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1992 Suzuki King Quad 300 Help


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Hi All,

I have a 1992 Suzuki King Quad 300. I got it in rough, picked apart condition on Facebook marketplace. The previous owner was not mechanically inclined and threw parts, and deleted parts to get this to "run". To give you an idea of what I am dealing with he put a non vacuum carb on with a separate fuel bladder mounted on the rear rack. I live in CT and things are a bit high here so I got the atv with a plow for $400. The atv came with (3) Carbs, 1 OEM, (2) petcocks 1 OEM. What I have done / found is the neutral safety switch was ate by mice (probably the original problem), fixed that, reinstalled (cleaned and put in a new needle and seat) OEM carb, the diaphragm is a little clapped out but still flexible, installed new Fuel pump, cleaned and reinstalled OEM petcock (non vacuum) has slight drip every now and again as I did not replace the tank side gasket when I installed and installed a brand new battery.  doing all that the quad fires and runs but briefly.  On the handle bar the choke paddle is broke off, I ordered that and looks like you need to remove the grip to install so haven't done yet and If i can get some direction on that as well, So that is "floating" in  the carb as I do not have the correct choke cable connector, I took the one off the Chinese carb and it somewhat holds it in place. The air box and system are gone and it has a stubby K&N cone filter on it currently.  So the way I start it is pop off the air filer, hold my hand over the carb to get a good enough vacuum to get to the bowl, then it will run for a few seconds. The tank is filled to the top, to help it out. Does anyone think I am missing anything before purchasing the entire air box system (If I can find it). This will be a yard machine for work and will not be taken out recreationally, cool little machine I would like to keep it, but unsure if I will spend the money on a airbox system as it for sure seems I am not pulling a good enough vacuum with out it. 

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I did take a look at the intake manifold boot, no signs of dry rot and looks well seated. I would say the vacuum slide is working because when I get the bowl full the quad will idle decent and rev up and down with out any bog, nice and smooth. I did pull the vacuum line off the fuel pump and held my finger over it and can feel it suck. I do have a cheap fuel pump on it from amazon and the elbow where the vacuum line goes on can be pulled out of the socket and rotates like its on a bearing. Maybe I will try rebuilding the OEM one. 

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The fuel pump vacuum has to be pulsating. If it's got a steady vacuum then you have a restriction in the hose somewhere or the hose is too thinner walled.

If the carb is full of fuel, then it should run. Check the fuel is getting to, and into the carb by undoing the drain screw on the bottom and checking fuel keeps coming out after the bowl has emptied. It should flow by gravity if the tank is full.

Then, if you take the fuel hose off the carb and lay it in a bottle it should be pulsing out fuel when it's idling.

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I think you might be running  lean after you check to make sure your fuel pump is pumping gas as Mech suggested, try enriching your mixture a little bit see if that helps, you can also check for manifold leaks with it running spray wd 40 carb cleaner what ever you have right where manifold meets the engine and where carb meets manifold if idle increases you have an air leak. As far as getting hand grips off I pry up the rubber a little and squirt a little lubricant around the grip and use compressed air to blow it loose from the handlebar. 

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If it runs ok when the bowl is full then you need to figure why the bowl isn't staying full.. 

When the tank is full the fuel will/should flow out the carbs fuel hose if you pull it off.. You should check that happens first. 

If there is fuel getting to the carb then use the drain bung to check it's flowing through the float needle and into the carb fast enough.

If there was no fuel to the carb then check for restrictions or vacuum in the tank. That new pump might restrict the fuel when it's not getting vacuum.

To test the fuel pump you lay the fuel hose from the carb into a bottle. Lay it on it's side with the hose laying flat. If the hose is dangling down you won't see the fuel pumping out properly. Then suck hard two or three times on the vacuum hose going to the pump, and then let the vacuum off suddenly. You should see a single slug of fuel come out of the fuel hose. The slug should be full diameter of the hose and about ten mills long. If that works then your pump is ok and will work if it's getting good pulsating vacuum.

To test the vacuum you reattach the vacuum hose and start the motor and let it idle. It should pump fuel out of the fuel hose into the bottle at full diameter of the hose and slugs about eight mils long. If that works then the pump is working and it should start and idle at east.

Then you need to check the vacuum is still strong enough when the motor is under load. To check that you leave it all as is but sit on the bike, put the brakes on hard, engage first gear and open the throttle until the motor starts straining against the centrifugal clutch. As the motor starts to labour the pump will likely slow down it's delivery of fuel, but it should keep pumping some. If it stops pumping then you have weak vacuum or a malfunctioning pump.

The vacuum has to be strong, and pulsating when it gets to the pump. If the vacuum hose has been swapped with some soft thin walled stuff the pulsations can get lost as they suck the vacuum hose flat and then let it out again. Low vacuum can be caused by low compression, tight valves, or air leaks.

Edited by Mech
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I did not even think about the vacuum line being non oem and folding on itself, as I had to use my heat gun and warm the end up real good to get it to fit on the aftermarket fuel pump, however it was on the previous one and it looked OEM. I will check that later this week. Do you know what size it is supposed to be? I can not find it online.


Thank you

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I think it's eight mill/five sixteenths. Fuel hose works.

Also, some aftermarket carbs don't have the large sized vacuum port on the carb, the brass fitting. The originals had a hole in it about five mills but I've seen aftermarket with a smaller hole, about,,er..  a bit over two mills I think it was from memory..  That didn't work and I swapped brass fittings.

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