Midwest Ride In

[400brian]

Katy and I traveled up to Elk Rviver, MN for the 2022 Midwest Ride In, and the celebration of 50 years of Deere snowmobiles.

For me the event had some parallels to our first trip to the Ride with the Champs back in 2007, where we met a whole bunch of people who up to that time we only knew from discussions held on the internet. On this trip we again met a group of people we were familiar with the names of, but had never met, this time mostly through Face Book. The Deere collectors were given our own section of the grounds, so we didn't have to go looking for each other too much.

On Saturday afternoon a situation developed in the parking lot that I found very interesting. I am not sure exactly how this situation began, but what happened is that the owner of a very freshly restored 76 440 Cyclone was having an issue with the sled while riding through the area. The sled was running well enough at low RPM, but at higher RPMs the engine seemed to loose power and sound a bit ratty. At some point several of the collectors I am familiar with got involved to try to diagnose the problem.

Apparently Dustin Elder had built the engine in the sled, Brock Weber had built the clutches, and Matt Gabler had had a hand in the restoration in some way. On this afternoon a whole lot of guys got involved in this clinic.

I was not involved at first, I was just an interested bystander, but I saw Jason Peterson bring out his wiring kit as there seemed to be a diagnosis that there was a grounding issue. So a ground strap was added between the CDI box and the fan tower, and I saw some other wiring going on. Tom Rehberg seemed to be the point man on this clinic. Tom and I had recently been messaging back and forth in the last couple of weeks, and I had just met him the day before.

[400brian]

After the wiring was complete the sled was tested and all involved were disappointed that there was no improvement. From what I heard, the sled was being driven around the grounds when it suddenly started acting up.

Next Tom checked the ohm values of the Hewtech rewound stator, which seemed to test good. Next they drove Kyle Cowell's 440 Cyclone over to act as parts sled. The Fireplug CDI was removed off that sled and installed into the sled that I later learned was owned by Karl Thorson.

[400brian]

After Kyle's CDI was wired in, the engine was fired up and ran through various RPM ranges with the track held up off the ground. At high RPM, the engine performance would degrade, almost as if the ignition was breaking down at speed. Listening to it, it didn't quite sound like it was running on one cylinder ( which sometimes can be hard to discern ).

The guys were getting frustrated at this point, the whole deal wasn't making sense. Ideas were being offered, but it just wasn't going anywhere. The problem seemed to be on the mag side. The plug was cold, and as colorless as new. I asked if the plug was firing laying on top of the engine, and was told it was. Questions were being asked about the plug boot and wires, but everything was new.

At some point, Tom leaned back and asked what I would do? I work on points ignition engines, and have struggled with CDI systems myself. I told Tom that the first thing I might do is drop a dial indicator down the plug holes and confirm the crank was still indexed correctly. As we didn't have those tools, the next thing I said was; I would like to put a timing light on it to observe the spark to see if there was any observable variation. It then occurred to me that I had an in-line spark tester in the tool kit in my sled. I went and got it, it was quickly put in place and the engine started. Tom shaded the tester with his hand while revving the engine, and quickly said; there is nothing wrong with the spark.

This was really getting interesting, it appeared that all the wrenching to this point was all for nothing. So what was it? The mag side plug was bone white and not particularly wet. There was no black goo running out of the exhaust anywhere to be seen. it was a head scratcher.

Then it was mentioned by someone that the exhaust springs were loose, and actually some wire had been twisted in place in an attempt to tighten things up. Tom suddenly got an idea. The engine was started, Tom grabbed the pipe and pulled it tight to the exhaust manifold, then reached up and revved it up. After he shut the engine off, Tom inquired if it sounded different? Guys on each side of the sled agreed that it had smoothed out!

The springs were then unhooked and the ball and socket inspected on the manifold and pipe.

[400brian]

We'd had supper at Cowboy Jack's on Thursday with Jesse Cypher, the guy that has a Cyclone set up for ice oval racing, and has had some success doing it. He had talked about the function of heat and the pressure wave in the exhaust in getting power out of the Cyclone. Here we were on Saturday finding ourselves dealing with those same principles.

The pipe has to seal well to the manifold for the pipe to work properly. If the pressure is allowed to bleed off, the wave doesn't push the fuel/air mix back into the cylinder properly. My understanding is the 76s were more prone to this issue, as the manifold and pipe junction angles were changed to a better functioning design in 77. I had already noticed that the ball on the manifold of the 76 Cyclone I have been working on is quite worn.

I hope this works out well for Karl, as the sled is too nice for it to not run well.

The photos used here were liberated from Karl's FB page.

[400brian]

Out in the parking lot on Saturday.

[ihengineer76]

It was great getting to talk with you, Brian, and a lot of fun working with the group on this sled. Everyone gathered any resources they had to help in the diagnosis and in the end, we found the root cause. This is my favorite part about these events. I need to make it up to RWTC to ride with you all. It always looks like a good time.