ATTN: ALL BTR Builders (Gravely Model L)

curtisfox · Mar 29, 2012

Question: rustycase brought to my atention that walk behind mowers have a seperate transmision like 5 speed shift on the fly and some of them are 20HP. How do you think that would work for a bike?
I have been looking around for a 2 speed of some sort for about 3HP maybe something like this would work?.....................Curt

wayne z · Mar 29, 2012

Hey Curt, Someone posted a pic couple days ago of a custom framed Green motorbike with riding mower transmisson and a briggs mounted with the flywheel facing foreward. I saved the pic to my office PC, I can posr it in the morning.

curtisfox · Mar 30, 2012

That would be great> Does it show what he used for a clutch...........Curt

wayne z · Mar 30, 2012

Here it is, it looks like the clutch is a belt and idler.

looks like it needs a physicaly larger motor in there.Imagine a Kohler or flat twin mounted that way.

butchl · Mar 30, 2012

That's the bike that first got me interested in these things.

curtisfox · Mar 30, 2012

You know his post? Sort of awesome................Curt

RicksRides · Mar 30, 2012

Thats a good looking machine ,But imagine a set of gravely's in that and a 4speed. I know Thats getting more into the motorcycle end of it needing tags and all. 60mph easy, Im going to do a 1913 HD twin tribute yup thats the one. Even bought a new tubing roller today. Ive been working on setting up everything in the garage.

wayne z · Mar 30, 2012

RicksRides said:
Thats a good looking machine ,But imagine a set of gravely's in that and a 4speed. I know Thats getting more into the motorcycle end of it needing tags and all. 60mph easy, Im going to do a 1913 HD twin tribute yup thats the one. Even bought a new tubing roller today. Ive been working on setting up everything in the garage.

That sounds awesome! I would hook the engines together with their firing order off like 270 deg apart, for that old syncopated v twin sound, you know, the built in miss sound that we love so much LOL

RicksRides · Mar 30, 2012

I used to build and dragrace Big kaws in the mid 90s, we do bikes at work and started with motorizing em couple years ago but Ive not built anything over 3hp in a long time. I was doing most of my building at work but have had to bring it home " complaints" was doing mine when shoulda been doing ours. So Im setting the garage back up. BIG Drill press w/tubing vice for fitting frames. Tubing bender and roller, English wheel, wire w/gas welder. 3 axis mill , Brake press sheer press combo, lathe, propane and oxygen torch set up. Then the normal erray of tools in a 4 stall garage. If I could do dragbike with all that should be able to build a couple old school look a likes. I hope :0 ..... Actually these are a little more indepth in some areas of the build

RicksRides · Mar 31, 2012

I need to order tubing monday and been trying to figure what size and gauge for this frame build I was thinkin 1 1/2 inch in a 14 ga. Any suggestions

curtisfox · Mar 31, 2012

I think 1 1/2" would look a little bulky 1 1/4 be better. Most motorcycle frams are 1"

wayne z · Mar 31, 2012

OK, I found out the difference in the 6.6 hp and 7.6 engines. This is from an old Gravely newsletter.
The newer head with the upright plug and small combustion chamber adds 1/2 horsepower. Dry air filter inatead of oil bath added 1/4 hp, and a larger venturi carb added 1/4 hp.

I bought a 7.6 head for mine off Ebay today, and I have a wisconsin v-4 updraft Zenith carby that bolts right up.

RicksRides · Mar 31, 2012

Id like to run a single mikuni smooth bore carb to dual engines, just not sure how well it would perform, have to make custom intake and connect engines together so they vibrated as a single unit anyone try this b4. any thoughts?

curtisfox · Mar 31, 2012

Should work good use the rubber cuplers between the engine. A lot of snowmobiles & motor cycles have them...............Curt

wayne z · Mar 31, 2012

RicksRides said:
Id like to run a single mikuni smooth bore carb to dual engines, just not sure how well it would perform, have to make custom intake and connect engines together so they vibrated as a single unit anyone try this b4. any thoughts?

So what configuration are you mounting the engines? With the cranks on the same line, or side by side with a chain connecting them. Either way, you could build a manifold similar to the old continental aircraft engines. They are designed to allow movement from vibration or thermal movement. They have a spyder like manifold with the carb attached, and elbows bolted to the cylinder intake ports with short sections of steel tubing in between, with sleeves of rubber hose and clamps covering the joints

wayne z · Mar 31, 2012

curtisfox said:
I think 1 1/2" would look a little bulky 1 1/4 be better. Most motorcycle frams are 1"

I would consider maybe a 1.125 single downtube under the engine an 1 inch for the rest. Or dual 1" downtubes.

charliechaindrive. · Mar 31, 2012

These are neat little engines, are any for sale rick?

RicksRides · Mar 31, 2012

Wayne, I was thinkin a single downtube to right above where it starts the curve under the engines,then y it into two to the same spot in the rear and then back to single tube.I believe 14 gauge should be enough. Ill use a headtube off an ol motorcycle as well as the triple trees and fabricate a sprung set of forks. Ill set the engines one in front of the other and use the same chain line, using a single starter. Ill mount a alum. plate on both sides of the engines making it look like a twin cylinder. I love your idea of the timing of being 270* off of each other.

RicksRides · Mar 31, 2012

charlie Ill be sorting and catologuing them this week, once I know what all ive got I will be selling some of them. they will be complete with all the accessories needed to make it run. They will need to be rebuilt, Ive not decided on price yet, I will by mid week. Will offer them to guys on this site b4 I sell any on Ebay

RicksRides · Mar 31, 2012

Wayne: I have to find the site again , but a company online is advertising a few after market parts for them. SS valves, copper head gasket,modern electronic mag( what ever the he** that is) and reground cams. It wont add much for power, but should add some RPM's

ATTN: ALL BTR Builders (Gravely Model L)

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