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Old 02-15-2015, 10:17 AM
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boxcar boxcar is offline
Motorized Bicycle Elite Member
Join Date: Dec 2014
Location: Astoria OR
Posts: 358
Default Re: Gravity or siphon gas line

Originally Posted by 2door View Post
Copper is not a resilient material.
I'm talking about rubber, silicone, foam, etc. All of those things people have tried to 'eliminate vibration'.

This has been posted here numerous times by me and others. You can not eliminate the vibrations produced by a single cylinder, 2 stroke engine. Trying to put rubber between the frame and engine only transfers the vibrations, and amplifies them, to the engine mounts and fasteners. Fastener failure is almost assured as well as in increase in the vibes felt in the bike and attached parts such as fuel tanks, fenders, handlebars, etc.

There is always the argument that motorcycles and cars use rubber mounts. That's like comparing apples to oranges. The mounting system is all together different. Simply sticking rubber between a Chines 2 stroke engine and the frame WILL NOT eliminate vibration.

Actually Tom , the copper tubing is to prevent the studs from being pulled out of the sheet metal tank.
The dampening system I refer'd to is at the motor mounts.
I use Gorilla tape as a dampener. Several layers. It does not have the compression issues soft rubber has, and can be tailor'd to the frame diameter.
I agree that slapping a layer of soft rubber between the mounts and the frame is a bad idea. To soft....
But a buffer is needed. And will reduce vibration.
As well as a well balanced engine / good quality fasteners and care when assembling the bike.

Also keep in mind that most motorcycles and cars do not rely on a single cylinder 2 stroke engine for power. Those that do either used the solid mounting concept or a resilient, sandwich, style of engine mount.
I have been in the motorcycle building business for 35 years.
While cars rely on multi cylinder engines as do larger bikes . The venerable single cylinder 2 stroke was the norm for not only nearly all dirt bikes but also most small road bikes for better than half of motorcycle history.
It only fell out of favor due to emissions.
All were rubber mounted .
All used the cradle mounting system , using lateral bolts ( at right angle to the motor).

I'm not fond of the sandwich description.
What you are describing is a " vulcanized motor mount" used in cars.
It's a way to bond the rubber to the mounting plate. This allows the mount to function without the need for a through bolt.
Motorcycles don't use that style mount.
They use a tube and bolt method where the rubber is in the tube with a steel sleeve through the center encasing the through bolt. More like a shock absorber mount.

The problem we are suffering from is caused by clamping the engines to the frame.
A necessary evil when one is trying to design an engine to fit so many different applications.
Transferring the vibration to the frame is a bad idea .
This will cause stress cracks . It's an engineering inevitability.

Finding the right material to use as a dampener is a far better idea.
Happy Trails......

Last edited by boxcar; 02-15-2015 at 10:51 AM.
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