1989 Honda CBR250R MC19 Carbies

[WALRUS]

Hey guys!

I've got a pair of these little bastards as track bikes. They've had a hard life, they're 28 years old, most of their life has been spent being thrashed, crashed, and abused by teenagers learning to ride, and now they're dedicated track/race bikes. I'm having an issue with the carbies though (I suspect)..

The engine turns over, fuel pump works but there doesn't seem to be anything getting through the carburetors. With enough "Start Ya' Bastard" sprayed into the top of the velocity stacks, they fire and run but they idle rough as fuck and eventually cut out, refusing to start again without the same application of compressed ether sprayed into the top of the thing..

My first guess is that it's a fuelling issue.. But I know nothing about Carbies, rebuilding them, cleaning them, etc etc... Do any of you brilliant humans have any suggestions or tips?

[OddDuck]

Might not be carbs at all, try checking the inlet manifolds. If there's a bit of aged, cracked plastic, or a rubber seal which has set over time, you could be getting vacuum leak (air leaking in). That'll give a super lean mixture and then the bike won't start properly or idle. It'll run OK with the throttles opened up though.

If you have vacuum gauges it's an easy check, otherwise it'll be take the manifolds off and visually check everything.

[nzspokes]

Undo one of the drain plugs on the carbs to see if there is any fuel there. I didnt think they had a fuel pump but a petcock valve. I could be wrong but check fuel in the carbs first. If nothing then check the vac line to the petcock valve is attached.

[spanner spinner]

Before you spend any time or money on these check the compression. I have worked on to many of these trashed to death pieces for shit, most that have the symptoms you describe have either no or very low compression. Can some times just need the valve clearance set for the first time in there life, some times there just stuffed. you are looking for 150psi minimum, good will be around 175psi. any thing less than 150 psi and they are hard to start. And buy the way you will need a 10mm adapter for the compression tester, these are not real common.