11hp flatty, simple things?

Beal

Beal

Member
#1
#1
So I have a 11hp e-start Briggs flatty. Its going into a baja heat minibike. Obviously, the frame will be modified to accommodate for it...

But, seems I have some questions...

For the frame,
What thickness of steel plate will be got for the motor mount?

For the motor,
What are some simple modifications for it? I plan to make a new air intake and new exhaust. Will I need to rejet the carb?

Could I gear it a lil bit higher and still go up hills I could go up with the 6.5 and stock gearing?

Not doing anything with the governor, it stays put.

Thanks
Beal.
 
Neck

Neck

Growing up is optional
#2
#2
Start like this

make it look like this

Make one of these out of 1/8" plate

Weld it in like this

And finish it like this

It's easy!
 
Beal

Beal

Member
#3
#3
Cool, I remember seein that somewhere... Do you have a picture of the finished bike?

Im doin it a bit different though...

Here the top part of the frame cut out, motor is just sitting there.

Here it is how in the end, I would like it to be.
Gonna need to do something about that space between the seat and fake tank...
 
Neck

Neck

Growing up is optional
#4
#4
Yeah I did this mod a couple of years ago, had to make the cradle about two inches wider and an inch and a half lower to move the engine as far forward as possible. I have an 8 horse in it now, and I have an electric start ten horse that just barley squeezes in there. I dont know what happened to the finished pic, somehow it got deleted, so as soon as I take another one I'll post it.
 
Beal

Beal

Member
#5
#5
Did you change your gearing any? I wouldnt mind going a bit faster, but not if I cant tackle hills like with the stock gearing.

I didnt want to lower it any, Ive gotten hung up on some humps and logs on our property(thats what happens when you go off the beaten path) I was thinking if I could get away with gearing it higher, just get some larger tires, or both? In the future I would like to get a comet 40 tc for it... When I have the money for one anyways.

What can I do to the motor though? (other than exhaust and air intake)
 
Neck

Neck

Growing up is optional
#6
#6
I built the motor plate the way it's tilted so it clears the TAV II. The 30 series has overdriven capability, so the gearing was left stock. I don't know exactly how fast top speed is but it's around 40, and that's at the governed engine RPM of 3600. It wants to wheelie from a dead stop, even with my 240 lbs. A$$ on it.
 
Beal

Beal

Member
#7
#7
Nice, so 11hp with a tc could very well be a wheelie machine with the stock gearing?

Ive got a Comet TC, but not sure if its a 20 or 30, whats the difference?
It needs those nylon button things to work proper, hopefully getting those soon. Its gonna go on my other baja heat.

Do you think I could build this thing to keep up with a 350 yamaha quad?
Major power difference I know... but worth a try.
 
Last edited:
Neck

Neck

Growing up is optional
#8
#8
UUUUUH Probably not! (keep up) How many cubic inches is the 11 horse? I know the 10 horse is 22. I'm not sure, but I think the Comet 20 is a steel back plate version of the TAV II 30 series. Is your 20 a symmetrical or an asymmetrical belt?
 
Neck

Neck

Growing up is optional
#10
#10
I don't know how well that's going to hold up on the side of that 11 horse, the 30 is rated to 8HP and I could feel mine slip under hard acceleration, but then I found out I had put the belt on backwards! hope you don't plan on using that in a wet climate, they really slide when their wet or damp!
 
Beal

Beal

Member
#11
#11
That tc isnt for the 11hp, its for my other minibke, its keeping a 6.5 clone.

Next year, I plan to get a TC for the 11hp. And i was thinking some 20in tires too.
I dont see this 11hp build being ridable this year.

How would I got about rigging up a pull start for this motor?
 
Beal

Beal

Member
#13
#13
Here, I would have to take that screen out, is it just bolted on?
I necessarily need a recoil starter, just wrap and pull would be fine.

Oh wait, I can just remove the bolts holding the screen on... looks like I can wrap a rope around it there. didnt notice untill looking closer at the picture.

Whats the synchro balance?
 
Neck

Neck

Growing up is optional
#14
#14
OK then what you need to do is get the one way clutch/flywheel nut like most all Briggs engines use, and replace the nut holding the flywheel on now, that is, if the crank has that straight shaft extending out from the existing nut, I cant tell from the photo.
 
Neck

Neck

Growing up is optional
#15
#15
Oh and also, that's a pump, so the PTO shaft will be straight 1 inch shaft, threaded on the end, with no key way cut in it. So you will need to have a key way cut , and to hold the clutch on, drilled and taped 7/16" at some point.
 
Beal

Beal

Member
#16
#16
Pump? Not sure what you mean.

So I went to take those screws out, thinking "oh this will be simple" no. Going to have to take the shroud off. Doh... Later today I will take it off.
 
Neck

Neck

Growing up is optional
#18
#18
Oh yeah, Synchro balance means there are additional weights added to the crankshaft to keep it from jumping up and down!
 
You must log in or register to reply here.
Top