I noticed another thread with a similar issue while searching for an answer to my problem, but I was afraid of hijacking, so I started a new thread.


I built LT80 for my sons, I did a few mods while it was apart (Boyeson reeds & ported reed cage, .030" head cut, 190 gram rear shoes, 4 rollers in front clutch, widened exhaust sleeve to match jug casting about .060", raised to match sleeve to port about .015") When I first put it together it had no power and a real weird knocking under low speed high load/high throttle which I thought for sure was piston noise. I took the head off, and it was fine, no head contact or excessive piston movement noticeable. Then I took the front clutch off and went from 4 to 6 rollers. When I put it back together, it ran great with no noise! For about 20 minutes. Now the noise and lack of power is back, and I've had the clutch apart 3 times with no change. I did notice that the front clutch had side to side play while at rest. Also, the rubber on the movable plate that retains the rollers allows a little bit of "rattle". It has bout 1/8" side to side and about 1/8" or so of rotational play at the outer face of the clutch. I suspect this is the noise.

Compression is somewhere in the 140's cold. I didn't write it down and my memory is crap. It took several cranks to get there. I'm used to 4 stroke car engines being done it 3-4 cranks. It took about 10 or so if I remember correctly.

I'm starting to look like a chump in front of my boys! I usually can get things fixed in short order, but this one is about to drive me up the wall.

Does anyone have any suggestions to try?

Thanks
Lynn

 

Arrow toward exhaust right???

 

Yes sir. Arrow is towards exhaust. Weirdest thing. I suspect the clutch, but who knows. It was there, I removed the clutch added 2 rollers for a total of six, ran great for a little bit. Now its back again, but fooling with the clutch doesn't change anything.

 

I'd double check the front clutch installation. It sounds like the roller plate notch may have gotten off the key (this happens).You can turn the key around for a good edge.
FYI: when you remove the clutch, the rollers will flip. No way to tell that aspect.
Check the splines on the crankshaft and fixxed face.

 

Thats one thing I was really worried about is the key going into the clutch. The one that came on the bike didn't engage well into the clutch, so I ordered a new one, and it is just as bad. It is engaged as good as I can get it. I think the rotational free play is due to the looseness of the 3 rubber isolators in the roller plate. What I am not sure of is how loose it should be.

I have another running LT80 here that I may start swapping parts from until I get it figured out.

Thanks
Lynn

 

Hey .. Just curios .. Did you rebuild with one of them$50 ebay kits or suzuki parts? I used the ebay kit and mine does same exact thing

 

I used one of the $50 kits. I also rebuild the crank using a bronco connecting rod kit so I had the whole shebang apart. Weirdest thing is, I took the head off to inspect for head to piston contact, and nothing looked bad. So, while it was in the shop I took the clutch apart and fooled with it. Immediately after that tear down it ran great for a little bit. I haven't fooled with it for a couple weeks. I need a break to cool my head. I am probably going to work on it tonight.

Lynn

 

The noise wound up being the head gasket leaking. The gasket that came with the rebuild kit was a thin stainless gasket. I cleaned up the aluminum gasket that was on the bike when I bought it, and it seems to be sealing up now.

Now the dang thing is ringing from the top end. I just can't catch a break on this one.

 

Just an update on the problems I was having. Every single problem had to do with the head. I initially had a head gasket leak. Once I fixed that, it started ringing in the top end. Turns out the milled head was getting hit by the piston. I don't know if it had been milled before I bought the bike or not. I do know after taking .030" off of it, there was no longer a margin on the inside of that chamber.

I replaced the head with an untouched stock head and it is running good now. We went to a local riding area, and my son rode it for three hours straight with no issues!

Thanks for your help and suggestions.

Lynn

 

It must have been shaved before.
I'm 100% positive that .030 off will not hit the head.