pretty simple engine. If the bigend went bang you might not have as mutch damage as you think you have.
My mental image is collapsed bearings mean maybee piston might have hit the head and the rod broke scratching the heck out of the bore.
Then bits of metal might be all through the bottom end.
Basicly--yea so what??
Lateral thinking here. Rip the head off and check to see if its been clobbered.If so is it still useable. Might have whacked a valve or two
Rip the barrell off and see if its scored -If so hey rebore if not --all good.
Then my thinking is that the trail bike version of your bike probably has a rod kit available --or even a crank/rod/piston kit.
It'll be a bit of work to flush out the swarf but other than that you'll end up with a brand new engine--ie the worn out bits are gonna be replaced

[phaedrus01]

let me know how you get on with this, I have a GB250 as well mine is an '83 but has the single carb, which seems a bit weird as like you say I thought they started out with the twin carb first?
Anyways aren't these essentially the same engine as in an RFVC XR250R/XL250. From what I understand they are all good for a swap as long as they are '85 thru to '98 or something? Might be alot easier to get than a GB engine.

[ZK-Awesome]

Thanks for everyone's help so far. They said it's not really viable to rebuild. Anyway I'm still looking, I'm down in Christchurch on Saturday so I'll be able to do some door-knocking at wreckers. So far on my list ofplaces to visit are Budget Motorcycle Spares in Waltham, and Japanese MC dismantlers on Tuam St. Can anyone recommend any others?

[ZK-Awesome]

Bought a second GB that will donate its engine to mine - it's being fitted so should be done on tuesday! Now I have a second GB minus engine, but with some "different" bits - very plush Kawasaki seat and home-made screen. If I could find another engine to put in it, then I could sell it to the old man...

So I'm still on the lookout for a spare GB/CBXRS engine.

[ZK-Awesome]

Quick update - sorted about a month ago. I got another engine off the person that sold me the bike.

Once the front end is back on (halfway through fork seals), I'll have a good bike for the summer.

[mnkyboy]

Quick update - sorted about a month ago. I got another engine off the person that sold me the bike.

Once the front end is back on (halfway through fork seals), I'll have a good bike for the summer.

That guy doesn't have any other GB parts does he?

Or do you want to sell me the exhaust rocker/cam out of the lunched motor?