older kt100 yamaha engine top rpms

had this engine long time still runs very good just dont know what the most rpms that it can turn and still make good power running on jackshaft setup
 
Its has been at least 12-14 years ago maybe with a G4 pipe ran this weekend it turn 13,800 to 14,000 rpms still run well.
Don't hold me responsible if it comes apart but I have an older (mid 70s) KT that was balanced and blueprinted at Cooks Racing engines many years ago , it's been rebuilt 1 time and presently on its 2nd top end refresh and and a 4 hole can but myself ,14k rpm is probably not hurting it at all and I have seen and read 16500 being used as a maxed out rpm , however I have been keeping up with a YouTuber his handle is 2strokestuffing and I'm not even gonna quote what I've seen his builds do but if the question is at what point would the engine reach its limits , I'd have to go with that all depends on what's inside it , what it's fueled by , and what pipe is on it . I've seen his running at a point that they no longer sound like a running engine but more like a very intense single ringing that is very high pitched . Go check him out .
 
Izzy,

twostrokestuffing's engines are typically 50cc.
This is true but man those things are making some Rs . I'd love to have one of them 50cc or not . I also am in the market for a complete running or complete not running Fairbanks Morse hit and miss engine but I'll get that when I'm older and can't really get in there and do work , lol , I'll just start it up and sit in the shop and drink beer (not budlight) and listen to it pop pop pop pop !
 
This is true but man those things are making some Rs . I'd love to have one of them 50cc or not . I also am in the market for a complete running or complete not running Fairbanks Morse hit and miss engine but I'll get that when I'm older and can't really get in there and do work , lol , I'll just start it up and sit in the shop and drink beer (not budlight) and listen to it pop pop pop pop !

Izzy,

Have you ever driven one of the older Formula Super-A karts? (European, direct drive... circa maybe 1995 or so)?

20,000 rpm on a sprint track was completely doable with those engines.

PM
 
Izzy,

Have you ever driven one of the older Formula Super-A karts? (European, direct drive... circa maybe 1995 or so)?

20,000 rpm on a sprint track was completely doable with those engines.

PM
You are completely right. i have seen them way over 20,000 rpm. The one I still keep doesn't have so much till it hits over 17,000 rpm but I do not puch it much, I am not willing to change the piston every day like they used to.
 
Yeah, formula A motors got really turned up but the only reason to do that is because they are direct drive on a sprint track. They got over reved down the straight so they could get off the tight turns. I built a direct drive SA Kt for an Australian dirt road course. Dude told me he wanted to turn 16,000. They had to use a piston made by Strike that was 54 mm and weighed 28 grams more than a stock std. KT. I had to counterbalance the crank so it was smooth at high rpm. It handled 16 with no issues which is a testament to how strong the lightweight rod really is. But, just because an engine will turn up that high doesn't mean it's the fast way around. It depends on the track.
 
Yeah, formula A motors got really turned up but the only reason to do that is because they are direct drive on a sprint track. They got over reved down the straight so they could get off the tight turns. I built a direct drive SA Kt for an Australian dirt road course. Dude told me he wanted to turn 16,000. They had to use a piston made by Strike that was 54 mm and weighed 28 grams more than a stock std. KT. I had to counterbalance the crank so it was smooth at high rpm. It handled 16 with no issues which is a testament to how strong the lightweight rod really is. But, just because an engine will turn up that high doesn't mean it's the fast way around. It depends on the track.
I do agree. Same for power, more power is not always faster. Depends on where you get thepower, torque, etc.
 
I don't have a wealth of experience with KT100's, but I've always heard peak horsepower on a stock (as in WKA legal stock) KT is in the 9500 to 10,000 RPM range, depending on what pipe and header length you're running? Running a KT on our sprint track (Avon), slipping the clutch at 9600 RPM gives us the quickest lap times, so I'm assuming 9600 RPM is probably about the HP peak? A few years back we were playing around with our vintage karts (MXK chassis/KT100 engines) on the local dirt track - a small, roughly 1/10 mile oval. We started out with them geared real low and we were hitting 14,000/15,000 RPM on the straights. As we got better we raised the gearing up so our peak RPM around the track was in the 11,500 to 12,000 RPM range and our lap times improved substantially.
 
Izzy,

Have you ever driven one of the older Formula Super-A karts? (European, direct drive... circa maybe 1995 or so)?

20,000 rpm on a sprint track was completely doable with those engines.

PM
Lol honestly Pete , the only place I've ever drove the current kart or any other was on a back yard flat track or up and down my concrete driveway . Now the driveway is almost 150 yards by 10 ft of rough surfaced concrete with a extra wide apron at the road and a 40ft diameter loop at the end . This is the only 2 stroke anything I've ever owned other than a lawn care device or a moped we use when we go to the beach or on vacation . If they are any faster or turn anymore rpm than what this this thing turns then I probably don't need to be around or in control of it . Lol , I'm a speed demon that has had a little more than my fair share of excessive indulgence in the art of breaking the law with a special focus on the traffic laws concerning speed , in fact I don't believe I'm even allowed to own a sport bike ever again so long as I live according to the state of SC and my current girlfriend . Not sure which is the law but I know which one I have to deal with the most so I kinda willfully dumb down and go along with the program !
 

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