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Discussion Starter · #1 ·
I just bought a 13 nightrod.
Rides considerably smooth to the 4-5k range in rpms and just won’t go any farther to reach the good rpms with all the power it is backfiring around 2500-3k Rpms as well. i cannot figure out what it can be I’ve been reading every forum I can find and checking that issue on my bike and just can’t make sense of this. The bike shows no codes and only has a k&n air filter and some non baffles slip ons. It had an old tab performance tuner on it and I thought that had to be the issue but tab says that those older tuners didn’t have a rev limiter set to the tuner so I removed after speaking with mechanic if it was safe to do. Not sure what to check at this point anyone ever have this happen? I’m looking at buying something to reset the tune to stock but can be costly and not positive it is the issues so wanted to put something on here first any ideas are very appreciated!!

photo of The tuner I removed
 

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I just bought a 13 nightrod.
Rides considerably smooth to the 4-5k range in rpms and just won’t go any farther to reach the good rpms with all the power it is backfiring around 2500-3k Rpms as well. i cannot figure out what it can be I’ve been reading every forum I can find and checking that issue on my bike and just can’t make sense of this. The bike shows no codes and only has a k&n air filter and some non baffles slip ons. It had an old tab performance tuner on it and I thought that had to be the issue but tab says that those older tuners didn’t have a rev limiter set to the tuner so I removed after speaking with mechanic if it was safe to do. Not sure what to check at this point anyone ever have this happen? I’m looking at buying something to reset the tune to stock but can be costly and not positive it is the issues so wanted to put something on here first any ideas are very appreciated!!

photo of The tuner I removed
First thing, check your fuel pressure. Black cap, R12 fitting , right side between the throttle bodies. Rent an old GM fuel pressure tester from an auto parts store. Should read a solid 57-60 and hold pressure for some time after engine is shut off. 10psi drop over a minute is acceptable but a fast instant pressure drop is not. This indicates a problem inside the tank with fuel leakages. If pressure is being held and it hits 57-60psi with key on only, engine not running , you could have a pugged up sock on the pump, not allowing enough fuel pressure at higher rpms.
Ron
 

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Discussion Starter · #3 ·
607644

First thing, check your fuel pressure. Black cap, R12 fitting , right side between the throttle bodies. Rent an old GM fuel pressure tester from an auto parts store. Should read a solid 57-60 and hold pressure for some time after engine is shut off. 10psi drop over a minute is acceptable but a fast instant pressure drop is not. This indicates a problem inside the tank with fuel leakages. If pressure is being held and it hits 57-60psi with key on only, engine not running , you could have a pugged up sock on the pump, not allowing enough fuel pressure at higher rpms.
Ron
 

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What Ron said! With the addition of. If your fuel pressure is reading accurate at idle. Do NOT let that be your only test. Drive the bike with the gauge attached to it and watch for pressure drop. This will take out any guess work. Which becomes expensive in a hurry. Very common testing procedure on anything with fuel injection. Not just a VROD.
 

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Discussion Starter · #5 ·
First thing, check your fuel pressure. Black cap, R12 fitting , right side between the throttle bodies. Rent an old GM fuel pressure tester from an auto parts store. Should read a solid 57-60 and hold pressure for some time after engine is shut off. 10psi drop over a minute is acceptable but a fast instant pressure drop is not. This indicates a problem inside the tank with fuel leakages. If pressure is being held and it hits 57-60psi with key on only, engine not running , you could have a pugged up sock on the pump, not allowing enough fuel pressure at higher rpms.
Ron
Alright I’ll go check that out today and let ya know what it says! Thank you!
 

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Discussion Starter · #6 ·
What Ron said! With the addition of. If your fuel pressure is reading accurate at idle. Do NOT let that be your only test. Drive the bike with the gauge attached to it and watch for pressure drop. This will take out any guess work. Which becomes expensive in a hurry. Very common testing procedure on anything with fuel injection. Not just a VROD.
Will do I haven’t done one before so I’m sure ill figure it out lol thank you!
 

