What happened to my crank?

[Octanee]

I got my case apart finally, I forgot to take pics so I did now, my cylinders, the nikasyl is still there so I'm going to take some muratic acid and clean up the scuff lines with it and I think the cylinders will be ready to roll after that,

heres some pics, Sorry for huge size, unsure how to shrink them, conventional methods using HTML does not work.

 

[Lund]

I got my case apart finally, I forgot to take pics so I did now, my cylinders, the nikasyl is still there so I'm going to take some muratic acid and clean up the scuff lines with it and I think the cylinders will be ready to roll after that,

heres some pics, Sorry for huge size, unsure how to shrink them, conventional methods using HTML does not work.

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Octanee, the reason your motor pooped the main rod bearing is because the rings on those pistons are worn out. Very simple diagnosis, the black carbon running down the side of your pistons on the wrist pin side is a dead give away.
Basically combustion gases were going into the bottom case and in time took your bearing out. This had nothing to do with the lack of oil or your oil injection system but everything to do with worn out rings.

Give your cylinders a good cleaning with the muriatic acid and they should be good to go. If you choose to use a hone go VERY VERY light or you stand a chance on screwing up the chroming on the cylinders. I generally DO NOT advise honing a chrome cylinder unless your an experienced builder and know how.
The rings you will get with the pistons are designed for use in chrome lined cylinders (Nikasil) and are softer then the chrome, during break in they will conform to the imperfections of the cylinder.
Inexperience backyard builders have a bad habit of honing too much thinking they are doing it good. Problem is that the rings will conform in the same matter by wearing out prematurely, plus your taking a chance on chrome damage especially near the ports, such as flaking.
Good luck, hope that helps.

 

[Octanee]

Octanee, the reason your motor pooped the main rod bearing is because the rings on those pistons are worn out. Very simple diagnosis, the black carbon running down the side of your pistons on the wrist pin side is a dead give away.
Basically combustion gases were going into the bottom case and in time took your bearing out. This had nothing to do with the lack of oil or your oil injection system but everything to do with worn out rings.

Give your cylinders a good cleaning with the muriatic acid and they should be good to go. If you choose to use a hone go VERY VERY light or you stand a chance on screwing up the chroming on the cylinders. I generally DO NOT advise honing a chrome cylinder unless your an experienced builder and know how.
The rings you will get with the pistons are designed for use in chrome lined cylinders (Nikasil) and are softer then the chrome, during break in they will conform to the imperfections of the cylinder.
Inexperience backyard builders have a bad habit of honing too much thinking they are doing it good. Problem is that the rings will conform in the same matter by wearing out prematurely, plus your taking a chance on chrome damage especially near the ports, such as flaking.
Good luck, hope that helps.

Hey lund thanks for shining in on the pics! I learned something new today! Those were/are stock pistons as far as I know and I know these sleds have the piston issues, I ordered up a MTNTK fix kit for it, so I know that'll take care of that.

I was also wondering if you or anybody would happen to know about how the PTO crank seal should feel on the crank, the MAG seal feels as I'd expect, a good seal/drag on the crank like the lips of the seal have a good seal on it, however I notice the PTO seal has little drag on and off, just curious if that is normal or not, IT appears like it has one little lip then a flat slightly tapered spot that's wide, Perhaps it figures the crank pressures in the case will push the lip of the seal onto the shaft. I'm going to get new seals as a pre-caution, also my water pump impeller looks like it chewed up something... odd... so That'll be replaced too.

 

[HotShotHarry]

I think you are doing the right thing. Change out all the seals while you are in there. The MTNTK fix kit is a good kit IMO. I have used it 3 times now and like the taller, tighter Wiseco Pistons that it comes with. It also comes with a spacer between the cyls and block to keep the port timing the same. This spacer increases the crankcase volume so you will gain a bit more horsepower as a result. The taller pistons will rock less in the bore so there is less of a chance of the piston skirts cracking. With the tighter cyl wall to piston clearance, more warm up time is required to lesson the chance of a 4 corner cold seize happening.

