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Discussion Starter · #1 ·
2007 650H1...Been trying to think this one through all day. Set the valve clearance (.005 exhaust, .003 intake) due to not being able to get past compression when starting. Went out for a ride, and can't get past 35 mph (55 kph) at full throttle, then at that top speed for a few minutes, will suddenly seem to backfire, but not out exhaust ....something not right. Completely stock, so not sure what is going on. Also notice it doesn't have the low end power it had before either.

Any suggestions on where to start?
Starts fine, idles fine....

Thanks in advance!!
 

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Discussion Starter · #3 ·
I have not...looks like that'll be an "intersting" undertaking...guessing them bolts aren't coming out in one piece....
 

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Have you been in the fuse box?
 

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Discussion Starter · #5 ·
Went and checked at lunch. Dont suspect any exhaust restriction or blockage, lots of force coming out of pipe. Seems to be getting plenty of air/fuel, as revs up to the limiter with no problem. Starting to wonder if it somethingin clutch/belt from when i pulled one way bearing a while ago..
 

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Discussion Starter · #6 ·
Hey doorfx, nope haven't been in the fuse box, and have read enough to know you are thinking the diode. Went and pulled it to make sure that it was correct and can confirm it is.
 

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There is more than one , correct?
Does it feel like it’s hitting the rev limiter , like the reverse override? Push the reverse override when it cuts out.
 

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Discussion Starter · #8 ·
No, just the one on mine. So went out tonight to play around and investigate more. Pulled clutch cover, found i had beltbin backwards. Rectified that, and verified that all working as it should with back wheels off ground. Took for a ride, same as before, max 55 km/hr at 4500 rpm. Checked fuel vent lines, can blow freely through them. Pulled out air filter. Not bad, but tore it, so will need a new one now. Took for a run without filter in and air box cover off. No change. Took Wallamatogus' question, and checked spark arrestor....only broke 1 bolt (yay me!!), it was black but could easily see through the screen, so guessing i can rule that out. Now what? Hmmm..... ...carb?
368612
 

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Discussion Starter · #10 ·
Just checked that the throttle cable is proper, both at the thumb lever and the carb. Also, just for the hell of it changed direction of diode as see that improper install often an issue as per doofx suggestion. Ran worse, so know it is correct and exactly as would be expected based on symptoms others have explained. I think it has to be carb related...
 

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A crack in the diagphram can cause mid range issues.
Check the intake boot between carb and head. The little nipple sometimes cracks or the boot itself.

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Discussion Starter · #12 ·
Removed carb, disassembled, looked clean, but carb cleaner and air compressed air through every single orifice, passage etc, diaphragnm good, reassembled everything. Idles nice, revs nice. Took for a run...50km/hr max. Another run with GPS to confirm....52 km/hr max. Still seems lean? Seems to run hot, and starts backfiring at wide open throttle. Tried new plug, properly gapped, same result. Sprayed carb cleaner all around carb, no change in idle, tried propane as well to be sure, same thing no change. Not sure where I go from here.
 

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What is the PMS set at ?
What size was the main jet ?
 

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Discussion Starter · #14 ·
Service guide said to set pms at 1-1/4, so thats where i set it. Never thought to check jet size, as at should be the stock jet, parts diagram shows 132. First time I've opened up and cleaned a carb....was quite happy when it actually started.
 

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Did you check/set the float ?
 

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Discussion Starter · #16 ·
Yes, but funny you ask this, had to do it twice as the first time the needle dislodged as I was assembling and had to remove again to correct as fuel kept overflowing.
 

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Was it at 17 mm ?
 

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Discussion Starter · #18 ·
Now i am second guessing myself
... I think I better pull it and confirm that i was measuring correct after doing some more research.
 

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