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carb overflow mystery

  • Thread starter Thread starter wompin
  • Start date Start date
barnbiketom said:
TRUST ME
make sure the individual CARB VENT lines are not blocked or hooked wrong ( to each other)

if in doubt just reach in with needle nose pliers and pull them oof the carbs then retest
Click to expand...


I just had the carb vents on #2 and #4 open with no tube on them. I figured vent through a hose or vent through a hose nipple is the same thing. Its still open to the atmosphere.

Obviously my #3 vent is providing vacuum to my petcock
 
I have seen that same suggestion list. I don't have a lot of experience jetting for mods like yours, so I can only repeat what I have heard from other sources.

What I have heard there (and seen many times here) is to add 2-4 sizes for a pipe (usually a 4-into1), depending on how free-flowing it is, and to add 3-5 sizes for pods. That would give you a range of 5-9 sizes, and you have only gone 3.

Also not sure how different it is jetting the VM carbs vs the BS carbs. We have two bikes that are non-stock. My #1 son has a 650L with pods and a pipe. I think the mains are 4 sizes larger than stock. #2 son has an 850G with a K&N insert in the stock airbox and a pipe. The mains are 2 sizes larger than stock. The needles have not been changed on either bike, nor have the pilot jets. The mixture screws have been adjusted for best mixture.

Hopefully someone with more VM jetting experience will speak up with some better suggestions. :D

.
 
Gas cap vent is functioning well and tumblers now freshly lubed. Thanks for the tip.

Ive got a hypothesis. I think since my petcock filter screen was missing and I had just put a faucet screen in its place, that some small particle must have made its way through the petcock, in between one of the float needles and its seat. During the test, it must have been cleaned out. When I cleaned out my gas tank there were a few rust flakes that may have been the culprit.

So, Ive ordered a nice in-line filter, and then I would bet that my overflow issue goes away.

Filter should be here either friday or monday. Ill let yall know how the next run goes.
 
wompin said:
I just had the carb vents on #2 and #4 open with no tube on them. I figured vent through a hose or vent through a hose nipple is the same thing. Its still open to the atmosphere.

Obviously my #3 vent is providing vacuum to my petcock[/QUOTE

again, make sure all the carb vents are open,

The HOSES MIGHT BE PLUGGED.

the #3 hose going to the petcock is NOT the bowl vent, it is a vacuum supply line.

the bowl vent for #3 is a different port. make sure they are all vented separately.
Click to expand...
 
[/QUOTE]
again, make sure all the carb vents are open,

The HOSES MIGHT BE PLUGGED.

the #3 hose going to the petcock is NOT the bowl vent, it is a vacuum supply line.

the bowl vent for #3 is a different port. make sure they are all vented separately.[/QUOTE]

When you say carb vents/hoses, do you mean the overflow vents/hoses? Sorry for the confusion. Ill check all my hoses anyway. Thanks
 
By VENT he means the ones on carb 2 and 4...the brass nipples up on the throat of the carbs. The nipple on carb 3 is the vac supply for the petcock. If the vents are plugged the air cant equalize bewteen the carbs and yes this will also cause an overflow of gas from the throats of the carbs.
 
Okay, just to clear up a misconception here, the pilot fuel screw should be at 1 turn as it only applies at idle

It does nothing above that.

If you went up 4 jet sizes, it's still lean. You should be at 122.5 or above

On the overflow issue, make sure the vents are clear and check the float bowl interior by taking off the float bowl, putting some gas in it and see is it leaks out the overflow
 
Well..actually Big T, it is also the primary circuit for up to about 1/8 throttle and its also functioning durrin g the transitional spots between accelerationg past the 1/8 throttle and then back to the idle position. And of all the things ive read here and from other very knowledgable men that were the dealership techs back then, the factory setting for the pilot screw was 3/4 out..just a teeny tiny bit lean but thats where it was to meet the EPA requirements for sales in the US. I have all my 1000s at 3/4 and all run great. They will run great at 1 out too, but then its actually high on the rich side.
 
Wow, Big T, do I really need to go up 11 sizes on my main jet? Stock jet for my vm26ss carbs is 95. Keep in mind I am going to baffle my pipes so exhaust flow will be reduced. For Now, I have ordered 5 sizes up.

I took Steve's advice and went with 3 sizes up for pods and another two sizes up for custom baffled exhaust. Prior to that I was going off a suggestion of 3 sizes for my setup. I dont want this beast to drink fuel like its going out of style, so Im leary of going crazy with main jet sizing.