 

[Lund]

Crank failures because of bad rings is extremely common and misdiagnosed a lot.
Most low mileage failure can be traced to poor original engine break in. But 1500 miles/almost 2400km on a set of rings is considered in some cases a lot, this is especially true on mountain sleds. If you would had checked the rings at about 2,000km, the crank would had been saved.
This is a practice all 2stroke rider's should do, but most don't till this happen's. Depending on your riding habits, some will go longer but aggressive rider's will poop out the motor much sooner.
Glad you said your replacing the seals.

 

[Dragonalain]

I had 3 reman cranks all lasted less then a thousand k, everyone we took out was a bearing failure. I ended up putting a axys crank in a 2012 pro rmk motor, was well worth the 1500.

For the cost of a reman crank it's physical impossible for them to replace all the bearings with good quality bearings. I heard once that they reuse the bearing on the crank of they are still in good condition. Not sure if that's true or they just use the cheapest of cheap bearings in the rebuild to keep the cost down. I always get my cranks rebuilt or buy new.


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[Octanee]

Crank failures because of bad rings is extremely common and misdiagnosed a lot.
Most low mileage failure can be traced to poor original engine break in. But 1500 miles/almost 2400km on a set of rings is considered in some cases a lot, this is especially true on mountain sleds. If you would had checked the rings at about 2,000km, the crank would had been saved.
This is a practice all 2stroke rider's should do, but most don't till this happen's. Depending on your riding habits, some will go longer but aggressive rider's will poop out the motor much sooner.
Glad you said your replacing the seals.

Good info! I bought the sled blown, got Er for a deal so it wasn't me who never really maintained it,. But here on out it'll get some love. I know as most find, these sleds suffer from bad pistons from the factory, I'm sure it'll be good after this rebuild and increased oil consumption. It'll be driven super easy regardless with a good break in. Going to be a spare sled/for my completely green to the sport fiance.

 

[Octanee]

For the cost of a reman crank it's physical impossible for them to replace all the bearings with good quality bearings. I heard once that they reuse the bearing on the crank of they are still in good condition. Not sure if that's true or they just use the cheapest of cheap bearings in the rebuild to keep the cost down. I always get my cranks rebuilt or buy new.


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Well ill sure find out if I got all new bearings.... The crank got delivered so I just gotta go pick it up. Price wise it's about ~2/3 the price of a new one for a Reman i was told, could be wrong, but I'd that's true I'd say the other 1/3 is casting new crank pieces and Machining and trueing it.

 

[Vance Matheson]

When your putting it back together you will only have one metal base gasket, but 2 surfaces to seal. I eliminated the gasket and used motoseal from canadian tire. Or you could use the yamaha stuff.

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[Chrisco]

When your putting it back together you will only have one metal base gasket, but 2 surfaces to seal. I eliminated the gasket and used motoseal from canadian tire. Or you could use the yamaha stuff.

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WTF!!!!!! Vance..... you can not do this.... get the other new base gasket.

 

[Vance Matheson]

Way to many miles later chris and no issues. That was at 400 miles and sold it at 2600.

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[Octanee]

That one way to do it lol, I did order another gasket,

The crank case is back together and sealed up. I cleaned off the bearing outer race as the crank came lubricated with a film of oil, I applied a bit of blue loc tite on the bearing surface in the case half, I know it's not green, but it'll help it grip a little if there was a chance for the bearings to attempt to spin in the case.

On the subject before of Reman cranks using old but good bearings, my crank was 100% new bearings. Including the center of the crank with the gear sprocket. It was all new. So for the price of a Reman over new..... Your just buying new metal basically.

 

[Vance Matheson]

What did you end up using to seal your case halfs. As far as gaskets go i usually end up making my own or using a gasket eliminator.

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[Lund]

What did you end up using to seal your case halfs. As far as gaskets go i usually end up making my own or using a gasket eliminator.

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LOL, that a good way to change your port timing. Do you guess or don't care?

