1975 Johnson

T-Bone · Post by **T-Bone** » Thu Mar 05, 2009 11:23 pm

Absolutely any information is greatly appreciated. It's a 1975 Johnson Rotary Powered 45. Pretty good shape for sitting behind a shed for 22 years. Needs a wash and a little bit of a paint job but is complete and the engine is free. I'm probably going to pick it up regardless but I'm having a hell of a time finding anything on line about this particular sled which kind of scares a relative newbie like myself.

Thanks,

T-Bone

JDT · Post by **JDT** » Fri Mar 06, 2009 1:03 am

Pick it up.
If you don;t want it I will come out to the river and get it from you.
Does it have reverse and E-start?

T-Bone · Post by **T-Bone** » Tue Mar 17, 2009 8:23 pm

Finally got the Johnson and Trailer it was sitting on home.

I'm ready to start looking at it while I finish up the 300. They are both due for a ground up resto once the weather warms a bit more. The Johnson is complete, minus the windshield and the engine is loose, wierd little spark plug on that bugger. Oh well another one to "figure" out. If you know anything in particular about these old Rotary Powered 45's I'd be interested. Have a feeling this one will be more of a

then the rest of them.

Later,

T-Bone

JDT · Post by **JDT** » Tue Mar 17, 2009 8:45 pm

I really hate to think that you will be racking your brain on this one so I will be happy to releave your the burdon.

Rotary engines use a very short reach sparkplug.

T-Bone · Post by **T-Bone** » Wed Mar 18, 2009 8:24 am

JDT,

I think I'll keep it around for awhile at least. I'll let you know when I get sick of beating my head against the thing. Some of the info I've read said you can use any good quality 2-stroke oil in the machine but the previous owner says the only oil to use is the rotary combustion oil??!!? I would hate to blow it up before I get it delivered to you so what's the scoop? Where should I start on this thing. I'd like to get it running before I start to tear it apart for refinish. Making it look nice should be pretty easy, getting it to run might be another story.

T-Bone out!!

JDT · Post by **JDT** » Wed Mar 18, 2009 8:59 pm

Finding RCO oil would be a trick these days.

Just use your favorite 2-cycle oil at 50-1 and you will be fine.

The regular regiment of things to do, fix or replace would apply to this engine and sled just like any other machine.

Special things to look at would be the track, idlers, drivers and boggies as Johnsons have sometimes problems with rubber/plastic parts. But if this one was never sat out in a tree grove you may be OK.

Carb and fuel pump need to be super clean. Leave your compression gauge on the bench as it will tell you little about a rotary.

S_Kyle · Post by **S_Kyle** » Wed Mar 18, 2009 9:18 pm

a guy I ride with is on his third set of drivers in his quite flight. They seem to be quite fragile in there old age.

JDT · Post by **JDT** » Wed Mar 18, 2009 9:22 pm

I have no idea who made OMC's drivers but if you look at them cross eyed they shatter.

S_Kyle · Post by **S_Kyle** » Wed Mar 18, 2009 9:32 pm

I have never had a snow cruiser driver break just the eventide's and Johnson's. Must have be done on purpose to improve the name sake sleds.

JDT · Post by **JDT** » Wed Mar 18, 2009 9:36 pm

Sorry Scott, I was referring to the later OMC models.
I have never worked on a SC.
But who know's, T-bones sled has 45 HP so maybe it will smoke them from sheer HP.

EricR · Post by **EricR** » Wed Mar 18, 2009 11:00 pm

There is a guy that posts on www.vintagesnowmobile.com and www.sledshack.com who goes by LOUDMOUTH JOHNSON, his name is Chris Dostal from Cedar Rapids, IA and he is a good source on knowlege on these sleds- he has a rotary he got as a garage find with low low miles on it sitting for years, he had someone tell him he needed to run Amzoil or such in it and he commented "I ain't puttin forty buck a gallon oil in my hundred buck rotary"

He has put over 1000 miles on it in the last two seasons- it has some quirks and they NEED elecrtic start- fuel thirsty as well.

I have a 1973 copy of Popular Mechanic's snowmobile guide with a rode report on the rotary, if you really want one I may be able to make a photo copy of it and mail it to ya.

What ever you do, leave that wierd surface gap or whatever it is plug in there, he says they live forever, it was a special plug made for them by Champion, if you screw another plug in it'll wipe out the rotor or something.

Here are a couple of posts from other places dealing with the OMC rotary-

http://www.vintagesnowmobile.com/cgi-bin/yabb2/YaBB.pl?num=1228409659

http://www.vintagesnowmobile.com/cgi-bin/yabb2/YaBB.pl?num=1234838702

S_Kyle · Post by **S_Kyle** » Wed Mar 18, 2009 11:19 pm

It seems that all 71 and up OMC's had bad drivers. The only guy I know that has wrecked a set of pre 71 drivers was on an evinrude. It would be nice to have rotary someday but I have a few projects to finish before I try to find one.

JDT · Post by **JDT** » Thu Mar 19, 2009 10:29 pm

The OEM spark plugs are like gold. I saw a pair on ebay go for $48 last winter.

There is a similar Champion plug that works and is cheap. The current app is chainsaws.
Bosch makes one also but I do not have the number handy.

The Rotary Engines have a following as the prices are always high. A running Rc-18 brought $600 last winter on ebay.

As for the electric start Eric mentioned it is nice. Many OMC's had the option. Most Cats did not.
The 303's seam like they start in either two piulls or thirty with no inbetween.

T-bone's machine is a mule as it has the ability to pull a load that no other sled can do. Low-end torgue is huge!

S_Kyle · Post by **S_Kyle** » Thu Mar 19, 2009 11:14 pm

Will the rotary's out pull the old opposed wide tracks? I wonder which will pull more, although I don't think I would abuse the rotary's the same way I would the opposed's. I was under the assumption that the OMC's normally came with the 505's.

JDT · Post by **JDT** » Thu Mar 19, 2009 11:31 pm

When I was refering to 303's I was talking about the Wankels.
OMC rotary was 528cc and had twice the HP of the 303 used by Cat, Polaris, Scorpion, Skiroule, Allouette and others.

Rotaries as a rule have a straighter torque curve than twins. I do not have raw numbers but I would exspect the torque to be higher and at lower RPM than the oppsoed twin.