BIG problem with Vstar 1100 missing & Popping

[stepop]

Hello Yall, This is my first post here. I have a serious problem with a bike that I have just owned for a few weeks. My 2003 vstar 1100 custom has just 3000 miles on it. It has the Cobra exhaust and has been rejetted. It ran perfectly when I got it. According to the previous owner it has run great for the entire 3000 miles with NO problems at all ever. Plenty of power in all gears.

Then all of a sudden and for no apparent reason it now only runs good at an idle or very low throttle. When I crank the wick even just a little bit the engine pops and sputters and looses power. Acts like it is either running out of gas or spark. There is a VERY definate spot in the throttle when it starts doing this. It doesn't quit running, just starts running real bad. When I let back off the throttle it smoothes out. It seems to idle down the street in any gear but cannot accelerate without this cutting out and missing. Does anyone have an idea about this? Oh, and it only does this when riding. It tacks up smoothly in neutral.

[Wizzard]

Sounds as if it may have been rejetted incorrectly . Or for a different altitude .
Regards, Wizzard

[stepop]

Wizzard,
I thought of that, but it ran really good here for 2 weeks before it started acting up. It sat in the garage for about 3 days after a short ride and the next time I took it out this started. Seems like if it were jetted improperly it would have started doing this right away. (It was rejetted at the dealership brand new before delivery and ran great for 3000 miles).

Isn't there a first and second section to the carbs? Idle and then everything after that?

[dr_bar]

Out of curiosity, what grade of fuel are you using? When I changed up to premium, that's exactly what happened to my bike. switched back to good ol' regular and the bike ran great.

Another thing that happened is a friend was washing his car and hit my bike with a hard spay of water right on the gas cap. I guess with the old gasket, some water got in there because again, it sounded a whole lot like that as well. A bit of gasline antifreeze and that was taken care of as well.

[stepop]

Thanks for that gas info. I DID change to premium recently enough for this to be the problem, but I cannot imagine how that could cause this???
Doesn't matter...I will be dumping this tank and replacing it with "good ole regular" to see what happens. I think I will taje the carbs off and clean everything too. Can I hurt anything by running carb cleaner through them while the bike is running like you do on a car? Also, could I have hurt anything by leaving the petcock on overnight?? Thanks
Stepop

[eugeart]

I've been told by mechanics not to put that stuff in your car and definitely not in a motorcycle. Too many sensitive gaskets and o-rings etc... Besides, there arn't many better solvents than gas itself in my opinion. Use some clean new gas to rinse out your tank and fill it up w/regular.

Petcocksleft open on older model bikes might flood the carbs and empty the tank? See if you have a fuel pump. If so it shouldn't matter.

[stepop]

Anybody know why regular would be better or why premium might cause a problem?

[stepop]

BINGO! I emptied the tank, drained the float chambers and filled it with regular gas and it runs like a bomb again. I DID put a new set of spark plugs in it too, but didn't really see anything wrong with the old ones. I think it was the gas.

2 or 3 people told me "NO it can't be premium gas that is doing it" But the one kid down the street who really knows all kinds of bikes told me exactly why it WOULD cause it to miss and lose power. I didn't totally understand it but it has something to do with the low compression ratio of the bike and the expansion of the fuel air mixture when it fires. Hey, I gotta go for a ride. THANKS!!!!
Stepop

[akabullseye]

Actually the explanation is pretty simple,

Regular is a lower octane fuel which burns much faster than a higher octane fuel like Premium. The reason for your issue was that when you run Premium in a lower compression engine the fuel burns slow and incompletely. The carbon build up can actually cause pre-ignition on the flowing strokes at higher revs giving you your symptoms.

Inversely, running regular in a higher compression engine can cause the pistons to actually be twisted from side to side during the burn rapid giving that distinct pinging noise.

[locaste]

IMHO I don't see the "grade" (aka octane rating) of the gas being the issue. If it was a knocking or pinging issue, sure, but not this symptom.