Changing jets (new guy question)

Steve Clark · Posted: Mon Jul 30, 2001 9:46 am Post subject: Changing jets (new guy question)

I have bought a shifter. It looks, sounds and smells great. I can go end to end on my driveway in a second.

How do I know when to change the jet at the track? I will be using and Alfano Pro to monitor water temp so nothing for EGT.

I would also like to know which way to go on the jet depending on what I see. (temp, smoke, etc)

Being new to the sport I asked the builder to leave the motor rich so I don't blow it up too quickly. It is not a stock motor but the deal was good. Not too good to be true though.

It is real smokey at the moment but as I said it smells great.

Michael Polizzi · Joined: 18 Jul 2001 Posts: 1565

Hello steve

Yes there will be days where you will make jetting changes though the course of the day.

You want to see your water temps right around 130 deg. you will start to loose power over 140 deg.

Higher temps (lean mixture) mean you need to go to a larger jet.

Check with your motor builder as fuel and timing can effect your motor as much jetting.
The ratio of your fuel/oil also effects your jetting decisions.

Michael Polizzi 69n
Full Bore Karting

[ July 30, 2001: Message edited by: Michael Polizzi ]

Tim Blaney · Joined: 18 Jul 2001 Posts: 1127

Steve,
You can get a RAD gauge from Longacre racing for about $110 +-. Once you get the jetting right, note the RAD. From there, when the RAD goes up, jet goes up. RAD down, jet down.. . or that's at least what Tackett taught me. The only time I have stuck a motor is when I mis-read those tiny numbers on the jets.

Steve, my advice is get something to organize your jets so you can hopefully avoid that little issue.

Charlie Tackett · Posted: Mon Jul 30, 2001 2:23 pm Post subject: Changing jets (new guy question)

Steve and Dan, I usually try to operate on the principal of KISS. Like Blaney points out...just get a RAD gauge. Takes into acount temp and barometric pressure. You'll have to find your own baseline.....plug/piston/pipe reading (hey...the three P's of tuning!!), but once you got your baseline established, you just follow the changes in your RAD and adjust the jetting accordingly.....but you do have to be sure you can read the #'s on your jets, of course.

(Tim, that's why there's a magnifying class in my jet case....som,etimes even teh bificals aren't enough)

I have found that changes in humidity are rarely result in having to have a significant jet change, usually has come out to less than 1 jet size, so don't really worry about it, especially at this point. Also remember, if you make any changes in the engine...diff pipe, differenet reed cage, etc., re-evaluate your baseline.

Hey Dan, was good to meet you at Grattan! Got another name that actually has a face connected to it! We will have to work on those 1:34s, though.

[ July 30, 2001: Message edited by: Charlie Tackett ]

Gary Kozuma1 · Joined: 26 Jul 2001 Posts: 386

[QUOTE]Originally posted by Tim Blaney:
[qb]Steve,
You can get a RAD gauge from Longacre racing for about $110 +-. Once you get the jetting right, note the RAD. From there, when the RAD goes up, jet goes up. RAD down, jet down.. . or that's at least what Tackett taught me. The only time I have stuck a motor is when I mis-read those tiny numbers on the jets.

Tim,

Thanks for the tip on the air density guage. Exactly what I need.

Gary K.

[ July 30, 2001: Message edited by: Gary K. ]

Tim Blaney · Joined: 18 Jul 2001 Posts: 1127

Charlie, I don't have mono-focals (eye doctor gave me a clean slate) so don't go pushing bi-focals on me!!!!!

John Van Nghiem · Advertiser Joined: 26 Jul 2001 Posts: 697

check www.eric-gorr.com.

he has some great 2-stroke tuning info.

John

Steve Clark · Posted: Mon Jul 30, 2001 4:29 pm Post subject: Changing jets (new guy question)

quote:
Originally posted by Charlie Tackett:
. . . You'll have to find your own baseline.....plug/piston/pipe reading (hey...the three P's of tuning!!), but once you got your baseline established,
[ July 30, 2001: Message edited by: Charlie Tackett ]

This is going to sound like a silly question but what process do I go through to establish a baseline?

I am thinking this is something I do each race day. How would you suggest I go about my first run in the kart.

Dan Meray · Posted: Mon Jul 30, 2001 4:54 pm Post subject: Changing jets (new guy question)

Charlie, yes it was good meeting you too. And I intend to do better then the 1:34's. Although my wife said I may have gone 1:32's, but I'll have to wait for Dave to post results on the MKC site. Hey that's only 10 seconds off the pace of the "5 foot wide" karts. Maybe I'll get one for next year.
Dan

Dan Meray · Posted: Mon Jul 30, 2001 5:21 pm Post subject: Changing jets (new guy question)

Any additional info on the RAD gauge? I can't seem to find it on their web site. Sounds better that what I was supposed to get, only one number to worry about.
Thanks,
Dan

Tim Blaney · Joined: 18 Jul 2001 Posts: 1127

Dan, go to the Longacre web site, the do a search on RAD. . it will come up.

TB

Michael Polizzi · Joined: 18 Jul 2001 Posts: 1565

Hi Dan

Do a serch for AIR DENSITY at www.longacreracing.com

Michael Polizzi 69n
Full Bore Karting

Charlie Tackett · Posted: Mon Jul 30, 2001 6:04 pm Post subject: Changing jets (new guy question)

Dan, also check out Comet's web site. I know they used to have the lowest price on it that I had found...but that was a year or two ago.

Tim Blaney · Joined: 18 Jul 2001 Posts: 1127

The Longacre site also have a forumla so you can set your gauge at first using, temp, altitude, and barometric preassure.

Dan Meray · Posted: Mon Jul 30, 2001 6:47 pm Post subject: Changing jets (new guy question)

Thanks, everyone, I found it @ Longacre and CKS. Just like the one I had years ago from Moon. I wonder where it went?

Steve, I second what John said about Eric Gorr's site. Plenty of info for baseline plus use your builders recommnedations to start, then read the plugs. Heck, if you come out to Gingerman, Charlie Tackett will look at your plug. Isn't that part of the moderator's job? But I am sure the guys from your local track will help. Also, Tom Turner's site has plug pictures in color to help @ tsrsoftware.com
Dan