Engine Problems

[JimmySummit]

Hey Guys

Just got the engine rebuilt on my 95 Summit 670. When it was all apart, I flushed out the bottom end a couple of times, passed a magnet around to make sure no loose bits were around...bolted everything back together (top end was done by a local shop) now that it's all back together she turn over once or twice then it something seems to be getting jammed. When it was a part I could grab both connecting rods and rotate them without any issues, the pistons and rings are the right size.

Any ideas of what may be going on? I'm wondering if it may be a piece of something still in the bottom end or could I have a bottom end issue here even though everything seemed fine before it was put back together.

Thanks in advance for any replies...just want to get this sled out at least once before the season is over.

 

[Modman]

Hey Guys

Just got the engine rebuilt on my 95 Summit 670. When it was all apart, I flushed out the bottom end a couple of times, passed a magnet around to make sure no loose bits were around...bolted everything back together (top end was done by a local shop) now that it's all back together she turn over once or twice then it something seems to be getting jammed. When it was a part I could grab both connecting rods and rotate them without any issues, the pistons and rings are the right size.

Any ideas of what may be going on? I'm wondering if it may be a piece of something still in the bottom end or could I have a bottom end issue here even though everything seemed fine before it was put back together.

Thanks in advance for any replies...just want to get this sled out at least once before the season is over.

Are you sure its the motor? Could be something in the starter recoil....?

 

[maierch]

Hey Guys

Just got the engine rebuilt on my 95 Summit 670. When it was all apart, I flushed out the bottom end a couple of times, passed a magnet around to make sure no loose bits were around...bolted everything back together (top end was done by a local shop) now that it's all back together she turn over once or twice then it something seems to be getting jammed. When it was a part I could grab both connecting rods and rotate them without any issues, the pistons and rings are the right size.

Any ideas of what may be going on? I'm wondering if it may be a piece of something still in the bottom end or could I have a bottom end issue here even though everything seemed fine before it was put back together.

Thanks in advance for any replies...just want to get this sled out at least once before the season is over.

Did you check the rotary valve/ water pump drive to make sure no bits made it into there? Looking up the exhaust ports with a flashlight while turning over may shed a little light on where your problem is.

 

[papajake]

sounds like a ring problem just did a 700 rmk rings wrong size for the bore turned over ran for 20 miles

 

[Summitric]

Did you put the raves in the correct way.... The rave valve will contact the pistons/rings if not in the proper way..... Also did the engine get bored out, and if so did you check the rave valve clearance? Or does the piston have too much clearance and its binding on the ports?? I would check all the above mentioned stuff, before tearing it apart again...good thread, but bad situation, as i know ya want to go riding!

 

[JimmySummit]

Thanks for the replies guys...all of them were good ideas and I'll be making a mental note of those next time.

I dropped off the engine to a local racing team that has been dealing with Doos for the past 30+ years and he was actually rebuilding the exact same engine for one guy and a 670 HO for another. He took it apart that night and called me with the news.

He said that it appears to him when the engine blew, the crankshaft spun out of sync enough so that when the piston reaches the bottom position, its hitting the inside casing of the bottom end. The bad news is, those brand new pistons I put in are all chipped now from hitting it He said this wasn't the first time he seen this happen.

His guess of what happened is that when the original owner sunk the sled, he never cleaned it out properly (which is true because he put it away for the season right after that because it wouldn't start) then he probably took it out (which he did and said it never ran so good...best sign somethings gonna happen), the water turned to ice, seized it up good enough to throw things out of sync (very possible because when I took it apart there was still ice in the chaincase)

So there it is...the engine will be ready for pick up next Monday and done right....can't wait I never new an engine could cost so much to rebuild....stock