Blower Carbs
05-12-2002, 12:04 AM
#1
Charter Member
Blower Carbs
What is the cause of a blower carb plate gasket to be saturated with gas. When I removed the carb, the rotors also had a film of gas on them. (Looks like they were sprayed with WD40.) There must also be a very small spitting of this raw gas being forced out from under the blower and intake past the o-ring seal as I get some 'specks' of gas sprayed on top of the valve covers. The blower and intake check perfectly flat and o-ring seal is good. Bolts are torqued to 30 ft lbs. I figure the gas is so thin that it can blow past the o-ring?? Or possibly the gas has ruined it some. Got new seal to install anyways. Also have some raw gas sitting on top of the intake valves.
Motor idles great, doesn't load up or appear to be so rich to cause this. Transom is clean too. Also notice a very strong gas odor after sitting a while. Fuel pressure set at 7 lbs at idle.
Thought of maybe a sloshing thing while trailering, but figured the floats would have to be set to high in order to leak thru vents. Floats are fine, if anything, a tad low. This has been going on for a couple of yrs, figure it's time to find the problem.
Sound like a siphoning thing? Anti siphon valve has been removed. How do you check for this?
Thanks,
Jerry
Motor idles great, doesn't load up or appear to be so rich to cause this. Transom is clean too. Also notice a very strong gas odor after sitting a while. Fuel pressure set at 7 lbs at idle.
Thought of maybe a sloshing thing while trailering, but figured the floats would have to be set to high in order to leak thru vents. Floats are fine, if anything, a tad low. This has been going on for a couple of yrs, figure it's time to find the problem.
Sound like a siphoning thing? Anti siphon valve has been removed. How do you check for this?
Thanks,
Jerry
__________________
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
05-12-2002, 08:53 AM
#2
Registered
Jerry:
It does sound like a siphoning problem, there are a few things that can cause this to happen. Bad metering block gaskets, (between the blocks, & main body) can become saturated with fuel, and cause this (replace them with new ones) The main body itself can be warped (check it with a straight edge) The power valve gasket can be torn (replace it) The idle air bleeds can be plugged up with debris (clean them out with carb clean, & compressed air) The siphon break in the metering block can be plugged up (clean out the metering block orifices)
Check to see if after shutting the engine down if you can see any fuel dripping out of the boosters, or anywhere in the carb itself, also after it sits (over night) drain both float bowls into a cup. If one is much lower than the other, this should tell you which side of the carburetor your problem is in.
Is it possible the fuel on your valve covers is coming through your flame arrestor ?
Doug
It does sound like a siphoning problem, there are a few things that can cause this to happen. Bad metering block gaskets, (between the blocks, & main body) can become saturated with fuel, and cause this (replace them with new ones) The main body itself can be warped (check it with a straight edge) The power valve gasket can be torn (replace it) The idle air bleeds can be plugged up with debris (clean them out with carb clean, & compressed air) The siphon break in the metering block can be plugged up (clean out the metering block orifices)
Check to see if after shutting the engine down if you can see any fuel dripping out of the boosters, or anywhere in the carb itself, also after it sits (over night) drain both float bowls into a cup. If one is much lower than the other, this should tell you which side of the carburetor your problem is in.
Is it possible the fuel on your valve covers is coming through your flame arrestor ?
Doug
05-12-2002, 01:03 PM
#3
Thanks for the tips Doug,
The joint between the blower and intake showed signs of blowby. I can wipe it and the VC's off and then take a couple min. run and it is back at both places. The groove of the o-ring had a gas in it when I pulled the blower off last night. So I have to assume it is raw gas being blown past the o-ring itself from the inside out.
Carb gaskets have been replace several times with all the work that has been done to the carb. The metering blocks are new as of last year. Condition was still there before the new blocks. Since carb is off and apart now, I will check for all flatness and blockage. I have never seen any drippage, unless it is happening under the throttle plates. Last year I hooked up a pump and bench tested it for any leaking. Tested fine even, with some shaking. But then it was more of checking for leaking needle and seats, not a siphoning condition. I will try the bowl draining check. Never thought of that. Also, I have been using the non-stick gaskets. These are about 3x the thickness of the standard ones.
Thanks again,
Jerry
The joint between the blower and intake showed signs of blowby. I can wipe it and the VC's off and then take a couple min. run and it is back at both places. The groove of the o-ring had a gas in it when I pulled the blower off last night. So I have to assume it is raw gas being blown past the o-ring itself from the inside out.
Carb gaskets have been replace several times with all the work that has been done to the carb. The metering blocks are new as of last year. Condition was still there before the new blocks. Since carb is off and apart now, I will check for all flatness and blockage. I have never seen any drippage, unless it is happening under the throttle plates. Last year I hooked up a pump and bench tested it for any leaking. Tested fine even, with some shaking. But then it was more of checking for leaking needle and seats, not a siphoning condition. I will try the bowl draining check. Never thought of that. Also, I have been using the non-stick gaskets. These are about 3x the thickness of the standard ones.
Thanks again,
Jerry
__________________
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
Some people are like Slinkies - Not really good for anything, but they
bring a smile to your face when pushed down the stairs.
05-12-2002, 08:37 PM
#4
Registered
Jerry:
Siphoning will only happen once the engine has been running, so you're not going to be able to check for it on the bench. Also some Non-stick gaskets will not work properly with unleaded pump fuels.
Siphoning will only happen once the engine has been running, so you're not going to be able to check for it on the bench. Also some Non-stick gaskets will not work properly with unleaded pump fuels.
