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Discussion Starter #1
I started to notice a miss in my accel around 4500-5500rpm. It started the next day after a fill-up. I have since added about 1/2 can of seafoam. It was not as bad today. There were a few lags, but not like that first time. I was almost on E when I got gas and the station was about 5-6 miles from my house. The next morning as I warmed it up for an oil change(the first on my own BTW) it would lag on accel. It was the worse on that first ride around town and its gotten progressively better since Wednesday morning. It was also OK above 6K. I would never notice anything on slow accel, just on a more open throttle. I'm not sure if it was doing it on a steady load on the interstate at that speed. It would seem like there was some kind of change in the engine sound, but I'm not sure if that was me not completely steady on the throttle of not. I had my extreme lean mix issue and believe that is cured as the mix screws are 3 full turns out.
Looking for some ideas to check out
 

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romeobravo172
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Dave, not to get off your subject but what did you get to take the blueing off your header? And where did you get it?
 

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Discussion Starter #3
Its called Blue Magic Metal Polish Cream. I got mine at Oreilly, but I've seen at at AZ, Wal-mart and so on. I got most of the blue out, Its now a faint tan it most spots. It could probably get better, but I ran out of elbow grease.. took a lot of HARD rubbing
 

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Crap, I WAS in 5th gear.
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Sounds like a clogged main jet, but before you go there, check float level, vents, petcock, plugs, wires and maybe coils.
 

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1986 VN750
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My 90 does this. I am suspecting it's more of an electrical issue.

I am checking my ignition system thoroughly. The bike also has a bad (grounding) stator.

Stumbles @ 4500-5500, but if you push past it it's fine.

I'll let you know if I figure out anything, and you can do the same if you dont mind. :)
 

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Discussion Starter #6 (Edited)
you'll probably find out before i do..i'm not good at diag. my main deal is this just started. I've had the bike for a couple of months now and this was the first time it happened. it may be a co-inky-dink that it started after i filled up at this particular gas station, but it had never happened before. I am going to put my new plugs back in and see if it makes any difference
 

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2FAS4U
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469 Posts
My bike died on a back road after filling up on a trip.
After several tests, I shook the bike a bit and it fired up. Freakin water in the tank.
Might try some water remover in the gas. Cheap and plentiful.
 

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Discussion Starter #8
i think i am going to chalk mine up to some bad gas.. i was out again today and had no issues on accel whatsoever. I'm still wondering is there is a slight dropoff at about 5k.. couldnt do much running right at that today with some traffic issues. hopefully i can get on a nice open stretch on a back road this weekend and do a little more research
 

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Crap, I WAS in 5th gear.
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I had a stumble around 5k rpm as well. I went up one size on my main jets and added two shims under my needles. Runs great now and didn't really notice a fuel economy decrease. The VN750 is jetted a tad lean from the factory.
 

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Discussion Starter #10
ok then.. if i wanted to re-jet...how hard a procedure is that or how much might that cost at a shop??
 

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Sparky!!!
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Dave, re-jetting the carbs is easy. so easy in fact I wouldn't even take them to a shop. I have a set of carbs torn down for rebuild and re-jet, I will post pics later today. What elevation are you at, what exhaust are you running, and what intake mods are done?
 

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Discussion Starter #12
I am in Arkansas..low elevation, Wiki says 285 ft. I have the stock exhaust but 4 1/4 holes drilled in baffles. I do plan on getting some V/h Cruzers eventually. But i am not a mechanic in any way. 43 and i just did my first oil change on my own. So what you say is easy is prolly a nightmare for me. Maybe with the pics, i can figure it out
 

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Sparky!!!
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I'm heading out to the garage.. I'll get those pictures.. and you will see that its not that difficult of a task. Besides carb maintenance is a annual procedure.
 

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FREEBIRDS MC CENTRAL NY
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try running a fuel stabilizer to negate the effects of ethanol.motorcycles aren't designed to run on e-10,and e-15 is even worse.my wing will lose the 2 left cylinders after only 2 tanks without any additive.
 

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Sparky!!!
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the jets are located under the float bowl drain screw as pictured below

the two brass slotted screws are the Jets, just unscrew them and replace with 140 main jets and 40 pilot jets
 

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try running a fuel stabilizer to negate the effects of ethanol.motorcycles aren't designed to run on e-10,and e-15 is even worse.my wing will lose the 2 left cylinders after only 2 tanks without any additive.
Just wondering is the fuel you have over there different to the UK, I have a Yamaha fazer and have had it for 6 years, it has never had an additve in all those years never ridden in winter and always parked up with gas in the tank over winter and started up about once a month and the carbs have never been a problem, it always runs perfectly when the spring comes and it gets used :smiley_th
 

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Linkmeister Supreme
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Just wondering is the fuel you have over there different to the UK, I have a Yamaha fazer and have had it for 6 years, it has never had an additve in all those years never ridden in winter and always parked up with gas in the tank over winter and started up about once a month and the carbs have never been a problem, it always runs perfectly when the spring comes and it gets used :smiley_th
Do you have 10% ethanol in your gas in the UK?
 

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Standard is 5% ethanol but 10% was introduced January 2011 but pumps have to have a warning on them as it supposedly causes damage to fibreglass fuel tanks and some aluminium


(Quote From UK MP)My Lords, petrol containing 10 per cent ethanol has been permitted from January 2011. Petrol containing up to 5 per cent ethanol is currently available and expected to be marketed until at least 2015. Petrol pumps dispensing petrol containing over 5 per cent ethanol must display a cautionary label. Research commissioned by the Department for Transport into the potential impact of ethanol on vehicle fuel systems showed that there could be compatibility issues for classic and vintage vehicles.

(Quote from UK MP)My Lords, I am grateful to my noble friend for his answer. He has a delicate way of putting it. In fact, ethanol attacks fibreglass fuel tanks, bits of aluminium, fuel filters and so on. Therefore it is important that he gives an undertaking that the 5 per cent limit will be consistently available and not be superseded by the 10 per cent limit
 

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1986 VN750
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This thread really has me curious about changing the gas. I didn't expect the gas to be bad, and causing the 4k-5k stumble issue, but it had never occurred to me.

I think I'll want to drain my tank and re-fill her up.

It's not really the jets causing the issue since I am at sea level, with stock exhaust and intake. I do agree that they are probably small and I should go up a size or so eventually.
 

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Sparky!!!
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This thread really has me curious about changing the gas. I didn't expect the gas to be bad, and causing the 4k-5k stumble issue, but it had never occurred to me.

I think I'll want to drain my tank and re-fill her up.

It's not really the jets causing the issue since I am at sea level, with stock exhaust and intake. I do agree that they are probably small and I should go up a size or so eventually.
you stock jets are fine for the stock intake/exhaust set up.. re-jet to compensate for altitude or intake/exhaust mods. the stock jets are desinged to work from sea level up to 2000 feet
 
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