Popping/stalling... air leak?

I had my 450 apart for a couple of weeks, I put new muffler, plastics, tank and air filter on it. I also put a Dr.D hot start on which involved removal of the carb.

Anyways, got it all back together and it ran fine, other than a rare drop in RPM while holding the throttle at a steady opening. It didn't happen all the time, and I didn't think much of it.

Today was the first ride, everything went well for 10-15 minutes or so. At this point I was riding down a fire road, hit a couple of puddles from the recent rain. The bike started popping on decel, I pulled in the clutch and the engine died. Let the clutch out and it fired back up, only to continue popping. Stopped on the side of the road for a couple minutes, then tried to re-fire. No luck.

Pushed the bike all the way back to the truck and let it sit for 10 minutes, maybe 20. It fired right up. Ran it around the truck for a few minutes, got real aggressive with the throttle. It ran flawlessly.

In any case, I'm thinking maybe I have an air leak. Carb? Pipe? Just seems weird that it's intermittent. I had a similar problem earlier this season and my headpipe turned out to be a little loose. I haven't had a chance to check it yet, but could that be the culprit again? Perhaps water from the splashing of puddles got in there?

My buddy had a carb bike and it was a jetting issue causing what you state. Could be if you changed Hot Start, it got stuck open or something weird. I believe it opens up a valve or soemthing to let air in leaning it out and allowing to start when hot. Possibly if it was acting up, could cause a lean condition. Im no expert, but if it didnt happen before Id recheck some of your work and go from there.

On the two occasions mine did that it was the pilot jet, clogged or partially clogged. Keihin uses some goofy sealant on the bowl o-ring to keep it in place during assembly. It starts to come off over time. It only takes the smallest of objects to clog even one hole on the pilot and you've got problems. An inline fuel filter keeps that from happening if it's coming in through the fuel supply.

Edited by rmzpegger

Given that it seems back to normal, is it reasonable to think that whatever it was passed? Or is that just some wishful thinking? :)

I checked the pipe, and carb, both are tight to the engine.

Thanks for the help, guys.

hit a couple of puddles from the recent rain. The bike started popping on decel,

Perhaps water from the splashing of puddles got in there?

Perhaps water splashed up on one of the connectors on the bike? Ie. CDI unit is under the front plastic on the handlebars.. or perhaps the "throttle response wire" or whatever its called.. the electrical cable that goes to the carb. Suggest cleaning and maybe spraying with some electric contact spray (CRC or similar)


Well I came up with a theory that maybe the new gas tank was bouncing up and causing an interruption of fuel. I forgot to put a couple of brackets on that hold it in place.

So, I put the brackets on and took the bike out yesterday.

Fired up fine, let it warm up, pulled in the clutch, put it in gear, gave it a quick snap of throttle and it backfired and died.

Waited a few minutes, it fired right back up and I rode it for a good 25 or 30 minutes. No more issues.

The only thing I can see causing this issue is possibly the new hot start I put on. Maybe the cable is snagging or stretching somehow? I'm just at a loss here, not sure what to do.

No more ideas? I really don't want to take the hot start off, it was a hell of a job getting it on there.

Mine did this yesterday and it was a 3 mile walk back to the truck. I didn't hit no puddles though. It was hot and I wad 4 gear about half throttle and then I heard the popping and then it was dead.

Air filter was a little dirty intake valves are @.007 and exhaust is @.010 and .008 need to shim one up a little bit but not sure what is causing this? Oil is dark but only 2 rides on it AND coolant didn't mix with the oil so not a head gasket? I am lost ?

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