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Discussion Starter #1
What could cause "rear cyl no combustion" at throttle positions greater than say 70%? Feels like a wicked rich A/F bog, so I tuned my PV the leanest it would let me 70-100% (13.0:1) and still does it. Not a lean hesitation or bucking feeling. I have always had this bog and tried many tunes and changes, but today was the first time I got an "Engine Light" during the bog. Never had it dyno tuned, just butt dyno, midrange and part throttle the thing runs really good but has always fell on its face with bigger throttle openings.
 

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I would recommend a good shop with a Dyno to look at your issues and tune it the right way.
Just my 2 cents

But you could have a bad injector
Are you getting any codes besides no combustion?
 

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Discussion Starter #3 (Edited)
No other codes. im goin to test my plug wires and coil tomorrow and see what I come up with and have a good look at my sparking bolts. Do some more reading in the manual and play with the tune again. See if there is a way to test the injectors. WOT really aint a big deal to me, only occasionally go past 50% when passing someone. Dyno's are great tools no doubt, but when my dyno instructor told me you can use one to diagnose a worn or loose drive chain, I said you can do that with your eyes and people have been tuning and diagnosing fuel/electrical/mechanical for decades without dyno's. Even one eyed Jack Roush still reads spark plugs.
 

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I would check the wires leading to the rear injector from the main harness. There is very little extra wire length to allow for engine movement and if the harness was installed just slightly out of position it will put a strain on those injector wires. Check the wires to the rear injector for a tight condition (little or no slack for movement). If they are too tight the wires can fracture within the insulation yet still carry enough current to operate the injector at normal riding, but when under heavy throttle the rubber engine mounts stretch just slightly more and allow enough movement to stress these wires beyond there ability to make contact.
 

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Discussion Starter #5
hey thought i should update this... I previously had a problem with low fuel pressure that the stealer fixed by replacing the in tank fuel line. i thought i'd have em check my fuel psi again to see if that wasn't the problem again. I have good pressure while pump is running (engine on or off) but bleeds off immediately after pump is off. they did not seem to want to get into it and said it shouldnt really be a problem. then later i read on this forum or the other one, where a fella was having trouble tuning his bike on a dyno, they came to the conclusion that the base map could have been corrupt somehow from the start. he and the tuner started over with a fresh new base map and cured their problem, so i thought i would try the same and see what happened. got a fresh new stage one map from dynojet and seems to have fixed it 99%. could probably stand to have it dyno tuned still, but i am pretty happy with it now so i think ill just let it be. still kind of confused about the fuel psi thing but untill it leaves me sit im just gonna let it slide. BTW im done with dealers, they put a new clutch in under ESP but managed to f-up the final adjustment, they didnt get the three ball bearings set in the ramps and when they seated it felt like the cable snapped, this happened in the parking lot at Lancaster HD before i even left.
 

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you may want to check into the pressure bleeding off, if the pressure leaves that means there is a leak somewhere which could mean your starving for fuel at WOT which is why the rear cylinder dropping , also if there is a leak it will not get better only worse and perhaps leave you stranded
 

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I'm a very basics only wrench guy - but a stray thought occurs to me. Wonder if the temp sensor could somehow screw up under a heavy load and accidentally shut down the rear cylinder? Isn't that the one that cuts out to minimize heat build up??
 

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Discussion Starter #9
Thanks for replies guys, i researched the fuel psi problem a bit and came up with several things it could be, one was the fuel filter, though i think mi e is different from the one in the thread mentioned above mine is an '06. Another suspect is the psi regulator housing, or it could be the internal line again. I watched the tech test it and held 60psi even at 3500rpm, so i kno my pump is good, shut the bike off though and went right to zero. I do plan to open the tank up at some point to check it, but i hate to have the bike apart when the weather allows for daily riding and pretty much the only time you notice the lack of fuel is when starting the bike.
 
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