Pop from exhaust when starting

[jzanutto]

this just started happening yesterday, when I first start the bike when cold I get a nasty pop out of the exhaust. Sounds like a gunshot. the bike doesnt do anything else abnormal, and it only pops on the very first crank of the starter. Choke or no choke, same thing.

anyone seen this before?

[VWTim]

Mine's done this before, but only on very cold mornings with the choke on and when it's time for Plugs. It wouldn't start right up, and when it did catch it would burn the excess mixture.

[SlyHawk]

I was going to post the same question. It just started happening. It doesn’t seem to affect the starting or the bikes performance. It’s just kind of embarrassing. I was wondering if maybe I have the jetting wrong, but I replaced the jets back in July and the back fire with the engine start has only happened in the last couple of weeks. I’ve replaced the spark plugs this year and it’s not really that cool (mid 60’s) and it starts right up.

[NT696]

Exhaust popping

Check the exhaust bolts, clamps and springs (depending on your exhaust)
The same thing was happening to me, seemed to be caused by a bit of air getting into the pipe due to a loose connection.

[SGT]

Like NT696 said - most likely your exhaust isn't sealed. Mine did this and I found that the front pipe nuts had come loose. One had actually fallen off. As soon as I tightened them, all was good again. Kind of a pain getting to them, though.

[surferdude]

Glad I used the search feature - this is exactly what my bike is doing now at first crank when stone cold.

I'll take a look at the exhaust bolts and might also need to add some better springs.

[Abquid]

Pop!

I had this problem, too. In addition to the possibilities already mentioned (plugs, tighten bolts, etc) you might also make sure that your battery is fully charged and healthy.

I put in a new, good battery (the one I had was pretty old) and plugs and haven't had the problem anymore. Then again, I live in Los Angeles and it never gets much below 40º F...

[surferdude]

Re: Pop!

I had this problem, too. In addition to the possibilities already mentioned (plugs, tighten bolts, etc) you might also make sure that your battery is fully charged and healthy.

I put in a new, good battery (the one I had was pretty old) and plugs and haven't had the problem anymore. Then again, I live in Los Angeles and it never gets much below 40º F...

Mine is new within the past couple of months and has a full charge. I rechecked all of the exhaust bolts and also sealed up the collector at the header pipes and muffler with gasket maker. It didn't backfire today but I also didn't use any choke to get it started; 69 F today, so it wasn't needed.

[AK_Hawk]

Had the same problem under similar cool conditions. going thru the entire bike this winter Will be replacing the plugs and exhaust gaskets so maybe that will fix the problem. Won't know until spring.

One other consideration: When adjusting the valves I found two clearances to be tight. Feeler guage wouldn't slide at all. Check them all for the correct gap. Doesn't cost anything.....