Why no talk about hopping up the stock engines

[rokcrlr]

I have a 91 G8 and instead of changing engines I would like to do a few mods to the stock engine. Why isn't there any talk on here about this? Is it that these engines can't take any or lack of sharing knowledge is a No-No? I was thinking of taking the head off and milling a few thou off to raise compression a little and clean up the ports. get a better exhaust and since my aircleaner is gone ,put on a K&N style air cleaner. Are there any cams out there that will work with these? Or has anyone sent theirs off to be reground?
Come on guys ,lets have some ideas flying around here, these engines can't be that weak not to take a few extra HP without ging a differant engine route.Afterall Yamaha does make some good bike engines .

[DustyWolfe]

well i agree there seems to be a total lack of info on upgrades to the stock engine(and the upgrades they have i.e.:torque kit have only to do with the clutch). but i have done a few things to mine that made some definite improvements. first of all the stock jet is far too lean. thats why they have major troubles if the airbox isnt sealed. but before you rejet id change the exhaust to something a little larger and more free flowing. my stock exhaust was something like 9/16 id. a good place to look is stock atv exhaust. i put my old stock muffler for my mojave 250 on there and noticed a major difference without a significant increase in noise(after the rejet) . also i would look into getting a pod filter. the airbox and exhaust were a very restrictive package. im willing to bet just changing those 2, and rejetting will give you 35% more power. and you can ALMOST never go wrong with more compression although i cannot really comment as i havent messed with any of that yet.timing advance keys are available although you can make your own(if you do "shave a key" every .06 is 1 degree of advance)

[Dave in VA]

http://www.plowmanscarts.com/highper.html

I'm thinking about getting their hot set-up and high performance pipe.

[rokcrlr]

When we built Flathead briggs we don't even use a key in the flywheel. We lap it to the crank and she holds just fine, well past the 7000 rpm mark.. But I don't think it would be a good idea to twist one of these that hard.
I have a mojave exhaust, I even think it is a hi-po one to boot.

[DustyWolfe]

yea i have a white brothers e-series tunable exhaust for my mojave but i think id like to keep that for the quad.(plus its SUPER loud like helmet required loud)

[cart de golf]

I hop up my G22 engine with the help of plowman's for a fraction of the cost

sure i dont have the torque of a briggs but the cart goes 35 mph


good for my needs at the campground + the sound levels are low

keeps the campers happy


merry chrismas

[DOOmsman]

You want to hammer fast
or hammer once?
nothing beats big.

[Dave in VA]

Originally Posted by cart de golf

I hop up my G22 engine with the help of plowman's for a fraction of the cost

sure i dont have the torque of a briggs but the cart goes 35 mph


good for my needs at the campground + the sound levels are low

keeps the campers happy


merry chrismas

Do you have a Plowmans exhaust? If so, which one?

[sho305]

Start searching and you will find info about it, just what you said in your first post. The issue is the cam, you have to have one made and that is expensive. You can't port that much on most stock heads without welding them/etc.

The problem is your cost to return for doing it, I mean when you can buy a 16hp (15hp) clone for 250 and a 50 adapter and have it run just like stock with near double the HP.....well why would you mess with the stock engine? Even a V-twin if you unload 1500 on one you will have way more power than same amount into the stock engine, and they have an oil pump plus much more displacement/etc. So its not really worth it.

Sure (doing it mostly yourself) you could cut the head, port a little, stick a muffler and carb from a MC/ATV on there and get some more but even 35% more power you have a whole 12hp or whatever, its hardly worth it unless you like to screw around with it, which is fine because that route you will not have much coin into it anyway its all fun. I would not recommend doing more than that, but do work on the clutches that can really help they must work properly to get the power to the ground....even 9hp. That helped mine and I never changed the spring. But I did a clone last summer and I can tell you in the spring, the welder will get fired up and a clone will be going into my cart for sure. (see the 'clone specs' thread I made about it here in yamaha gas)

Note that the G9 with the ignitor does advance the timing quite a bit, but if you look at the AGK gokart site you can find how to cut your own timing key if you need to.