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Red4x4neck

HELP my BRP is stumbling above 1/2 throttle

7 posts in this topic

Well I got a new FMF Q pipe and 55pilot /160 main jets for the stock carb installed them and now the BRP stumbles all over the place above 1/2 throttle. Idles like a champ :banghead: and revs pretty cleanly up to 1/2 throttle but that is where the response flat lines and starts "burbling" :applause:

No popping or back firing just burbling exhuast note and flat line throttle response.

I, for the purpose of testing, had my left side plate off since I haven't cut the top of the air box off yet and I run an K&N air filter.

I performed the "dave mod" iaw http://www.4strokes.com/tech/honda/xr650lcarbmods/ and everything went smoothly with the exception of installing the top diaphram seen Here. It seemed like mine had grown an extra 1/4 in in circumfrence and didn't want to fit back in the groove. I did my level best to seat it by half installing the lid and carefully pushing it into place with a small screw driver but I cant be totally certain that it is properly seated.

The only other thing that is different is the oil level, I changed it and in the process over filled it....dunno if that would affect throttle though...

Please help

Rob

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Well there are times I wish I didn't run to the forums so quick :banghead:

I have to eat a big bite of humble pie.

Immediately upon typing the above request for help I called a friend of mine who is a bit of a mechanic and fellow honda rider. He listened to what I had done with the carb and asked a couple of questions the last of which was "did you modifiy the slide spring? Stretch it or anything?" ............

I thought for a second ....Slide spring....DUH....:lol:

I ran back into the shop and guess what was laying right there on the bench (ie I had forgot to replace it when I re-assembled the carb).

Long story short I quickly (but carefuly) removed the carb just enough to reinstall the spring and now the Bike has a new lease on life. :lol:

Oh well alls well that ends well....

Now the bike is a whole new machine ...Thanks Dave :applause:

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don't feel bad, once i put the floats in upside down and my bike wouldn't start, so i almost cried. :applause: And another time i forgot to put the plug cap back on when i changed the spark plug and boy did i feel smart when i fixed that problem :banghead:

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Thanks for the thoughts

That same friend I called also informed me that if I had failed to make the seal on the top end I would have had a massive vaccum leak. Vaccum leaks equal erradic or no idle and or no start. Mine was starting and idling like a champ, in fact it would pull moderatly well up to about 45 mph but it sounded like it was trying to gargle its gas instead of combust it. :lol:

So there is a couple of notes for everyone: Slide diaphram, if not seated well, will result in poor start/idle. and on a Khein CV carb it will run with out the slide spring but will not accelerate. :banghead:

The funny thing was when I saw the spring on the bench, the very first thing that went through my mind was a replay of Napolean Dynamite "IIIDIOT...." :applause:

Happy riding

Rob

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don't feel bad, once i put the floats in upside down and my bike wouldn't start, so i almost cried. :lol: And another time i forgot to put the plug cap back on when i changed the spark plug and boy did i feel smart when i fixed that problem :applause:

i've done that.

worst one I've ever done though... was not put a spark plug back in :lol: and then wonder if something in the exhaust was leaking when it was making all those funny noises when I kicked it over :banghead:

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