Carbs keep plugging causing gas to come out overflow tube on 94 vmax

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brmurph

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Austin, TX
I have a 94 vmax 500 that I had at the shop where he took the carbs apart 3 times withing an hour (can't remember if it was the same one or not and sled was on a trailer) because the needle and seat kept getting plugged with some type material which resulted in the cylinder shutting down and gas out the overflow tube. We assumed it was dirt from the fuel so we changed the fuel filter and added a clear filter. The clear filter looks clean with no derbis but the problem still seems to exist (although maybe a little better then it was, not sure) so now I am thinking whatever keeps plugging this up is most likely coming from the intake.

The airbox is clean with a new foam gasket on top (although it doesn't seem to line up with the hood very well) but I don't have any of the foam filters in the hood, this is a new to me machine and to be honest I am not sure what filters/foam needs to go in the hood. Do I just need to add foam (some say to use gutter guard) to the hood? Is this foam just to keep snow out or is it to keep dirt out as well? This is my first sled since my 72 yamaha 338 and that had no filter at all :-).

Can I mod it and just add some type of filter to the air box and not worry about the foam in the hood?

Thoughts? Thanks in advance.
 
brmurph said:
I have a 94 vmax 500 that I had at the shop where he took the carbs apart 3 times withing an hour (can't remember if it was the same one or not and sled was on a trailer) because the needle and seat kept getting plugged with some type material which resulted in the cylinder shutting down and gas out the overflow tube. We assumed it was dirt from the fuel so we changed the fuel filter and added a clear filter. The clear filter looks clean with no derbis but the problem still seems to exist (although maybe a little better then it was, not sure) so now I am thinking whatever keeps plugging this up is most likely coming from the intake.

The airbox is clean with a new foam gasket on top (although it doesn't seem to line up with the hood very well) but I don't have any of the foam filters in the hood, this is a new to me machine and to be honest I am not sure what filters/foam needs to go in the hood. Do I just need to add foam (some say to use gutter guard) to the hood? Is this foam just to keep snow out or is it to keep dirt out as well? This is my first sled since my 72 yamaha 338 and that had no filter at all :-).

Can I mod it and just add some type of filter to the air box and not worry about the foam in the hood?

Thoughts? Thanks in advance.
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Are you talking about the foam on the top of the intake of the box.. just pull the box off completely in the shop and see if it will run without the crap being pulled in.
 
I think I am talking about foam that is supposed to be in the hood, currently there is nothing there but I have read there should be some type of foam (not really sure to be honest). The foam on top of the air box is there and new. Currently it seams to run fine in the shop even with the air box installed. Unfortunately I can't let it run too long as it smokes up the whole area (have a new oil pump that I hope will fix the smoke). Last year I only put about 50 miles on it and one cylinder kept dying out and gas was poring out the overflow (this is after after the shop removed the carb 3 times to clear the needle and seat for same issue). BTW it did run for the first 25 miles trouble free after he worked on it. I am thinking something is getting into the intake and plugging the needle and seat but all I really know is gas keeps poring out the overflow.

Maybe I am over thinking this and it just needs a new needle and seat or maybe a float? I am just going by the fact that the mechanic said something kept plugging the needle and seat when he was working on it.
 
brmurph said:
I think I am talking about foam that is supposed to be in the hood, currently there is nothing there but I have read there should be some type of foam (not really sure to be honest). The foam on top of the air box is there and new. Currently it seams to run fine in the shop even with the air box installed. Unfortunately I can't let it run too long as it smokes up the whole area (have a new oil pump that I hope will fix the smoke). Last year I only put about 50 miles on it and one cylinder kept dying out and gas was poring out the overflow (this is after after the shop removed the carb 3 times to clear the needle and seat for same issue). BTW it did run for the first 25 miles trouble free after he worked on it. I am thinking something is getting into the intake and plugging the needle and seat but all I really know is gas keeps poring out the overflow.

Maybe I am over thinking this and it just needs a new needle and seat or maybe a float? I am just going by the fact that the mechanic said something kept plugging the needle and seat when he was working on it.
Click to expand...

