Jetting for purple plate

K

Kartracr18

New member
What is a good Jet size to start with for a purple plate flathead? How about blue plate? Just bought a Kart and motor and was told I could run it in either class. Thanks
 
Just the opposite, the smaller plate lowers fuel pull at the jet so you have to run a bigger jet to compensate. I know that sounds odd but trust us ;) Brian at Carlson is correct on verifying pipe id, spring pressures etc as there's a number of differences in a flathead from purple to unrestricted, even a few from purple to blue in a max effort. Good Luck!
 
Stunner Racing Engines said:
Just the opposite, the smaller plate lowers fuel pull at the jet so you have to run to compensate.
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seeing as how there is no such thing as pull, or suck, (when talking fuel flow in the carb, everything gets pushed) and I have no doubt you are right about the smaller plate, it makes me wonder exactly what is going on? 56 to 60 is a 14.8% change in jet area. Not disputing your advice on jetting, just wondering.

.056 to .057 is a 3.6% change. .059 to .060 is a 3.4% change. This is a change in area not diameter.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
I knew it was coming as sometimes I think you use the search function to find jetting post to comment on lol. Let's keep it simple for beginners and put them in the ballpark with information that will get them started and terminology they understand...... I almost didn't comment because I knew this was coming. That's a shame. There's plenty of other carb post I haven't commented on for this simple reason. You're obviously a very intelligent man and have created some really good spreadsheets but every jetting post gets old. Sorry.
 
Agreed. Why does the nomenclature or terminology matter to the original poster who was requesting jetting recommendations? Suck/pull or push/atmospheric or low pressure/vacuum, or pressure differentials.....I agree with Stunner, the constant badgering gets old and discourages folks from contributing valuable information.

Al, please explain to us how a pulsa-jet carb really works (in whatever words you choose.) We're all ears -- you've got the floor.
 
CarlsonMotorsports said:
Agreed. Why does the nomenclature or terminology matter to the original poster who was requesting jetting recommendations? Suck/pull or push/atmospheric or low pressure/vacuum, or pressure differentials.....I agree with Stunner, the constant badgering gets old and discourages folks from contributing valuable information.

Al, please explain to us how a pulsa-jet carb really works (in whatever words you choose.) We're all ears -- you've got the floor.
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I really don't understand this reluctance to hear all opinions. You know I'm not wrong, I'm just different. I'm past dying young and I'm not going to ride away.

You want to talk down to newcomers, that's your privilege, but I choose not to. The learning curve in karting is steep enough without having to deal with dumb downed answers to serious questions.

It seems I continue to ask embarrassing questions, questions that you, apparently, can't answer, I assume of course, and I think I have an understanding of your baiting tactics. Go fish in someone else's creek!

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Once again, AL, this post would have been sufficient at post #8 - happy ending and all.
But Noooooooooo, you've got to make everything into a debate.

Please answer my questions and we'll take it from there.
Why does the nomenclature or terminology matter to the original poster who was requesting jetting recommendations?
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No one is talking down to you. You are entitled to your opinions (right OR wrong) on here. No baiting tactics (whatever you mean by that).
You're a smart man, tell us how the Briggs pulsa-jet really works.
 
I'm sorry I got everybody in an uproar, I asked a simple question trying to do the right thing for my kid to enjoy his karting experience.
The answers I got were very helpful. The carb had a 52 jet in it and a purple plate restrictor and would not turn any RPM's, 4600 no matter what gear I tried. Hopefully putting the correct jet in there will make a little difference. Just trying to learn and have a little fun. I understand if we get more serious about this there is more things to consider, but for right now we just what to get around the track in one piece. Thanks again.
 
You should gain quite a bit with a 59-60 jet from a 52 with the purple plate. Be sure to ask some of the other dads in the class what clutch and rear gear they're on to get you in the ball park. Most are willing to give you some information up to a point. Where are y'all racing? Maybe there's someone on here that runs the same track that could help you out.
 
Stunner Racing Engines said:
You should gain quite a bit with a 59-60 jet from a 52 with the purple plate.
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a change from .052" to .060" is a 33.3% change in area. If a .060" is right, (and I'm not saying it's not) I can't imagine the engine even starting with the .052" jet, let alone running.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
I bet if the original poster installs a 60 main from a 52 in a purple plate flathead it not only starts but starts easier and will run much better. Maybe he'll post the results. From experience, I can tell you for a fact it will start and run with a 48 main and make laps just not fast ones. I understand math, but I'm giving information that answers the original posters question and helps him and his child get going not to prove I'm smarter than anyone else. Thanks.
 
Stunner Racing Engines said:
I can tell you for a fact it will start and run with a 48 main and make laps just not fast ones. I understand math, but I'm giving information that answers the original posters question and helps him and his child get going not to prove I'm smarter than anyone else. Thanks.
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048" to .060" is a 56.2% change in flow. You decide.

There's no way that I can prove that I'm smarter than anybody. For the obvious reason, it's not true and I don't want anybody to think that I think any different.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
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