How long will a crankshaft last?

[LoudHandle]

I've heard of guys checking their runout after blowing a belt to find out that it was either out of spec, or just barely in spec. Checking it again after a few rides it seems to have healed itself. Is that possible or should they buy a new dial indicator?

They can and sometimes do retrue themselves somewhat depending on the condition of your cases, the tolerance of the press fits and thermal cycling. It is stated that blowing belts can and does do bad things to the crank to make people aware. If you blow a belt and start having issues, excessive / abnormal belt wear, increased vibration, decreased performance, failure of drive clutch or crankshaft, etc. The first thing to look at; is the crank still true? I personally have not had a catistrophic belt failure since I was running triples but it can happen and something to be aware of.

Then depending on your level of give-a-sh!t, do you adjust your clutching / gearing to not destroy your belts or do you just swap engines instead of caring for your sled?

 

[Indy_500]

Fwiw I had an 07 IQ 600 HO between me and my buddy I sold it to it has completely destroyed 4 belts running 90+ mph 8000+ rpms has over 6k on the ticker. Yes it obviously isn't no good for the crank when you let one loose but the constant pinning and letting off over time will do much more harm than a little stinking belt breaking and the motor free spinning. Too many people are into the he said she said game. I do countless burnouts and drifting in my pick up with 130k miles on it between the rear end tranny and motor spinning at 5500 rpm it keeps on going anyone who says a belt blowing will damage your crank is just hogwash. Belt getting stuck behind clutch and damaging seal is a different story.

 

[Sheetmetalfab]

Fwiw I had an 07 IQ 600 HO between me and my buddy I sold it to it has completely destroyed 4 belts running 90+ mph 8000+ rpms has over 6k on the ticker. Yes it obviously isn't no good for the crank when you let one loose but the constant pinning and letting off over time will do much more harm than a little stinking belt breaking and the motor free spinning. Too many people are into the he said she said game. I do countless burnouts and drifting in my pick up with 130k miles on it between the rear end tranny and motor spinning at 5500 rpm it keeps on going anyone who says a belt blowing will damage your crank is just hogwash. Belt getting stuck behind clutch and damaging seal is a different story.

You're the man!
Dont let anybody tell YOU what to do.
Obviously you have many years of experience to back you up!
Wait............
For it..........

 

[mountaincat 800]

Pretty common problem on sleds (crank runout-phase issues) during rebuilds (if you look) no matter what brand. Way back when too.
Must be some reason this is more common on sleds lol.

Really good info from Indy Dan. Wish I didn't have to learn things the hard way all the time lol. Even before I got into this lightweight CFI motor.

On a side note, I've read complaints about vibration on the Pro. Mine is one of the smoothest 800's I have every owned. Lucky I guess lol.
I have less than a thou. on both ends (crank) and as best as I can tell with pistons installed a perfect phase.
I still have a degree wheel I used in the 70's to time CZ's and Bultaco's lol. Used to see one hanging over every mechanics bench when I was young. Along with a dial indicator, magnetic stand and plug hole adapters. Just daily "tune up" tools lol.
Some things never change eh.

Geo,
You seriously are one of the lucky ones. I guess you were due. With all the bad luck I have had with cranks the last three years I hope my luck changes sometime soon. Could you please explain to me your theory that slight detonation is taking out the connecting rod bearings? I would like to cover my bases when it's time get mine up and running again. Thanks.

 

[Indy_500]

You're the man!
Dont let anybody tell YOU what to do.
Obviously you have many years of experience to back you up!
Wait............
For it..........

Might as well remove my age as that's the first thing everyone wants to point out. I've been working on sleds quite awhile rebuilt over a dozen motors without a problem. Rebuilt over a dozen clutches as well. My buddies 800 etec has ripped 5 belts to shreds still keeps going with over 5k miles on it. If the crank/bearings can't hold up to a belt blowing the engineers are doing something wrong. My buddy sold his 03 x edge 700 (oh no not a ves big block crank!!!!!) With 8500 miles on it last year between him and the previous owner (another buddy) that thing has blown over 10 belts. Never fogged or summerized. All I'm saying is show me proof and I'll believe it...

