High Performance Engine Mods and Trouble - Question...

Mark Boesen Sun Jan 15, 2012 7:33 pm

Isn't a Venom crank is lightened? If so, that might be the issue?

**Cribbs74** Sun Jan 15, 2012 7:47 pm

There is only a few variables. Out of balance prop or prop hub, out of balance or bent crank or piston/ rod issues. Maybe, and this is a stretch,perhaps harmonics? Hope you get it sorted and with your experience level, you probably will. Let us know what the fix is.

Much like an out of balance car tire there is a certain RPM that the wheel smoothes out.

microflitedude Sun Jan 15, 2012 8:33 pm

cribbs74 wrote:There is only a few variables. Out of balance prop or prop hub, out of balance or bent crank or piston/ rod issues. Maybe, and this is a stretch,perhaps harmonics? Hope you get it sorted and with your experience level, you probably will. Let us know what the fix is.

Much like an out of balance car tire there is a certain RPM that the wheel smoothes out.

+1....

dckrsn Sun Jan 15, 2012 9:06 pm

cribbs74 wrote:There is only a few variables. Out of balance prop or prop hub, out of balance or bent crank or piston/ rod issues. Maybe, and this is a stretch,perhaps harmonics? Hope you get it sorted and with your experience level, you probably will. Let us know what the fix is.

Much like an out of balance car tire there is a certain RPM that the wheel smoothes out.

I agree 100% with Ron.

In addition, if the vibration occours during the transition from idle to open, I suggest swaping in a stock crank.

Lightened cranks are great for wide open performance but, I think these engines can use the weight during throttle up.

I wonder how a set-up like this would work with the even heavier car crank and case.

Bob

Mark Boesen Sun Jan 15, 2012 9:54 pm

Exactly, at high RPM's the counterweight on a crank becomes greater, that's why they're lightened to run smoother at high RPM. If that same engine is running at a much lower RPM it will not have enough counter weight to balance it out.

High Performance Engine Mods and Trouble - Question... Stk_vs10

High Performance Engine Mods and Trouble - Question... Stk_vs10

dckrsn Sun Jan 15, 2012 10:35 pm

Mud,

All this aside, that is one beautiful Black Widdow.

Bob

Mudhen Mon Jan 16, 2012 9:17 am

Mark Boesen Mon Jan 16, 2012 9:40 am

Hi Mud,

Congrats on your win! Thats some pretty impressive RPM's. It really did need safty wire, lol!

I wonder if a quick fix to the vibration problem would be a mini 'heavy hub', Cox used on the AT-6/SNJ, its a pretty good chunk of metal and might be enough to smooth things out.

fit90 Mon Jan 16, 2012 2:14 pm

You might be able to balance the prop to the crank a little closer. Take the cylinder and piton off and see how the prop banances while on the engine. I have never tried this before but I have thought about it many times (which is worthless).

Mudhen Tue Jan 24, 2012 9:15 am

**Cribbs74** Tue Jan 24, 2012 9:36 am

Glad you were able to get it sorted Mud, I knew you would. Appreciate the follow up with the fix action.

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High Performance Engine Mods and Trouble - Question...

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