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I need help guys and gals, I just bought a 1999 Yamaha v star 1100 and its only running on the rear cylinder. sent it to a shop and paid $475 and still nothing, they did the carbs plugs gas all that. it is getting fuel and spark but no bang??? please help with any ideas!!
 

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Paying for them to fix the issue and it isnt? What did they say it could be?? The spark outside the cylinder may be fine but under compression it might fail. Try swapping the coils around to see if it moves to the rear cylinder. What is the compression on the front? Is there an air leak on that cylinder?? fuel supply sufficient...how wet is the plug??? What about the valves...esp the exhaust

Good luck
 

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They said it must be something electrical and they could not do it with what they had. I checked both coils and primary and secondary and they were 4.7 ohms on the primary and 22,100 ohms on the secondary. I also have 12.5 volts going to both coils. at one point I did try to swap the wires to the coil and it ran worse. Exhaust valves were adjusted properly. both carbs were looked at by three different people and said were good to go also synced. as far as compression all they said is it was good in both cylinders. I may try and divert all the fuel to the front cylinder and see if its not getting enough or will even fire, I do get random backfires and some times it does come alive but quickly dies. I'm at a loss right now Thanks for your help!
 

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It needs to go BACK to that shop and STAY there until you actually get your money's worth. That is, until it is running right.

Sometimes it is near to impossible to get the tiny low speed jets in a gummed up carb properly cleaned.
A replacement carb might be required if fuel delivery is really the problem.

With everything assembled, squirting a little propane or starting ether into the failing air intake should tell the story.
The key phrase is "a little".
 

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You cannot simply swap the coil wires over you must change the coils over. The firing order will have been all stuffed up doing it the way you did.
 

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Hi all, this is my first post.

my 2000 1100 custom is also having similar symptoms and idling on one cylinder. at first the front cylinder wasn't firing at all but the carbs were cleaned which has helped somewhat but it's not quite there. it idles on one cylinder but when you apply revs the front cylinder kicks in somewhat under-powered but then 'lurches' into full power and falls off again.

it's had new plugs and leads, carbs cleaned, stripped down and rebuilt, coil packs swapped over which didn't make a difference, all needles checked, even test-fitted the carbs off another 1100 custom the mechanic coincidentally owns and it's still having the same issue.

any advice or a point in the right direction would be very much appreciated as I use it to get to work every day.

thanks in advance :huh:
 

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The fact that the carb clean helped a bit points to the problem being fuel related IMO. But as you say the alternative carbs didnt help so what else could be making the offending cylinder miss? Is there a crank sensor to signal which cylinder is to fire? What about a signal generator?

A wiring diagram is a must at this point I would think. I cannot believe a mechanic is unable to isolate this problem, not only yours but the op's too. Maybe the carbs or cables are so out of sync the front one is barely getting any fuel except at wider throttle openings? Air filter/s? fuel filter/supply to that cylinder?? How is the fuel system set up??

I'm no mechanic but it must be one of these. If it were mine given the symptoms I would be running some heavy duty carb cleaner through it and leaving it a couple of days to work its magic, and if that works would be asking for my money back.
 

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The fact that the carb clean helped a bit points to the problem being fuel related IMO. But as you say the alternative carbs didnt help so what else could be making the offending cylinder miss? Is there a crank sensor to signal which cylinder is to fire? What about a signal generator?

A wiring diagram is a must at this point I would think. I cannot believe a mechanic is unable to isolate this problem, not only yours but the op's too. Maybe the carbs or cables are so out of sync the front one is barely getting any fuel except at wider throttle openings? Air filter/s? fuel filter/supply to that cylinder?? How is the fuel system set up??

I'm no mechanic but it must be one of these. If it were mine given the symptoms I would be running some heavy duty carb cleaner through it and leaving it a couple of days to work its magic, and if that works would be asking for my money back.
Thanks, a few interesting thoughts there. My mechanic is struggling to believe it too, he got a second opinion about it from another mechanic too and he couldn't narrow it down either. Definitely worth trying some heavy duty carb cleaner, what kind would you suggest?
 

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Definitely worth trying some heavy duty carb cleaner, what kind would you suggest?
Berrymans B12 Chemtool.......at twice the normal recommended dose.
Run until the engine is hot, varying the engine speed a bit.
Let it sit overnight.
Repeat up to two more days.

BUT.......if the carb swap really was with known good carbs and done properly......that should rule out a carb problem and no amount of cleaner will help any.

So then you might be down to a manifold or head problem or even a warped or burned valve problem maybe.
Has anyone looked for oil in the radiator ? Has anyone considered doing a compression and leak-down test ??
If you introduce a little extra fuel into the bad intake does it pick up speed and smooth out ???

There is a mostly standard set of tests that needs to be done, ALL of them, to identify a cylinder problem.
Any real mechanic would do them.
 

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They said it must be something electrical and they could not do it with what they had. I checked both coils and primary and secondary and they were 4.7 ohms on the primary and 22,100 ohms on the secondary. I also have 12.5 volts going to both coils. at one point I did try to swap the wires to the coil and it ran worse. Exhaust valves were adjusted properly. both carbs were looked at by three different people and said were good to go also synced. as far as compression all they said is it was good in both cylinders. I may try and divert all the fuel to the front cylinder and see if its not getting enough or will even fire, I do get random backfires and some times it does come alive but quickly dies. I'm at a loss right now Thanks for your help!
I know what's wrong. I had the same situation for a whole year my only wheels not running, and no one could figure it out. A dealer had it for 6 weeks, and even a gen u wine Yamaha tech said "it SHOULD run". So much for small town living. After wasting a bunch of time and money on parts etc, I moved to Riverside CA and left it at Malcolm Smith Motorsports. The tech there simply installed a NEW BATTERY, and it started and ran. When the battery gets old, even though it cranks the motor, the voltage becomes unstable and the electronics won't like it. Best of luck to ya.
 

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I need help guys and gals, I just bought a 1999 Yamaha v star 1100 and its only running on the rear cylinder. sent it to a shop and paid $475 and still nothing, they did the carbs plugs gas all that. it is getting fuel and spark but no bang??? please help with any ideas!!
It's probably the coil. It's an easy fix. Just replace it.
 
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