uncorked bike backfires and dies when stopping?


9 replies to this topic
  • xrbrp

Posted March 17, 2004 - 04:38 PM

#1

I went for a ride this afternoon with some friends, I noticed my bike would die if I let off the throttle very fast when I came to a stop. the bike was then very stubborn when I tried to start it. It seem as though it was flooded, I did notice a small amount of fuel under the bike. I tried to Kick it several times while holding the kill swith and throttle open, but the bike would not do anythig and then back fire after about 15-20 attempts, I then resorted to bump starting it, (thank god for the hills). I used the specifications mentioned in the "Pig Pen" site, and had the dealer install them due to lack of time and I figured a Ben-Frank was money well spent.

I did notice the dealer used another type of jet not the honda 68s, could this be the problem.

the bike would also pop went I was riding and let of the throttle in any gear.
Oh by the way the 13T front sprocket was outstanding. what a huge difference, finally get to experience 3-4 gears.

  • Roll_it_on

Posted March 17, 2004 - 06:53 PM

#2

you might want to look at the plug to see how it looks from a jetting standpoint. Sounds like your carb settings are off. I do know that the 65s or 68s is the only way to go. My bike came from the dealer with the 65s and I later went with the 68s and it made a big difference. I think it is easy for folks to mistake a standard pilot jet with the s type. They are not the same. After the change my bike starts easier and has better response right off the bottom.

  • Old_Man_Time

Posted March 17, 2004 - 07:28 PM

#3

There should not have been a small amout of fuel under the bike. Sounds like you still have the stock float setting in the carb. The stock setting it too high for most applications. The float was set at the factory for baja wide open throttle type racing. Set it about 2mm lower (so the fuel will shut off with less in the bowl). That should prevent any fuel from back flowing into the air box. What you are experiencing is a flooded bike. Oh, and get a true honda 68s slow jet. And when its flooded you need to hold the decompression lever in and the kill switch and the throttle wide open. Then Kick it over about 7 or 8 times. If it doesn't start 1st or 2nd kick run through the same procedure again.

  • TimBrp

Posted March 18, 2004 - 08:03 AM

#4

This is true of the float??

  • Old_Man_Time

Posted March 18, 2004 - 11:46 AM

#5

Yes it is true of the float. When you climb hills the bike angle causes fuel in the float bowl to drain into your airbox. If you look at the side panel on the air filter side of the air box, down at the bottom of the panel there is a soft black rubber spout that allows the fuel to drain out onto the frame and ground. This usually happens after climbing hills. When it backfired you should have been able to feel it in the seat of the bike cause you were sitting on the explosion. Just change the float level and you will emiminate the problem. I took my carb off the bike and hooked it up to a fuel tank and turned the fuel on. I then angled the carb as it would angle when the bike was climbing a hill. It didn't take much angle at all and fuel began flowing out the back of the carb. I kept adjusting the float untill I could tip it up as if I was climbing a pretty steep hill without fuel back flowing out of the carb. Believe me there are many guys who's 650s flood simply cause they ride a lot of hills instead of flat desert racing for which the bike was designed. Change the float level and save yourself a lot of grief.

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  • larry650

Posted March 18, 2004 - 02:44 PM

#6

The symptoms you describe could also be a fully seated fuel screw. Get on thr right side of the bike and look at the carb. You should see a small adjustment screw closer to the motor side of the carb. Gently try to turn that screw clockwise. If it is tight that is fully seated and the source of the problem. Turn it one, to one and a half turns counter clockwise. If you can turn it clockwise disregard its not the problem. All your problems seem to be happening when the throttle is closed, and the fuel screw circuit in the carb deals with idle to 1/8 throttle. Just a thought and it only takes a second to check. Good luck. :)

  • aussiexr

Posted March 18, 2004 - 05:03 PM

#7

G`Day
Try looking at the float level ,the valve clearance,and the fuel screw (take it right out to check if the little o`ring hasn`t come of and is blocking the circuit carb body.)
The same thing was happenihg to mine give it some to get up some narly hills then it would stop at the top with gas coming out of the carb over flow tube.
Best of luck
Steve B

  • xrbrp

Posted March 18, 2004 - 08:21 PM

#8

I was changing the oil tonight, that's another problem, but I tilted the bike on its side using the kick stand, in an attempt to drain the oil and fuel began gushing out of the overflow tube. I didn't have this problem until I uncorked it. don't get me wrong the bike it outstanding, excellent power, no throttle delay, just a couple of bugs to work out.

  • TimBrp

Posted March 19, 2004 - 04:26 AM

#9

Oldman- I would have to bend the float to hang lower in the bowl in other words right? So it wouldn't be parrelell with the mating surface right? Bend the tang down a bit? This would probably explain my burnt air-filters huh?

  • Old_Man_Time

Posted March 19, 2004 - 06:58 AM

#10

No, you don't actually bend the float. Dead center of the float is a little tang that actually pushes against the Fuel shut off valve. The shut off valve has a silver spring wire that attaches the valve to this tang on the float. All adjustments are made by bending this tang. Bend it towards the shut off valve. What happens is, as the float raises it pushes on the shut off valve sooner thus closing it sooner. Also be very careful when putting the carb back together. There is a brass rod/tube that is angled and if it is not lined up properly when putting the bowl back on it will jam the float. Everything should fit together with no resistance. If you feel resistance while putting the two halves together something is not lined up. Its not hard to do you just have to take your time while your putting it back together and don't force anything.

Yes it explains your burnt filter. The fact that fuel flowed out the overflow when you put the bike on its side stand definately implicates the float as the problem. I suppose there is even a chance that when you put the two halves together that you did not line that brass rod/tube up with the slot it slides into and that it is jamming your float. Even if that is the case you should still adjust the float tang so the valve closes sooner.





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