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Fuel system issue?

Old 09-23-2012, 10:37 AM
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Fuel system issue?

So, twice while riding on the highway I have experienced loss of power as though my fuel is slowly being shutdown. I had to stop. First time the bike backfired while slowing down - first time ever. Second time I just stopped and started again without problems. Also, when I pull the choke cable in the morning the rpm's are high but slowly go down to 1000 without me pulling choke back to normal. Lastly, a very strong stench of gas comes from the bike while riding or idling. Bike is 1998 with 30k miles and I picked it up a couple of months ago. I replaced the oil/oil filter and air filter. I just put a can of seafoam in the gas in hopes of cleaning the carbs. In normal riding conditions the throttle response is OK, so I don't think they are too bad. It seems like I would need to take them apart and clean after all. Any suggestions of what mucst be causing the strong smell and those two symptoms? Thanks for any info!
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Old 09-23-2012, 12:21 PM
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Hey bostonhawk, I'm sorry I forgot your first name, I think we met briefly while me and Ruv were riding a couple months back...

Anyways on to your issue, what has been modified on your bike before you bought it if you know? When you replaced the airfilter what kind of filter did you take out and put in?

The smell of gas is normal depending on how strong the smell is, as these bikes are carbeurated perfect AF ratio is hard to maintain in every situation and its better to run slightly rich then slightly lean IMO...

The idle will go down a little atleast in my experience and I believe its caused by both the bike warming up and the physical design of the choke pull **** vibrating itself back in a little as there is tension when its pulled out...

I recommend pulling the plugs and seeing what they read, and if there has been an aftermarket air filter or exhaust on the bike chances are there is a jet kit in the carbs that may need some tweaking
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Old 09-23-2012, 12:38 PM
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Originally Posted by bostonhawk View Post
So, twice while riding on the highway I have experienced loss of power as though my fuel is slowly being shutdown. I had to stop. First time the bike backfired while slowing down - first time ever. Second time I just stopped and started again without problems. Also, when I pull the choke cable in the morning the rpm's are high but slowly go down to 1000 without me pulling choke back to normal. Lastly, a very strong stench of gas comes from the bike while riding or idling. Bike is 1998 with 30k miles and I picked it up a couple of months ago. I replaced the oil/oil filter and air filter. I just put a can of seafoam in the gas in hopes of cleaning the carbs. In normal riding conditions the throttle response is OK, so I don't think they are too bad. It seems like I would need to take them apart and clean after all. Any suggestions of what mucst be causing the strong smell and those two symptoms? Thanks for any info!
Check the petcock diaphraghm...
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Old 09-23-2012, 12:43 PM
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Hey Scottiemann, my name is Dani. Yes, I am the guy you met at the Blue Hills! The bike is stock as far as I can tell with stock exhaust and had an old stock air filter. I read about the air filters and decided to put OEM back so as not to mess anything up. No idea about jet kit or now. As for the petcock diaphragm...I will check that. I am not sure what that is. I thought about checking a petcock, but realized this bike has a fuel low light :-). I am a newbie when it comes to mechanics...will look into the Fiche. Thanks tweety!
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Old 09-23-2012, 01:18 PM
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Take out the 2 bolts on the top of the gas tank, remove the seat and lift the gas tank up... at the back of the tank, the device with the 3 hoses coming off it is the petcock...

There's a few threads about removing it and rebuilding it which will have pictures...
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Old 09-23-2012, 01:19 PM
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I wish I had a low level fuel light...
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Old 09-23-2012, 01:41 PM
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Did you put a whole can of seafoam,if so,it might have hurt it more now.probably not.
It's 1oz for every gallon of gas.
So put it in only on full tank,4oz of seafoam.
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Old 09-23-2012, 04:45 PM
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Very likely that this loss of power and smell of gas has happened shortly after fillup. If you go above the tube that you see in the tank you will likely get gas in the vent line. The way the vent line is routed causes that fuel to be trapped and a resulting vacuum lock in the tank. Simply opening the filler cap allows the fuel to drain out of the tube on the left lower by the motor. This is where your smell of gas is probably coming from. So, don't fill the tank all the way up and don't wheelie or stoppie shortly after filling up.
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Old 09-23-2012, 08:24 PM
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Interesting replies...so, I have to say I am guilty of filling up to the top since our tanks are so small...I guess I can fill up only 3 galllons. Thanks for the advice about the petcock - I will look into it. I don't think one can of seafoam will damage anything - will likely clean. If you use it regularly, than follow the bottle instructions. otherwise, for the 4 gallons of gas I had, it will not damage anything.
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Old 10-04-2012, 05:18 PM
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Petcock diaphragm arrived

Hopefully, at some point this weekend late at night I will tackle doing this in the garage when no one is bothering me
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Old 10-07-2012, 05:59 PM
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OK, so stuck with two kids at home this weekend and no spouse, I got to play in the garage with my four year old boy at 8am while my 9 year old girl was sleeping. Tank removed following all the directions. I did have a hard time removing the vent and overflow hoses as the bike is old and they look to be nice and original-dry. Now, was trying to be very gently with the pertcock as to not harm the fuel filter, but could not figure out how to remove it with moderate force. So, decided to do the change of the diaphragm while the petcock was still attached by the fuel filter. Worked alright and guess what? My original black diaphragm was torn! You guys are geniuses! What a great forum! I connected everything with the new diaphragm and spring. The choke now works properly and the bike doesn't smell of gas. Could not take it for a ride because of the kids, but at least in the driveway it sounds and runs well.

Thank you guys!
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