Morini M1 Sprocket Stuck - Shimmed Incorrectly?

mike sweet /

Jan 19, 2019 11:02PM

Just picked up a Sebring, in pieces, with a Morini M1 engine, rebuilt by the previous owner, but not installed.

I noticed the output gear (dunno what its called in Morini terms) #80 was absolutely impossible to spin by hand. Thought hmm that cant be right. I popped off the clutch cover, and removed the clutch and bell. I was able to turn the countershaft? #52 and output shaft #80 but veryyyy difficult.

Decided to mount and run the engine and see what the deal was. Runs fine but sounds like an engine that needs bearings. Takes very high RPM to get the output gear spinning. Obviously not right.

Today I opened the engine back up. As soon as I loosened the case half bolts from the magneto side, the output gear was no longer stuck, and spun well. So what's the deal? I have no experience with these engines and I've seen some mention of shimming. Is it possible the case halves were simply torqued too tight?

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

Don Ohio /

don45640

Jan 19, 2019 11:25PM

Sounds like a bunch of shims are out of place. It's so easy to forget their position and which ones go where if a person isn't super careful.

The manual should have a step by step listing of assembly/disassembly for you.

Don't start it up and wear on it until you have it right. Make sure all parts are lubed with 20 or 30W non-detergent oil and it is filled to the correct level.

Those are very dependable,tough engines. I just hope it hasn't been hurt too bad.

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

Don Ohio /

don45640

Jan 19, 2019 11:46PM

Here's an M1 manual for it.

https://martysgarage.info/manuals/moriniservice.pdf

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

mike sweet /

deweysmopeds

Jan 20, 2019 12:22AM

Yeah I have it open on my bench right now. Ill get it the rest of the way apart and see if I can't find something out of place. Thanks.

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

mike sweet /

deweysmopeds

Jan 20, 2019 05:58PM

Took the whole thing apart and attempted to assemble according to the diagram. The result: still stuck.

Then I decided to install only one shaft at a time, to see which was too wide for the cases, and causing the binding. Item #71 in the exploded view is the culprit. any shims on the tapered end that slide into the bearing cause binding. No shim and it spins freely. Going to run it without the shim unless someone can give me a reason not to. I don't see any issue with the gear riding on the bearing's inner race.

It's a mystery why it wont fit with the shim. The only thing I could think was the bearing wasn't set properly, but I reset it and same result.

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

mike sweet /

deweysmopeds

Jan 20, 2019 06:19PM

^or alternatively the center gasket is a hair too thin/ bearings are a hair too thick

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

Don Ohio /

don45640

Jan 20, 2019 09:47PM

How thick IS that shim. Morini used lots of sizes. Better to find a thinner shim if it contacts a rotating suface.

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

mike sweet /

deweysmopeds

Jan 21, 2019 12:27AM

Like I said, I assembled each shaft within the cases. Only one shaft at a time then closed and bolted the cases. I tried every shim combination and even the thinnest .3mm was too much and would bind up when the cases were tightened.

Its riding on the inner race of the bearing, so they're both rotating. Can't envision it being a big issue.

Though this engine will definitely need to come apart again. Not loving the way it sounds when it's running.

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

Don Ohio /

don45640

Jan 21, 2019 12:39AM

Is it fitting well in the bearing? Not sloppy? Noise when running is usually loose main bearing noise.

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

alex . /

Go to branch

alextetreault

Jan 21, 2019 02:32AM

i had this problem with my m1. never got it spinning right despite several install cycles. ran it with no shim on output shaft. 2k miles later it's still good. i hit 9k on it regularly

shrugface

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

mike sweet /

deweysmopeds

Jan 22, 2019 12:12AM

> alex . Wrote:

> -------------------------------------------------------

> i had this problem with my m1. never got it spinning right despite

> several install cycles. ran it with no shim on output shaft. 2k

> miles later it's still good. i hit 9k on it regularly

>

> shrugface

Interesting. Glad to know someone else has had the exact issue.

Really thinking the reproduction case half gasket must be a hair too thin, therefore the cases fit too tightly together.

Re: Morini M1 Sprocket Stuck - Shimmed Incorrectly?

mike sweet /

deweysmopeds

Jan 22, 2019 12:13AM

> mike sweet Wrote:

> -------------------------------------------------------

> Like I said, I assembled each shaft within the cases. Only one shaft at

> a time then closed and bolted the cases. I tried every shim combination

> and even the thinnest .3mm was too much and would bind up when the cases

> were tightened.

>

> Its riding on the inner race of the bearing, so they're both rotating.

> Can't envision it being a big issue.

>

> Though this engine will definitely need to come apart again. Not loving

> the way it sounds when it's running.

Main bearings, like crank bearings?

MOPED ARMY

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