How to Measure 2 Stroke Engine WEAR! Is My ROTAX Still Good?? -Ski-Doo Super Olympique 370-
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- Опубліковано 5 вер 2024
- In this episode, we follow Matt as he continues his vintage 1968 Skidoo Super Olympique (Olympic) project. After tearing down the old opposed cylinder Rotax 370cc he now must measure the cylinders and pistons for wear. This video is a how-to on measuring a two stoke piston to cylinder clearance using two common methods and two sets of basic measuring tools. After some simple calculations a chart is made and we can determine if the engine is still within spec or if it needs a rebuild.
If you enjoy mechanics and working on old engines, this Rotax 368cc is a fun one. Made only in 1967, 1968 and 1969, skidoo offered these super 370 opposed engines in Olympique and Alpine models. They put out 18.5 hp at 5000 rpm. They have a single Tillotson carb mounted on the rear cylinder. This particular example, seems to have had a little water damage, but hopefully can be brought back to life. Stay tuned!
Music:
FCPX
It would be nice too put your videos in a series ok. Thanks for sharing this video.
Yeah I will once I finish the rebuild… Hopefully I’ll have it done by this season! Thanks for watching!
You can have the piston skirts knurled , then hand fit them for better clearance. We did that on unobtanium parts such as Norton motorcycle pistons!
Thats a really cool idea! I really appreciate hearing your insight and comments. Thanks for taking the time to write!
@@mattsws at one time I had a local piston ring co. make me a set of rings for an old 247 Rotax. I just had to adjust the end gap. Course they are now long out of business,but may be an option if you can still find someone doing it!.
Could'nt be more realatable ! i'm juuuust back from the garage pulling my elan twin motor out. my piston are scored but my cylinders looks fine ! good luck on your rebuild ! Hopefully, we'll be able to ride again before spring !
Keep me posted on the progress of your engine! I’m getting ready to start re-assembly soon. Hopefully gonna have this bad boy on the snow before it melts!!!
@@mattsws Back from my friend's garage, it was bottom end time. Turns out my crank is in pretty good condition !!! We've cleaned it, put new seals and closed it back !! My pistons and rings are done but HEY ! it's 120$ for both so no big deal ! Keeping the fingers and toes crossed to ride those beast soon ! Very nice videos by the way, you're one of my fav channel right now. Chill and interesting ! Cheers !
@@morrron5 Wow thanks! Glad you are enjoying my content!
Cool, you got another parts motor. You can use the outer schroud for the rewind holes that were bad. Back in highschool small engines class,I honed out my 335 Rotax jug for a 1st oversize piston.I didn't know exact specs for clearance though at the time. Releying on the teachers opinion as it being good enough. Seemed good to me I was just a 15 year kid. Turned out, the engine ran great until it got hot. Then pow! The Piston would seize in the cylinder and kill.😞 I didn't quite go far enough on my honing. My dad took it a machine shop to accually get rebored.The machinist said I was just about there but not quite. Very tricky, the tolerance, allowing for expansion. Live and learn, I was a student that learned a hard lesson, the hard way.
to me, it's better o try but fails then to just don't try ! you gotta learn at some point and some stuff has to be broken ahah !
@@morrron5 At the time, it was a tough to take it. But I eventually got over it.I had a 292 T'nT motor in that same Skidoo which was my favorite.But one day the connecting rod broke and sent it right through the crankcase, bang!! I ended up walking home that day. That motor was beyond repair.😞
Lol! Cool story!!! Because I am reusing the same parts, I’m not worried about the engine seizing, but you are right that you have to know what you are doing when you bore a cylinder for a new piston. I am glad I got that parts motor, because I have to admit, the recoil shroud had a little too much work to get it back to usable condition. I would have probably cheated and drilled new holes in the recoil to use the other set of shroud holes.
Well said!!!
Thanks Lars, ah so sorry I meant, Matt, a great video to watch though other than installing a piston in a Honda 50 step through motorcycle 50 years ago ( I was 16yo and I'm 66yo now), it worked, it's great to follow and learn a few things, I can't wait to see the next installment
Hahaha!!! Glad you enjoyed! Rock on! 🤘
Thanks for the series on the Super Olympique. I can't find the next video on this project. Can you tell me which one comes next?
I filmed and posted 4 vids last season on the 370 restoration. I have a fifth one already filmed from last year (but not edited or posted yet) and hopefully I will finish the series by February…. Glad you are enjoying so far and stay tuned for more!
@@mattsws thanks Matt. I’m anxious to see how things came out!
Im at caseville michigan
👍
Why not just measure piston clearance with feeler gauges?...if you know min/max clearance specs.
I know where your coming from...I bored many a cylinder in my 42 yrs. As a powersports service tech!
Then you have far more experience than me! I like the feeler gauge idea. I’ll be sure to give it a try and compare with my bore gauge measurements.
Hey bro i have a mint original 70 oly 335
Cool!
Those engines are not easy to find NOS pistons for- I was told they used the same pistons as the 163cc single used on the earlier years. I'd reuse those parts.
You are right about the 163cc singles. They share the same pistons and head gaskets, but parts for a 163 are just as hard to find! I’m comfortable reusing the parts I have, but wanted to take the whole engine apart, so I would damage it with a possible unknown problem….
I know nothing about these 370’s but if it has a 62mm pistons it seems like the head gasket and maybe base gasket from a 185cc 9.5hp would work. Parts available at Wateraxe for the 185’s.