Yamaha G16 Airbox Mod Carb Issue - Help!

ddeem

I recently got the bored & honed motor back into my G16 cart (.50 over running royal purple oil and 93 octane fuel, carb completely cleaned with new gaskets). I slightly ported the head and have the Plowmans Air Filter & Jet Kit (Main Jet and top Jet), CPP Clutch Spring. Governor nut is tightened all the way.

The cart ran pretty well and had a slight hesitation at low speeds. I removed the airbox and did the mod to open up the inlet and a few extra holes in the restrictive places.

Now, when I step on the gas, it chokes and dies unless I ease in to it. At top end it runs great (21MPH GPS with stock tires). Also, it idles well. Can anyone offer up how to get these carbs to run better? I played with the only adjustment on the carb and it does not seem to make any difference. It is currently out 1 1/2 turns. Does anyone think I need a bigger main jet? Does the main jet effect idle to mid throttle and what does the top jet do? I just want to be able to step on the throttle and have it take off...

Thanks for any help on this and I really appreciate the feedback,

Dave

BGW

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TheNewGuy

I would try increasing the size of the main jet. It takes some trial and error to get everything working together. Did you mod the exhaust? What does Plowman say to do?

Ron


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ddeem

I have not made any changes to the exhaust. I will contact Plowmans to ask what size jet they sold me (could not read the size on the jet before I installed). Do you know what the one adjustment does? Is this for idle?

Finally, it seems like some people run some pretty large jets. Maybe I am a little lean... I am just confused because the plug looks pretty good and once moving, it takes off well. Just the initial top 1/3rd of the pedal is the problem... So to be clear, it is from idle to 2000 rpm that is the issue and once above that it runs great.

shawn.m

I don't think that carb has a mid range adjustment. it is idle jet and then main jet. This makes the carb very sensitive to the mid 1/3 of throttle as you transtion from idle jet to main jet.

best advice is to go buy a bunch of jets from a bike shop and start playing with it. Basically keep increasing the main jet until it bogs on the top and loses the crispness in the response.
It sounds like the carb just does not like losing all of its vacuum when you open the thorttle plate full bore.
when you are slowly opening the throttle, you are giving the motor a chance to keep the vacuum up.
if you are still running the stock muffler then you have created a dual issue. First you made the motor flow much better on the front but did not get rid of the backpressue on the exhaust. I would look at buying Dons muffler for the G16 as it is supposed to flow better.
Modifying stuff can be frustrating at times until you find the right mix. I think in the end you will have a power house of a motor.
What you are building is real close to Dons G16 power motor kit.

ddeem

Thanks for the feedeback guys...

Shawn - Your exhaust backpressure and intake vacume comment makes a lot of sense. That is exactly the way it feels like when it is running. Once you get the rpm's up slightly it gets enough pressure build-up and takes off.

I ordered a 52 jet to try and will find out what the Plowman's jet is. Also, I think I am going to take a shot at cutting the bottom off of the muffler and removing the stuffing inside. Does anyone know - is this what Plowman does with the air cooled muffler for the G16?

Exhaust flow should really get it going...I just don't want it to be loud...

Thanks again,
Dave

shawn.m

what type of jet are you getting that is a 52?
On my G9 which is smaller than the G16 I went from the stock 110 dynojet to a 153 dynojet when I had the Dirt bike muffler on it. I have gone back down to a 132 dynojet with a stock muffler that is opened up. You can get the jets from denniskirk.com for $1.30 each

I would think it would be cheaper and faster to keep the stock muffler stock and weld a different muffler in. Use a 4 cycle dirt bike muffler or a supertrapp muffler.

If you don't want to guess at the muffler just buy Dons muffler, it is only $159 with shipping. It will be pretty quiet and more free flowing.
no I don't know what he has done to his muffler. He has never said when I have talked to him, only that he opened it up while keeping it quiet. That is a art that I don't have, so I respect what he has done.

ddeem

Jet I ordered is a 152 not 52 that I listed...

I will see how it does and will order a few more from Denniskirk...

Thanks again,
Dave

cart de golf

Get a set of drill bits to clean cutting torch tips

& get a dial indicator to measure your drill bit sizes this way you will get exactly what you need.

Just go very easy on the drilling you can go over pretty fast