Has anyone here had any experience with lt 80 mods [clutch, pipe, etc ]

 

has anyone had experience with LT-80 performance mods?

 

I bought a junked LT 80 a few years ago for my son and had to rebuild it - siezed piston and many other worn parts. As I rebuilt it I figured I'd modify it at the same time. I bored it out 2nd oversize and put a Wisco piston in it . I also ported it myself - I don't have too much experience with that so I compared it to the porting job I had done on my LT500 and tried to match it taking into account the size difference. The only thing I didn't dare do was to raise the top of the exhaust port as high as on the LT500 so I went about half way between stock and where the 500 was. Mostly I just opened up and smoothed the ports. I also raised the compression to 14:1 (Total volume to compression volume) so I have to run 100LL avgas - much cheaper than racing fuel and almost as good. I put a CT pipe on it and found that it didn't even half the performance of the stock pipe until I modified the clutch. The LT80 has a centrifugal clutch that engaged way too soon for the pipe so I experimented on the old clutch by cutting about half of the material off of the weights so the clutch doesn't engage until about twice the original rpm - I don't know what that rpm was or is only that it is a lot higher now. The shifting part of the transmission is like a snowmobiles' clutch but it never disengages at low rpm. It has six rolling weights in it and with a lot of experimenting, I finally got down to tthree weights that were lightened by drilling ou the center holes in the weights to (if I can remember correctly) 5/16 of an inch. This allowed the engine to rev much higher into the power band that the pipe is designed to run at, before starting to shift the gear ratio. The way the clutch was originally set up, the transmission started shifting even before the clutch engaged! After these mods were done the engine ran so much better that it starved for fuel through the float valve in the carburator so I had to drill it out a little. This made the float valve leak a little and would flood the engine when it wasn't running so I put an inline valve in the gas line to prevent that from happening. I have since replaced the float needle and corrected the problem. Thae way the engine is running I think it could use a larger carb on it but when I tried a 20mm carb aff of an old Honda 4 stroke, the engine wouldn't run right so I went back to the stock carb. I set the LT80 up to run in the sand dunes and climb the steepest hills, which comprimises its high speed performance on the flat. I clocked it at 39 mph on flat after modification. I understand that when properly geared and clutched, the LT80s will hit 60 mph but I didn't want that. After modifcation, my 70 pound son could climb higher up the sand dunes than a 160 pound adult on a stock blaster. This was with paddle tires on both machines and no high speed run at the bottom of the hill which would favor the Blaster. I don't know how many readers are familiar wi the St Anthony sand dunes in Idaho, but my son has ridden the LT80 over the face of Thunder mountain from the ridge in the middle - about 200 feet high and I have a picture of him going up Devil's Dune, also at about the 200ft mark. I'm sure that other LT80's have also been highly modified but I've never seen one that even came closed to ours. I weigh over 200 pounds and I once rode it out through the small dunes ( 50 to 75 foot high) for 6 or 8 miles while my son rode the Blaster and I got a lot of finger pointing and laughter from other riders who couldn' believe it. I looked like a circus clown on one of those miniature cars. Now my son is older and wants a 250R, Banshee, or LT500, but he still has fun on his LT80

 

Looks like 6ppc pretty much got the right idea by chance and some good thought.

On the LT80, Trinity Racing in Anaheim, CA makes a 105cc kit that includes a 20mm carb that fits, a reworked cylinder and head as well as some substantial transmission and clutch mods. 6ppc was correct on lowering the amount of roller weight but reducing the number of rollers from 6 to 3 is a bad idea for the long term. I have the replacement rollers in various weights to that the load is properly placed on all 6 rollers. On the rear pulley in the trans, I am working on a conversion that will change the manner in which the transmission changes the gearing ratio. Constant rpm is the goal.

Let me know if you have any other questions.

 

raptor720: sounds like you have done a lil homework, but still need a lil help. I'd be glad to give ya some help. Chances are that i can show ya what to do w/your tranny mods [img]i/expressions/face-icon-small-smile.gif[/img] as far as the 105 kit,,mine was clocked at 53 mph,,i think i'll stay around 50mm [img]i/expressions/face-icon-small-smile.gif[/img]
good luck on your LT adventures
Jack

 

Actually, I only build the LT80's for friends who did not buy the Kasea. After going through most of the new mini's, I believe that the Kasea is the best of all. In sand trim, we have the Kasea doing 60+mph. For tight MX tracks, we setup for acceleration. There are many many more parts available, including water cooled cases for the Kasea motor.