Engine help please

Posts: 29

I have a 150 sahara with a mikuni tm 24 it runs very strong but lately when I ride it and it heats up it will start to sputter at 3/4 throttle any help would be appreciated

Posts: 201

You haven't given much info. Have you done any mods,how old is the cart ect. However if I understand you correctly,the kart runs fine when cold than starts to sputter at 3/4 throttle when warm. If this is fact than I would start looking for 1) loose spade connecters at the rear of coil,2) check for vacume leak.However if you can supply more info it would help.What happens after 3/4 throttle? does it keep on sputtering or does it straiten out. TOM

Posts: 2640

im leaning towards the same... leak, or possibly an adjustment... I know the mikuni is somewhat tempremental, and to me it sounds like there might be too much fuel or too much air getting by... What does your spark plug look like... how does it idle after warm up?

Please, let us know what other mods you have!!! I am interested to hear about your combo.

John Very Happy

Posts: 6290

Howdy neighbor! I would take a look at the plug and let us know what color it is. That used to happen to my Sahara and if I remember correctly, it was either the coil wire or that rubber intake had a leak. Not sure. The color of the spark will tell a lot.

-Jamie

Posts: 325

All r good answers!!I would like to add 1 more. If its only happening when it gets hot take a compression test cold and than hot the valves may b expending and not seating when hot. Just something to think about.

Posts: 1215

Posts: 29

Thanks for all the suggestions guy's this is the first time I have been able to get back on since I asked the question. As far as more info it has the tm 24 with a uni filter thats it for engine mods, it also has 9 gram rollers 1500 spring and a 39 tooth sprocket not that the last three mods should have anything to do with it. as far as the plug when I pulled it out its perfect a real light tan color. It seems like once it gets to a certain temp you just cannot give it more than 3/4 throttle it will not die it just sputters real bad. Again the suggestions are apprecaited not sure when I will get to it getting ready for a camping trip but I will try some things and get back to you Thanks

Posts: 4286

also check the fuel line. if its to close to heat it will vapor lock, also the fuel line might be collapsing.

Posts: 201

Again you should check that the wires going to the coil are tight and secure,loose wires will create this problem.Also check the valve clearance,if the valves have too much lash in them you will run lean at the higher throttle.This may not be evident when cold because the enrichment valve(choke) is allowing a rich mixture until it warms up than the engine will lean out,and if the valves are too loose this will cause fuel/air starvation.Intake should be .003-.004 and exhaust should be .004-.005 . If after these checks and adjustments the problem still exhists than when the engine is warmed up find a long stretch of somewhat flat road 500 feet to 1/4 mile and drive pedal to the metal never taking your foot off the throttle than cut the ignition still keeping your foot to the floor until the engine stops running than stop the kart and pull the plug and note the color of it.What you want to accomplish is wot reading on the plug with no idle time .you may find that the plug is now running lean which is an indication of lack of fuel due glogged jet or vacume leak. TOM

Posts: 2583