Generac 7.8 hp gn-220 motor mods

[V8 BUG]

Hi,

I have this motor powering my son's kart. Is there anything I can do to make it rev a bit higher. What is a safe limit. The motor seems very solid and was brand new when I purchased it. Here's a pic of one like it. I have a comet torque a verter on it as well with a 60 tooth gear and golf kart tires on the kart.

Thanks Kevin

 

[anderkart]

There doesnt seem to be much high performance info posted on the net about these engines, evidently Briggs has these built to their specs somewhere overseas. Supposedly its not a standard Briggs or Honda/clone design but I'd imagine it would still benefit from removing the govenor, building some sort of header, installing an open/race type air cleaner/re-jetting the carb and advancing the timing a few degrees like most all other (fairly simalar) small engines do.

After removing the govenor, (and any of the other mods I mentioned) I'm guessing your valves will most likely start to float somewhere between 4500 to 5500 rpm due to its relatively weak valve springs that were probably designed to operate at around a 3600rpm max. You'll both hear and feel this phenomenon when it happens... In my opinion, your safe operating rpm will most likely be anywhere right up to that point the valves just start to float.

 

[V8 BUG]

thanks, I have searched google and all and didn't find much either. The motor runs very well but rev. May be asking too much from it. It already has a "header" with matched flange. I didn't do any head work as it looked pretty smooth already. Below are a few pics of the kart we built. It has a late 70's vette body to cover all the tubes.

 

[mike75925]

nice looking kart, but where's the body? is it an '80s vette? and how much did the generac set you back?

 

[anderkart]

Wow, that thing looks really cool. Nice build

Have you taken any plug readings and re-jeted the carb a bit richer yet?

Those look like some pretty tall tires, I was wondering if your gears might be too tall keeping your engine from reving very high. Have you already figured your final drive ratio?

If not, what tooth count are your jack shaft and axle gears? Also whats the circumference of your rear tires.

Last thing, using seat belts in a kart without a roll bar is kinda dangerous

 

[freakboy]

oh u dont plan on usin that seatbelt without a roll cage do ya? i hope not

 

[V8 BUG]

Hi,

Below is a picture of the body and a fiew of the new front suspension and rack and pinion steering I built. I just put the bigger tires on this week. The kart is a work in progress. I have a 60 tooth gear on the back and a comet torque a verter on it. I am not sure what the stock gear on that unit is. The tires are 18.5" high and it'll do about 60kph currently. I am in the process of making a tube bender out of my Princess auto compact bender. After that I am building a 1" dia. roll cage that will bolt on to the frame over the body. The cage of coarse will connect directily to the frame. I have only let my son drive it a couple of times with the throtle stop and the remote kill. He is only 6 so I have a bit more time.
Oh ya the motor set me back 100 bucks at princess auto. Was 2/3's off.

 

[dpaxson]

thats a really nice looking kart you've got there. did you make that rack and pinion for the steering?

 

[mike75925]

cool, a stingray. you might want a grease zert or 2 in the rack body. is that a computer steering wheel? i like the 3/8 drive universal joint for a u-joint. is the upper frame copper pipe..., nope the others pics show a light rust. and it looks like the spindle's arms are only tacked.

 

[V8 BUG]

Yes I designed and built the rack myself. There are groves inside the rack body to hold grease and I should put a fitting in. The rust is from hitting a snow pile on the road that was full of salt. They salt the roads here in winter. The steering is just tacked because I wanted to see how it would work before I fully welded it.

 

[mike75925]

so what about the steering wheel? it is a nice piece, i think i can read momo on it, but is it a computer game wheel?

 

[ironman]

great lookin kart looks fine without the body on.

 

[V8 BUG]

Ya its a logitech force feedback unit. It was outdated and taking up space so I cut it up. I milled out the center fit a 1/8 plate to the inside and outside and welded an adapter to the outer plate. It works alright and my son gets a kick out of the extra buttons.(they don't do anything yet)

 

[mike75925]

nice, yet. you planning a three stage nos kit?

 

[Doc Sprocket]

Nice Kart! Do yourself a favour and at least install a roll hoop! As for the steering, I'd like more detail on the rack, please. I was messing around with something similar using a sprocket for the pinion gear, and a length of chain welded to flat bar for a rack. What did you do?

 

[V8 BUG]

The rack is made up of aluminum and crs. The rack and pinion gears were purchased from Reid Tool Supply. I am not sure how to post the .pdf drawings. PM me your e-mail and I would gladly give you the design I can dig up the pt#'s if you want from reid as well.

Kevin

 

[Jmanguitar]

Thats a nice set up. I have a generac 7.8 220 motor and a Comet torque a verter. Is your motors shaft tapered. If it is how did you go about setting up the torque a verter on yours.

 

[r_chez_08]

Hi Jmanguitar,
This is an old thread, and the member appears to be inactive. Start your own new thread and I am sure you will get more replies and help.
Rob