650R won't start, backfires

I have a 2001 BRP that I bought as a project bike (I'm supercharging it, but that's a WHOLE different story).

I rode it stock (except uncorked) while working a tour in Mexico. As the tour progressed, it seemed to get harder and harder to start, but always did. I ran the very last of the Mexican fuel out and filled it with Amurican premium before putting it away.

I went to start it a few weeks later and it just wouldn't come to life. It is still stock except uncorking- no supercharger or similar wierdness) And I tried every trick- choke, no choke, half choke, gas, no gas, etc, etc. After about 1000 kicks over a couple days, I was kicking it and gas started running out the carb. I tried the smack the carb with the screwdriver trick to no avail. I kicked it anyway. At either this point or earlier (I forget). It backfired a bit upon kicking, but still wouldn't start.

I took the carb off to work on fitting the blower. At this point I found a bunch of carbon dust in the intake tract (from backfiring I ASSUME). I took the float bowl off and the float apart and everything looked good.

Now I need the bike running (without blower) to work another tour this weekend. ANy ideas before it put it back together?


Could it be a plugged or gummed up pilot jet??? I've had bikes that were too lean on the pilot backfire when trying to start. As dumb as it sounds, I'd put a new spark plug in it too (if you haven't already).

Your intake valves are probably tight.


Your intake valves are probably tight.


That makes sense too.

Check the valves

Check the valves as stated. The intakes tighten up. Also was the bike sputtering a bit on the low end prior to the not-start issue. My bike got something in the pilot and acted similar. Had to keep it in the midrange to continue running.

Adjust your valves and replace the spark plug...............

Keep us informed............. :naughty:

call xrs only

Is it fludded? Have you check the sparkplug? Does the exhaust smell like fuel after kicking?

I just looked at it some more.

Valves are pretty good (.005" - .008"). Plug looked OK.

I put the carb back on, plug back in (don't have new one yet) and wore out my right leg.

Results- it teased me, running for a few revs and dying- but only with choke ON. With choke OFF it didn't even think about running. When I pulled the plug back out- it was wet (after kicking with choke on). Seems too rich, but it only thinks about running with choke ON. Also a slight dribble of gas from the carb, but not flowing like last time.

I will get a new plug and some carb cleaner tomorrow and report back.


Clean the carb. Sounds like a plugged pilot Jet/Circuit. Check to make sure your air filter isn't over-oiled either. This will lead to a rich condition. Your bike should run rich when first started as it needs more gas to warm up, hence the choke. Seems like fuel starvation to me. However, it could be electrical too.

Had the EXACT same problem. It was the plug. Wore my leg out. Pulled the plug- it looked fine- replaced it anyway and the beast fired on the first kick. Go figure.


It lives!

I put in a new plug and kicked to no avail. Then I took the carb apart (3rd or 4th time) and douched everything with brake cleaner. Then I noticed that the float bowl was really sticky (didn't float up and down well). So I thoroughly cleaned the pin and hole so it moved freely and reassembled. No more drip out of the carb at least. Then I kicked and kicked, then I finally put on my MX boot and REALLY kicked (I had a blister on my foot from kicking in hiking boots). Then it finally lit! It blew some nasty smoke for a while (soot inside the engine) then cleaned up. A quick spin around the block and it seems fine.

This thing has always been a hard starter. I think this time it was a combination of things. This has me worried about starting it with the supercharger.....

Replace the Keihin with an Edelbrock, twist the throttle 3 or 4 times, starts first time, every time. :naughty:

Mine starts great with the stock carb. 2 kicks max any time. The only exception is if I allow it to stall out before it has warmed up a little bit. Then she can be a little cranky.

Yeah, how long did the bike sit since the last ride? The plug may have been foulin' (evident the backfire session and hard starting) on the last ride and depending on the length of time you let the bike sit between rides, the gas could have went dead. Then the combination of the weak plug and three to six (or more) month old gas did you in. I would think about rejetting if your bike is hard to start w/ new gas and a plug, especially if it fouls on this next ride.

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