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Gasoline Flooding Airbox

  • Thread starter Thread starter mk
  • Start date Start date
M

mk

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After changing the air filter on my '79 GS750L (to K&N from OEM), I took it for a test ride. Everything seemed smooth until I accidentally released the clutch on 1st gear at about 35 MPH while coasting to a stop. The bike did a little nosedive and there were immediate throttle problems (lagging and surging). Two blocks later, headed back to the house, the engine died and fuel was running out of the airbox covers. After draining the new air filter for 10 minutes ( :roll: ), the bike restarted and ran (again with surging/lagging throttle response) for a mile and flooded again. I repeated the process and made it home.

From other posts, it sounds like it might be a vacuum problem. If so, I'd appreciate help with solving it. The bike has the fuel petcock with only two settings, ON and RES, and the VM carbs common to '79 models. Also, does the air filter need any revival after the gasoline soakings (it's K&N "charger" type with oil)?

Michael :cry:
 
Also, does the air filter need any revival after the gasoline soakings (it's K&N "charger" type with oil)?
Click to expand...

Can't help you with the flooding issue (beyond saying it sounds like something is not shutting off properly... 8O ), but you can certainly re-use the filter. It should be cleaned in fresh gas, then dried off and re-oiled. Presto! Good to go again.

Mark
 
I don't think K&N recommends cleaning their filter with gas. I would be a filter cleaning kit that consists of filter cleaner and filter oil and it doesn't necessarily have to be K&N either. If the filter did get soaked with gas, it will need to be re-oiled. I would use hot soapy water and then rinse it thoroughly before I would use gas and make sure you let the filter dry properly.

AS far as the flooding goes, I'm not sure what you could have done to cause that. It sounds like it could be a stuck float so you may want to gently tap on the float bowls with a rubber mallet or screw driver handle to see if that helps at all.
 
Thanks for the posts - you're right about the cleanup Bandit, according the K&N directions for cleaning after long use. I'll try tapping on the float bowls, but my real concern was what to do about the vacuum line in case there's gas in it and that's what's causing the flooding.

Michael
 
MK: I've done the tapping thing and it worked well. I drained my carbs before doing it though. If you have the petcock set to on with the bike off you should be able to drain the carbs without a constant flow of gas. Then, with the carbs drains open pull the suction line off of whichever carb it is on and suck on it. If the gas flows out of the carbs and not the vent you're okay in that area.

Good luck, Steve
 
Re: Gasoline Flooding Airbox

Its possible you have a faulty petcock witha leaking diaphram, BUT even if you did, gas would not flood the airbox if there was no fuel flowing through the carb. If your float bowl needles were working as they should, no fuel could flow as it now does. Your float heights are either set wrong, or your float needles are worn out and leaking like rusted out bait bucket.
Remove the carbs, turn them upside down, remove the float bowls, measure the float height (should be 24mm) and while still upside down and the weight of the float pressing the float needle down, try blowing air (with your mouth) through the fuel fitting on each carb. If you can blow any air through, the the needles are leaking.

Earl


MK said:
After changing the air filter on my '79 GS750L (to K&N from OEM), I took it for a test ride. Everything seemed smooth until I accidentally released the clutch on 1st gear at about 35 MPH while coasting to a stop. The bike did a little nosedive and there were immediate throttle problems (lagging and surging). Two blocks later, headed back to the house, the engine died and fuel was running out of the airbox covers. After draining the new air filter for 10 minutes ( :roll: ), the bike restarted and ran (again with surging/lagging throttle response) for a mile and flooded again. I repeated the process and made it home.

From other posts, it sounds like it might be a vacuum problem. If so, I'd appreciate help with solving it. The bike has the fuel petcock with only two settings, ON and RES, and the VM carbs common to '79 models. Also, does the air filter need any revival after the gasoline soakings (it's K&N "charger" type with oil)?

Michael :cry:
Click to expand...
 
Problem solved - thanks for the tips!

Steve, you were right. I didn't know how to drain the carbs and found the drain bolt location in Clymers manual. I also noticed that the bolt is good for draining the sediment trap at the bottom of the carbs, and some sediment came out in the process. An interesting thing was that there wasn't much gas in number 4, but the others were about equal. Couldn't get the vacuum tube loose (without cutting the line) so I decided to give it a try after "drain and tap". Great results - the engine has never run smoother for me and no gas in the airbox. I did notice both bolts missing on the airbox in this process and replaced them, but that was after the leak test so my best guess is that the problem was a stuck float.

Periodic draining of the VM carbs to clear the sediment traps seems like a good idea to me.

Thanks again for the help,
Michael
 
That's good to hear. The same problem started my crash course in motorcycle maintenance two years ago. It's incredible to think of how much I've learned here listening to people with dead bikes. :? You still have to figure out where the sediment is coming from and put a filter on your bike but that should be easy. You may be in for a ton of junk in the gas the first time you set the tap to reserve.

Steve
 
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