A week ago, our LT quite. No compression. I've rebuilt it 3 times in 2 years and its bored 80 over. Looking into what to do next I discovered the bigbore piston is roughly 30 thousandths larger than where we are now. The sleeve would then have roughly 108 thousandths, wall thickness. And from what I've seen this is still thicker than most 400+ cc quads when they are bored. Does anyone have any info on if this can be done? Right now I'm going to put a new piston and rings in it (80 over), along with some shadetree porting and see what happens. I don't see where I have much to lose since a new jug is in my near future anyways. Any one have any thoughts on this?
Thanks !!

 

You can indeed put the big bore piston in the stock cylinder sleeve.
Yes it's thin [img]i/expressions/face-icon-small-happy.gif[/img]

You figured out what the sleeve company's don't want you to know [img]i/expressions/face-icon-small-smile.gif[/img]

FYI: The 2004 cylinders have a very slight difference. It is this difference that may make the 2004 cylinders unable to go to 105.

 

Jack,

Any advise on clutch mods for a ported motor? I've got the exhaust port and transfer ports raised about 2mm-3mm, also widen them about 3mm and have everything blended together better. The exhaust port - runner, has also been opened up quite a bit. I think thats where I'll stop, other than honing the cyclinder a little to help clean it up some. I am still very interested in getting you to do our motor later, I just didn't figure on having to redo it this soon, and with it bored as big as it is, I igured I really had nothing to loose by trying some porting myself. Any thoughts? (Other than how stupid I am for trying this, my wife takes care of all those! lol!!)

THANKS!!!!

 

It sounds like your doing as well as can be expected. It takes alot more machinery and work to go any farther than you have.
Give it a whirl [img]i/expressions/face-icon-small-smile.gif[/img]
Have you shaved the head? You may need to shave it .030. (raising the exhaust port decreases compression, shaving the head corrects it.)

 

I had the top of the sleeve shaved .025 a couple of bores ago. A local guy could chuck the sleeve and jug up in his lathe and shaved it for me. He stoped at 25 for some reason (really don't know why) and I told him that was fine. (can;t beat free work) I was thinking of taking the head gasket out and trying it. What do ya think on that? Maybe to much, not enough or just right? I think part of our problem this last rebuild is our gas. I've been using our farm gas which is 92 octane, but I'm afraid we've been getting rust or something in with the gas. (from the tank) I'm going to put a good fuel filter on this time and I thought I'd try running some race gas in it to see what , if any, it would do. Right now I'm just trying to get this going until winter. Hopefully by then I can get you to build it for me. (the right way) Do you think I should do anymore clutch mods? I've drilled the front rollers, but thats it. I should have it back together tomorrow night (hopefully)

THANKS!!

 

One more question. What do you think of switching the front clutch bushing for one of the older, longer ones? Would this give some more low end? Does it hurt the top end? I assumed it held the pully halfs farther apart, thus letting the belt ride lower in the front clutch, which soulds like it would lower the over all gearing giving it alittle more take off power. Is this true and would it even be worth it? Our front clutch just barely touches the key in the crank. Is this a common problem? Is there anything I could do to help make the contact area alittle more? Is it supposed to be this way, I mean it does work, just looks like its about to come off the key and spin free.

I thought about PM'ing you these questions, but I thought that there might be someone else out there trying some of the same things I am and looking for more information.

 

OK [img]i/expressions/face-icon-small-smile.gif[/img]
You can shave off .010 to .020 off the starter gear. This will give you a lil more keyway strength.
Yes going to the old style longer front clutch bushing is recommended. (this is part of my kit)
.025 off the cylinder is good. (I take .032)...So the head shopuld be good as is. Check compression, if low (130 or less) try removing the head gasket. I recommend using solder and checking the piston/head clearance before trying to start motor.
Gas:: If rust was an issue, I'd think the jets would be getting clogged often. Still use a good filter. [img]i/expressions/face-icon-small-smile.gif[/img] Old gas can be an issue depending on the actuall compression.
Compression dictates octane. I feel that (compression versus octane) 100-130= 89/92 octane 130-150=92 octane 150-175=100/105 octane 175-200+=110+ octane.
You may need a rear clutch spring.
You deffinitly need to lighten the rear clutch shoe weight. Go to 170 grams each (exact) to start. We'll go from there.
[img]i/expressions/face-icon-small-happy.gif[/img]

 

Lt 80 please tell me how to get ahold of you for the mods pleeeeease. You really know your stuff

 

I had thought about changing the rear spring. (in the rear clutch) Should I replace the stock one with another stock one? I am planing on lightening the shoes.
Right now my biggest problem is getting parts. It is SOOOOO frustrating trying to get parts for this thing!! I'm waiting on a cyclinder base gasket right now. I'm suppose to have it first thing in the morning. (we'll see!!)

 

Lets leave the stock spring in till we see how it reacts to the motor. [img]i/expressions/face-icon-small-smile.gif[/img]