Slow for kart to come in

JryKlnr

Member
Running junior 206 sprint. Kart takes half a run to come in, fastest laps are always the last 3 or 4. Good speed then, qualified second 2 races in a row. Just losing 2-3 positions in heat or main, karts comes in and often fight to get one or 2 positions back. It’s a real roller coaster of a day.

Bandit y2k kart, maxxis tires. Been steadily increasing pressure to try and get it to come in early but that doesn’t seem to be doing it. When karts comes in its a smidge loose and fast. Track has a sweeping bank turn and long stretch that everyone pulls away from us on first few laps until his kart comes in. Then he can hold or even make up ground in closing laps.

Any ideas we should be chasing? Anything specifically with the motor or clutch that would cause any of this? Thanks for any thoughts. First year racing, 7th race. Still working hard to figure it all out.
 
Not using enough prep or the wrong prep is a big part of this happening, you need something to Fire them off quicker that will create the same grip as later in the run once they get up to temp. It's NOT once the chassis comes in that your better it's once the TIRES come in.
 

kart5nyc

Member
Yep, it's the prep in the tires. Sucks, but that's the truth

Could be as simple as cleaning the tires between heats
 

JryKlnr

Member
Have tested starting running from 11 -14.5. Almost always come off the track at 15.5 - 16.5. Been making small increments, haven’t fully swung to start at 16-ish yet.

Sandy Hook in MD
 

flattop1

Dawg 89
Somtimes a big swing is needed to see aprricable changes.
The fact its coming off near round 16 is imho good enough reason to start there .
 

gary10

Member
16-18 is a reasonable starting pressure for some tires at some tracks. Add more air until you can run a decent lap by lap 4-5
 

ClarkSr

Member
Listen to Gary, he knows his stuff.
We road race , so it's a different animal...but in the CIK 206 class, we increase the tire pressures until it acts funny!! Then back off a little.
Works very well for us. We start at about 16 PSI and go up from there...the sky's the limit. You'll be surprised how high you can go before it gets twitchy. But it will also keep getting faster.
Clark Gaynor Sr.
 

JryKlnr

Member
Thanks for the replies and help. next club race 8/4 where we will be running these tires and take a big swing at it to test. I’ll update after that. I’m not ware of anyone else at our track running these tires at that high of pressures.

Will be practicing at a new track for us tomorrow (Nicholson) and probably run different tires. Will be interesting to see if we experience same symptoms with different tires. Will post updates Thursday.
 

Dan Brown

Member
We ran the AKRA series at Nicholson a couple years ago. It's a small track, not too technical but lots of fun. We ran Vega blue tires and had good luck around 12 psi, any less they picked up a ton of rubber. Not sure what brand of tire you are running there, but Gary gave you some great advice, don't be afraid to play with pressure during practice . Making a big change will tell you rather quickly if the kart is better, or way worse. It will get you headed in the right direction tuning, after that you just need to make small changes to dial it in. Good luck.
 

JryKlnr

Member
Been awhile since I posted because I’m just perplexed. We change motors about a month ago and the problem went away. We now get results we anticipate with tire pressure changes. If we set things up correctly, we can run our fastest lanes in the 2-4 lap range vs always the last few laps.

So, what could have been going on with the previous motor that would have taken it 8-10 laps to “come in”. When it did, it was fast. Qualified second 3 out of 4 weeks. The fast times were just set at the end of the session.
 

flattop1

Dawg 89
No idea . Never saw a engine do that .
Speculation maybe engine was down on power kart was tight , after track or kart changed it freed up and got better , now the new engine has the power to overcome that .
 
Very interesting! Without my being rude, don't want you to think that, may I ask a few questions? Do you keep a record of lap times? Seems to me you would need to know those numbers to verify that your driver is slow on the first few laps. Also, that the other drivers are not slowing down in the later laps. It's possible, even very likely, that your drivers engine is running rich at the start, and then later, as the engine gets hot, it leans out slightly. The other drivers, may be tuned right on, and then later in the race, as their engine gets hot, they lean out some and slow down. I'm just speculating of course, but I don't believe it's in I like a you are working in a you a great a beyond the realm of possibility.
 

Ted Hamilton

helmet painter and racer
Usually, tires can be tuned to come in early (high start pressure) and "overheat" late race and lose time -- eg. you pass early, but then have to "hang on...." to finish. Or they can be set to come in mid, or late (low pressure to start, kart comes to you as you go, at risk of losing leaders.) Rare to be able to have it "right" the whole race. A potential option is bleeders, (not legal in some cases) or deciding where you want to be strong. If your track has lots of yellows, YMMV.
 

JryKlnr

Member
Al - yes, we keep a record of every lap time. It was very strange. No matter what we set the tire pressure for coming in early or late, we always just picked up almost a half second 8-10 laps into the run. It’s was like flicking a switch. Yes even watched competitors times. They were coming in early, mid late, but what we saw wasn’t us coming in late and them falling off, it was definitely an issue of some sort supported by lap times.

We have since replaced the engine and new clutch and not experienced the issue since. Now when we adjust tire pressures we get expected results and can setup for when we want are bets lap times to be run during the race.

I like the running rich idea and then it possibly leaning out. Might be on to something there. The engine we had the issue is a backup now and we intended to get it gone over in the off season.
 
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