I just bought my daughter a 98 lt80. The man I bought it from said he hadn't had any problems with it until he put an 20mm carb on it. When I picked it up it started fine and ran ok but the bottem end was very sluggish he said he thought it could be taken out by just jetting it down. I took it out yesterday and it fouled a plug pretty fast and the new plugs I put in afterwards. The plugs were soaked in fuel so I went down to my local bike shop and it had a 58 pilot jet and a 102 main. I put a 52 in the pilot jet and took it back out today. Today it would run great for about ten to fifteen minutes and then it would stall out as if the plug had been fould . So I took out the plug and looked at it. The plug looked completely dry and chocolate brown. I put a new plug in and it ran great for another 10 to 15 minutes and then stalled out. I kept switching these two plugs out back and forth for a couple of hours. When the bike would die I would put the previous plug back in and it would run fine. Then packed it up and came home. Does anyone have any idea about what might be going on? The only other mod this bike has is an aftermarket DG pipe and silencer. I also checked the owners manual to make sure I was using the right plug type BPR7HS

 

The jetting is close. When I ran that carb we had 48/115 jets.
There could be a cpl problems here. By chance, was the spark plug cap on the plug correctly when the machine would quit?
Did you get the stock carb with the machine?

 

thanks for replying. I 'm sure that the spark plug wire was on correctly. The spark plug cap is aftermarket I think, it says NGK on the top. I did not get the original carb. I'm considering buying a stock carb and exhaust it's my daughters first bike and she's a new rider. I thought that maybe I should replace the coil. It seems as if as soon as the bike heats up it quits and with the time it takes to put the new plug in it's cool enough to run for a little longer. I just wanted to get an opinion or two since the coil is about $150.00. I suppose I shouldn't complian I bout the bike for $825.00. If theres any more ideas please let me know.

 

See if you can barrow a coil and CDI box form some one close to test your bike. Cash is the hard way to fix it if its not broke. Then you will know which part is faulty.

 

I agree! Borrow one if you can.
The NGK cap is the stock one and known for popping off at times. That's why I asked about that.