New to site, need help with some Yamaha info. Been wrenching on Doos and Poos for 20+years. Picked up my first Yamaha, a 2000 500 vmax deluxe with 800 original miles beginner sled for my kids. It had sat for years in a heated shed without running. When I took possession it would not start due to varnished carbs. I done a complete go through, new belt, carbides, hyfaxes, transmission oil, and of course a thorough cleaning of the carbs. When put back together it just wouldn't run right. When I took possession on my initial checkout it showed that it was running rich by inspecting plugs and pistons. I lowered main jets from 151.3 to 150. It runs awesome from 7K to 8K rpm. But from idle to about 6500 to 6800 it blurbles bad giving me every indication its still running rich 7000 rpm and below. I Heading had the carbs off several times and cleaned again thinking I overlooked something or had something still plugged but to no avail it was all clear. Plugs and pistons showed pig rich so I began jetting down for Iowa riding 0-1000 ft. Left the 150 mains in place and lowered the needles twice. First moved clip to top slot and still rich so removed both .015 shims from needle and dropped all the way. Has cleaned up throttle some and plug electrode straps are starting to dry up but still black. Pistons are also cleaning up with about a 1/4 inch of wash around the intake and exhaust side of ports. I'm just baffled that I need to lean out this much and am still not there coming off of what I think are Yamaha factory set up ? Was hoping someone can tell me what the stock pilot/needle/mains should be in this sled and fuel screw setting for this sled. Rode today and done some plug chops at 5500 and 6500 / both show rich still.Fuel screws are at 2 turns out and feeling rich. Currently I'm at the point now of where I think I need to lower a pilot size and maybe lean the fuel screw to 1.5 turns.
Pilot 45
Needle 8CFY14-56, clip position 2
Mains 151.3
Fuel screw 1 3/4
Maybe double check that the choke is operating properly, and not out of adjustment or hanging open a bit even with the lever in the off position.
Probably too early to tell, but keep an eye on your fuel mileage and oil usage. Seems like this sled should get around 10-12mpg, perhaps a little better especially in good conditions.
Needle 8CFY14-56, clip position 2
Mains 151.3
Fuel screw 1 3/4
Maybe double check that the choke is operating properly, and not out of adjustment or hanging open a bit even with the lever in the off position.
Probably too early to tell, but keep an eye on your fuel mileage and oil usage. Seems like this sled should get around 10-12mpg, perhaps a little better especially in good conditions.
Thanks, haven't had enough ride time to check fuel/oil mileage cause it runs so crappy. Currently in the forties this week and snow going away fast but gonna get a good arctic blast of cold after this weekend, hopefully some more snow will accompany it. Gonna pick up a smaller pilot today and will dial back the fuel screws some. Have checked the choke and the cable is a little sticky but plungers are retracting all the way. Will remember to give her a shot of lube. Think I'm getting close based on how the pistons and plugs are beginning to look. It has yielded better results with each adjustment so far but not much I can do with the pilot circuit other than changing jet itself.
Well, I've had the vmax out on a couple little short 5 mile rides around home and have had the carbs off the sled several more times. Currently I have one size lower on pilots, spacers removed on needles and clips all the way up so needles are as low as possible without going to a leaner needle. One size lower on main jet. Basically have leaned out the entire fuel circuit. Still runs blubberly up to 6800 rpm and then it really takes off. Got some snow yesterday (finally) and put a hundred miles on it. Still no fun to ride it cause it just don't seem to want to make any power until you've really got the throttle opened up, so would not be a good starter sled for my kids. It is absolutely horrible on gas mileage. 100 miles and 19 gallons of gas. So just barely 5 mpg. I know this should do better on fuel than this, what could possibly be wrong ??
