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starting up after carb rebuild - gas not staying in aux fuel bottle

  • Thread starter Thread starter d_hoffman
  • Start date Start date
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d_hoffman

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I have a '84 GS1100GK with Mac 4-to-1 pipes and stock air box. I installed a Dynojet kit stage 1
First - Many thanks to all for helping me get through my first carb rebuild. Without this site I never would have been able to do it.
Question - I have a quart bottle "gas tank" hanging from the handlebars and the vacuum line to carb #2 plugged. I noticed that the gas in the bottle will slowly "leak" away as it sets there without the bike running. Is that normal? Or should I pull the carbs off and watch to see what's going on? I don't see any gas on the floor, under the bike, and I haven't noticed the oil level rising. I'm wondering where this gas is going. I expected the float bowl needles to shut off the gas once the bowls are full and that any extra gas would just stay in the bottle. This is like leaving the petcock on prime. I've read a couple of threads suggesting that gas will leak out of the air box vent tube (??) if left on prime. Is that correct? Sure seems weird.
 
Sounds like your float needles are not holding quite as tight as they should. Yes, it is very much like leaving the bike on prime. Many suggest that the needle and seat should hold back the fuel, even on prime, but I suggest that it is a better practice, not to trust the seats for that. If you are seeing no fuel on the floor and none in the air box, then the only place that it has to go would be into the crankcase. Smell the oil fill hole and see what you come up with.
 
So you're telling me to get a petcock with a "full" off position and not to trust the needles and seats. I already bought a new OEM petcock and so I'm not really wanting to do that (at least not until I have to)
I took the carb rack off, set it up on the bench, hooked up the aux bottle, filled it and found that #1 carb has a slow drip. The float height is set at 22mm. I suppose I could set it at 21mm and see if that stops it. Is there a place you can get needles with rubber tips? I think those would seal better.
 
OEM petcock is fine, it shuts off when the engine is turned off. Did you replace the O ring on the needle seat ??
 
Yes I did replace those o-rings. Got the kit from cycleorings. I pulled the needle seat and cleaned it again with carb cleaner and compressed air. Also the needle itself. Everything looks ok but gas can leak though the smallest places. I'm still a little surprised that there aren't rubber tips on those needles. Anyway I ordered some seats and needles from carbkitscapital. Hopefully that will fix it. The whole reason I dove into the carbs was gas in the engine oil. I must have emptied out a pint of extra oil just to get the level down to the full mark in the sight glass. The tank has been cleaned and sealed (lots of rust), new petcock, sealed the air cleaner, value shim adjustment, new o-rings everywhere, oil change with filter and carb rebuild. Maybe I'm just paranoid but it bugs me that gas is still dripping into the crankcase. I know you're correct and in theory the petcock should only open when the engine is running and supplying vacuum. But I'd like to know the needles and seats are doing their job too.
 
You're right in replacing the float needle and seats.
If you had them out did you mix them up? Once used they should always be a matching set.
 
one other point

one other point

the aux tank shouldnt sit any higher than your usual tank does - as that would add pressure to the valve needles, increasing the chance of a leak
 
chef1366 - I worked on one carb at a time so I didn't mix up the parts. I didn't put the seats in carb dip because they have a screen on them held on by a plastic ring which rotates. I wasn't sure how to get that plastic part off and didn't want to break it. Do you just pry it off and hope for the best? I'm guessing that the new seats won't have those screens and I'll have to move them.

psyguy - I hadn't thought of that.... however the bottle I'm using is small. Holds about a pint of gas. I'm not sure that amount would cause more pressure than the normal tank. But then again I'm no physics major. I'll try lowering it.
 
I pry them of with a small screwdriver. Make sure to do it somewhere where they don't go flying!
 
d_hoffman said:
psyguy - I hadn't thought of that.... however the bottle I'm using is small. Holds about a pint of gas. I'm not sure that amount would cause more pressure than the normal tank. But then again I'm no physics major. I'll try lowering it.
Click to expand...

it is the height only that makes the difference in the pressure, not the quantity of gas (as the pressure surface area stays the same)

i know, it sounds counter-intuitive... but thats how it is (in this case)
 
new float valve kits fixed it

new float valve kits fixed it

I found float valve kits on carbkitcapital.com for $10 each. Comes with float valve, o-ring installed and float needle. I replaced all four of them and now the gas is staying in the aux bottle tank. I also had to reset the float heights to 23mm. The springs in the new needles are a bit better than the 24 year old ones they replaced. I also made sure the bottle was about the same height as where the gas tank sets. Now I'm ready to open the Colortune and Carbtune kits. I wish I knew someone in eastern Iowa who could give me a few pointers on using them. They could gladly use them on their bike in exchange.
 
d_hoffman said:
I found float valve kits on carbkitcapital.com for $10 each. Comes with float valve, o-ring installed and float needle. I replaced all four of them and now the gas is staying in the aux bottle tank. I also had to reset the float heights to 23mm. The springs in the new needles are a bit better than the 24 year old ones they replaced. I also made sure the bottle was about the same height as where the gas tank sets. Now I'm ready to open the Colortune and Carbtune kits. I wish I knew someone in eastern Iowa who could give me a few pointers on using them. They could gladly use them on their bike in exchange.
Click to expand...


I have two Colortune kits. Haven't had a chance to use them yet though. They're really easy to use, and there's pretty good instructions in the package. Just follow along with what they're saying, and you should be golden.
 
the same with carbtune - just follow the enclosed instructions
you biggest prob is going to be fiddling with the vacuum bolts at the intake manifold and the adjustment screws on the carbs, as they are not that easily accessible
 
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