1 dead cylinder

[Summiteer]

Sorry.. i thought you said compression was good on both sides. As far as the reeds go I may need to educate myself on the 670 rotax.

Oh you Cat guys:d:d:d

 

[Deano670]

So did you fix the mystery or does it still stand???

 

[posnick]

the mystery will get fixed this coming week. After speaking to to machinist, he also agrees that the few scratches must be the cause for the lack of vacuum. I will let you all know how it turns out once its back together. And thabks to everyone for their suggestions!!!

 

[timbo]

while you got jugs off you should split bottom end.replace crank seals and check your rotary valve shaft drive gear. this gear is brass and it can strip.
timbo

 

[posnick]

The only problem with splitting the block is about $800 difference between just doing the top end

 

[Scotty]

scotty

Oh you Cat guys:d:d:d

"Throw me a Fricken Bone... I've been Fricken frozen for Thirty Fricken Yeeeeaars... Need the Info..." :d:d

Sorry... could'nt resist

 

[timbo]

why $800, seals $25, gear maybe $35.good time to do it. just my opinion.
timbo

 

[posnick]

ive never been into the bottom end before so i will have to pay to have it done.....whats all involved in splitting the block and resealing it?

 

[timbo]

remove clutch, flywheel, stator, motor plate,not that hard.have a manual to walk ya through it.

 

[posnick]

i downloaded a shop manual for it. it should say in there somewhere shouldnt it?

 

[Deano670]

Biggest piece of advice on this part of the job.... DONT lose the position of the rotary valve on the shaft,especially being a mod engine. If the valve isnt in stock form or has been advanced on the shaft it will be crucial to put it back exactly the way it came off.

 

[posnick]

shop manual says 6.8 hrs to do seals on cranckcase which means 10 hrs for me. its a 1997 manual. mine is a 98. same thing?
I am mechanically inclined so with some guidance......piece of cake? any special tools required? i have the basics like a pully puller, torque wrench etc.

 

[timbo]

have you got the jugs off yet. maybe i could have a look at it for ya.
you will need metric bolts for puller, metric socket for flywheel nut, clutch puller.give me a call goin out that way this aft.

 

[Modman]

shop manual says 6.8 hrs to do seals on cranckcase which means 10 hrs for me. its a 1997 manual. mine is a 98. same thing?
I am mechanically inclined so with some guidance......piece of cake? any special tools required? i have the basics like a pully puller, torque wrench etc.

670's are pretty close to the same thing with the exception of the X and the DPM/electrics, the internals were all the same (with the exception of the X and different head design and maybe slightly lower pin position on the pistons, can't remember exactly). The timing was different for the X but won't affect the internal structure of the motor. Rotary valve, pistons, crank, rods and case basically. Like Deano said, mark the Rotary Valve (RV) in at least two positions where it sits at TDC BEFORE you take it off. This is super critical on the 670's, take pictures after you mark it and before you take it off (or make a drawing). Don't think you can re-install by memory. If the crank run out is ok and you measure the play in the rod bearings using feeler gauges and both are within spec, there is no reason to do the bottom end right now. It is a good idea but if you can't afford it then that's OK, we all know what its like. If they are past spec though its pretty much a no brainer. $800 now or $800-1500 later for a set of matching cases or a new motor after your buddies tow you out of the bush.

Let us know what the problem was.

 

[timbo]

so how ya making out? take any pictures?

 

[posnick]

ok. found the culprit. its rd to create vacuum if the bottom end isnt sealed, right? well the seal btween the clutch and the block had popped right out. im in the middle of dissasembly but ran out of corona! have a look. and man is it dirty. needs a real good clean. i hope when i get inside the bearings are still ok

 

[99summitx]

Good troubleshooting, better now than 50k in the backcountry.

 

[Summitric]

Dam, we're good..... Had it pinned down to a lack of vacuum problem. Good job. Just do the rings and possibly pistons and get the crank seals done, and you're on the trail!!! are you getting bill to do the top end??