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super1c
Super Moderator
It obviously sounds as if you know your way around sleds so i dont want this to sound demeaning. But its not a fuel circuit problem and if you continue to lean this sled out you will burn it down with todays gas. My best advice is to put it back to stock specs as mentioned above and here http://www.totallyamaha.com/snowmobiles/AAATuning Chart/Specs.htm . The problem is somewhere else from sitting. Did you check the reeds? Have the clutches been checked and cleaned? Plug caps ohm'd (should be at five) but i would just replace anyway they are old and most are out of spec now anyway? A bad spark will give ya same effect. Mice make a home in the exhaust? Flywheel rusty? Oil pump in spec? Post #4 for adjustment, I think yours is still this type. http://www.totallyamaha.net/forums/threads/58734-97-600SX-oil-pump?highlight=mark .
I totally agree with ya about leaning it out. Just came back from shop and plugs are still solid black, pistons carbon is all cleaned off now with good wash marks. Just filled back up with oil and gas to calculate ratios. I think it was pretty close... 19.7 gallon gas to 48 oz oil in 101 miles / It's the 5mpg that is killing it. It runs exactly like the guys sled in the second link you attached, but my oil pump seems to be fine ?
I've checked all that you listed except flywheel and plug caps/ would a weak battery contribute to this ?? The headlight is considerably dimmer than all the other sleds in the group.
The sled screams like an srx when you open it up, having to run so much throttle to keep it rolling totally explains the poor mileage. Was kind of wondering if it could be weak spark/ignition ? Whats a good way to check for this ?
This might be a stretch but I'm going outside the box trying to figure this dang thing out. The one other thing I noticed when I was in the carbs were the slides cutouts. There is barely any cutout at all. There is a brass collar that extends about 3/8" into carb throat that the needle jet drops in and out of. It is cut away on one side facing the engine. Is it getting enough air across the jet to atomize the fuel well to make power ? Once throttle is over half way then the slide clears the top of the brass collar and gets a direct charge of intake air atomizing fuel completely and making the power at heavy throttle.
Will swing by Yamaha dealer and pick up 2 new plug caps. Is there an updated cap I should look for/ part #. Or can I get a sufficient one at auto store ?
I've checked all that you listed except flywheel and plug caps/ would a weak battery contribute to this ?? The headlight is considerably dimmer than all the other sleds in the group.
The sled screams like an srx when you open it up, having to run so much throttle to keep it rolling totally explains the poor mileage. Was kind of wondering if it could be weak spark/ignition ? Whats a good way to check for this ?
This might be a stretch but I'm going outside the box trying to figure this dang thing out. The one other thing I noticed when I was in the carbs were the slides cutouts. There is barely any cutout at all. There is a brass collar that extends about 3/8" into carb throat that the needle jet drops in and out of. It is cut away on one side facing the engine. Is it getting enough air across the jet to atomize the fuel well to make power ? Once throttle is over half way then the slide clears the top of the brass collar and gets a direct charge of intake air atomizing fuel completely and making the power at heavy throttle.
Will swing by Yamaha dealer and pick up 2 new plug caps. Is there an updated cap I should look for/ part #. Or can I get a sufficient one at auto store ?
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barry
New member
just a thought have you checked float height settings.meant to add check needle and seat for sealing also.my2cents good luck with it
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Sounds like a reed problem to me , Are you sure the reeds are seated properly down, they might look fine with the naked eye but not seated fully
Well, pulled the carbs again today and returned jetting back closer to stock. Checked flywheel and she's clean as a whistle. Spark is nice and blue. Was able to loosen track quite alot. Did have some melted hyfax material built up on track clips. Took it for a short spin and it does coast much better when you get off the gas so am pretty sure this was contributing to overworking it. The engine just doesn't have that crisp throttle that I'm use to, think i've got it about as good as it can be. Thanks for all your help guys.
horkn
New member
How's the oil consumption? Yamaha had some bad oil pump issues and the used a ton of oil on their twins in the proaction chassis. Granted mine failed open with over 5k on it. It woke up with A new oil pump not dumping in extra oil.
A couple of bucks
VIP Member
This is BBBBYYYYYY FFFAAARRR the best,most detailed post from a new TYer that I have EVER seen.
Did you look at the top hats?
I seen early on signs of excessive oil with the carbon on pistons. I adjusted oil pump some and seen a 2.1 oz to gallon ratio. So it appears to be working correct. I bumped it back up a tad when I rejetted yesterday.