Honda C90 smoking heavily at high revs and wont rev out

[Cheekywig]

My Honda C90 has apparently had a new piston and barrel before I bought it. It wont rev to the max and seems to hesitate when in the higher rev range and loads of smoke from the pipe and manifold when it gets up there. Has plenty of compression , fires up easily but is burning a lot of oil. Any suggestions? thanks.

[trickywoo]

Oil level too high maybe?

Easy first check anyway.

[Cheekywig]

Oil level is half way, thanks.

[Krikkit]

Sounds like a piston ring issue to me...

[Cheekywig]

Thanks, will check the ring.

[poo at Paul's]

Cheekywig said:

Thanks, will check the ring.

ooohhh Matron!

[jchesh]

Are you quite sure it's burning oil? If the smoke's blue then it is oil, but if it's more black than blue smoke then it's because it's running very rich at those revs which would also very possibly cause the running issue you describe. If this is the case then it could be a blocked air jet in the carburettor.

[Turn7]

c90's always burnt the exhaust valave out as the cold clearance was something silly like3 thou iirc.....

[Cheekywig]

The timing was out which sorted the rev issue, but still smoking heavily. Need to pull it down further...

[Cheekywig]

poo at Paul's said:

ooohhh Matron!

[stu67]

Pull it and put one of those mad 190cc pit bike engines in, I’d love to build a sleeper like that

[Birky_41]

2 Clicks of rebound...that seems to fix most going by recent FB comments I've read

[3200gt]

Valve guide oil seal.

[Rubin215]

Piston ring on upside down.

And as a Brucie Bonus you're going to have to strip it right down to find out.