Just bought a sled with a bad piston - need some advice

S

sleeper_dave

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I just bought a '94 V-max 600 ST with SLP pipes and an extended track. Ran great, but I forgot to bring my compression gauge to check it out. Bought it anyway for $800. Got it home and checked the compression, found it at 135 and 90. D'oh! :o| #$%&*

Tore it down and found a nice chunk missing from the mag side piston. Cylinder still looks beautiful. Looks like the PTO side has a wiseco piston and the mag side has (rather, had) a cheaper, probably cast piston. In any case they are mismatched. The previous owner mentioned doing a top end 2 years ago, not sure which cylinder he did.

So, looks like I need:
- head
- 1-2 pistons
- base gasket
- head gasket
- thermostat

So, questions:

What pistons should I run? Should I get another wiseco and leave the good one alone?

What piston clearance should I run? Should I just be checking it with a feeler gauge? I don't have a bore gauge. I'm assuming I can just check it with a feeler gauge - Is the measurement half of the size gauge I can get in on one side, or is that the actual measurement? Say I get a .006 gauge in there - is that .003 clearance (since when centered there'd be .003 on each side) or .006 clearance? Not sure exactly how it's measured.

Anybody got a good used head for sale? Or can I just clean this one up and run it? It looks like it got beat up a bit.

At least the cylinders and crank look okay!
 
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Found that a single wiseco is $115. The kit I was looking at must have been 2 pistons. I'll probably go that route. Found a clean head on ebay. Sport mart has a gasket kit for $75, i'll see if they have that and the thermostat in stock tomorrow. Hopefully I'll have it running again next weekend.
 
Do the pistons in pairs because you'll be bouncing from side to side fixing stuff. Besides you'll know that they are both the same brand and weight keeping them balanced. Put a '95 headgasket in it as it is (I believe) the thinnest of all of the years(I know for a fact the '96 was thicker).
 
Good advice on the piston - except the model number is printed clearly on the top of the wiseco so I'm confident that I can get an exact match. That one's in really good shape so I think I can save the $100 and re-use it. I'll probably reuse the rings since they're already mated to that cylinder but i'll probably toss a new wristpin bearing.

It's going to depend on what sport mart has in stock tomorrow. If they have the full wiseco kit with both pistons and all the gaskets and bearings in it for $250 I may just get that. I don't think the single piston wiseco kit comes with bearings, so adding in bearings and the gaskets I might be close to $200 for just the one piston. For an extra $50-$60 I might as well just do both. This $800 sled is turning into a $1200 sled mighty quick.

Normally I'd be happy about getting 6" of snow the day I bought a new sled! But it's going to be a week before the replacement head gets here. :(
 
Sounds like the previous owner dumped his problems off on you.

I had a 94 vmax 500 that I put twin pipes on and I ended up putting the stock exhaust back on. They are so much more reliable in stock form. Not to mention, the 500 and 600 twins are horrible on gas even with a stock pipe. The fuel usage with twin pipes was rediculous.

Here is what I would do,



Pull the pipes, put them on ebay.

Get a comple stock exhaust system pipe, silencer, springs and gasket

Get a fresh OEM top end from Yamaha IE pistons rings, gaskets and a nice used head on here in the classifieds or ebay.

Jet the carbs to stock setting and ride.
 
I might be picking up a 600 twin cylinder vmax next weekend here locally.

I will sell you the entire top end and exhaust a far cry from what you would pay new.
 
(cheap route) Get a piston,reuse gaskets(black rtv gasket maker them little),buff head,no stat.Hear of guys reusing gaskets all the time.
If new or old head gasket.Some are 5 layers,,grind rippits, take apart,,only use 1 or 2of thinnest,,,high test gas,,
but whatever
or
do right thing
get new stuff and you,ll be good

Finally got snow and I,m waiting for parts too! :o|
 
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I have the stock exhaust and I already ordered a nice clean head off ebay. from the pics it looks like the motor it was on never came apart. Getting a thermostat with the head.