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Will do I haven’t done one before so I’m sure ill figure it out lol thank you!
With a carb unit as long as there is any surplus pressure beyond the demand no ill effects happen. In EFI systems, the whole fueling is based on a spec psi for the calibration to work correctly. It's the starting point of diagnostics.
Ron
 

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Sounds like it's running extremely lean to me when I bought my R model it wouldn't rev beyond 6000 Rpm ! Fell flat on it's face stammering, misfiring - turns out it was running pig rich as the original owner took off open pipes and put original ones on but never leaned out fuel mixture back to original setting. Leaning using fuel tuner fixed it. Ron can confirm but I believe when you remove a Dobeck type tuner the ECU reverts to the OEM H-D tune, hands off. This may be too lean for your open unbaffled mufflers and air filter as the engines tuned quite lean right from the factory with restrictive mufflers. Did you try to enrichen mixture with the TAB controller before you removed it ? Maybe it was mis-adjusted far too lean for some reason. If fuel pressure checks out install a set of OEM factory mufflers or install baffles or restrict the outlets of those open non baffled slip on's as a quick test to see if engine returns to normal. If it does re-install or buy a new TAB or another fuel controller and get tune set properly for open unbaffled exhaust or leave baffles in and tune it. Revo engine needs a bit of backpressure to run the best - open takes a lot of fuel to keep engine running at correct mixture. (y) :cool:
 

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Discussion Starter · #9 ·
Sounds like it's running extremely lean to me when I bought my R model it wouldn't rev beyond 6000 Rpm ! Fell flat on it's face stammering, misfiring - turns out it was running pig rich as the original owner took off open pipes and put original ones on but never leaned out fuel mixture back to original setting. Leaning using fuel tuner fixed it. Ron can confirm but I believe when you remove a Dobeck type tuner the ECU reverts to the OEM H-D tune, hands off. This may be too lean for your open unbaffled mufflers and air filter as the engines tuned quite lean right from the factory with restrictive mufflers. Did you try to enrichen mixture with the TAB controller before you removed it ? Maybe it was mis-adjusted far too lean for some reason. If fuel pressure checks out install a set of OEM factory mufflers or install baffles or restrict the outlets of those open non baffled slip on's as a quick test to see if engine returns to normal. If it does re-install or buy a new TAB or another fuel controller and get tune set properly for open unbaffled exhaust or leave baffles in and tune it. Revo engine needs a bit of backpressure to run the best - open takes a lot of fuel to keep engine running at correct mixture. (y) :cool:
I did try to adjust the tuner it ran the same whatever I was doing as far as the rpms go I can reinstall and keep trying but it’s set to the pipes I have on the bike and I honestly have no real idea how it works I just went off what the tech guy was telling me which was barely any help at all.
 

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Discussion Starter · #12 ·
R12 fitting is the one you want. Older GM tester.
Ron
Okay so ignition with engine of is 40 psi and while Running is 60 I didn’t ride with it on there but I’m kinda leaning towards it being this tuner even tho I removed it I guess im
Gna put it back on and do some more adjustments and see if it gets any better. Kinda my last hope lol
 

