Hitchcocks Forum

Hi

I've had some work done on a classic bullet 500 engine by Tollgate classics. I've been fettling the bike now for several months ( recently moved so didn't do much to in after got engine back from rebuild ). Essentially had roller big end, HC pistol, alloy barrel, HC oil pump, flowed and recon head. I've been fiddling to get the timing right ( sorted ) and the carburation ( Amal concentric 930 ) which now also seems okay.
When I start the bike from cold - it needs full choke and will emit a bit of white smoke ( assumed sump clearing ) until warm, then on tick over no real smoke just exhaust gas, when revved hard ( up to 5k revs it runs with no smoking at full revs, however on overrun and up/down revs in mid range there is sometime clouds of smoke from exhaust. I have Hitchcocks breather kit fitted and the bike is oil tight - also doesn't seem to use any appreciable mounts of oil.
Bit worried as the smoke is white that somehow i'm burning oil, plug seems okay though - not oily or blackened. Could the HC oil pump be putting too much oil into top of head and down valve stems ? There are no valve stem seals.
In a quandry - don't want to strip down engine again as its pretty much as built from Tollgate and piston, barrel were new - but unless I can sort may have to check out rings and valve guides.
What do you think ?

could just be the new piston and rings needing to get bedded in, can take 1-2k miles to bed them in properly. ed

Burning oil usually means blue smoke. White smoke is usually condensation. Has it had a good run to really warm everything up?

Hi Chris,
It may be wet sumping a bit, but if it is not using oil and only recently rebuilt, working well and not leaking, why not carry on using it and let it all bed in? Chances are it will settle down with a bit of mileage done, as already mentioned. Some MK I Concentrics I have encountered have had the float height set too low - the float top surface should be parallel to the face of the float chamber when it closes the float needle. The needle seat can be drifted in either direction to adjust it if needed. If it is too low, the choke will be needed for nearly all starts, but there is a tickler to flood it for starting as well.
I would keep using the bike, but maybe check your carb settings and keep an eye on the engine oil level, just in case. Cheers, Paul.

I totally agree with the others, if it was excess oil there would be much blue smoke. It sounds like you just need to get out there and ride it, bed everything in correctly and not worry too much. This time of year, assuming you're in UK, you will get a lot of harmless white exhaust.

Hang on - just read your post again. "revving hard" "full revs" ?
Did you JUST have the engine rebuilt?
If so you'll need to go easy on the new barrel and piston for a bit.