Written By Gavin Dowse. Photos By Gavin Dowse.
Dan is the kind of guy that would give you the shirt off of his back and the last dollar he had. He’s a big genuine guy that loves helping people and pizza. Nothing like pulling down his driveway to see a black shirt and blue jeans come out of the garage with the warmest of welcome. Also there is a immediate fear of getting mauled by his dog but that is besides the point. Next to his house among a slew of small motor projects is Dan’s garage. Dan has a wonderful little shop setup in what was a garage that a he trailer ed home on the back of a flatbed. Yeah, they picked up his future shop and moved it down the street early one morning. From what Dan has told me is he started in the small motor and ATV repair a long while ago and has been doing it ever since. Today was a bit different than most days for us though.
We started today off by me asking whether or not I could use his 20 ton shop press to get a cooked universal joint out of my front drive shaft. For everyone that wouldn’t know why this happened is because my Tahoe is falling apart… Regardless Dan gladly agreed to help a kid out. 30 minutes and two engineering students later we managed to get the old one pressed out and bend a yoke ear. Dan then decided that he was going to ripped the third free jet ski’s apart. Yes you read that right, he has gotten three free jet ski’s. Two of which actually run, drive and are currently insured. SO for him giving me so much of his time I was not only eager to help but equally excited in hopes of seeing a motor getting torn down too.
Fast forward past the jet ski shuffle where Dan and I moved two of the three onto a trailer and got the third onto a dolly he built and into the garage. Now Dan has an absolute perfect setup space wise because all of the space is used super well.
Unlike I all of Dans tools are in a shop space and not in the back of my Tahoe which is nice because finding everything is super easy. But onto the tear down of the ski do.
This ski do in particular is a Rotax powered two stroke that for the displacement make super solid power numbers. Now what makes this different from a traditional 4 stroke is that this motor has a spinning half moon disk. This when spinning properly controls the opening and closing of the air in/exhaust out. The disk substitutes as a valve train system. When I got back from an errand Dan already had the intake and exhaust system unhooked and ready for the motor to get yanked. Unfortunately I smashed my finger on a motor mount but the motor came out relatively easy. The only snag was my finger and this cockroach from hell.
Once the motor was all out and on the bench the dis assembly to assess the damage was on its way. The reason it was free was that the previous owner said that the motor was OK and for sure needed a new starter. So for the low price of free Dan took the opportunity to try and revive the old girl.
The first thing we ripped off the motor was the starter to really see in what condition it was it. Turned out to be COMPLETELY seized. So we moved on to find that the motor did turn over and had compression which was a very uplifting feeling. Feeling optimistic he decided to continue on the front of the motors tear down.
We got the fly wheel off along with the front case and alternator. All of which came off super easy because the bolts are stainless steel. Stainless is a none rusting metal which allowed for a fast tear down. Unfortunately the thing we found most apparent was the massive amount of sand in the engines coolant passages. Which was not a good sign. Once the front of the motor was completely stripped off the block we started on the head to assess the possible internal damages. And what we found wasn’t good….
What we found was not a good sign. It had already appeared that the motor had been out of the jetski previously. All of the hoses and electrical lines were labeled neatly as one would do if you had already removed it. We got the head cover off along with the Rotax disk valve thing off to find that one of the pistons had an ABSURD amount of play. It came down to the fact the needle bearings surrounding the crank from the piston were absent. There easily was a 3/8ths inch play up and down…. We decided that it was still early enough to split the cylinder walls off, removed the exhaust manifold and the bottom of the case.
What we found was unpleasant. It appear to have four corner seized which is when cold the engine is revved up far too fast. This causes the piston to expand far faster than the cylinder walls causing everything to rub together. Even worst than that was finding the left cylinders main cause of crank failure… A fairly large coolant passage way was absolutely packed with sand. As you can see in this pictures below the nice brownish color rod is exactly how it should look. While the more bare metal one shows massive signs of overheating.
After a long pondering of the interwebs me and dan pulled the crank assembly out and assest what the best course of action would be. That being either fix the whole motor, drop a newerish one in or just part it out. Now I’m not positive to what his plan was but this small motor stuff is interesting as can be. Especially since getting this one working is north of $500. Regardless this was some of the most fun wrench in a long while because I also smash bolts or something goes horribly wrong. I hope someone reads this through and if you make it this far CHEERS!