Exhaust Smoke

I’ve got a baffling conundrum which I’m sure someone can help me with. My 500 fires up nice and readily and revs freely; however, almost immediately she starts to emit white smoke from both ( standard ) exhausts. She also fires out bits of straw and twigs etc ( I’m not joking) so its likely that the collector box I bought from the States was once a home for a mouse or other type of rodent. To my mind the white smoke is possibly coolant i.e. a dodgy head gasket but I don’t get bubbles or pressure in the header bottle and the cylinder compression is equal - 140 / 150 on all 4 pots. My next job is to remove the collector and see if its still stuffed with mice stuff but before I take the heads off to check the gaskets is it possible that cyl compression can still show normal even though there’s a coolant leak into it ? My hooter / nose is unable to distinguish between oil smoke smell and coolant steam smell.

Hi Martin. …
If it ticks over ok and your getting no excess pressure in the system or bubbles in the header the I don’t think it would be the head gasket…
If the smoke slowly disappears after a 5 or 10 minutes I would guess at condensation in the collector and silencers. Especially if the bike is only being started and warmed up in the shed…
Could also actually be whatever is in the exhaust that’s burning off.
Could also be petrol burning off in the exhaust if you have a leaking float valve… Although you would probably have uneven tick over…

Thanks Pete - that’s reassuring. I have to say this 500 is proving to be much more finicky and sensitive than the 1000FF. I’m going to drop the collector and have a good peek inside before deciding on the next step.

Coolant is a pretty distinctive smell. If it goes away after a few miutes then yeah, I agree, it is probably condensation.For info, your compression test results mirror mine. I have three engines and they all give similar results.

You can buy really inexpensive endoscopes these days off Ebay. You can even plug them into mobile phones and tablets. Amazingly useful gadgets. Would make peering into your collector a cinch.

Collectors can be very difficult to get off btw. I had to take out the swingarm and beat down on the collector with a lump mallet to get it off.

I’d say the collector box is just full of something, water, unburned fuel, twigs, etc etc…would all cause this.

Has the bike sat for a while? gummed up rings would cause this. Had this very same issue with my 500 (which had sat for 8-10 years before i fired it back up). It went away over time.

Thanks gentlemen, all good info from experienced people. I’ve got the box off and no obvious signs but these are cleverly designed so they look like they just pass straight through but they actually have damping areas which may have liquids of some sort causing the smoke when they get hot.
I going to re-assemble the carbs and pipes and give it a good thrash up the road to find out once and for all.


Your oil level isn’t too high is it?

Hi Rob, it actually turned out to be a coolant leak into the cylinder on number 3. New head gasket fixed it. Thanks for your suggestion.