Leaderboard

If fuel is getting into the vacuum lines it means the diaphragm in the pump, or tap, depending on which vacuum hose it is, has a hole in it. And yes some are quite sensitive to their airbox and filter... Some other bikes, it doesn't seem to make a lot of difference. I always make sure the filters all oiled and wrung out correctly before adjusting the carbs.

The fuel pumps are fussy about their vacuum. They need thick walled vacuum hose because if you use thin walled hose it partially collapses and dampens the pulsing effect the pump works on. If you attach it to the wrong vacuum port they can get too steadier vacuum too and not pump properly. They also don't work as well when going up a hill because the vacuum drops when there is a load on the engine. They might have disconnected the pump because it wasn't working properly going up hills. Here's how to test the pump... To test the fuel pump you lay the fuel hose to 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 vacuuum. 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 mills 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. Low vacuum at high revs can be caused by a blocked exhaust.

Have you adjusted the idle mixture Joe ? Are you sure the choke's going right off ? Valves don't cause smoke. I'd recommend leaving those alone at the moment. They are very particular about their clearances and you need to allow for the wear when you are setting them. If you get it wrong it will be adding a complication to checking and adjusting the carb. The smoke might clear after the bikes had a run and been warm for a while. Those bikes originally have two vacuum lines, one to the fuel pump and one to the automatic vacuum operated fuel tap if it's still fitted. I think that carb will have the vacuum port for the fuel tap on the front(near the engine) right, and the bigger vacuum hose for the pump comes off on the left and about in line with the slide I think from memory, or perhaps a little forward of that. The bowl breather will be right rear and the fuel inlet left rear.

Not sure which vacum line you are referring to vacum line off the carb or off the engine, if its off the carb it may be there for a vacum petcock and yours may not have that but the carb fits many different models. For checking the valve lash remove the valve cover, turn the engine over until both rockers are loose, use a feeler gauge to check the clearance have looked at your manual but should be intake 002 and exhaust 004 or somewhere in that range.

If it was on it when you got it it should go back on, might take a little finagiling, like turn it to the side get it started in the rubber connection and then turn it to where its straight the rubber should give a little bit so you can get it in there. If you prefer to get another one i have had good luck lately with aftermarket ones, i prefer OEM but a good used one is hard to locate, i have tried on several of my projects.

Its different from OEM, waas it on the bike when you got it.

Did you notice that they didn't have that diaphragm on the bottom of the bowl ? Would that make the difference between fitting and not fitting ? I'd suggest sending that carb that doesn't fit back, and cleaning the old carb. Unless the idle mixture screw is seized in, or there is huge amounts of play between the slide and body, then it will be the best option.. the aftermarket carbs hardly ever run right without some adjustments and work anyway.

https://www.partzilla.com/catalog/suzuki/atv/1991 There are four 1991 quadrunner's listed, and several models of carb. Some of the carbs are similar to that one you have except they don't have that enrichener valve that hangs off the bottom of the bowl. Check carefully though because there are several different jetted carbs, each for a different market, for different fuel, altitude, climate and possibly engine. It appears your carb isn't availiable, but, if you identify your model bike, then choose the correct carb in the listing and double click on the part number, it will take you to a page where, if you scroll down a bit, you will find a list of all the other models that carb fits. One of those other bikes may still have it's carb availiable, or you google search for the original part number for an after-market carb.