1999 vmax 500 - seems like its missing at lower rpm and getting 4 mpg

xsivhp

xsivhp

Active member
Joined
Dec 11, 2004
Messages
1,537
Age
55
Location
Eau Claire, WI
This sled has 4400 miles on it and it's super clean. I am at a loss as to why it runs so crappy. Any thoughts? It will still pull 8100 rpms and makes all the right noises at higher rpm - just not good at all down low. Plugs are black. Starts up and idles fine. Kinda sounds funny at idle almost like it is missing but when I pull plugs wires it keeps running like its firing on both cylinders. I really like ths sled - would like to get it figured out.


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totallyamaha.net

6 mpg problem solved.

I am one of several owners on this site of 90's yamaha 600 twin motors that are/were getting poor mileage. It was frustrating to me because when new the sled got 12 mpg. Tried a lot of fixes over the years but none had any affect on mpg. Finally heard of something new(to me) and it sounded like...
totallyamaha.net totallyamaha.net
 
MrSled said:
New plugs? Cleaned carbs? Drink a lot of oil? How’s the clutching? So stock?
Click to expand...

Hi Mr Sled! Happy to see you've got the site up still! I just picked this up last week. New plugs, new belt and I adjusted it so that it sits right in the secondary. PO cleaned carbs, i could do it again. Not sure on oil consumption as I only rode 34 miles. This sled is super duper clean I am surprised that there is any issue with how it runs, but here I am - looking for some help! :)
 
74Nitro said:
totallyamaha.net

6 mpg problem solved.

I am one of several owners on this site of 90's yamaha 600 twin motors that are/were getting poor mileage. It was frustrating to me because when new the sled got 12 mpg. Tried a lot of fixes over the years but none had any affect on mpg. Finally heard of something new(to me) and it sounded like...
totallyamaha.net totallyamaha.net
Click to expand...

Thanks 74Nitro - I found that thread - that sounds like it could be my issue. Any idea where to find the NOZZLE, MAIN - 8AY-14141-56-00?
 
xsivhp said:
Hi Mr Sled! Happy to see you've got the site up still! I just picked this up last week. New plugs, new belt and I adjusted it so that it sits right in the secondary. PO cleaned carbs, i could do it again. Not sure on oil consumption as I only rode 34 miles. This sled is super duper clean I am surprised that there is any issue with how it runs, but here I am - looking for some help! :)
Click to expand...

As long as we have the interest I try to keep it running. I did see those nozzles on ebay but it was used.
 
MrSled said:
As long as we have the interest I try to keep it running. I did see those nozzles on ebay but it was used.
Click to expand...

I saw them on ebay t0o - some about 5 miles from me, but they could be just as bad as what I have got. unfortunately Yammi dealers near me are closed today. I'm going to call Hauck tomorrow - maybe they have some.

I met you a long time ago at Joanies in Iron Belt - you had the new 4S Phazers you were trying out. Loooonnng time ago! lol
 
xsivhp said:
I saw them on ebay t0o - some about 5 miles from me, but they could be just as bad as what I have got. unfortunately Yammi dealers near me are closed today. I'm going to call Hauck tomorrow - maybe they have some.

I met you a long time ago at Joanies in Iron Belt - you had the new 4S Phazers you were trying out. Loooonnng time ago! lol
Click to expand...
Holy Crap that's was a really long time ago..WOW
 
It's a shame Yamaha doesn't offer these parts anymore. That sled you have looks to be in mint condition!
I have wondered if I could find someone to repair the old ones.
Maybe machine the top hole out even more and then a proper stainless steel insert pressed in back to stock hole size....?
 
74Nitro said:
It's a shame Yamaha doesn't offer these parts anymore. That sled you have looks to be in mint condition!
I have wondered if I could find someone to repair the old ones.
Maybe machine the top hole out even more and then a proper stainless steel insert pressed in back to stock hole size....?
Click to expand...

Hopefully it doesn't come to that. 🤞
 
I picked some up a couple years ago by having the dealer do a search. Not sure any are left but it is worth a shot. It did wonders for how the sled ran by the way. About 11,000 miles and still in the original family.
 
4300 miles on this one. Already got the foam for the airbox and got it installed. :) Now I just need to get it running better, and I'll have something!


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she is over rev ing as the twins should be around 7800 peak.

she should get around 8-10 mpg when driven at constant cruizing speed. mine always drank more oil than my brothers viper but i figured oil was cheaper than motors. i just used cheaper synthetic injection oil.

have you gone through all the skid and chassis bearings? odd are a few are dry and dragging down the fuel mileage. missing track clips hurt the mileage too. i ran a clipped every 3rd ripsaw on mine and if there was low snow, it was a bear on gas.
 
Maim said:
she is over rev ing as the twins should be around 7800 peak.

she should get around 8-10 mpg when driven at constant cruizing speed. mine always drank more oil than my brothers viper but i figured oil was cheaper than motors. i just used cheaper synthetic injection oil.

have you gone through all the skid and chassis bearings? odd are a few are dry and dragging down the fuel mileage. missing track clips hurt the mileage too. i ran a clipped every 3rd ripsaw on mine and if there was low snow, it was a bear on gas.
Click to expand...

I greased the skid and checked the wheels - everything is good to go. Very well maintained sled for its age. But it does not sound right low - mid rpms and she burns a lot of gas.

 
did you check the reeds? sounds blubbery to me. fuel pump might have a hole in diaphram too. i did do the reed cage stopper notch to mine and it made a difference in how it started and ran.
 
Maim said:
did you check the reeds? sounds blubbery to me. fuel pump might have a hole in diaphram too. i did do the reed cage stopper notch to mine and it made a difference in how it started and ran.
Click to expand...

Blubberry is a great way to describe it. Seems to start fine. I'm gonna dig in more this week.
 
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