1996 yamaha v-max engine failure - Snowmobile Forum: Your #1 Snowmobile Forum

Kirk36 · 02-19-2008, 01:40 PM

I had loss of power last weekend, I took these pics last night after I pulled the head off.

Any thoughts of the culprit.

Lean mix?

crank seals bad?

Carbs out of wak?

I did have a bolt missing on the exhaust manifold on the bad side of the motor. Would this be the culprit?

metal parts jammed up inside the spark plug

Thanks,

Kirk

ramblnman · 02-20-2008, 09:25 AM

when was the last time you had the carbs cleaned? looks like a lean issue.jets clogged

Kirk36 · 02-20-2008, 11:07 AM

I bought this sled a month ago, the seller told me he cleaned the carbs before this season. I will take them apart and cleaned them when I get the motor fix up with new parts. I just don't want to freshin the top end up, and than find out the bottom needed stuff too.

I am going to put everything back togather and start her up and test for leaks around the crank with some go jo, and make sure she is getting oil also.

From the look of the cylinder I am lucky there are no grooves in the walls.

One thing I noticed was that when the piston gets to the bott of the stroke the gap between the piston and the wall gets bigger. Is this normal or is the cylinder worn down around the ports?

**smallengineguy** · 02-20-2008, 11:29 AM

It's normal for that to a point. You'd hear it (piston slap) if it wasn't.

Kirk36 · 02-20-2008, 11:49 AM

The piston just looks like something got in the combustion chamber and shined it up, and beat the edges of the piston to a point that it chipped off, than smashed those pieces into the spark plug.

Or it could have been just an overheated piston to a point that the alum. starts chipping off around the edges cuz of the heat generated?

I don't recall any idiot lights coming on on the dash for a overheated condition, if they work.

I guess when I take the cylinder off it will tell the rest of the story.

Oh yeah there are to dings on the edge of one of the ports.

Kirk

ramblnman · 02-20-2008, 11:50 AM

you will need to mic the cylinder at the top then the center and at the bottom to find out for sure. if this was mine and sled was in descent shape, i would pull the engine out and split the base and check everything. crank bearings, rod bearings, install new seals check and doublecheck everything.dont want to get it all together to find out you have to pull it out and apart again! them carbs in the picture looks like they have been on there a while to me(pretty grungy)sorry you are going thru this but lookin at the bright side in the end you will know what you have andyou will be all the wiser!

SnowRida · 02-20-2008, 12:17 PM

That whole engine looks rusty.

highcountry · 02-20-2008, 12:18 PM

My polaris had the same problem and when I took the cylinder off the piston skirt had broken and put a hole in the crankcase. I hope this isn't the case for you.

Kirk36 · 02-20-2008, 02:27 PM

Thanks everybody.

Kirk

bdavis1 · 02-21-2008, 07:40 PM

make sure your getting oil! my piston looked like that when my oil pump failed it was clean, no carbon build up i needed a whole new top end

Kirk36 · 02-22-2008, 12:55 PM

A little note.

Before the engine let go I went through 7 Gals +- of gas in about 29 +- miles. I think this is a little excessive. I am not sure what the gas milage is for this sled, I heard it was a gas hog.

How do I check to see if the oil pump is working, I have the engine sort of taken apart?

Kirk

bdavis1 · 02-22-2008, 03:52 PM

if its a mechanical oil pump like mine you can take the oil pump off the engine and hook it a drill and see if its pumpin oil or when u get the sled runnin run mix gas as well as the oil and take the lines of and see if the pump is pumping that way

SnowRida · 02-22-2008, 04:42 PM

Quote:

Originally Posted by Kirk36

A little note.

Before the engine let go I went through 7 Gals +- of gas in about 29 +- miles. I think this is a little excessive. I am not sure what the gas milage is for this sled, I heard it was a gas hog.

Kirk

I was getting 5 miles/gal. last weekend. My plugs were oily so It's running rich. I'll have to drop the needles some and maybe rejet it. You should get at least 10/11 miles/gal on these sleds.

Kirk36 · 09-21-2008, 11:12 PM

Hello all

I finially got around to pulling apart the engine and the skirt is gone on both sides of the piston see pics. Is this from the last install not honing the cylinder and not using maybe .20 over pistons. I have heard that it is from too much cylinder clearance. I would think that my carbs and oil is running correct, it was just a bad top install? I will take the cylinders to the machine shop and have them sized and honed out to fit 2 new pistons, and than put her all back togather clean carbs and air box, they are dirty.

Also I need to put studs on my track (the track is worn out) anybody know what size woody's to go with without damage to my cooling rack 3/4" 1" 1-1/4"? If the track is worn out aren't studs a way to get more traction and still get some life out of your track? I would rather spend $100 for studs rather than $400 for a new track. Iowa always has lots of hard packed snow and ice to ride on.

Kirk

**smallengineguy** · 09-22-2008, 07:29 AM

That is from too much piston-cylinder clearance. If it's .020 over, it seems someone did the bore too big, OR put the wrong pistons in it. Let us know what the machine shop says.

Kirk36 · 09-22-2008, 09:44 AM

smallengineguy,

I checked online and it looks like the studs can be 7/8" size for this sled?

I also will need to check but I would soon like to bore this sled out to 700cc if it can. Since I got everything apart I might as well get her bored out bigger. I guess it just depends on the stroke of a 700cc bore size. It would be nice to bore it out to 800cc if it can LOL? I should as well put some better reeds in also. Any advice on reeds? Or boring bigger? Shaving the heads down?

Kirk

Kirk36 · 09-22-2008, 02:11 PM

I took the cylinders into the machine shop they micro the walls and they were within .001 at top mid and bottom, which is good news. He calibrated the cylinder walls at 2.971" or 75.46 mm. OEM Wisco list for this sled says 2.944" or 74.8mm, so I am a little big on my bore, how much is bad? 2.971" - 2.944" = .027 (clearance) too much? Should only be .012 to .024? Can I bore these cylinders out to the next oversize piston? Wisco says .50 oversize is all they have for this sled. What size is a .50 in inches .50 is not 1/2" is it? lol or is it 1/2 mm not sure.

If I put new OEM pistons in these cylinders I will have problems, but how long will it take to damage the pistons again. What is the risk that it happens the next ride after the install?

I guess I might need to replate or resleeve?

I am not sure which way to go it looks like it is only .003" to big? real small.

Kirk

**smallengineguy** · 09-23-2008, 07:23 AM

.50 is a half a millimeter. If Yammi offers them for it, get those. Wisecos can be a finicky piston. Whatever you choose, bring the new pistons to the machine shop and make sure they are matched correctly to the cylinders.

Kirk36 · 10-21-2008, 10:47 AM

I finally ordered the parts for the motor. I need numbers for torque specs for this motor, head bolts, base bolts, exhaust bolts, and any other torque specs that I might need.

I cleaned the carbs out, jets were good and clean, soak them, they were pretty clean to be honest. The air box had foam crap in it from the foam seal, cleaned that out also.

I should have her running Sat.

Thanks

Kirk