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Discussion Starter · #1 ·
Hello,
looking for a bit of advice.

I bought a 2003 V-star 650 from an older gentleman, i rode it around the block and it did just fine (should have gotten on the highway)... Long story short, after warming up, the front cylinder only fires occasionally. by occasionally i mean hardly at all, i can drastically feel the difference from when one is firing and both are firing. i replaced the spark plugs and coil pack with one i found on amazon (prolly not the best in retrospect). The coil pack ran me about 30 bucks, i spoke to a couple mechanics and got different opinions from all four. one told me the amazon coil packs are trash and thats my problem, said it doesn't put out enough spark under load... second guy said if that bike sat for awhile then i need to rebuild my carbs, because they are notorious for gumming up in the bottom float...? third guy said my "tpv sensor" needed to be replaced... tpv sensor might not be the correct terminology, its been a few weeks since i spoke to them now. any insight would be appreciated. Thanks!
 

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TPS is probably what he meant, throttle position sensor.... and I found two out of three to be guesses at best and poor ones at that. The carbs gumming up is possibly an accurate diagnosis....but a rebuild may not be needed. Run some good quality carb cleaner through and leave it for as long as possible....day or two.

If this doesn't clear the problem then check the fuel supply to the offending cylinder check for kinked fuel hose, float height....drain that carb to see how much fuel comes out and what condition it is in and that all settings are the same for both cylinders. If it has vacuum carbs check the diaphragm for pin holes by holding it up to the light.

Is the coil pack you replaced a double ended one....runs both cylinders from one coil....if so swap the ends over to see if the problem moves to the other cylinder....probably best to use the original one for this.

Good luck
 

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Run some good quality carb cleaner through and leave it for as long as possible....day or two.
Good suggestion. That does NOT mean SeaFoam. It is NOT a "good" fuel system cleaner.
Berrymans B12 Chemtool or original Gumout are the best.

Also.....are the intake and exhaust stock ?
Have you checked the air filters for blockage ?
How about loose or cracked vacuum lines ??
 

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Discussion Starter · #4 ·
TPS is probably what he meant, throttle position sensor.... and I found two out of three to be guesses at best and poor ones at that. The carbs gumming up is possibly an accurate diagnosis....but a rebuild may not be needed. Run some good quality carb cleaner through and leave it for as long as possible....day or two.

If this doesn't clear the problem then check the fuel supply to the offending cylinder check for kinked fuel hose, float height....drain that carb to see how much fuel comes out and what condition it is in and that all settings are the same for both cylinders. If it has vacuum carbs check the diaphragm for pin holes by holding it up to the light.

Is the coil pack you replaced a double ended one....runs both cylinders from one coil....if so swap the ends over to see if the problem moves to the other cylinder....probably best to use the original one for this.

Good luck
Hi Steve,
thanks for the reply, i will get some good carb cleaner and soak them for a couple days to see if this continues. Also as far as the coil packs, it has two separate coil packs, one for each cylinder. i will swap out the coil pack from front to back and see if the problem persists before dousing the carbs with cleaner. also i will check all the hoses for kinks and blockage. thank you for the input. i will post again in a few days with updates.
 

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Discussion Starter · #5 ·
Good suggestion. That does NOT mean SeaFoam. It is NOT a "good" fuel system cleaner.
Berrymans B12 Chemtool or original Gumout are the best.

Also.....are the intake and exhaust stock ?
Have you checked the air filters for blockage ?
How about loose or cracked vacuum lines ??
Thank you Easy Rider, i will get the Gumout later today and start tearing it apart again. Intake is stock, but the exhaust is "cobra" pipes is im not mistaken. ill take a look this evening when i get home from work today. Yes, im slacking at work right now trying to figure out my motorcycle issues hahahaha. im honestly not sure witch lines are the vacuum lines, but i will figure it out later today and check them. when i replaced the coil pack i removed the air filter and gave it a look, didnt look out of sorts, but ill check it again this evening. thank you for the input, i will start checking these things and repost again in a few days. thank you.
 

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Thank you Easy Rider, i will get the Gumout later today and start tearing it apart again.
With an engine that will actually RUN, it is not necessary nor desirable in most situations to
remove the carbs or take them apart to do an internal cleaning.

Just put a bit more than the recommended dose in the fuel tank and run it a few times over a couple of days.

While a lot of people have never heard of Berrymans B12 Chemtool, it really is the best and can be found in most auto parts stores and even WalMart sometimes.
 
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