Hi, I recently bought a 1998 LT80 for my nephew, and a 2000 LT80 for myself. I've got both of them running, but they need some work. GPS says the 98 tops out at 20 MPH, the 00 tops out at 22 MPH, I weigh about 160 LBS. I was hoping the LT80s would be a little faster than this, my nephews clapped out KX65 is much faster than both of the LTs. Do those speeds sound right?

Compression on the 98 is at 105. I pulled the carb and cleaned it out, but it looked like it didn't need it. Installed some Boyesen reeds, and a 90 main jet. There was a NGK BP7HS plug in it, I swapped it for a BPR7HS. Planning on taking off the clutch cover tomorrow to see what's going on in there.

The compression on the 00 is at 180. Seems high. It's got a factory cylinder. Ran a bore scope down the plug hole, saw some carbon build up, but nothing crazy. Any clue what's going on there? Milled head? Over sized piston? It was running a NGK BPR6HS. Should it be running a hotter plug with raised compression? It's running a new Chinese carb, identical to the factory carb, idle screw and needle only can be adjusted. Ordered a new intake boot, the one on it is torn. I plan on running the Boyesen reeds on this one too. Do I want to drop the main jet to a 90 here as well? The exhaust pipe is rotten, its got a couple holes, and is in overall bad shape. I can get a used OEM for $150, or I can get a DG locally for $200. Should I just get the DG? Planning on pulling the clutch cover on this one as well.

Any help will be appreciated. Don't know much about these things, only what I've read lurking around on this site.
Thanks,
- J

 

Lol I just need help learning how to post sorry

 

Both should run faster. Clutch maint should cure that somewhat. I suspect hardened grease.
Yes, 180 is high. Something had to be done imo.
Your call on the pipe. The DG is loud.
Stock jetting is fine. Going to a 90 won't cure anything.
FYI: a lower number on a NGK is hotter.
Let us know what you find in the clutch's.

 

So I decided to give my nephew the 98, I'm keeping the 00. Started tearing apart the 00 to powder coat the frame and get it all cleaned up.

Meanwhile the 98 went from 20 MPH to 26 MPH after carb clean, new air filter, reeds, and 90 main jet. Took the clutch cover off, what a pain that was. There was dried grease everywhere. Took hours to clean. Put the front clutch assembly in the ultra sonic, got everything looking nice, put some lighter rollers in, with just a little bit of grease on all of them, 6 rollers 42 grams total. The bike is now slower getting up to speed, but still hits 26 MPH. Here's where things get weird. The bike starts running worse throughout the day, goes from 26 MPH down to 24. When I get it home, I check the compression and its now at 95. It was at 105 last week. I'm guessing this things on it's last leg and needs a rebuild? Checked the oil injection, and it works, the plug was a little lighter than I like, but I can't think of anything I could have done to hurt it. Any ideas?

Jack, are you still working on these engines? I gave you a call and left a message.

 

Sorry, I been way too busy.
Yes I do but am backed up for a month or 2.

 

Ok, went back in the clutches. Opened up the variator again, 2 rollers turned on their sides, I lubed them and reinstalled them correctly. Rear clutch shoes were binding a little, took the assembly apart, cleaned everything, lightly sanded the drum and pads, wire wheeled and greased the pins a little, reassembled. Bike runs much better now. Gets up to speed quickly, feels like it has a low gear now. Going to try to lighten the rear clutch tomorrow. Unfortunately it still tops out at 26 MPH.

Compression is 105 cold, 95 when warm. Tested 3 days in a row and got the same results. Never seen that before.

Jack, no problem. If I don't hear from you, I'll try again in a couple months. Thank you.

 

Glad it's better.