NKK Gearing or another issue?

jscholt

Member
My son is new to karting, just got into it last year and raced twice in Jr 1 (Green plate Clone) but not at Newton. Bumped up to Jr 2 (purple/blue plate) Clone this year, raced twice at Newton Kart Klub with the purple plate but getting beat down the straights...

Few things to note. Kart has been professionally scaled. He has to weigh 300 for his class, scaled to 297 - hit 303 on the scale at the track. Prepping Maxxis tires during the week prior to event and use prep at the track to get bite into the tires.

Started off in hot laps with a 4 wheel drift - track was pretty slick. Had 6 lbs in rights / 5 lbs in lefts and started with a 16/65. Left gearing alone for 1st heat but reduced right side to 5 lbs to eliminate 4 wheel drift. Track tightened up but he was only hitting 6100 RPMs - should be closer to 6400, but lap times were around 10.6. Seemed to be about .2 tenths off from the lead group. RPM drops in corners were 500-600 as to be expected at the track and he was in the gas the whole time. Since we were not hitting RPM range, dropped to a 15 tooth driver and a 63 rear gear for Heat 2. Lost .2 tenths and RPMs only hit 6100 again...

For Feature, went back to 16 tooth driver and a 66 rear gear. Lost another tenth per lap but saw a jump in RPM to 6200. Seemed I was probably going the wrong direction with the gearing and potentially what drove the slower lap times? RPM drops remained the same each time out and he was in the gas the whole way round, kart was hooked up just not fast.

With NKK potentially only racing 2 more times, not going to get the practice to attempt other gears. Curious on anyone's thoughts that has raced NKK before or has some general advice for this rookie Crew Chief. NKK is a 1/5 mile semi-banked dirt oval - momentum track for sure.

Thank you!
 

racing promotor

Moderator
Give more details on prepping, what are you wiping during the week ? and how many times , what are you wiping at the track, and are you heating the tire ? Do the tires have Internal prep ? If so how much and when ? Now the track you say pretty slick, slick why moist soft ? moist but sealed over ? dry slick ?
 
This will fall into the general advise category as I'm not familiar with NKK. Did your engine builder give you the 6400 RPM target for a purple plate? If no, I wouldn't chase that many RPM's. It sounds like you were best at the lowest gear ratio you ran (16/65) even with a handling issue. It sounds like you slowed down compared to the prior run each time on the track. Did the track speed up or slow down? In my experience, most tracks I've been to stay the same but generally get faster as the show progresses. If the track was getting faster you might have gained RPM's staying on 16/65. You potentially would have been better going to 16/64 if the track was picking up.

I think RP is pointing you in the direction of you'll find the .2 tenths with tires.
 

racing promotor

Moderator
This will fall into the general advise category as I'm not familiar with NKK. Did your engine builder give you the 6400 RPM target for a purple plate? If no, I wouldn't chase that many RPM's. It sounds like you were best at the lowest gear ratio you ran (16/65) even with a handling issue. It sounds like you slowed down compared to the prior run each time on the track. Did the track speed up or slow down? In my experience, most tracks I've been to stay the same but generally get faster as the show progresses. If the track was getting faster you might have gained RPM's staying on 16/65. You potentially would have been better going to 16/64 if the track was picking up.

I think RP is pointing you in the direction of you'll find the .2 tenths with tires.
Yes, BUT came back on to go the same direction you did here, 6400 rpm for a purple plate on a momentum track is to much ,6200 max I'd target little less than that even, good chance when you were on the 16/65 you were on the start of being gear bound and when you changed to the 15 driver and added the tooth with the 16 it made it worse, if so you cannot count on your tach reading being 100 % accurate, comparing that gearing to a 1/5th mile here that makes good grip we would be on like a 16/60, sounds like where your running doesn't grip up as well so 16/63 should get it done, with tires being right, and if you had done that instead of going to the 66 at that timing in the event you might have found you would have maintained rpms at 6200 but been faster.

When I know our gearing is right and were chasing rpms it's always tires, that's another reason why I'm asking questions tire related, once you give those details we'll try to figure it out.
 

flattop1

Dawg 89
Post 97+ in the go to thread addresses this some what .
Newton is definitely momentum . I do not think there is a flat spot anywhere there even the front strech has a slight slope .
Uphill outta 2 across the backstrech then down hill through 3/4 onto the front stretch . Pretty sure we ran a 15 in adult classes .
How old are the tires and what prep ?
 

jscholt

Member
@racing promotor Thanks for your quick response. Prep used week of race is Pink Magic, applying twice a day up to race day. This specific set of Maxxis I am using at NKK is new as of May this year, seen the track at Newton twice and KC Raceway once. No inside prep. 1 1/4" stagger in the rear. Applying a non-aggressive prep at the track, a bit more aggressive than Pink Magic and its a solution provided to me by my engine builder. No heating of the tire as I'm not familiar of what I would need to do there. The track was really wet to start on Sat but then slicked up, moister certainly in the dirt as the night went on.

