Big-Blockin' the G1
 

I would like to thank the members of this Forum, past and present, who provided the inspiration and information to make this project possible.

Project goal: to Big-Block a Yamaha G1 in the same manner as later 4-stroke models.

On G2 and up models, a ~20hp engine is transplanted to replace the stock ~8hp engine. On a G1 an engine transplant usually results in losing reverse gear, since reverse is accomplished by shutting the engine off and starting it with reverse rotation. Most engines will not run backwards unless designed to do so.
With some research I discovered that a Yamaha Bravo snowmobile engine is of the appropriate size for this project, and design-wise will accept the ignition system from the original G1 engine. This will retain reverse.
This is where I started:

A badly battered and beaten Bravo with a good engine.
A 1982 G1 gas with a blown engine and rough body (the stars & stripes one)
A 1982 G1 electric with a good body and a bunch of other good parts to replace worn ones on stars&stripes.

Re: Big-Blockin' the G1
 

And !!>>!!///...

Re: Big-Blockin' the G1
 

Step one:
Remove the engine from the Bravo, strip it down and clean it. Remove the body from stars&stripes and assess what it will need to do the conversion.
Get a Comet clutch off ebay.
Remove the ignition system from the old G1 engine and bolt it into the Bravo engine. Small amount of modificatin needed.
Fabricate a mounting plate for the engine for proper clutch alignment.
Lots of measuring, planning, thinking, and inspirational fluids were required at this stage.
More pix as the job progresses.
What do you think of the project so far?

Re: Big-Blockin' the G1
 

I think you got every thing you need to make this project work, that you have thought this out and planned well, that you are going to scream and pull your hair out along the way, and then you are going to have a very nice, very fast ride!

Re: Big-Blockin' the G1
 

Yup, you got that right. There has been a lot of head-scratching and liquid inspiration involved for sure. Several things had to be redesigned or redone, but it is coming along well. I was shooting for "more powerful" rather than "fast" as I will be using this as an off-road utility cart.

Re: Big-Blockin' the G1
 

That engine just normally will want to wind it out, you'll certainly have more power, but it will be in the upper range of the RPM curve.......

Re: Big-Blockin' the G1
 

Cool project, nice work so far...keep the pics coming!!

Re: Big-Blockin' the G1
 

neat idea a yammy sled motor in a yammy cart! going to be fast for sure! and the bravo is 25 hp so should be enough power

Re: Big-Blockin' the G1
 

What year Bravo engine will work as I see they were made a number of years??

Re: Big-Blockin' the G1
 

I don't know if there is any difference from year to year. I found the machine I used locally on Craigslist and got it cheap because it was so beat up. I don't know what year it was, but the ignition system from the buggy fits and works. That was my main concern. Any idea how to tell the year of a Bravo from the serial number?


More pix coming soon.