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Discussion Starter #1
The Original carb on my panther 500cc engine is no good dont work for crap after cleaned and adjusting it. So i tried a carb off a trailcat 340cc that i just got off my friend today for 20 bucks :) engine on that is perfect but i just bought it for parts. My panther engine starts right up now and runs great like it did when i had my jag carb on it before it burned up. The original carb had a 280 main jet. The carb on it now has a 200main jet. I was wondering if its a good ideal to change the air jets and the pilot jets or if the ones already in the carb should do. I need to change the main jet to a 280 but i dont know how to get the jets off of a butterfly carb. I'll post a pic and if someone could tell me how to get the main jet out that would be great thanks. Also i dont know how exactly to calculate what new jets it might need besides the main jet since the original carb is a 1978 roundslide carb and the 1980 carb off the 340 is a butterfly carb.

1980 carb specs Would i be able to tune my carb to the 1980 panther specs and have it work right on the 1978 panther engine. i would assume they would be about the same just the 1980 panther came with a butterfly carb.
 

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as long as the carbs are the same size, they will fit just great, (which it appears they do as you say its on there now),,, but you need to have the correct jet for the motor that it is on, not the one it came out of. If you had a carb there that would have good jets in it, you could always swap the jet out of the bad carb to the good one and then your set,,,,
 

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Discussion Starter #3
I know i need the correct main jet for the engine its on now but i was just wondering if i should consider changing the idler jets and the air jets. Or will the main jet do just fine? Also on the carb i do not know how to access the jet its not just the screw out type. Some help there would be nice. Thanks
 

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your pilot jet and your main jet are the only 2 you are going to change,,, you dont have an air jet, its a screw that you should tighten till lightly seated, then turn it back out 1 1/4 a turn as a starting point. You do want the correct main and pilot jet though,,, as long as they are both mikuni carbs, the jets should swap over,,, if you are still unsure, try posting a picture of what you have and we can help you from there,,,
 

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Discussion Starter #5
Here is a diagram of the old carb i have that doesn't work


Heres a diagram of the carb i put on it.
In the diagram on this carb it shows the main jet and how everything tears down but when i try to unscrew the tube from the top of the carb #18 on the diagram i'm afraid its going to break off one of the weak tabs for the screwdriver and then i will never be able to get the jet out but i'm pretty sure thats all i need to take out to get to the main jet on that carb. I can easily take out the jet off the 1978 panther carb but i dont think that the pilot jet will swap from that carb to the 1980 trail cat carb since its a butterfly carb. Both carbs are mikuni except the original carb is a "ROUNDSLIDE" style carb and the carb i'm using now is a "BUTTERFLY" style carb.

Got all this off of brownsleisureworld.com
 

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Discussion Starter #6
No one has had any experience with butterfly carbs?
 

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What do you mean Idler Jets? There is a air speed Idler screw that should be turned out 1 +3 /4 turns . I have a lot of experience with them old carbs thats why I don,t think you do ? because if you did you would know that the butterfly carb is not dead and can,t be unless you hit with a hammer or stuck a srewdiver in it because you did not know how to set it . Just ask there are a lot of us around that where working sleds before you could even sit on a seat
 

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Discussion Starter #8
by Idler jets I meant the pilot jets which is the same thing as they both work at low speeds. And no the butterfly carb I have is a good one. The roundslide carb is the one that dont work. I did seat the airscrew and turn it out 1 3/4 turns that does nothing for it. I'm pretty sure that it just needs a carb rebuild kit but I like the butterfly carbs better so i'm converting over to one of those. But all that i need to know how to do now is remove the main jet from the butterfly carb which no one has been seeming to help me with. And i'm not dumb i just havn't had any experience around butterfly carbs. I know on the roundslide ones its only takes about 1min to take off the bowl and unscrew the jet and change it.
 

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I cant ever recall buying a kit to rebuild a carb,,, I have bought a new gasket if I tore the old one, but that doesnt happen often either. My guess is your old carb is not cleaned good yet,,,, I have had some rough ones that I ended up going through 3 or 4 times to finally get all the crap out,,, as you hold the carb stripped down in your hand, you should be able to see where each of the passages go,,, make sure EVERYONE of these passages are good and clean. Once you get them all freed up,,, you should be fine.
 

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Discussion Starter #10
I already did that. and yes you can buy kits that come with new gaskets o rings and main jets. I used about the whole can of carb cleaner on it sprayed in every hole did this serveral times and still nothing.
 

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I know you can buy the entire kit,,, I simply stated that I try not to do if its not needed. Why spend the money if you dont have to???? I have had tough carbs that I have unloaded more than an entire can on and had to go with the old pipe cleaner to get them freed up,,,, I am not stating that this will fix yours, you make that decision,,, I can only let you know what I have ran into in the past,,, Sorry I evidently cant help,,, good luck
 

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Discussion Starter #12
Its ok. But all that i need to know now is how to get the main jet out of the butterfly carburetor.
 

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Use a needle nose with a cloth and trun it out counter clock wise note how many turns and install the new one with the same amount.
 

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Discussion Starter #14
i figured it out the other day. it just pulls out lightly and pops back in with little pressure.
 

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The Mikuni roundslide is a superior model to the butterfly. You may have problems other than dirty as an out of adjustment float, leaking needle and seat or a float that has a hole in it. Any of those three problems will cause the fuel level in the float bowl to incorrect which usually results in a rich fuel mixture. Another overlooked item is a sticking or fauly choke adjustment which has the same results.

Mikuni.com has excellent information available on carburation theory.

If your heart is set on using the butterfly carb be very careful with selecting the correct main jet as the carbrators will not have an equal air flow rate. The jet size for the roundslide may not be the correct size for the butterfly. Read your spark plugs carefully. If you are unsure of the color have a friend or experienced 2 cyle guy read the color for you. An error on the lean side will cetainly result in engine failure.
 

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Discussion Starter #16
thanks yea its running a bit rich now so i need to go down to a 270 or 260 from the 280 jet and it should be good... also need to pick up a new set of plugs :p. thanks everyone
 
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