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

yammy said:
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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I understand that. That's why I'm jetting it up before I premix.

I'm not worried about the oil pump, im worried about the oil line. A broken oil line cost me an engine last year.
 
My DX came with Pipes and as much as i love them on my XT that is setup perfect the DX had them tossed on and they were not setup properly (sounds like yours may be in this boat). The clutches were also still in stock configuration which made for horrible backshifting and reving. This made for an easy decision, sold the pipes for a whole motor in pieces (no pistons) and Single GYT pipe. Basically what i am getting at is if you find the sled is clutched and carbs are setup close then run them and enjoy the extra power (tons of fun on the XT :) ) if however they aren't you are much better off going back to "stock" and running that way.
 
Got the parts today. Finished going through the carbs and got most of the set up done. Going to the bar now.

Sanded the cylinders with 600 grit lubed with WD40 to deglaze them, not sure I did anything though. That nikasil is hard. Washed them down with brake cleaner and WD40. With the new pistons the cylinder to piston wall clearance is about .0025, maybe .003. The box says to run .0025. The service manual says .0028-.0030. I'd like them a touch looser but i'm going to keep it a bit rich so I should be just fine there.

Filed the rings slightly, set them at just higher than the wiseco recommendation (they say .012, they're probably about .013). The manual says .018-.024. What should I run? Wiseco says .004 per inch of bore - which adds up to .012. Should I go higher to be on the safe side?
 
I've got the motor together and i'm trying to pressure test it, but I can't get the exhaust flanges to seal up against the cylinders. Like they're not perfectly flat or something. I replaced the gaskets.

Is there some kind of sealant I can use on the gaskets to make them seal properly?
 
sleeper_dave said:
I've got the motor together and i'm trying to pressure test it, but I can't get the exhaust flanges to seal up against the cylinders. Like they're not perfectly flat or something. I replaced the gaskets.

Is there some kind of sealant I can use on the gaskets to make them seal properly?
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permatex red
 
sleeper_dave said:
Got the parts today. Finished going through the carbs and got most of the set up done. Going to the bar now.

Sanded the cylinders with 600 grit lubed with WD40 to deglaze them, not sure I did anything though. That nikasil is hard. Washed them down with brake cleaner and WD40. With the new pistons the cylinder to piston wall clearance is about .0025, maybe .003. The box says to run .0025. The service manual says .0028-.0030. I'd like them a touch looser but i'm going to keep it a bit rich so I should be just fine there.

Filed the rings slightly, set them at just higher than the wiseco recommendation (they say .012, they're probably about .013). The manual says .018-.024. What should I run? Wiseco says .004 per inch of bore - which adds up to .012. Should I go higher to be on the safe side?
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best thing to wash barrels etc etc that need to be really really clean ............................put them through the dishwasher.


.......................there speaks a single man, with odd tasting kitchenware.

really though, when cleaning barrels after honeing a few buckets of boiling water, her best rubber gloves with a good generic de greaser will get you there. Blow dry and spray with oil of you choice.
 
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sleeper_dave said:
I've got the motor together and i'm trying to pressure test it, but I can't get the exhaust flanges to seal up against the cylinders. Like they're not perfectly flat or something. I replaced the gaskets.

Is there some kind of sealant I can use on the gaskets to make them seal properly?
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Take a straight edge to the flanges and make sure they're flat if not they'll need to be qualified flat and that should take care of most of your issue. When you said you cant get the flanges to seal it popped into my head that this will cause a poor running machine and also cause a burndown.
 
SHIT!

I need crank seals :(

I sealed up the exhaust flanges with copper RTV. Supposedly good to 700°F. Not sure what kind of temperature that sleeve will see, but hopefully it's not enough to cook the RTV off. Managed to get everything else sealed up good, and found a leak at the crank seal on the PTO side. Can't get to the one on the mag side because, well, the magneto is still there. SHIT!

Can I do crank seals without pulling the top end back apart? I'm thinking pull the motor, pull the magneto (after removing the cover, water pump, etc), pull the primary, unbolt the case, lift the crank up just a hair, pull the seals, clean the mating surfaces, clean up the sealing surface on the crank (1000 grit? 2000 grit?), install new seals, yamabond on the cases, reassemble. Sound plausible? Or am I missing something that's going to have me pulling the jugs again?
 
Sxr700Bandit said:
Take a straight edge to the flanges and make sure they're flat if not they'll need to be qualified flat and that should take care of most of your issue. When you said you cant get the flanges to seal it popped into my head that this will cause a poor running machine and also cause a burndown.
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The thought crossed my mind, and the recommendation from SLP to use black RTV also shouted "poor quality" at me. I ended up tossing it together with some copper RTV. I may just go back to the stock y pipe and exhaust, it's probably higher quality and more likely to seal without RTV. I'll probably pick up some more exhaust gaskets when I get the crank seals...
 
sleeper_dave said:
SHIT!

