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While rejetting may be a good thing and many have been successful doing it, I would caution about doing this until you know your bike is running good again. If the bike ran fine and your circumstances haven't changed, i.e. you haven't moved several thousand feet in elevation or something to this effect, then something besides "your jets are too small" has gone wrong and you don't want to start modifying your carbs "while" you have a problem. This could start a snowball effect and you might get in deeper than your waiders.

I have a feeling that you got bad gas, probably some water or other garbage in there, and my gut feeling is that the seafoam will probably, if it hasn't already, fix your issue and restore the fuel system back to the way it was. Give it a little time to do it's magic...
 

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FREEBIRDS MC CENTRAL NY
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ethanol absorbs water and forms little crystals that reak havoc on carbs if it sits a little while.it can also attack rubber seals and cause leaks on old gaskets.the pumps over here also have to say whether it is e10 or e15.i read in cycle source magazine that some new motorcycle warranties won't cover damage caused from e15,so be cautious.:wow:
 

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Discussion Starter #23
I have run a tank with about a half can of Seafoam and I still notice a bit of an issue but its very minor and seems to only happen from about 4800-5200 on the tach. It also only seems to be on accel through that range. I dont seem to notice it at a steady throttle at that range. Could it possibly need some for Seafoam or some other additive
 

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1986 VN750
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3,255 Posts
I have run a tank with about a half can of Seafoam and I still notice a bit of an issue but its very minor and seems to only happen from about 4800-5200 on the tach. It also only seems to be on accel through that range. I dont seem to notice it at a steady throttle at that range. Could it possibly need some for Seafoam or some other additive
Leaning towards ignition issue, honestly. :doh:
 

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1986 VN750
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meaning what.. are we talking the coil..im not the most savy
Well, there are several things in the chain in regards to ignition. Here are most of them.

-Igniter - not prone to fail, but it could happen.
-Ignition Coils - You have one for the front and rear. This is the things the spark plug wires come from.
-Spark-plug Cables and Caps - self descriptive
-Spark Plugs

First step is to check and clean all the connections, ensure the grounds are clean, tight, and making good contacts. Then there are a number of tests you can do on each with a multimeter. They should be in the PDF manual, as well as the Clymers manual.

Can you determine what cylinder is dropping out, or both?

I personally can rev fairly freely on my 90 in neutral, but I can make it stumble if I hang out about 4500-5500. I will start to notice backfires, etc; I am currently running on this being weak ignition. She seems fairly good up to 4500ish, then instant power loss, and stumbles when riding. She'll make it past it, though, and seem OK. I just prefer to shift prior to the stumble.. then again, I don't ride her.

Then again, it's not the best idea to ride with a grounding stator that is pushing 14v @ idle, and low 13s under load. It's just.. weird. Charging, but .. it's just not right! Stock stator and R/R. I am sure it's not good for something.

I'll be playing with my bikes tomorrow, so if I make any progress that could help I'll let you know.

Wow, I rambled for-freaking-ever. :blah: Sorry?
 

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Discussion Starter #27
I upgraded to the Iridiums today..and I concur with everyone else.. it does seem more powerful and running smoother, esp if you need a quick throttle for a pass and don't downshift..took right off.. As for the missing at 4800ish.. It seemed less after the plug change. Still a llittle there but not as bad. What made me think bad gas on mine was it started the morning after a fill up. The first time through that range. it missed and coughed badly..Its gotten less and less every time since..Maybe some more seafoam or other additive will clear out the rest..yes??..No??
 

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Won't hurt to use SF, and may do a world of good. Cheap, easy fix if it works.
 

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Discussion Starter #29
i'm gonna run another 1/2 can of SF and go to a ethanol-free gas station for awhile. If that doesnt clear it up.. I've been reading on draining the carbs but am lost on filling them back up..cant figure out how to do that
 

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romeobravo172
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PM sent!
 

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1986 VN750
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3,255 Posts

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romeobravo172
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Pittdave----Sorry
 

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I've been reading on draining the carbs but am lost on filling them back up..cant figure out how to do that
If you mean refilling them with straight Sea Foam, a syringe with the needle removed works well. Get used ones from my vet for free. If with gas, just crank the engine. The vacuum will pull gas through the petcock.
 

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Discussion Starter #34
i'm chalking mine up to bad gas.. drained today.. some more seafoam and no misses or coughs whatsoever..rode great and picked up a new riding jacket and was smooth all the way
 
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