 

[Cooksend]

Might as well remove my age as that's the first thing everyone wants to point out. I've been working on sleds quite awhile rebuilt over a dozen motors without a problem. Rebuilt over a dozen clutches as well. My buddies 800 etec has ripped 5 belts to shreds still keeps going with over 5k miles on it. If the crank/bearings can't hold up to a belt blowing the engineers are doing something wrong. My buddy sold his 03 x edge 700 (oh no not a ves big block crank!!!!!) With 8500 miles on it last year between him and the previous owner (another buddy) that thing has blown over 10 belts. Never fogged or summerized. All I'm saying is show me proof and I'll believe it...

Sorry Indy but I gotta swing with the old guys on this one. Take a motor that is designed to operate at a certain RPM while loaded. Instantly take away the load and throw an over rev at the motor and crank damage can certainly take place. I would believe that a perfectly balanced crank and clutch could be an exception. Certainly don't believe that I have a perfectly balance motor and clutch!
On another note what in the heck are your buddies doing blowing so many belts??? Maybe your clutch rebuilds are a bit off . In over 50,000 miles of riding I have not blown 10 belts! I have replaced more than 10 but not blown that many!

 

[Idcatman3]

Because it's never happened to you isn't proof that it doesn't happen to anyone. Read around, the cat 900 for example, is known to do this once the cranks get some miles on them. They weren't that tight stock.

We had some poor clutching on our 1500 the first couple rides after we got it together. Disintegrated a belt at WOT, and threw 2/3 of the crank ~40 degrees out of phase.
Thought I had some pictures of that around, but can't find them at the moment.

Good for you that you've never had it happen, but many of us have.

 

[rmscustom]

Aah, to be young and know everything... Not sure if I miss them days or am embarrassed by them now...

 

[Indy_500]

Sorry Indy but I gotta swing with the old guys on this one. Take a motor that is designed to operate at a certain RPM while loaded. Instantly take away the load and throw an over rev at the motor and crank damage can certainly take place. I would believe that a perfectly balanced crank and clutch could be an exception. Certainly don't believe that I have a perfectly balance motor and clutch!
On another note what in the heck are your buddies doing blowing so many belts??? Maybe your clutch rebuilds are a bit off . In over 50,000 miles of riding I have not blown 10 belts! I have replaced more than 10 but not blown that many!

I never touched the clutches on any these sleds. I certainly understand where everybody is coming from but what bugs me is how everybody treats sleds like they're the most fragile piece of junk.

 

[mountaincat 800]

I never touched the clutches on any these sleds. I certainly understand where everybody is coming from but what bugs me is how everybody treats sleds like they're the most fragile piece of junk.

HAha. This is snowest bud. Get used to it! Everything is a fragile piece of junk!
Especially people's ego's.

 

[Cooksend]

HAha. This is snowest bud. Get used to it! Everything is a fragile piece of junk!
Especially people's ego's.

Very well said. I am impressed!

 

[geo]

Geo,
You seriously are one of the lucky ones. I guess you were due. With all the bad luck I have had with cranks the last three years I hope my luck changes sometime soon. Could you please explain to me your theory that slight detonation is taking out the connecting rod bearings? I would like to cover my bases when it's time get mine up and running again. Thanks.

It's a long summer so I'll try to help lol. Have an issue typing on this forum now, so it will be real short form.

Slight deto can be caused by many little things. Most of it occurs during the short period of time the ex-valve opening and fuel don't quite correlate. Could be just one cylinder. Leaner mixtures allowed by port injection is a double edged sword lol. Don't let your valves open late is a good rule today.

Today's fuel. Not the best. Pick of head is huge. When fuel had octane # that wasn't modded with eth., you could run safely at 155 to 160 cranking. I don't go over 135 today. Get some of your power back with design and dimension of squish. Or, if you got the cash, buy real fuel.