I need crank seals :(

I sealed up the exhaust flanges with copper RTV. Supposedly good to 700°F. Not sure what kind of temperature that sleeve will see, but hopefully it's not enough to cook the RTV off. Managed to get everything else sealed up good, and found a leak at the crank seal on the PTO side. Can't get to the one on the mag side because, well, the magneto is still there. SHIT!

Can I do crank seals without pulling the top end back apart? I'm thinking pull the motor, pull the magneto (after removing the cover, water pump, etc), pull the primary, unbolt the case, lift the crank up just a hair, pull the seals, clean the mating surfaces, clean up the sealing surface on the crank (1000 grit? 2000 grit?), install new seals, yamabond on the cases, reassemble. Sound plausible? Or am I missing something that's going to have me pulling the jugs again?
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YOu should be able to split the cases and not have to pull the cylinders. Do as you stated, and use scotchbrite to clean the crank by the seals, and don't forget the add greas to the seal lips for lubrication. If you need a hand give me a yell(if you still have my number).
 
I still have your number... thanks for the offer, I appreciate it!

Problem is i've been traveling a lot for work. No more time to work on it today, going to spend some time with my girlfriend. Then I'm out of town until Friday. So it'll be next weekend before I can even start! Hopefully sport mart has the seals in stock.

At least i'll be able to pressure test it on the bench before installation, that should be a bit easier than doing it in the sled. Everything is still plugged up too so hopefully it'll be a 1 day operation. And assuming "oil seal" in sport mart lingo means the same as "crank seal" it should be a relatively inexpensive fix.

Do you have the tool to pull the primary off the crank? I've never actually pulled that off before so i'm going to need to get my hands on the tool. I have a generic 2 / 3 bolt puller that should work for the mag rotor.
 
I have a clutch puller... You may want to try a place called Maximum powersports for the crank seals(at least they are OEM), they are located in a town called Peru, Indiana and have been dealing with them for about 12-13 years and get a pretty fair deal on parts, they just changed owners last summer they used to be called Max Pitts cycles. They will UPS the parts right to your door. Call me if your interested and I'll give you the details. I am available after 3:30 on Fri and Sat.
 
I found maximum powersports online. I'll give them a call tomorrow to make sure they can get me the seals this week before I order them.

Sport mart has a clutch puller in their catalog that says it'll fit both my phazer and my vmax, for $25. If they stock it i'll probably just buy that one.
 
Talked to the guy that helped me build my waverunner motor. He said .0025 piston to wall clearance is too tight, and recommends .0035. He builds mostly quads and sleds, so I believe him. I was thinking .0025 was awfully tight myself, especially with forged pistons. I ran more than that on my waverunner with cast pistons. He has the diamond stones needed to hone nikasil and offered to do it for a case of beer. So I guess it's coming apart again. Oh well, easier to do the crank seals with the top end apart anyway, and the rings will seat better with a fresh hone. I'm sure the base and head gaskets will be fine with a little copper spray, esp. since it was never run or filled with coolant.

Crank seals should be home when I get there this afternoon. Too bad I have to leave town again, and won't have time to touch it this weekend. Looks like I'm SOL on riding this one until fall! Unless I can find a grassy field I can tear up in the meantime.
 
sleeper_dave said:
Talked to the guy that helped me build my waverunner motor. He said .0025 piston to wall clearance is too tight, and recommends .0035. He builds mostly quads and sleds, so I believe him. I was thinking .0025 was awfully tight myself, especially with forged pistons. I ran more than that on my waverunner with cast pistons. He has the diamond stones needed to hone nikasil and offered to do it for a case of beer. So I guess it's coming apart again. Oh well, easier to do the crank seals with the top end apart anyway, and the rings will seat better with a fresh hone. I'm sure the base and head gaskets will be fine with a little copper spray, esp. since it was never run or filled with coolant.

Crank seals should be home when I get there this afternoon. Too bad I have to leave town again, and won't have time to touch it this weekend. Looks like I'm SOL on riding this one until fall! Unless I can find a grassy field I can tear up in the meantime.
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you can borrow a hone from auto zone and save some beer..it dos'nt need to be diamond stone!
 
To do it right you kind of need the diamond hone. Plus while i'm there I can probably have him chamfer the ports if they need it, and he might even insist on a mild porting job. Plus he can measure the pistons and cylinders with the proper tools and give me a better measurement of piston clearance than i've been getting with the feeler gauges. If the thing wasn't studded I might have him run it on the dyno, too, to see how the jetting is and what the power looks like. I would have had him do that with the waverunner, but he hasn't ponied up for the water brake yet.
 
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