Hello everyone ! I have a 1991 Trail Boss 250 that starts and runs fine until you run it for a while and shut it off then, sometimes it will not have spark ? I've cleaned all the connections I could find, replaced the plug many times, new battery and bypassed the throttle override. B.T.W. I have to hold the throttle open when warm to start ? What main jet should be in for 1500' summer use ? Thanks for any help ! Chuck S. [img]i/expressions/face-icon-small-confused.gif[/img]

 

did u try checking it with a spark indicator checker? It is easier to see the spark & u can leave the plug
in the motor too. check your coil mount for good ground, check plug wire & cap, check engine stop switch,
ignition switch, & all the wires to & from them, cdi box wires, stator wires, your e.t.c. housing wires
& switch, good luck!!! as far as the main jet my 02 tb has a 130 main not sure if your 91 tboss is the same

 

Thanks Dirt I'll try to find or buy a spark indicator and go thru all the grounds and connections again. If I still have no spark I'll need a diagram and Ohm/resistance readings, where can I find these ? Thanks for any help Chuck fax 814 226 1579

 

the service manual has a diagram & the ohm specs in it, I bought one for my 02 & they are very helpfull,
I got mine at the dealer for about $40.00, they are put out by the year & model so get one for a 91 tboss 250, as I am not sure if the specs & diagram are the same as mine. again I highly recomend getting the service manual, lots of good info!!

 

Just a guess, but it sounds like your coil may be breaking down when it gets hot. In the automotive field we experience this quite often and it is along the same lines. Hope I helped.