kt 100 power

hi guys, newbie here. I have a spare kt 100 not blue printed that I would like more power out of on gas. compression porting more fuel are my thoughts now. do you have suggestions on what I can do? I have heard of trimming the bottom of the piston also. this will be a hot lap engine only. thanks, chuck
 
Put exhaust at 90 degrees, transfers at 115 to 116 degrees, intake at 90 degrees, squish at .030 14degree angle 10CCs . Jon Brogden has a post about boring the carb bigger follow that along with intake passage to fit carb, you can play with the timing, doesn't make that big of a change with these basic changes on a stock bore and stroke. if you try to put a TT75 or any crank that's 50 mm bore the engine then use Buller's 54mm piston for a Yamaha put exhaust at 88 degrees the rest the same this will make your engine 115cc ?
 
thanks michael, does anyone know if the original owners manual has the info needed to bring a kt 100 up to 20ish hp? thanks, chuck
 
Chuck,

Whatever Mike Collins wrote is probably going to be as good or better than any other information you can find. He has done TONS of testing on stock AND modified Yamahas and has been building engines for decades. Highly recommended!

PM
 
thanks ted, It wont be legal. Im to old to be rubbing and racing.LOL I raced at one time, Im just hot laping to get that rush again before I cant. thanks chuck
You should come long-track roadracing... the physical demands are less, and the racers in most classes are typically more patient. Plus you get to run at cool venues... People into their 60's, 70's, and even a few beyond are doing it...
 
@Pete_Muller -- recommend a 9cc head if it's non-legal engine for better conrod life and a touch more power?

I'm a fan of compression, no question about that. I think it always has to be "tempered" a bit though, and the "big picture" (gear ratio, exhaust pipe configuration, even weight of the kart) can all come into play. When the gear ratio is low, the kart is light, and the exhaust pipe is "mild" (e.g. early direct-drive European type racing), the compression and ignition timing can be amazingly high. But slip a clutch to 10k using a radical exhaust pipe on a 400 pound kart/driver combo, and that same compression will quickly melt parts! :oops:

That said, I don't feel 9cc (7cc in the chamber) is too high for most "sprint kart" applications with a mostly stock KT100. Might not be a bad idea to run one heat-range colder plug though.

PM
 
You should come long-track roadracing... the physical demands are less, and the racers in most classes are typically more patient. Plus you get to run at cool venues... People into their 60's, 70's, and even a few beyond are doing it...
Ted if you think road Racing is less demanding I'll let you drive my laydown for over 40 min. I would take 30 on my shifter or my UAS anytime instead, believe me. Long track is not so bad on sprinters but try anything else. Those old timers are in much better shape than many youngsters.
 
I'm a fan of compression, no question about that. I think it always has to be "tempered" a bit though, and the "big picture" (gear ratio, exhaust pipe configuration, even weight of the kart) can all come into play. When the gear ratio is low, the kart is light, and the exhaust pipe is "mild" (e.g. early direct-drive European type racing), the compression and ignition timing can be amazingly high. But slip a clutch to 10k using a radical exhaust pipe on a 400 pound kart/driver combo, and that same compression will quickly melt parts! :oops:

That said, I don't feel 9cc (7cc in the chamber) is too high for most "sprint kart" applications with a mostly stock KT100. Might not be a bad idea to run one heat-range colder plug though.

PM
 
Hi guys, back when I raced I did a road race at sears point in n. california. I raced 4 times with 2 firsts a second and a 4th. I loved it. most of my racing was sprint ikf div 7. pete my kart will be 320-330lbs. with an l&t wet 3 disc wet clutch. thanks for all the insight. chuck ps. a hartman blimp pipe.
 
@Pete_Muller -- recommend a 9cc head if it's non-legal engine for better conrod life and a touch more power?
If you take a head that's been cut to 11cc for IKF or WKA and try to cut it down to 9cc you will get the plug to close to the piston, if you are starting with a NEW head at 9cc, plug depth will be farther away to start with which when I have that option I'm OK with 9cc. My reason 10 is you can get to that without sacrificing plug depth to much. Just my thoughts
 
Mike,

Have you ever tried switching between conventional and recessed-gap plugs on the dyno?

PM
Yes I have and when the plug gets to close I run the recessed plug to move the heat away but if you try to recut a head that was set at 11cc and trim to 9 or even trying to get to 10, sometimes it will have the plug so close that it doesn't matter what plug you have. What I shoot for is 1.100 to 1.070 for plug depth from TDC, I do this with a caliper through the plug hole and roll the engine over TDC and look for the distance to where the plug seals to the piston.
 
If your lucky enough to have a bone stock head, you can cut all the relief down to 0, about .050 cut. And with the clearances recommended by MC you'll have right at 9.5 cc's at TDC without any re cutting of the squish band and pocket. When you go that route and are running gas for fuel, with stock ign. timing , high test at the very least, it may need more.. watch for signs of detonation.
 
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