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Discussion Starter · #1 ·
I was driving down a trail, a nice straight trail, anyway I let off to slowdown to go around some guy walking, thats when the sled started to make a sould like the plugs where bad so I let off and stopped on the side of the trail. Tryed starting it again and no go, pulled the plugs, no metal on them. After about 30 mins after the sled quit some guys come by and get my sled towed to the road and I trucked the sled home.
At home we checked the fire, and i looked down the plug holes and didnt see anything wrong but my dad put his thumb on the holes, the clutch side has alot but the mag side has none.
so if u could tell me maybe what you think happened and hopefully its only the rings

oh yea its a 1991 yamaha exciter 2 570 - all stock
 

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My guess is a hole through the top of the piston. Just a guess.
No compression at all? Take the head off and check. You'll be able to inspect the piston and cylinder walls too.
An easier way to check would be to take the exhaust off and put you finger on top of the piston and feel for a hole or anything abnormal.
D
 

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Discussion Starter · #3 ·
thanks, im gonna try to pull the top end off tomorrow and maybe even the cylinders, i think its time the motor could get some new parts
 

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Discussion Starter · #5 ·
at first before i had a chance to check the compression i tought maybe it was a fuel issue because it liek kinda bogged/died and it went about 200 feet more before actualy dieing out. that 200 feet was me desideing to ride it al lthe way to the road or stop, in the end i endded up stoping haha

by the way crazed, i like your exciter with the silver spring covers
 

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Discussion Starter · #7 ·
haha indeed, i used to have a windsheild like yours, it was all scratched and it said exciter 2 on it so i opted for looks over function with my winsheild, its like 2 inches over the gauges and thats it.
 

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Discussion Starter · #8 ·
update: the reason was the mag side piston was scuffed bad on the exhaust side, now what makes that happen??
 

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Scuffed up bad as in scoring? Many possibilities. Any chance of a picture? Things to check are colour of plug & piston first. If it is still stock the oil is injected into the fuel line just ahead of the fuel pump, so a defective carb will not only make it lean (burning it up) but will starve it for oil too. Check all carb circuits especially main jet. Might as well go through both while they are off. Jet chart should be on belt cover. 320's are stock on that thing. Coolant level right up? Water pump & belt OK? These things like to pull air in around the crank seals and that will burn 'em up too. There is a factory setting for the oil cable too but that should have picked on both cylinders. Whats the other look like? I know a lot of members will probably strongly disagree with me on this one - but if you want a RELIABLE sled resist the urge to hop it up while it's apart. If you must destroy- I mean tweak it up, I'll trade you my ported jugs & pipe for your stock stuff. Seriously though, if you want to ride without problems leave it stock. Some of the guys on this forum have gotten over 10,000km on these Exciters.
 

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ya,it's a ring issue
 

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Discussion Starter · #11 ·
ya the clutch side piston is like new, but the thing thats got me is that the pistons dont have much carbon on them, like i said they almost look new, and the oil level droped alot from the last time i filled it up on monday. i might pull the carbs and clean them out to be sure and also check the crank seal on the mag side.
thanx for the info guys
 

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Discussion Starter · #12 ·
just finished working on it some more,took almost the hole mag side apart to get to that damn seal to check it out, going to get a new one anyway. do you know how they come out anyway?? and i got the pics of the pistons so here they are:
mag[attachment=57962]clutch
clutch[attachment=57966]mag
clutch[attachment=57968]mag
 

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OUCH!! Looks pretty damn lean to me. I've never changed crank seals on these but according to the manual you gotta split the crank case. There is a lip that sits in a machined groove to hold them in place. Again, might as well do them both. I have the factory service manual for that sled if you need any torque specs. Also check the carb needle jet height. Should be in clip #3 (middle) position. There is supposed to be a tiny plastic spacer above & below the "E" clip. Curious to know what killed it.
 

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Discussion Starter · #14 ·
thanx, i looked at the crank seal and it didnt look to bad, but then again i dont no what iam really looking for, but man what a job to get to it:p lol but yea i would like the torque specs if u dont mind, and ill try to pull the carbs tomorrow, i just dont wanna get all the lines mixed up and f something up, and hey how high does ur exciter rev up to?? mine had stock clutching except the secondary spring was moved around and it goes from 3200/3400 all the way up to 8100/8200
 

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Both crankcase & head are two step torque. Crankcase 1st step 9.4ft-lb 2nd step 19ft-lb. Head 1st step both nuts & bolts 14ft-lb. Then nuts to 24ft-lb followed by bolts to 20ft-lb. If you tell me how to post a picture I'll scan in the sequence. Have you had carbs apart before? If you are unsure of the lines mark them with a felt or paint stick. My sled engages around the same RPM and maxes out around 8000. They are supposed to engage slightly higher (3800) but I have not bothered to chase that down yet. With time the crank seal gets hard and starts to leak. You will probably see damp oily staining around the seals.
 

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Discussion Starter · #16 ·
alright, i guess the seals are ok, but ill check them over, im going with stock size wiseco pistons, and i have the cylinders being deglazed today and the pistons should be in on thursday or friday, and as for posting pictures u have to hit reply, then theres a bunch of buttons you can click on, well there a really long row, and at the end three paper clips. The first of the three means to upload from your computer.
 

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Discussion Starter · #18 ·
yup turns out its nickel plated, and ya i dont think ill go with ur jugs and pipe, although i do like the sound of a pipe, its just not worth blowing it up again for the money i paid for it. what kind is it anyway??
 

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Not 100% sure but I think its a PSI. I was just kidding about the jugs, I wouldn't give them to my worst enemy. Nickle plated or not, they are screwed after some idiot hogged them out with a die grinder. At $585 a pop thats it for this season for the '91. What was kinda funny was the '89 properly jetted was faster. It's totally stock under the hood. All I've changed on that one is suspension & track. Honestly the pipe improved top end a little but I lost a little in the midrange. With my type of riding I rarely get to hold it open very long and am usually in the mid range. So both have stock exhaust now.
 

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Just going by the pictures and your description,
it looks like a standard lean melt down to me.
Just a guess:
Was it a colder day than what you've normally ridden on?

For future use, spend the $25 on a Bend O Light.
Pull your plugs and use that light to check your piston wash while you are getting it dialed in again.
I'd start out with about 2 sizes richer on your mains as well.
 
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