@Burris Racer My mistake - RPM top range was 6300 not 6400, checked my setup sheet. So in my opinion we were close. Track certainly got faster, we just got slower. More than likely in the responses so far I went the wrong direction in gear ratio and should've been pulling teeth off the back.

@racing promotor 2nd response - yes thanks for the confirmation, I think you confirmed I went the wrong way with gear selection. Next time will start off with 16/61-62.

@flattop1 which thread are you referencing? Thanks for the input! Tires mentioned in my above comment, prep at the track comes from Waller I see you have reference to Waller in your footer. I think if I was on the Blue Plate a 15 driver would be right, I think its the purple plate that is throwing me off and went the wrong direction.

Rookie Crew Chief mistake.
 

flattop1

Dawg 89
General Karting Discussion .
A stickey at the top .
A go to for new or newer karters .
Its short and not much feed back .
You really should have inside prep .
 

racing promotor

Moderator
@racing promotor Thanks for your quick response. Prep used week of race is Pink Magic, applying twice a day up to race day. This specific set of Maxxis I am using at NKK is new as of May this year, seen the track at Newton twice and KC Raceway once. No inside prep. 1 1/4" stagger in the rear. Applying a non-aggressive prep at the track, a bit more aggressive than Pink Magic and its a solution provided to me by my engine builder. No heating of the tire as I'm not familiar of what I would need to do there. The track was really wet to start on Sat but then slicked up, moister certainly in the dirt as the night went on.

@Burris Racer My mistake - RPM top range was 6300 not 6400, checked my setup sheet. So in my opinion we were close. Track certainly got faster, we just got slower. More than likely in the responses so far I went the wrong direction in gear ratio and should've been pulling teeth off the back.

@racing promotor 2nd response - yes thanks for the confirmation, I think you confirmed I went the wrong way with gear selection. Next time will start off with 16/61-62.

@flattop1 which thread are you referencing? Thanks for the input! Tires mentioned in my above comment, prep at the track comes from Waller I see you have reference to Waller in your footer. I think if I was on the Blue Plate a 15 driver would be right, I think its the purple plate that is throwing me off and went the wrong direction.

Rookie Crew Chief mistake.
I'd say NO internal is your biggest issue, get atleast 75 cc internal, plus not wiped up enough for wet conditions, for sure 6 and 5 was to high air for hot laps, Id leave the 65 to start just pull rear gear as the night goes on, Or you can just see if the track comes to you.
 

flattop1

Dawg 89
If we used anything besides krug it would have been some added
Goat or straight goat . Prolly too much for a jr .
I would have a quart of krug though .
 

jscholt

Member
@racing promotor @flattop1 Appreciate both of your responses. I am not overly familiar with Prepping inside having just got back into the sport after 22+ years away. I believe I'd need a tire roller for this process, correct? Based on your responses, I believe I have a better starting point for NKK when we get a chance to go there next and see how it goes. Thank you!
 

racing promotor

Moderator
@racing promotor @flattop1 Appreciate both of your responses. I am not overly familiar with Prepping inside having just got back into the sport after 22+ years away. I believe I'd need a tire roller for this process, correct? Based on your responses, I believe I have a better starting point for NKK when we get a chance to go there next and see how it goes. Thank you!
Yes you need a roller, You get internal in that new set and prep little more aggressive when track conditions match what you ran on and you'll make up MORE than that 2 tenth you need.

Good Luck !!
 

jscholt

Member
@racing promotor Thanks. 2 questions on rollers - best place to get one? And and best practices in rolling tires, is it a week of the race type thing that people do? Just want to make sure I head in the right direction. Any help would be appreciate. 20+ years ago, I never prepped a tire...lol This is all new to me, just want my son to be competitive.
Thank you!
 

racing promotor

Moderator
The best place would probably end up being local to save shipping and in the end total cost, do some research on pricing, I prefer KKP but in the end all they need to do is turn the tires, most all bigger karting product shops carry them, I know J.C Specialty does 717 837 0042.
As far as when you roll that depends on the tire, and track conditions your setting up for, in your case I'd roll that set the week of the race, which that method is used a lot, some 2 weeks out or more but that takes experience racing at tracks that require that, then you have the Burris 33 game that you'll want some rolled and put back to cure 3 or 4 months before you race them. For now just roll the week of the race. The Amount of cc is more important then when.
 
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