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Discussion Starter · #1 ·
Hi guys,
New to the forum and have an engine question.
I've got an 03 V Star 1100 Classic. Been running great ever since I bought it new. Went to start it the other day and it was running rough with the choke on, and even after it warmed up, still running rough.
8,000 miles, I knew the plugs probably needed to be changed, did that today, and still the same rough running problem.

Any ideas?

Thanks
 

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Hi guys,
New to the forum and have an engine question.
I've got an 03 V Star 1100 Classic. Been running great ever since I bought it new. Went to start it the other day and it was running rough with the choke on, and even after it warmed up, still running rough.
8,000 miles, I knew the plugs probably needed to be changed, did that today, and still the same rough running problem.

Any ideas?

Thanks
Could be a number of things. Plug wires, carb adjustment, broken valve spring, worn valve guide, sticking choke, and a few others. If you can't diagnose the cause of the miss/rough running engine you may have to take it to a motorcycle tech. There are some good independents and their prices are more reasonable than the dealers. Shop around.
 

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Discussion Starter · #3 ·
Some extra info for you guys:

Drove it to work the day before the problem started, ran like a champ. When I went to ride it the next day, that's when the problem showed up.

Any ideas on a common cause for it to just suddenly start running rough?

Changed plugs, checked the fuel filter, checked the air filter so far.

Thanks again...
 

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CARB-SYNC!!!

Had a similar problem on my GT650 sportbike. Started running rough for apparently no reason. Like you, I replaced the plugs. I sprayed carb cleaner into the carbs, yet still running rough.

Built a carb sync tool (very easy) and in less than a minute my problem was solved. My front carb was drawing a bit more vacuum than the rear. A coupe of turns of a single screw and she was purring like a kitten.

Building sync tool:

Items needed:

Wooden yardstick
8' of clear tubing (used aquarium pump tubing)
zip ties
some tube fittings (1/8" to 1/4")

You basically make a U shape with the tubing (leaving about a 2" loop at the bottom to prevent kinking) and zip tie it to the yard stick. Keep the lines separate and parallel.

You should have a foot or so of tubing free at the top (needs to be long enough to reach the vacuum lines on both carbs (adjust if needed).

Fill the tubing with motor oil (I used some Royal Purple I had laying around as it would be more visible). You want to fill it with enough liquid so that when it settles it is just about halfway up the yardstick. MUST NOT HAVE AIR BUBBLES!! If you do get some, squeeze them out.

I am not familiar with the 1100 at all, so you would have to locate the proper vacuum lines and adjustment screw.

Fit the appropriate tube fitting on each end of the tool. attach one end of the tool to the forward carb vacuum line and the same for the rear.

Locate the adjustment screw. Start the bike. You will see the carb with the stronger vacuum pull the liquid up it's tube. If the vacuum is too strong you will have to shut off the engine and adjust the screw. Repeat until the liquid stays as close to even in the tubes.

Whew!! It really is easier than it sounds.

Tool should look something like this to give you and idea(not mine):
 

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Discussion Starter · #5 ·
Great idea Tweak! I didn't make the tool, I'll do it when I get home Sunday night.

I did play with it a bit since it couldn't hurt. I turned the adjusting screw one way and it got worse, went back the other way past my starting point and it started smoothing out. Played with it awhile till it wasn't backfiring etc.

Went for a 20 minute ride and it's running like a champ. I have a slight backfire when down shifting occasionally, but I'll make your tool and fine tune it later this weekend.

Again, thanks for all the help.
 

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That's pretty awesome! You made what looks to be a manometer (mah-nom-meh-ter). They were used in refineries to measure pressure levels. They're still used in refineries, just not as often. :) Good job!

CARB-SYNC!!!

Had a similar problem on my GT650 sportbike. Started running rough for apparently no reason. Like you, I replaced the plugs. I sprayed carb cleaner into the carbs, yet still running rough.

Built a carb sync tool (very easy) and in less than a minute my problem was solved. My front carb was drawing a bit more vacuum than the rear. A coupe of turns of a single screw and she was purring like a kitten.

Building sync tool:

Items needed:

Wooden yardstick
8' of clear tubing (used aquarium pump tubing)
zip ties
some tube fittings (1/8" to 1/4")

You basically make a U shape with the tubing (leaving about a 2" loop at the bottom to prevent kinking) and zip tie it to the yard stick. Keep the lines separate and parallel.

You should have a foot or so of tubing free at the top (needs to be long enough to reach the vacuum lines on both carbs (adjust if needed).

Fill the tubing with motor oil (I used some Royal Purple I had laying around as it would be more visible). You want to fill it with enough liquid so that when it settles it is just about halfway up the yardstick. MUST NOT HAVE AIR BUBBLES!! If you do get some, squeeze them out.

I am not familiar with the 1100 at all, so you would have to locate the proper vacuum lines and adjustment screw.

Fit the appropriate tube fitting on each end of the tool. attach one end of the tool to the forward carb vacuum line and the same for the rear.

Locate the adjustment screw. Start the bike. You will see the carb with the stronger vacuum pull the liquid up it's tube. If the vacuum is too strong you will have to shut off the engine and adjust the screw. Repeat until the liquid stays as close to even in the tubes.

Whew!! It really is easier than it sounds.

Tool should look something like this to give you and idea(not mine):
 
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