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Discussion Starter #1
I’m dyin over here. 2011 BF750 No power above half throttle after it runs for a min - not a fuel vent issue - no FI light flashing.
Idles very smooth, starts right up - seems to have gotten a little worse, Last weekend it would take 5-10 mins to run shitty. Top speed is 28mph. Light Poppin through intake light poppin through exhaust.

Fresh top end with complete valve job
Double checked valve lash
80 psi compression
Fuel pressure 43psi (even tried another fuel pump)
Cam timing double checked (rear cam first at TR line, clockwise 270 to TF then front cam)
Ignition timing checked at idle with timing light
Tried belt reset (light wasn’t on but I’m willing to try anything)
Injectors ohm 12.1 each
New air filter
Spark plugs are only a few hours old.
I killed ignition while riding WOT for about 20 seconds and plugs lightly rich, very lightly.
Crankshaft sensor checks good
Exhaust is clear.

From what i read in the manual, if the FI light isn’t flashing a code, then all components attached to it are operating normally.
Any ideas??? HEELLLLLLP!!!!!!
 

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I’m dyin over here. 2011 BF750 No power above half throttle after it runs for a min - not a fuel vent issue - no FI light flashing.
Idles very smooth, starts right up - seems to have gotten a little worse, Last weekend it would take 5-10 mins to run shitty. Top speed is 28mph. Light Poppin through intake light poppin through exhaust.

Fresh top end with complete valve job
Double checked valve lash
80 psi compression
Fuel pressure 43psi (even tried another fuel pump)
Cam timing double checked (rear cam first at TR line, clockwise 270 to TF then front cam)
Ignition timing checked at idle with timing light
Tried belt reset (light wasn’t on but I’m willing to try anything)
Injectors ohm 12.1 each
New air filter
Spark plugs are only a few hours old.
I killed ignition while riding WOT for about 20 seconds and plugs lightly rich, very lightly.
Crankshaft sensor checks good
Exhaust is clear.

From what i read in the manual, if the FI light isn’t flashing a code, then all components attached to it are operating normally.
Any ideas??? HEELLLLLLP!!!!!!

Ok, and what is the battery voltage before starting and after, and at 3500 rpm? What is the coil voltages?
 

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Discussion Starter #5
I haven’t done a leak down test, I can try that. What we did have happen was the compression release on the rear cyl stuck (Flyweights out) and I got 190 psi in the rear, then it stuck on the front and I got 180. I’d have to say that’s a pretty tight top end! Pretty sure it was coincidence being it all happened while we were working on it. Subsequent checks were 80psi.
 

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Discussion Starter #6
Leak down check seems good. Put 90 psi in both cyl. No noise from air box, exhaust or dipstick.
Both plugs are lightly sooty, not black, but not nice and tan.
 

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Discussion Starter #8
Agreed. Any ideas on how or what to check? I’m out of ideas. How can mixture be so far off on an efi system with no fault light indication? I hate to take it to the stealer so they can just throw parts at it until ir runs. Very frustrating.
 

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Agreed. Any ideas on how or what to check? I’m out of ideas. How can mixture be so far off on an efi system with no fault light indication? I hate to take it to the stealer so they can just throw parts at it until ir runs. Very frustrating.

I hesitate to say it because it's rare..but..she might have a bad ECU. But lets check for leaking injectors first as well as double-dog check the valve timing cause..without the comp releases your numbers are a bit high for stock compression..hell they are high for 12:1s...lol


By the way... thank you for your input so far!!!
Welcome. Hope we can find the issue.
 

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Discussion Starter #11
I’ve had the rocker boxes off three times to check valve timing. Each time hoping it’s a tooth off! Always the same result tho. Lol. I’ll have to find if there is a procedure to check the injectors. Haven’t read up too much on them.
Know of anyone willing to lend an ECU for a quick plug in check??!!
 

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I’ve had the rocker boxes off three times to check valve timing. Each time hoping it’s a tooth off! Always the same result tho. Lol. I’ll have to find if there is a procedure to check the injectors. Haven’t read up too much on them.
Know of anyone willing to lend an ECU for a quick plug in check??!!

Nope...sorry.
 
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