Predator engine on Doodlebug shakes real bad

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ebrammer252

New Member
#1
#1
I installed a brand new Predator 212 on my Doodlebug with an OldMiniBikes adjustable mounting plate. New 12T clutch from OldMiniBikes as well, not a Maxtorque, just a basic one. Also replaced steering neck bearings and wheel bearings,

Just puttering around at low speed is fine, but as soon as you give it 1/3 throttle or more it vibrates like hell, like vision goes blurry vibration, until the clutch fully locks or it hits a certain rpm/speed as far as I can tell. I've double checked my chain tension, I've checked all of my motor mounting bolts, I've made sure my chain is aligned, just put new tires on. I don't know if this is just how it should be or something is just way out of balance?

Very familiar to this post - https://oldminibikes.com/forum/index.php?threads/predator-engine-shakes-bad.55626/

Anyone have any input on things to look for/check?
 
ole4

ole4

#2
#2
First disconnect chain and clutch from the engine so you can determine if they are the cause of the vibration or if it is the engine/frame combination. If the govenor is still installed you can gradually increase the rpm and see if you can get the vibration at a certain RPM. If your vision is going blurry then it seems like the seat is vibrating which seems to be extreme. Usually you will hit a speed that causes the handlebars to vibrate due to hitting their resonant frequency and adding lead to the ends of the bars can fix or at least change the rpm it happens at. If the whole frame is shaking either engine came way out of balance or your frame mounting plate or some other location may be cracked or the mounting plate has some cracked welds. Let us know the results of removing clutch and drive chain. Also look for areas that seem to be vibrating.
 
E

ebrammer252

New Member
#4
#4
ole4 said:
First disconnect chain and clutch from the engine so you can determine if they are the cause of the vibration or if it is the engine/frame combination. If the govenor is still installed you can gradually increase the rpm and see if you can get the vibration at a certain RPM. If your vision is going blurry then it seems like the seat is vibrating which seems to be extreme. Usually you will hit a speed that causes the handlebars to vibrate due to hitting their resonant frequency and adding lead to the ends of the bars can fix or at least change the rpm it happens at. If the whole frame is shaking either engine came way out of balance or your frame mounting plate or some other location may be cracked or the mounting plate has some cracked welds. Let us know the results of removing clutch and drive chain. Also look for areas that seem to be vibrating.
Click to expand...

I will check/test in a little and report back.

In the meantime, some further reading I see some people stating that if you're heavier (I'm 220lbs) you need a higher RPM engaging clutch/clutch spring as that can be causing some vibration issues as well?

Also, should have mentioned as it might be related that I'm tossing the chain off frequently too, I see that can be a symptom of excess vibration.
 
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Mr. Pink

Mr. Pink

Well-Known Member
#6
#6
It could be an issue with SOME Predator 212's.
My Harbor Freight wood chipper with the 212 vibrates like crazy at 1/3 throttle.
But of course you would never use it at that setting.
The blades on the chipper are about 14" in diameter. So maybe it's some sort of harmonic thing and has nothing to do with the engine?
Luckily, I do not have that issue on my Doodlebug, also with a brand new 212.
 
Minimichael

Minimichael

Well-Known Member
#7
#7
toomanytoys said:
I had a little motovox that would shake so bad my eyes felt like they were swimming. It was such a weird feeling!

oddly though I’ve had predators what were smooth as glass. I’ve had them that vibrates like crazy. Seems like it’s luck of the draw to me.
Click to expand...
Wow, so it's likely the predator? This is a theme this week on the site..
 
Minimichael

Minimichael

Well-Known Member
#8
#8
Mr. Pink said:
It could be an issue with SOME Predator 212's.
My Harbor Freight wood chipper with the 212 vibrates like crazy at 1/3 throttle.
But of course you would never use it at that setting.
The blades on the chipper are about 14" in diameter. So maybe it's some sort of harmonic thing and has nothing to do with the engine?
Luckily, I do not have that issue on my Doodlebug, also with a brand new 212.
Click to expand...
And it wouldn't be a clutch issue in Mr. Pink's case...
 
E

ebrammer252

New Member
#9
#9
ole4 said:
First disconnect chain and clutch from the engine so you can determine if they are the cause of the vibration or if it is the engine/frame combination. If the govenor is still installed you can gradually increase the rpm and see if you can get the vibration at a certain RPM. If your vision is going blurry then it seems like the seat is vibrating which seems to be extreme. Usually you will hit a speed that causes the handlebars to vibrate due to hitting their resonant frequency and adding lead to the ends of the bars can fix or at least change the rpm it happens at. If the whole frame is shaking either engine came way out of balance or your frame mounting plate or some other location may be cracked or the mounting plate has some cracked welds. Let us know the results of removing clutch and drive chain. Also look for areas that seem to be vibrating.
Click to expand...
Clutch off, chain off, sitting on the bike 1/4-1/2 throttle vibrates the bejesus out of you still. All welds on the frame and motor plate look good.
 
E

ebrammer252

New Member
#11
#11
River Rat Ron said:
Take it back to HF and swap it out.
Bad casting on the crank, bad crank bearing, un balanced fly wheel ?
Click to expand...
Just called my local HF and they said I can do as long as I get all the gas out of it.

While I have your ear though, another Q. I took my clutch apart and cleaned/oiled it and noticed it looks like only the leading edge of the shoes are engaging?
 

Attachments

SAS289

SAS289

Well-Known Member
#16
#16
ebrammer252 said:
Just called my local HF and they said I can do as long as I get all the gas out of it.

While I have your ear though, another Q. I took my clutch apart and cleaned/oiled it and noticed it looks like only the leading edge of the shoes are engaging?
Click to expand...
In the first picture wear does look somewhat questionable. But the second picture is better because it shows the slip area on the shoes which should be there. These clutches slip until fully engaged. What you don't want is what looks like the slip area but all the way across the shoes.
 
DaddyJohn

DaddyJohn

Well-Known Member
#17
#17
toomanytoys said:
I had a little motovox that would shake so bad my eyes felt like they were swimming. It was such a weird feeling!

oddly though I’ve had predators what were smooth as glass. I’ve had them that vibrates like crazy. Seems like it’s luck of the draw to me.
Click to expand...
Same experiences here. Every now and then, you get a paint shaker. :confused:
 
Minimichael

Minimichael

Well-Known Member
#18
#18
Interesting. Just chiming in here...

I'm trying to imagine what the culprit might be. An unbalanced crank like I think RRR said, or the piston pinned backward, or is it more of a nuanced combination of stars not aligning? Conflicting compression harmonics? Now I'm just making shit up, sorry.
 
toomanytoys

toomanytoys

Well-Known Member
#19
#19
Minimichael said:
Interesting. Just chiming in here...

I'm trying to imagine what the culprit might be. An unbalanced crank like I think RRR said, or the piston pinned backward, or is it more of a nuanced combination of stars not aligning? Conflicting compression harmonics? Now I'm just making shit up, sorry.
Click to expand...
it could be a multitude of things. I’d probably lean towards a poorly balanced flywheel. I never tried changing one out to see if it fixed the problem. I just exchanged them.
 
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