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post #1 of 4 (permalink) Old 12-14-2017, 11:05 AM Thread Starter
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M8 Harmonica, Darn!

Well something was going to go. I'm not seeking a warrantee

My M8 has developed a pretty harsh harmonic vibration, ~3250 - 3800k.
- There is no knocking
- It is pretty darn smooth at 3k
- Down shifting it vibrates pretty much everywhere in the RPM range
- Pulling the clutch in not mobile the motor vibrates in the same 3250-3800k range

This was about the time I yanked the Power Commander out and started using a ThunderMax.
Pretty sure at this point I have eliminated, at least in my mind, this is not the source of the problem.

I have pulled counter balancers out of race bikes and at this particular moment that is what my best description. Someone extracted that organ out of my M8.

Unfortunately, the garage is a total mess to get this party started and won't be till mid January.

I have seen on the hdforums "New M8 Blown" and that I believe is what will happen if a continue to ignore the situation.

Couple of things.

Looking for thoughts as to what I might test before doing a deep dive into the problem. To be fair I haven't even dropped the oil plug .

Also, open to thoughts what parts to replace with what when the deep dive happens. Fuel Moto is like a candy store.

I have thoughts of just pulling this motor, putting it in a crate and shipping it to someone that is a professional and has garage space, unlike me at the moment. Suggestions there.


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post #2 of 4 (permalink) Old 12-14-2017, 11:19 AM
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The shafts have been shown to fail if over rev'ed. And there are reports of bearing cage failures.

How high was the rev limiter set, and do you hear anything?


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post #3 of 4 (permalink) Old 12-14-2017, 12:53 PM Thread Starter
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No noise (knocking), like a rod bearing gone.

My suspicion after looking at the internal details of the counter balancer is possibly the case bearing for it. My guess is the oil is going to look ok, I did pull the dip stick and it looked fantastic.

The shaft failures and what they were, I would like to know more about.

If the shaft can't handle the stress of a.... Turbo and can bend (the picture looks like it is pretty thin out to the weight to me) that would sure match up to the symptoms.

The rev limiter is stock, I certainly have hit it more than once.


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2017 RGU Turbocharged

Last edited by rdeeming; 12-14-2017 at 12:54 PM. Reason: my bad spelling
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post #4 of 4 (permalink) Old 12-14-2017, 03:00 PM
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Quote:
Originally Posted by rdeeming View Post
No noise (knocking), like a rod bearing gone.

My suspicion after looking at the internal details of the counter balancer is possibly the case bearing for it. My guess is the oil is going to look ok, I did pull the dip stick and it looked fantastic.

The shaft failures and what they were, I would like to know more about.

If the shaft can't handle the stress of a.... Turbo and can bend (the picture looks like it is pretty thin out to the weight to me) that would sure match up to the symptoms.

The rev limiter is stock, I certainly have hit it more than once.
The one I saw that failed, is said to have let loose on a run with the limiter set to 6800. And it looks like the mass caused it to bend. But hard to say for sure, as the big end of the rods kicked it out the side of the motor. As for the bearings, they seem to show up more or less at random. But there has to be a lot of wobble being contained by those bearings.

It's been a while since I read about it, but IIRC, they thought the case had failed.


I think the fix is to forget to put them back in.


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Last edited by Thermodyne; 12-14-2017 at 03:06 PM.
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