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Discussion Starter · #13 ·
Sounds like it's running extremely lean to me when I bought my R model it wouldn't rev beyond 6000 Rpm ! Fell flat on it's face stammering, misfiring - turns out it was running pig rich as the original owner took off open pipes and put original ones on but never leaned out fuel mixture back to original setting. Leaning using fuel tuner fixed it. Ron can confirm but I believe when you remove a Dobeck type tuner the ECU reverts to the OEM H-D tune, hands off. This may be too lean for your open unbaffled mufflers and air filter as the engines tuned quite lean right from the factory with restrictive mufflers. Did you try to enrichen mixture with the TAB controller before you removed it ? Maybe it was mis-adjusted far too lean for some reason. If fuel pressure checks out install a set of OEM factory mufflers or install baffles or restrict the outlets of those open non baffled slip on's as a quick test to see if engine returns to normal. If it does re-install or buy a new TAB or another fuel controller and get tune set properly for open unbaffled exhaust or leave baffles in and tune it. Revo engine needs a bit of backpressure to run the best - open takes a lot of fuel to keep engine running at correct mixture. (y) :cool:
So turns out the tuner was turned all the way up As Rich as you can get it, just reinstalled returned to zero for all dials and going to work it from there and see if I get any good results
 

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That's basically what was wrong with mine - but those wide open slips on's need a lot of fuel where my OEM mufflers did not so you'll probably end up on the rich end of adjustment again if you don't put baffles in them. You might want to install some new spark plugs before you start tuning as well. Good Luck !! Hope it works - (y) :cool:
 

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Discussion Starter · #15 ·
That's basically what was wrong with mine - but those wide open slips on's need a lot of fuel where my OEM mufflers did not so you'll probably end up on the rich end of adjustment again if you don't put baffles in them. You might want to install some new spark plugs before you start tuning as well. Good Luck !! Hope it works - (y) :cool:
Yeah I set it back to zero and started adjusting and doing the same regardless what I do I did just change the spark plugs no clue what it could be now
 

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You already know the PSI is down with key on engine off. We will trust that you have checked to make sure your battery connections are tight. WITH A WRENCH! And you have 12 volts with the key on engine off. And you already said you played with the settings on the controller with no change. What will make that different now? Your PSI test are incomplete. If you will complete the diagnostics. You Will find the problem. Parts throwing and Guessing, is a bad way to go about it.
 

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Discussion Starter · #17 ·
You already know the PSI is down with key on engine off. We will trust that you have checked to make sure your battery connections are tight. WITH A WRENCH! And you have 12 volts with the key on engine off. And you already said you played with the settings on the controller with no change. What will make that different now? Your PSI test are incomplete. If you will complete the diagnostics. You Will find the problem. Parts throwing and Guessing, is a bad way to go about it.
Not guessing I’m doing what I am comfortable doing I’m not a mechanic just trying to troubleshoot what I can before sending it to a dealer for half the season or more I didn’t know 40 psi with the bike was off. when I started it jumped to 60 so I figured that was normal? Also yes just replaced the plugs and made sure all is tight and well, clearly I’m not sure about all diagnostics or I wouldn’t be asking for help on here... I will run it down the road e with the fuel pressure checker on in a moment
 

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The pump should supply the 57 to 60 psi with 12 volts. It shouldn't take 13.5 to 14 that the charging system puts out to get to that psi. More volts will make the pump work harder/put out more PSI. Which can give the correct reading at idle. But fall under load. That's why it's so important to test the psi under load. With any restriction/leak under load. The PSI will fall. If yours is still okay under load. Then you won't have to wonder about it. Scratch it off the list. And move on to other areas. Sure does sound like fuel psi though. And since your controller was set to the richest settings. It could be because someone was trying to compensate for low fuel psi.
 

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I would bet I fix at least two or three cars a week that folks think their transmission is out. When all it took to fix it was tightening the battery cables. They always "look" okay. But a wrench will tell a different tale. The basic stuff will get you sometimes. Important to make sure things are tight. Don't trust the eyes. Trust your hands. A strong battery with 12 volts in it to start your testing with, is a must. A bad/loose ground can cause more problems than you could imagine on modern vehicles.
 

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Yea it all revolves around the proper fuel pressure as Ron & noechamp say 09-muscle-V-Rod - if you don't have that base of proper fuel pressure the fuel scheduling will be way off and no tweaking of the TAB fuel controller will compensate for it and make the engine run correctly. Did you get a chance to complete the fuel pressure tests ?
 
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