Det is an explosion. Picture taking your head off and taking a tiny hammer and tapping on the piston. Picture the needle bearings and pins absorbing these tiny shocks. Eventually,,, small dents in the pins (brinneling) or little flats on the needles can occur
Once started, mechanical failure is going to happen.


Cranks are not all built the same. After rebuilding a few hundred lol, you can tell while disassembling if you will see a lot more.
One example from when I worked on instead of playing with toys; a Honda crank would take 4000 to 5000lbs to crack a pin lose and need 1000lbs to push out on a shop press; I could rebuild a Yamaha crank with a big shop vise.
Both brands were good. One was just tougher and more resistant to abuse.

 

[mountaincat 800]

Thanks Geo.
I understand what deto is. But the slight deto you talked about is confussing me. I believe that you also correlatted it with the TPS. How can I be sure I'm not slight detoing? (new word) I was running what I thought was good non ethanol fuel. Same fuel that ran in all my sleds. 88 oct.

 

[PaasoRacing]

Does anyone have any experience with the Hotrods complete cranks?

 

[kiliki]

Thanks Geo.
I understand what deto is. But the slight deto you talked about is confussing me. I believe that you also correlatted it with the TPS. How can I be sure I'm not slight detoing? (new word) I was running what I thought was good non ethanol fuel. Same fuel that ran in all my sleds. 88 oct.

all this talk of deto so i have a question. does this motor have a knock sensor?
does it work?
is it set to low for the Geo theory to apply?

 

[Leftys]

Does anyone have any experience with the Hotrods complete cranks?

I have used their cranks in many Dirt Bike Engines and have had great success with them. They only make a couple of complete Polaris Snowmobile cranks that I know of. Some 600cc and 700cc applications. Don't know of any 800 applications. However, they do make Con Rods and I have used them. They have worked well with no troubles.

 

[Leftys]

all this talk of deto so i have a question. does this motor have a knock sensor?
does it work?
is it set to low for the Geo theory to apply?

Yes the Engine has a knock sensor. It does work and in my opinion the parameters are set to retard the ignition to quickly. I have noticed on more than one 800 and more than one occasion that if you are hitting a lot of uneven draws on and off the throttle a lot or even under heavy load (deep wet snow) on the trail the ignition will retard. I believe it is due to the knock sensor. If you let off the throttle and get right back in it the ecm resets and you are back @ WOT. I do believe this is what is happening on many posts when you hear of people complaining of a bog.
FYI: Ski Doo had an issue like this when the 800R engine came out in 07'.

 

[rmscustom]

Yes the Engine has a knock sensor. It does work and in my opinion the parameters are set to retard the ignition to quickly. I have noticed on more than one 800 and more than one occasion that if you are hitting a lot of uneven draws on and off the throttle a lot or even under heavy load (deep wet snow) on the trail the ignition will retard. I believe it is due to the knock sensor. If you let off the throttle and get right back in it the ecm resets and you are back @ WOT. I do believe this is what is happening on many posts when you hear of people complaining of a bog.
FYI: Ski Doo had an issue like this when the 800R engine came out in 07'.

I have no idea if the knock sensor has control over what your describing but it sounds like you might be experiencing the "detune" that happens when the water temp is more than 129.

 

[PaasoRacing]

I have used their cranks in many Dirt Bike Engines and have had great success with them. They only make a couple of complete Polaris Snowmobile cranks that I know of. Some 600cc and 700cc applications. Don't know of any 800 applications. However, they do make Con Rods and I have used them. They have worked well with no troubles.

I haven't put my hands on one yet but Hot rods has a complete 800 crank listed in the 2014 Parts Unlimited catalog.

 

[Leftys]

I haven't put my hands on one yet but Hot rods has a complete 800 crank listed in the 2014 Parts Unlimited catalog.

That's a strange one. They don't even offer one on their direct website. Maybe something they and Parts Unlimited have hooked up. If it is legit, it should be a good product.