Im trying to start my kt100 that I let sit for 2 years. New battery in starter, starter spins engine fast, fresh fuel, plug is getting spark, fuel is getting to the carb, disassembled carb, tried all different position on the high and low needle. It wont fire up… it looks like there is fuel coming out the exhaust when I try I start it?..any help is appreciated. john
Carb kits are cheap, grab one and make sure all the gaskets are fresh esp the diaphram. Also make sure screen isn’t clogged in carb but I doubt that is the culprit if you are getting gas to the carb.
Double check pop off pressure, racers run 9-10 psi but it causes a rich condition, something in the 12-14 range might help get it started.
Set the high needle fully closed and run about 1 1/4 on the closed for cold start. You will need to richen it up to drive it but on the stand at lower RPM this setting works best
If you are getting fuel out the exhaust it’s likelu flooded at this point, throw a new AR 51 on there.
Best of luck.
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Actually…before doing any of that check the compression. When these sit the rings can rust to the iron liner in the cylinder and cause loss of compression when it breaks fee.
If you don’t have more than. 100 PsI it won’t start no matter what you do.
If you leave it for more than a few days you should put some oil down the spark plug hole and rotate the engine a couple of times to lube everything.
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I checked compression. 75psi. So it looks like its internal. Thanks for your help. john
rings are cheap…if you’re not looking to compete at the national level throw a ring at it and run a dingle ball hone through the bore a few times and have a it. Could be up and running for $50-75 and an hour or so of your time.
Set ring gap between .010 and .012
You’ll might find that the ring is just gummed a bit with oil. You could clean in/around it with brake cleaner, put a cloth in the crankcase to keep it from going in there. Put it back together and see if the compression comes up some.
Other things you need to be aware of after it’s been sitting.
Hardened or oil/kludged up diaphragms in the carb.
Stuck open or closed inlet needle.
Hardened crank seals causing an air leak.
At 100 psi I should at least give a kick and fire up.
I still have quite a bit of fuel coming out the exhaust when I try & start it…here are some photos of the head & piston. Anything look really wrong? 
Hmm, that ring around the edge of the piston makes me concerned that the main/crank bearings are done. When the play gets excessive the piston can contact the head, removing the carbon.
Honestly at this point you might as well just spend the 400$ send it to a shop to have them get it running.
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I agree. Having seen inside of it, it’s time for some fresh parts.
I had a KT specialist examine the motor and the piston ring was worn out. I had the crank straightened, cylinder honed, carb rebuilt, new ring and a new head gasket (piston was hitting head). All is good. Thanks for everyone’s help.
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What was the bill? Just curious.
$333 for everything.
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That seems like Pretty fair price
So I’m finally getting around to troubleshooting my KT today. I ran it a couple weeks ago at my local sprint track. It fired right up the very first time so I did a few shake down laps and came in. When I tried to go back out, it wouldn’t start. After fiddling a bunch, it seemed maybe flooded so I put a new spark plug in and it ran pretty well. For each session thereafter, I would lean both needles out to start it (to make sure I didn’t flood it, 1.5 turns on the low needle, 1/8 on the high) before turning them up once on track. It ran fairly well most of the day doing this but but it didn’t quite seem to want to rev up like my other motor but seemed ok. So the following day was when I went road racing. It was running great all day, but again not seeming to rev like it should but not far off. However, it wouldn’t fire up on the grid for the last race of the day. I fiddled and did whatever I could but no go so I missed the last race. I was thinking maybe my starter didn’t have enough juice. But today, fully charged starter, still the same thing and today I noticed fuel in the pulse line. What does that indicate? I’ve never experienced that before. I rebuilt the carb before all of this. 
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Air leak. Check pulse line for cracks and tight wire tie or clamps.Replace pulse line.
Pump gasket leak, pump diaphram cracked “maybe”. Replace both.
Check the pump cover screws. Are they tight?
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Also, double check the order you put the gasket and pump diaphragm on to the carb body. Diaphragm to carb body, then the gasket and cover.
I’m guessing it wouldn’t run if this was wrong…but…
Thanks, I’ll look into those things. The diaphragm and gaskets should be good, because I just rebuilt it, and I’m fairly certain I put it all back together right. What really confuses me is that it had been running firing up no problem on the stand and on the ground for several sessions and now it’s not.
Air leaks can creep up on you slowly.
Did you find anything?
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