1976 cyclone 440 / Kioritz 22a - great idle, lousy high end

[Bigtonka]

This is the 2nd year I've owned this cyclone. Starts easy (electric), idles great. When I lift the sled off the ground, I can get it to about 50+ mph.

When riding it - it hesitates at 20mph - will creep past 20mph, and eventually get up to 30. It does not sound like its bogging - it just doesn't go.
Compression in both cylinders is 125psi. Spark looks strong on both.

As a test, I put 2 new plugs in (BR9ES) today - and took it for a 15 minute full throttle ride. Pulled the plugs and found this.

The left plug is the PTO side (clean, a little wet) , the right the mag side (dark, hot).

What does this indicate? It's a single carb - all factory jets and settings applied. No - I have not changed crankshaft seals - would that cause this?

[AirborneX4Special]

Reading plugs is difficult if not impossible. That said, Deere claims brown is proper. So the white or light tan is lean and the black one would be sooty or rich. If you have no point of reference for the crank seals you need to change them. Seals are way the Sam Hill cheaper than pistons and jugs and will eliminate that variable.

[Bigtonka]

The service manual shows changing the PTO seal without splitting the engine - is the fan side the same?

[AirborneX4Special]

I've not had that pleasure but plenty of members here have so I'll defer to them.
Was looking at the picture again and the visible portions of the cylinder tops and fins match the condition of each spark plug. I guess it could be spark related but only if the wires are failing because they clearly don't match. Crank seals are always an issue with a Kawasaki powered Deere versus a Kioritz but both require attention when the sled has been parked unused for even a couple years. Unmatched plug reads tend to be a dead giveaway for seal failure when all else seems normal.

[Bigtonka]

Do you believe it would be worth swapping coils to see if the behaviour follows the coil?

[Bigtonka]

Was looking at the picture again and the visible portions of the cylinder tops and fins match the condition of each spark plug. I guess it could be spark related but only if the wires are failing because they clearly don't match.

Please clarify - are you saying the left fins are clean like the left plug?

[AirborneX4Special]

If I understood the picture layout correctly, the plugs were sitting adjacent to their respective locations on the engine, so the cleaner plug was installed on the cleaner looking side and vice versa. Yes definitely swap out the coils and see if the behavior persists. If you believe or suspect that it sat several years mostly untouched I'd change those seals regardless. A compression issue would show radically differing plug reads but that's not in play since they're showing equal psi on both sides.

[Bigtonka]

UPDATE:

Please check out this video:
https://www.youtube.com/watch?v=uzUOkXB7wnI

In the video I start up the sled and goto about 1/2 throttle. I wedge my thumb in there so it doesn't move. I focus the camera on the speed. It hovers at 34mph. I don't move the throttle at all. After about 15 seconds it shoots up to 55mph. I haven't moved the throttle at all. It will stay up there too.

In another run, I squeeze the throttle to full. It quickly get up to 50mph. After 15 seconds it shoots up to 70+ mph.

CDI???

[AirborneX4Special]

Is your carb squeaky clean? Pickup fitting in the tank has a screen and check valve system and the pickup line is a big time candidate for issues.

Sled sure looks nice from the limited picture perspective.

[harleysportster]

All great points, it also looks like the right side cylinder is running rich, possibly the spark is dropping out. is the CDI box still the oem Prestolite? . They are know to fail and cross fire. Get an Inline spark tester and check each spark plug with it running. Something else to check is the high speed winding. You can ohm out the stator following these guidelines.
https://secureservercdn.net/166.62.107. ... _rev_a.pdf

[jep_800]

The answer on your crank seals is yes, you don't have to split the case. There's ways to pull the old one out using a drill and screws you can attach to it and pull it out. Same on both sides of the motor. To install, I've done it exactly as the Service Manual says using a solid block of wood with a large diameter hole drilled out so it fits over the crankshaft. Grease the inside well and the crank shaft (I use white lithium grease), then tap it in.... Take your time so it doesn't get cock eyed and it works good.

It may very well be the fuel system being dirty, or as Pat says, could be the ignition components. Hewtech (Scott Hewlet) makes great replacement CDI's, and they will re-wind your stator when you send him a core. Doing that and going with new coils generally has eliminated any electrical issues I've ever experienced.

[jep_800]

Here's one I tapped in, not splitting the case.