98 500 VMAX XTC high fuel usage

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uncletom43

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Joined
Jan 9, 2005
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20
Age
63
Location
Owosso,Mi
i have a problom with high fuel usage last year half way through the season my 500 started using fuel and i cant figure it out you cant go faster than 60 miles an hour with over half the throttle left so i took the carbs off and cleaned them and found nothing so i put them back on and rode it and nothings different so someone told me that the clutchs could be binding so i took them off and replaced all the bushings and checked the jack shaft and everything rolls free so we went out this weekend and rode and i thought i had it licked it ran fine for the first 2 hours and then the samething again 38 miles and 9.5 gal. later now o dont know where to look can anybody help thanks T Case
 
what size mains do you have in it? i had a 94 vmax 500 had 151.3 mains in it stock before i put pipes on it and re-jetted it
i put pipes on it and jetted it way too rich and had the same fuel mileage you were getting
 
choke plunger springs

one of the things I would check first is to see if the choke is returning to the off posistion, and this is at the plungers on the carbs, some had weak springs and would not return the plungers to seat and this will cause a rich condition and drink the fuel. With the choke in the off pos. can you push the plunger any amount more closed?? use a small penlight screwdriver and see.
 
the choke cable wasent letting the choke return so i adjusted it so it had slack and i pushed the plungers and they felt like they were all the way in and it didnt change any thing and would you think the float is adjusted to high
 
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do the float level next

yep, the next step is the float level. You pushed on the plungers with a small screwdriver right? not the metal bracket that pushes on them but the small head of the plungers, right? What do the sparkplugs look like after its running, wet? black? When was the last time the compression was checked? Just running thru the things that come in mind.
 
well i checked the compression last week and the mag side was 125 and the clutch side was 120 so rulled that out ,yep i pushed the plungers not the bracket! the spark plug on the mag side was black and wet and the clutch side was not as black but you could see some of the white porclin middle on all black bit wet and i dont foul any plugs could the float just start overflowing for no reason?
 
needle and seat

if the needle and seat are going bad, yes, I think 24mm comes to mind to the correct float setting, sounds like thats all thats left to do in the carbs. One last thing, hows the spark look ? nice and bright blue?
 
well the spark is the only thing i havent checked but i will!! but if it not would it be in the stator or is the coil breaking down? thank for all the help it gives me somewhere to look
 
Redo your carbs, totally dissassemble them and blow through all the passages, I like to blow some carbcleaner through them as well. Check both floats, make them within the factory spec and the same on both sides.

I had great luck running 150 mains, and also lowered the needles 1 position from stock, which was 1 washer thickness. I also run a tempaflow with great success, even in Ontario 2 years ago -40*! So, I went from 11mpg stock to 14mpg when hauling ***, and the clutch set up didn't hurt either.

Keep at it, you'll get it!
 
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