Ill get a photo of my carbs up.

Ive set my fuel screws at approx 7/8, hows that? I suppose air screws will then be at approx 1 3/4. I do have my pilot jet up one size from stock too. throttle stop screw is set at 2 turns in from just touching. Anyone got issue with these settings?
 
wompin said:
Wow, Big T, do I really need to go up 11 sizes on my main jet? Stock jet for my vm26ss carbs is 95. Keep in mind I am going to baffle my pipes so exhaust flow will be reduced. For Now, I have ordered 5 sizes up.

I took Steve's advice and went with 3 sizes up for pods and another two sizes up for custom baffled exhaust. Prior to that I was going off a suggestion of 3 sizes for my setup. I dont want this beast to drink fuel like its going out of style, so Im leary of going crazy with main jet sizing.

Ill get a photo of my carbs up.

Ive set my fuel screws at approx 7/8, hows that? I suppose air screws will then be at approx 1 3/4. I do have my pilot jet up one size from stock too. throttle stop screw is set at 2 turns in from just touching. Anyone got issue with these settings?
Click to expand...

That's the baseline you should go for -122.5, info taken from what others have had success with for pods and a 4-1. Most people end up in the 120-127 range

You'll find your fuel mileage to be aorund 30, rather than mid 40s like stock
 
Thats good info to know. The main reason I went for pods was to eliminate the hassle associated with pulling the airbox/carbs. Its a matter of convenience for me. If I end up needing to jet at 120+ and wrecking fuel economy, I may just put that airbox back in...

Ill not give up just yet tho. One thing I do know is that opinions and information on pods and jetting varies about like opinions on politics or religion. Ultimately, I like to verify advice first hand. Wish me luck and thanks for the heads up.
 
wompin said:
The main reason I went for pods was to eliminate the hassle associated with pulling the airbox/carbs.
Click to expand...
I am always intrigued by reading this statement.

Just how many times were you anticipating removing the stock airbox? :-k

If you clean your carbs properly and winterize the bike properly, you won't have to remove the airbox for many, MANY years.

Yet, you are willing to go through all the hassle of removing the carbs MULTIPLE times to get the jetting right for the pods and pipe. :-\\\

.
 
122s will have ya way to rich...you can go there if you want, but 102.5 to 107.5 will be more to the bikes liking AND youll have less cussing and swearing doing the fine tuning of the system. Remember, once it up and running, you tune from the "bottom up" on VMs. Meaning you screw IN or OUT the pilot jet screws to get the best idle and lower range RPM ( think about 1/8 open throttle here ) response. Then you do plug chops or use something like a Colortune and adjust the mixture screw ( on the side of the throats).
 
Steve said:
I am always intrigued by reading this statement.

Just how many times were you anticipating removing the stock airbox? :-k

If you clean your carbs properly and winterize the bike properly, you won't have to remove the airbox for many, MANY years.

Yet, you are willing to go through all the hassle of removing the carbs MULTIPLE times to get the jetting right for the pods and pipe. :-\\\

.
Click to expand...

I guess we all have our own brand of crazy, steve. Anyway Im mostly enjoying the learning process of this build. Hell, 5 months ago I had wouldnt have known a GS from my ASS. :)
 
Last time I had my air box off before this rebuild was probably 12 years ago.
 
UPDATE:

I installed my dipped and rebuilt petcock, inline fuel filter, and carbs. I was unable to get my bike to fire up after much tweaking of pilot fuel/air screws and throttle stop screws, and choke. I even tried heating the garage (only got it up to 45 deg. or so). Note that I did install glass packed, perforated baffles in the pipes.

So, I was a bit at a loss. I decided to redip my carbs just for good measure. Before I put them back on I may try to wedge in that air box just to eliminate possible suspects. If the airbox supporters are right, this should be a cure all (or most) for the gremlins Ive been dealing with. If this works, Ill ditch the pods and rejet closer to stock. If it doesnt work, I think most likely my head will just explode right there on the spot.
 
keep us posted!!

Although pods or airbox makes no difference in the initial post.. gas flowing out of the wrong place!!

gotta be carb problem not pod/airbox UNLESS cheepo pods are covering up the air bleed holes in the back of the carb then that's another can 'o worms haha
 
Honestly, unless your tank is extremely rusted inside, you don't need the inline filter and maybe restricting so much fuel as they just don't work the same with our petcocks/carbs like they do on cars. Try getting rid of that too when you put the airbox on for testing purposes.
 
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