What kind of thickness should I be looking for on the head gasket? I'll either be getting it in the wiseco kit or in the top end gasket kit from sport mart, so i'll just measure it with some calipers. I can peel layers to get the desired compression. The previous owner only had 2 layers in there to bump up compression. What thickness is stock and what thickness should I be looking for?

The carbs are supposedly "dialed in" for the pipes as it is. I want to leave the pipes on and see how it runs. Judging by the wash on the good cylinder, it's running pretty rich. I'm going to go through the carbs anyway to be on the safe side but I don't think i'm going to rejet them right away. I'll probably run the motor on 100:1 premix on top of the oil injection to be safe, so if anything i'd just go a little fatter.
 
I had a 600 vmaxx. I would be lucky to get 90 miles out of a tank, I put psi pipes on it and dropped the needles one full clip pos. Did not change the mains and did not thin the head gasket. Not only did it improve the performance , but also the gas mileage.. Thats right , I actually got better gas milage with the dual pipes!( I got over 100 miles to the tank) and NEVER Had reliability issues . To this day i wished I had never sold it!
 
Just ordered the wiseco top end kit, p/n sk1257, and 2 wristpin bearings. Got the head and thermostat coming off ebay. $375 later and i'm on my way.

I'll just run the head gasket as is, do a pressure test on the motor before putting it back into service, and run premium with a 100:1 premix on top of the oil injection. Jetted fatter to compensate. The cheat sheet for the pipes says jetting should be awfully close to stock, just richer on the air screw. I'm going a step up on the main jet anyway. Let it run rich, i'll bring extra plugs. Rich is safe.

Called wiseco and they said .003-.004 for piston clearance, maybe up to .005. I checked with feeler guages and it's definitely more than .0025 and less than .006. The .006 fits but it's real tight, the piston falls through with the .0025 in there. I'd call it .003-.005, which should be good. Maybe a touch less with the new pistons because of no wear on the skirts.
 
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I know the sled you are talking about it was my buddies. I welded the pipes on it after they blew out, Thats why they look all frankenstein. If it were mine I would take the pipes off and run it with the stock pipe and stock jetting. Also adding premix to it is going to foul out plugs like no buddies business. The sled was on the fat side already because of the pipes. He had no idea btw that one piston was down on compression though. I had a 97 twin with pipes and melted down a few pistons in that sled, Those engines just aren't the best for putting pipes on. They will last a long time stock though. Just my opinion Im sure people will say they had a twin with pipes and it was fine forever yada yada.
 
Im with you on this one Yammy. I still have a 97 600 with PSI pipes. Over 4000 miles on the sled with them. Just had to rebuild because of the piston pin deffect. No sings of running lean what so ever even running it a radar runs. Do your jetting and it will be just fine. Another thing I never run fuel with ethanol!!
 
I have a 97 vmax 600 twin with 11,600 miles on it. I have gotten up to 110 miles on a tank of gas and average about 11-12 mpg. I have stock pipe/canister, v-force reeds. I have re-built the top end two times, and use wiseco pistons. I recommend using pistons that are the same, whether stock or wiseco. I weighed both pistons, and the wiseco are lighter than the stock pistons. If you mix them, you could cause a vibration problem. Cometic sells gasket kits for these motors. I went with a thinner head gasket from Cometic (need 93 octane) for more compression. It really woke the motor up.
 
Stock jets are supposedly 52.5 pilot, 156.3 main, 1 1/8 turn out on the air screw. SLP says to run 52, 155, and 1/2 turn with the pipes.

I got into the carbs and raised the floats (set to spec, SLP reccomendation is the same as the service manual) and changed to a 160 main jet. I plan to run 100:1 (or a little leaner) premix to guard against oil line failure (which cost me a motor on my phazer last year). Plus I like to err on the rich side.

The pilot jets are stock. So my jetting should be good for either pipes with just a tweak of the air screw.

