millard
Registered user
The bike is Honda CRM250 MK1, 1989.
I bought it about a month back and it was running fine so took it for a trail ride on Salisbury Plain and drowned it in a very muddy puddle. On the way home it started to develop symptoms of an air leak as the revs wouldn’t fully die down when shutting the throttle.
It’s fine when cold, very responsive, but after it warms up the revs don’t die down.
If I raise the needle thereby enrichening the mixture the problem lessens but is still aparent, so it's just masking it rather than fixing it.
Long story short - I rebuilt the bottom end with new rod, big end, small end, mains and seals but the problem still persists. I didn't touch the bore or head as I was advised they're fine.
I have blocked off the exhaust and inlet and pressurised the cases to 10psi and slopped soapy water all over. This revealed a small leak on the reed block gaskets which I’ve sorted but the problem is still there.
I removed the airbox so I could see down the throat of the carb and the slide shuts off fully.
I've stripped the carb three times and cleaned with carb cleaner then blown through with an airline, the jets are all clear.
I reset the float height.
The Power valve and oil pump are set to spec.
I then put some Castrol R in the gearbox to see if there was a leak to crank case from it but there was no smell of the R burning.
Then I filled the cases with petrol but there's no leak from the seals.
The carb is standard jetting and all else is very much standard and was running fine before I drowned it, so I'm fairly sure it was something that happened when I filled the engine with muddy water rather than during the rebuild.
I’m now at a loss as to what to do next.
Someone from another site has suggested a mate as a good local mechanic but he seems too busy as I can't raise him so I'd be happy to take it to a recommended mechanic if anyone else knows one in the Southampton area.
Or does anyone have any suggestions? as I'm much better at breaking four strokes than stinkers.
Cheers
Millard
I bought it about a month back and it was running fine so took it for a trail ride on Salisbury Plain and drowned it in a very muddy puddle. On the way home it started to develop symptoms of an air leak as the revs wouldn’t fully die down when shutting the throttle.
It’s fine when cold, very responsive, but after it warms up the revs don’t die down.
If I raise the needle thereby enrichening the mixture the problem lessens but is still aparent, so it's just masking it rather than fixing it.
Long story short - I rebuilt the bottom end with new rod, big end, small end, mains and seals but the problem still persists. I didn't touch the bore or head as I was advised they're fine.
I have blocked off the exhaust and inlet and pressurised the cases to 10psi and slopped soapy water all over. This revealed a small leak on the reed block gaskets which I’ve sorted but the problem is still there.
I removed the airbox so I could see down the throat of the carb and the slide shuts off fully.
I've stripped the carb three times and cleaned with carb cleaner then blown through with an airline, the jets are all clear.
I reset the float height.
The Power valve and oil pump are set to spec.
I then put some Castrol R in the gearbox to see if there was a leak to crank case from it but there was no smell of the R burning.
Then I filled the cases with petrol but there's no leak from the seals.
The carb is standard jetting and all else is very much standard and was running fine before I drowned it, so I'm fairly sure it was something that happened when I filled the engine with muddy water rather than during the rebuild.
I’m now at a loss as to what to do next.
Someone from another site has suggested a mate as a good local mechanic but he seems too busy as I can't raise him so I'd be happy to take it to a recommended mechanic if anyone else knows one in the Southampton area.
Or does anyone have any suggestions? as I'm much better at breaking four strokes than stinkers.
Cheers
Millard