To me it sounds like you need new needles and seats. The float should be fine unless its not floating. As far as the smoke, make sure the split in the oil cable where you adjust the line is pushed back togather under the rubber part of the cable.. its in the middle area.
 
No he didn't replace the filters (well he added the clear fuel filter but nothing on air intake), I am still not sure, are they filters or snow baffles, currently there is nothing there??. I actually live in Austin TX and was only in MN for a week, the mechanic was doing me a favor by jumping right on my problem as I wanted to ride that day, he admitted he doesn't work on Yamaha's too much. The dealer wouldn't take a look (too old) even though they admitted they were not busy because of low snow.

I think it was always the same carb but not 100% sure now (which I guess would point to a carb problem vs dirt but the mechanic said he cleaned out dirt each time from needle and seat). One thing I do remember is the air intake on the carb (air horn?) was kind of messed up (kind of gouged out is the best way I can describe it) we both thought that was odd but didn't think it would cause an issue (it did run great for the first half of the ride with no fuel leaking for 25 miles or so).

I am interested in the link you sent but I don't think it works?

Thanks.
 
It's a fine mesh internal carb filter. Part # 1J7-14994-00-00
But yea ... like Super said, 24 year old seats for sure should be changed. And you might just as well replace the needles while your in there.
 
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The gutter guard(cheaper replacement filter) serves only to keep snow from entering the intake/slush box. Removing it would have the same effect(in essence),as dropping 1/2 a jet size. As this will unrestrict the air flow.
Now on the reverse side of that, if you replace that snow filter with a finer mesh, this would have a similar effect as increasing jet size. As this would decrease the flow of air entering.
This isn't apples to apples and oranges to oranges. But you get the idea.
It a more complete burn or incomplete burn of the fuel.
 
OK so new needle and seat it is. Should I just buy the needle and seat (looks like they are still available) or should I get a carb kit? If you think a carb kit is better, anyone know where I can get one :-)?

Also since the cylinder kept going out during the last 20 miles or so (probably 25% of the time, if I pinned it the cylinder seemed to come back) do you think this most likely caused damage? I keep reading about blowing motors by running them lean, seems shutting the gas off like this would be about as lean as it could get.

Thanks guys!
 
I worked on an ATV with a similar problem about the carb overflowing. In my case it was a plugged vent line on the carb body.
 
Respectfully, the entire fuel system needs to be inspected, cleaned and adjusted for the motor to run right. You have a new fuel filter in the tank and added a fuel filter in the supply line. I would disconnect the lines from the pump to carbs and purge any crap that may be lingering in there. Clean carbs, inspect / replace needle and seats, small vent screens and check small o-rings as this may be the culprit allowing fuel to pass by causing the flooding condition.
 
northern srx said:
Respectfully, the entire fuel system needs to be inspected, cleaned and adjusted for the motor to run right. You have a new fuel filter in the tank and added a fuel filter in the supply line. I would disconnect the lines from the pump to carbs and purge any crap that may be lingering in there. Clean carbs, inspect / replace needle and seats, small vent screens and check small o-rings as this may be the culprit allowing fuel to pass by causing the flooding condition.
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Agreed. The shop I had it at replaced the large fuel lines when he added the inline filter. I have a new fuel pump I will be putting on shortly and will replace those lines at that time. I have also just ordered some carb parts listed below, this is the best list I could come up with if anyone has other suggestions on additional parts let me know. I bought some used carbs off a 1996 VMAX from ebay (supposedly updated carbs for the 1994 model so hope they will work with maybe better gas mileage LOL). My plan is to have two sets of carbs ready and will swap them out if one set doesn't work..

1AE-14190-15-00 - NEEDLE VALVE ASSY 4 $65.16
1J7-14994-00-00 - NET,FILTER 4 $36.64
89A-2199J-00-00 - SHIELD,NOISE (foam filter in hood) $36.69
8AY-14147-00-00 - O-RING 2 $8.34
8F2-14147-00-00 - O-RING 4 $14.68

Thanks and any other comments/suggestions greatly appreciated.
 
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