M7 Crank,magneto,cylinders Questions

[calgarysledguy]

Ok ill try and make this short.The crank went out on my m7. I'm pretty sure its cracked.Ill probably have it out tomorrow for further inspection.I got my rotor/flywheel off.Sled has 4000 on odometer.
Questions

1: is there anything i need to mark to make sure my timing goes back to where it was??? It doesn't look like anything adjust under there like my old Polaris did.

2:Should i have this crank fixed or buy a rebuild? I have seen the prices at Recreation Supply and cvtech.Anywhere in Calgary?Or is that the best price I'm going to find.

3: Can i just go to Auto value and use a cylinder hone and give them a Lite hone befor this all goes back together.I will be putting in new pistons and rings

Thanks Darrell.

 

[prairiepulling]

I would go for the rebuilt one, less downtime etc and it should have some kind of a guarentee. As far as honing your cylinders, if they don't look bad I wouldn't go near them with a hone due to the nicasil. Depending on how many miles you have on your sled, might not be a bad idea to throw a set of rings to it while you have it apart. John @ JAB Motorsports might be able to steer you in the right direction for a crank or may have one for you.

 

[calgarysledguy]

I would go for the rebuilt one, less downtime etc and it should have some kind of a guarentee. As far as honing your cylinders, if they don't look bad I wouldn't go near them with a hone due to the nicasil. Depending on how many miles you have on your sled, might not be a bad idea to throw a set of rings to it while you have it apart. John @ JAB Motorsports might be able to steer you in the right direction for a crank or may have one for you.

Thanks for the reply.I will be putting in new pistons and rings.It has 4000 on odometer.

 

[MrHankey]

4000 miles or km ? mine has 3500km and thinking of doing pistons rings

 

[calgarysledguy]

4000 miles or km ? mine has 3500km and thinking of doing pistons rings

Pull your power valves and y pipe and take a look at them. If they look ok then you should be fine.

I'm not really sure what the gauge was set on.I only use the gauge for RPM and dummy lights.I really never payed attention. Just remember seeing 4000, probably miles I'm guessing. The pistons looked ok other then a few marks they got from whatever let go in the bottom end. I did not get the crank out today. Bolt supply house wasn't open today and couldn't get my primary off without a 9/16 fine thread bolt from them to hydraulic pop it off with water trick.

 

[calgarysledguy]

Ok i got the motor apart.

Here is a picture of the crank.PTO bearing is seized.Not sure if that bearing seizing caused the crank to crack. Or maybe the Crank was cracked there causing that bearing to go out. I do recall a hammer being used to get a clutch off last year.(1 tap) But probably 1000 miles since then....Knowing that using a 9/16 fine thread bolt with Teflon tap and water will take a clutch off. I will never use a puller or hammer again.Live and learn.(the expensive way)

Question.

Do i need to get the cases line bored or something like that if i buy a brand new crank.Or can i just put one into it?

 

[smokindave]

Holy cow Darrell,now thats BROKEN!!!

 

[calgarysledguy]

Do i need to get the cases line bored or something like that if i buy a brand new crank.Or can i just put one into it?

 

[slomo]

no you do not have to get it line bored,as both of the case halves are still being used and they were bored together

 

[TROLLCAT]

where the bearings make contact inside the cases the sufaces are not rip up you be ok , the bearing closest to the clutch is the one to check ,inside of the cases should be smooth

 

[calgarysledguy]

where the bearings make contact inside the cases the sufaces are not rip up you be ok , the bearing closest to the clutch is the one to check ,inside of the cases should be smooth

The surfaces are smooth where the bearings contact. The next one over has has a little edge that you can feel with your nail.But its smooth.Sorry hard to get a good picture close up.

 

[TROLLCAT]

Line bore it , rebuilt crank , pistons , dont cut corners on a rebuild you will be why happer in the long run

 

[slomo]

Line bore it , rebuilt crank , pistons , dont cut corners on a rebuild you will be why happer in the long run

and were are you going to find the bearings that have a larger o/d to fit
they are a roller bearing that do not spin as they are pinned in the case halves,the case halves are line bored when assembled after that,you cannot
rebore it,as he is still using the same halves

 

[calgarysledguy]

and were are you going to find the bearings that have a larger o/d to fit
they are a roller bearing that do not spin as they are pinned in the case halves,the case halves are line bored when assembled after that,you cannot
rebore it,as he is still using the same halves

Ya that is the part i couldnt figure out.If they went bigger how would the bearings fit??Shims around the bearing?

I talk to a guy that replates cylinders he told me when i put it back together use loctite on the outside of the bearings and i should be ok.Any other thoughts?

 

[TROLLCAT]

where the cases join together they mill a few thou off then bolt cases together the bore is now smaller bore that to orignal size drop in rebiult crank shaft rock & roll I have this done in prince george alot you need there phone number pm me

 

[calgarysledguy]

where the cases join together they mill a few thou off then bolt cases together the bore is now smaller bore that to orignal size drop in rebiult crank shaft rock & roll I have this done in prince george alot you need there phone number pm me

I thought about this to. but the water pump goes over both case halfs. So wouldnt that cause any problems??

 

[TROLLCAT]

I tryed green bearing retainer locktite about four hours operating time later the crank broke the cases looked about the same as yours , when took it back apart there was no sign of green locktite anywhere the bearings on the crank must be sqeezed in the cases or catastrafic failure will be your new best friend.

 

[TROLLCAT]

good point , monday I will talk to the machinest about clearances I still think you will be ok the distance between the pump shaft and crank should not change that much , its the piston to the head clearances , they dont take very much off to make it look like new. and you get a little more compression

 

[calgarysledguy]

See how the water pump goes over both halfs of the cases.If they take some off the cases it wont line up properly. Then i would be worried about the gear on the crank lineing up with the oil/water pump gear as well.This would make the crank sit deeper in oil/water pump gear.Not sure if that amount would matter.........

 

[TROLLCAT]

I see the senerio most of of the case work I have had done has been on polaris 800 big bearing bahbah, I going ask monday about M series cases,they got to be doable