JA KT100 setup questions

Harold Hammerly · Joined: 24 Jan 2012 Posts: 24

I would like to know what are the reccomended RPM for gearing and clutch engagement that I should be adjusting for JA KT100 (engine builder MCR reccomend 14000 and 7000 respectevelly with a pipe engine).
I also would welcome initial setup reccomendstios for an 08 CRG Kali and engine maintenance (engine has 9 hr since bluprinting, chlinder looks ok with hone marks looking from the exhaust port, compression is 140 whith cylinder temp at 150deg)

Thanks
Harold

Joe Ricard · Posted: Thu Feb 23, 2012 6:31 am Post subject:

Sounds like you have a pretty good start. Those recommnedations seem sound.

How experienced is your driver? Please take no offense as I learned the hard way my driver is not as fast as the other kids. Not much I can do about it except get him tons more seat time. and learn to translate his funny look after a run into pushing like a dump truck or the motor is not running right. ( it could mean either) Rolling Eyes

Gears will be different nearly every course. Locals tend to be shorter slower and tighter. National level courses usually are faster longer and more open with cones stretched much further apart. Yea we had trouble with that as well. Day one of a tour was 3 DNF's and he had no clue what cone he missed.

Good luck and be patient.
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Arrow AX-8/ Rotax Sr.

al nunley · Joined: 13 Nov 2006 Posts: 3065

A pipe engine reaches peak torque right around 10,000 RPM. On a sprint track that’s were I would have it coming in. Your type of racing has other things to consider. Like how tight is the track. If you’re on the clutch all the time, it could get hot. That’s bad.
Below “peak” torque the power drops off quite fast. It’s really low at 7,000 RPM. I would try higher clutch RPM’s till you find a good compromise. You want it as high as possible. without burning it up.
We found the KT, with a pipe, could reach 15,000 +, with no problem, on the top. Unless the track has really long straights, that’s what I would be going for.
Compression, on a good KT, (we have seen 160psi) can be different, and it depends a lot on your gauge. Compression is a relative thing, meaning you want to check it from the start and think about rebuilding when it goes down from it’s peak.
Lap times will tell you when you’ve got it right.
_________________
If the data does not support the theory, get a new theory. (Al Nunley)
All else being equal; Compression is the Holy Grail.
45 years, in and around karting

Harold Hammerly · Joined: 24 Jan 2012 Posts: 24

Joe,
My son has been autocrossing part itme for two years with a hand me down roller and a $45 motor 5hp briggg from a snow blower at our local events, I now feel that he has shown interest where this kart will take him to the age where he can change it to a shifter or co-drive wih me if he chooses to.
My main focus in autocrossing is to have a good time and have pushed him in that direction, I don't want him to be a professional driver (been arrownd racing and that is not what I would preffer for him), secondly is to learn how to drive and setup a car, that part is more difficult with a kart as you mentioned.
I'v had positive results when recodring his runs and having a quick review between runs. I'm sure that we will have a very steep perhaps rough learning courve with this kart and added HP and adjustability and want to do my part to give him the best setup I can.
Thanks for the advise.
Harold

Joe Ricard · Posted: Thu Feb 23, 2012 8:26 am Post subject:

Great, We seem to be like minded. Yep it's all bout hanging out with his karting friends in the trailer playing video games that get interupted by a few autocross runs.

Interesting stuff from Al. he does know his stuff and that's why I steered from it.
_________________
Arrow AX-8/ Rotax Sr.

Harold Hammerly · Joined: 24 Jan 2012 Posts: 24

Thanks Al,
I was not sure of what RPM that motor would like to run with the can, perhaps having it loose a little top end by reving past the sweet spot in one part of the track will yeld more power everywhere else.
I suppose tha a Hortsman wet clutch ( although heavy ) could handle a bit of slipping on a solo environment where it runs for 2 minutes and has 15 to 20 to cool, perhaps replacing oil every event and cooling it with the garden sprayer between runs would help, I will adjust it to come in a little higher RPM when we have a test.
How about raising the frame as high as it will go? We have very rough courses her in the Midwest and this kart has 1/2" of adjustment, it is now on the lowest frame height.
Thanks. Harold

al nunley · Joined: 13 Nov 2006 Posts: 3065

Harold Hammerly · Joined: 24 Jan 2012 Posts: 24

Oops, he will be running with a 4 hole can and WB3A carb, the motor was built for a pipe...
That is what I meant when I said that the builder reccomended those rpm for a pipe, and asumed that he reader knew that FJ runs on a can.
I would like to know what a can needs to run at...
Meant and said are not the same in this case, sorry and thanks for the advise.

al nunley · Joined: 13 Nov 2006 Posts: 3065

Harold Hammerly · Joined: 24 Jan 2012 Posts: 24

Thank you for the tips, I will up the clutch engagement RPM and try it on the next test and tune session, regarding the fuel, can I run pump 93 octane or need a 93 & 110 octane mix or 100 low lead av gas?
Thanks
Harold

Harold Hammerly · Joined: 24 Jan 2012 Posts: 24

Thank you for the tips, I will up the clutch engagement RPM and try it on the next test and tune session, regarding the fuel, can I run pump 93 octane or need a 93 & 110 octane mix or 100 low lead av gas?
Thanks
Harold

al nunley · Joined: 13 Nov 2006 Posts: 3065