Only question is the needles. Both are at the top notch, which is as lean as they go. This should lean it out in the midrange. I'm contemplating putting them at #3 pos and adjusting from there if it bogs (lean) or loads up (rich) in the mid range. My issue is the little plastic washer next to the clip on the needle. One had it below the clip (raising needle, rich) the other had it above the clip (that's the cylinder that let go). Where does this spacer go? Does this give me a 1/2 jump to the next clip position?
 
97srxXT said:
I know the sled you are talking about it was my buddies. I welded the pipes on it after they blew out, Thats why they look all frankenstein. If it were mine I would take the pipes off and run it with the stock pipe and stock jetting. Also adding premix to it is going to foul out plugs like no buddies business. The sled was on the fat side already because of the pipes. He had no idea btw that one piston was down on compression though. I had a 97 twin with pipes and melted down a few pistons in that sled, Those engines just aren't the best for putting pipes on. They will last a long time stock though. Just my opinion Im sure people will say they had a twin with pipes and it was fine forever yada yada.
Click to expand...

Thanks for the reply. I was kind of wondering about the pipes. Glad to hear it was an honest oversight and that he wasn't trying to screw me.

I'll probably go to the stock pipes at some point. But I do want to try it with the pipes first.
 
sleeper_dave said:
Stock jets are supposedly 52.5 pilot, 156.3 main, 1 1/8 turn out on the air screw. SLP says to run 52, 155, and 1/2 turn with the pipes.

I got into the carbs and raised the floats (set to spec, SLP reccomendation is the same as the service manual) and changed to a 160 main jet. I plan to run 100:1 (or a little leaner) premix to guard against oil line failure (which cost me a motor on my phazer last year). Plus I like to err on the rich side.

The pilot jets are stock. So my jetting should be good for either pipes with just a tweak of the air screw.

Only question is the needles. Both are at the top notch, which is as lean as they go. This should lean it out in the midrange. I'm contemplating putting them at #3 pos and adjusting from there if it bogs (lean) or loads up (rich) in the mid range. My issue is the little plastic washer next to the clip on the needle. One had it below the clip (raising needle, rich) the other had it above the clip (that's the cylinder that let go). Where does this spacer go? Does this give me a 1/2 jump to the next clip position?
Click to expand...
You are correct in your thinking of the spacer is a tool for richening to the next step. I am not sure here but my newer('00) sled has 2 spacers not sure if yours should too - need to find a manual to verify...
 
sleeper_dave said:
Stock jets are supposedly 52.5 pilot, 156.3 main, 1 1/8 turn out on the air screw. SLP says to run 52, 155, and 1/2 turn with the pipes.

I got into the carbs and raised the floats (set to spec, SLP reccomendation is the same as the service manual) and changed to a 160 main jet. I plan to run 100:1 (or a little leaner) premix to guard against oil line failure (which cost me a motor on my phazer last year). Plus I like to err on the rich side.

The pilot jets are stock. So my jetting should be good for either pipes with just a tweak of the air screw.

Only question is the needles. Both are at the top notch, which is as lean as they go. This should lean it out in the midrange. I'm contemplating putting them at #3 pos and adjusting from there if it bogs (lean) or loads up (rich) in the mid range. My issue is the little plastic washer next to the clip on the needle. One had it below the clip (raising needle, rich) the other had it above the clip (that's the cylinder that let go). Where does this spacer go? Does this give me a 1/2 jump to the next clip position?
Click to expand...
Thats all fine and well if it gives you peace of mine, But just remember ,Just because you put more oil in your mixture dose'nt necessarily mean you are making it richer! In fact the opposite is true...You are actually leaning it out!......More oil...means less gas...less gas means leaner mixture! These are two stroke motors, gas and oil mix together with air to burn and to keep it lubricated...un like a four stroke motor. I would use the reccomended gas oil ratio that the sled calls for. Besides I believe when the pump goes bad it goes full open so you should never have an issue with not enuff lubrication!
 
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