Carb Adjustment

gilzuckie
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gilzuckie
Edited Date/Time 2/11/2015 4:58pm
Hello, I recently picked up my wifes old 1973 xr75 that has been sitting at her moms house in the garage for years. It is in still very good shape and it does run, but not great. Need carb adjustments. Been searching everywhere to just find out how to adjust the carb. Can anyone please help with how to adjust the carb. Pictures would be great also or diagram of the carb. Not sure what the two screws on the side are. Thinking middle screw is fuel and the lower left screw is air. Thanks
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Dragoo168
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Dragoo168 2/10/2015 1:06pm
2/10/2015 1:06pm Edited Date/Time 2/10/2015 1:07pm
The screw towards the front of the engine (on the side) should be fuel, and the one in the middle should be the slide adj. After you disassemble and clean the carb, especially the jets, then set the fuel screw to 1 1/2 turns out to start, and turn out the idle screw to where it lets the bike idle without hanging up in the rpm's. I usually turn it out completely, then turn it back in until it'll barely idle, then start turning the fuel screw in or out, 1/4 - 1/2 turn increments to smooth out running. Then adjust idle up slightly, but not so much to as affect rev or decelleration, but to a steady idle, with clean throttle response.

http://cdn.partzilla.com/diagram/honda/131530/ILLUST/E1315/3012.png
gilzuckie
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gilzuckie 2/10/2015 1:31pm
2/10/2015 1:31pm
This picture looks more like the carb I have. Which screw is the Idle screw?There are 2 screws



Dragoo168
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Dragoo168 2/10/2015 1:43pm
2/10/2015 1:43pm Edited Date/Time 2/10/2015 1:45pm
The one in-line with the slide (The middle) is the idle. Yours looks like the one with the purple mark is an air screw, but setting it 1 1/2 turns out is still a good starting point. I was looking at the diagram i posted wrong, it's an air screw also.
gilzuckie
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gilzuckie 2/10/2015 2:08pm
2/10/2015 2:08pm
OK, that helps a lot. I've been reading conflicting opinions on what the screws were. Thanks so much for the advice.

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Wahtash
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Wahtash 2/11/2015 5:20am
2/11/2015 5:20am
Adjustment is not going to help if it has been sitting for years with fuel in it. It needs to be taken apart and cleaned and then adjusted
Dragoo168
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Dragoo168 2/11/2015 11:21am
2/11/2015 11:21am
Anytime man, have fun with that old bike, wish i had one laying around to putt, LOL!
project racer 2/11/2015 4:58pm
2/11/2015 4:58pm
Just buy one of those China knock off carbs from ebay. I have used several on various pit bikes, and just bought one for a PW50 , new, for $18. All have worked well, start right up, and run good.

Could not even buy a needle and seat for the PW for what the China carb cost.

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