 

[Octanee]

I just used your general gasket maker silicone stuff, I usually use the copper high temp but this time opted for the gray stuff, then rub it all over with the ol finger.

And cylinder gasket wise, I bought new one/s,

 

[Lund]

I just used your general gasket maker silicone stuff, I usually use the copper high temp but this time opted for the gray stuff, then rub it all over with the ol finger.

And cylinder gasket wise, I bought new one/s,

I'm glad you went with a new base gasket.
FYI, did you know that the base gasket is a crucial part of the engine tuning? With the base gasket you can alter the port timing for either more top end or more bottom end. Put that in your hat of knowledge.

 

[Vance Matheson]

LOL, that a good way to change your port timing. Do you guess or don't care?

LOL well i know that the bond works. We used to make gaskets from printing paper and copper coat when we were kids. Or whatever we could get our hands on. As far as changing port timing...meh nothing noticeableI just wish i still had that sled. Worked better than this new one.

 

[Octanee]

I'm glad you went with a new base gasket.
FYI, did you know that the base gasket is a crucial part of the engine tuning? With the base gasket you can alter the port timing for either more top end or more bottom end. Put that in your hat of knowledge.

yes indeed it can be and just the right thing to do haha! and yes the more you know!.

I got the sled out today, It ran.... great! starts first pull. I turned up the oil injection adjustment screw to be flush with the lock nut, She smokes a bit at idle like a 2 stroke should now, the adjustment screw was probably a good 2/3 the way up. in fact the alignment marks on the pump housing couldn't of been within the < on a lean side when I got the sled. now it's on the lower bit being richer should make it last much longer I'd hope, It only went 30km today of trail riding so it used up little oil but hopefully it should get down to 35:1 ishhh. as to the factory's.... ?? super lean ratio.

The sled sure has a different feel than my apex haha...

 

[nosaj82]

Where is a guy to get a good crank. I lost my motor 14km up the Clemina trail on my first day of the trip. Pretty sure it's a crank issue but haven't torn it down yet. Fix kit installed at beginning of last season. Ran flawless all season. It's a 2011 Pro


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[Lund]

yes indeed it can be and just the right thing to do haha! and yes the more you know!.

I got the sled out today, It ran.... great! starts first pull. I turned up the oil injection adjustment screw to be flush with the lock nut, She smokes a bit at idle like a 2 stroke should now, the adjustment screw was probably a good 2/3 the way up. in fact the alignment marks on the pump housing couldn't of been within the < on a lean side when I got the sled. now it's on the lower bit being richer should make it last much longer I'd hope, It only went 30km today of trail riding so it used up little oil but hopefully it should get down to 35:1 ishhh. as to the factory's.... ?? super lean ratio.

The sled sure has a different feel than my apex haha...

Octanee, don't pamper the sled. That is a big mistake lots of guys do and what happen's is the piston rings don't seat properly into the cylinder's. This can cause many issues like blowby the rings like you experience and then crank failure. It will also cause the cylinders to glaze and then you will never get the full power potential out of the motor, the only way to fix that is to bore out the cylinder's. You don't want to do that.
What you need to do is get the piston rings to push hard into the cylinders so they can seat in. You can only do that by taking the cylinder pressure up, that can only happen at WOT for a stretch. Then let the rings relax and the heat dissipate, then doit again.
Do this about 10-15 times with no rest. WOT for a count of 5, rest for 30sec. WOT for count of 5, rest for 30sec.
It shouldn't take you more then 10min to fully break in a motor.
I recommend you do this near your truck should it blow up, if it blow up, we say that is a good thing. Why because it would of blown up anyways and the rebuild was not good. A good rebuild WILL NOT blow up.
I have done hundreds of rebuilds over the years, many for racing and that's how its done.
Good luck.

BTW, our hillclimber's and drag race sleds we start at a count of 5 at WOT but push the count higher every time. A good strong motor will take after a break in a solid 30sec WOT pull no problem. A weak rebuild might just grenade, better it grenade by the truck then deep in the back country.