I pressurized the gas tank to push gas to the tillotson carb (I removed the inlet cover so gas would flow freely). The starter cranks nicely. HI and LO screws are at 1 turn open. I pulled the plug, connected the high voltage lead and set the body of the plug on the head and turned it over, seeing no spark. I then wheeled it into the garage out of bright light, cranked it and witnessed what appears to be a very weak spark. The plug gap is 0.021". I have double checked all of the connections on the harness. The ground wire coming of the coil is grounded. Could there be some kind of adjustment on the magneto that should be checked?
The spark can be hard to see so that might not be a cause for concern. If you likle you can grab an old plug, open the gap to 5mm and see if you can spot it then.
Are you choking the airbox (or carb inlet) with your hand while cranking? It will probably need a little choking even when it’s primed.
I dunno about pressurizing the fuel system without cracking the screw on top of the carb.
Spark plug gap sounds small.
Agree with @KartingIsLife about choking.
That first start takes a minute normally.
Ok, sounds like I should not rule out a fuel supply issue. The documentation warned me about excessive cranking so I did not crank for longer than 10 seconds or so.
I see Fox and Sons recommends 0.030" plug gap.
I did notice that the plug seemed dry each time I pulled it out which does seem suspicious. I will try covering the holes on the air box when I crank next time. I’m sort of used to my KT100 firing up quickly.
Also try cranking for a bit without spark plug. You should smell fuel, if not and the line is full, then your problem is in the carb
Other things to check:
1.) make sure the reed cage and reed intake manifold are oriented properly and the pulse holes are lined up.
2.) make sure the carb gasket is not upside down and blocking the pulse holes
3.) take off the airbox to choke it; cover the carb entirely with your hand and it should pull fuel in quickly. It should start and stumble. Put the airbox back on and it should start up cleanly.
Try disconnecting the kill switch. Commonly faulty on KA100
I think you have good advise with priming the carb by covering the air box holes. We have to do it always when cold. Your gap is a little small, you found the .030 spec and is recommended. You won’t see much of a spark with any daylight. It should fire right up with more fuel.
First start on a KA or X30 takes a lot of cranking. Even if the fuel is primed through the top of the carburetor, all of those tiny little passages take a lot of pulses to pump fuel through.
Next time I run direct-drive I’m using a float carburetor because the fuel is right there and ready.
Well I did have the carb and reed cage off so I better make sure those holes are lined up.
SUCCESS. I checked the all pulse holes on the gaskets and reed cage. Then cranked it with my hand over the two inlet holes on the air box. It fired right up and purrs like a kitten. Thank you all for your guidance!
Charles, what kind of direct drive motor do you have? Mt friend that got me into karts 2 years ago runs an older Birel with a IAME TT37 rotary valve DD. For many of the young kids at the track it is the first time they have seen a DD kart. Its got a lot of hours on the bottom end but accelerates like a raped ape. We run at Avon in NY, one of the oldest tracks (built 1959) around.
Glad you got it going. These motors are easy to live with once you learn them. So you run at Avon? I run at LMP. Are others making the switch from Yamaha to KA? We ran there last year and it was just one other karter. Wish their spec weight was higher too.
Not too many KA100 at Avon compared to KT100. There are still a bunch of guys that keep the KT100s running. Weather permitting, we are planning on going to LMP on Saturday 20 May to run the new Birel/KA100 and older Birel/TT37 direct drive. I went there once last year with my Briggs 206 and really enjoyed the track. Very smooth. BTW, Batavia was purchased by a guy that is renovating it and allegedly re-paving.