Suzuki ATV Forum banner
1 - 3 of 3 Posts

5 Posts
Discussion Starter · #1 ·
Hello All,
Thanks for allowing me to join.
I am a retired full service mechanic and all around fix it guy.
Well except for motorcycles ...just now venturing into them.
I bought a used Suzuki lt250 quadrunner (1991) for my daughters
kids on the farm. It started and ran fine but was kind of a dog but
I just figured that was age. Plastic was all broken up so I put a couple boxes
of pop rivets and some aluminum stitching in it and now she is called
Frankenstein. Has all of the original mudflaps. Fixed the starter and gave it
to her with balding tires.
Well they let it sit for about 5 years so I drug it home. Looked it all over,
painted the frame, freed up and redid the front brakes, new rear tires, battery,
all of the boots are fine. A wee little bit of play in the U joints. Lights and all that work.
Since I am introducing myself I should tell you my problems....It would take a big couch!
took the carb apart. the bowl was dirty so I cleaned all that and just put it back together.
OK i dont know the part names but the carb has a throttle butterfly AND a rectangular piston
with a metering rod that slides up and down. At the top of the piston is a rubber diaphragm. I figure the diaphragm was supposed to pull the puston upwards or open. Buttoned it all up, reinstalled the carb and air filter and started the machine.
I can tell that that diaphragm was the problem because now this thing is a bear up to maybe 3,000 rpm.. At a certain point the motor starts spitting and sputtering and to me acts like it is running out of gas.
The fuel line has a vacuum operated fuel pump on it. With the motor running there is a lot of vacuum getting to the fuel pump. With the motor off and using the electric starter to turn the motor fuel trickles steadily out of the disconnected fuel line which has to run uphill to the pump. When putting thumb pressure on the fuel line while operating the starter the fuel pump does not seem to build up any pressure.
From what i have told you I am looking for possibiilities why this thing stutters badly
when it gets up to a certain rpm. It is great down low.
Any ideas?
Thnanks in advance gary

9,802 Posts
Did you clean out the jets within the carb as well..? At this point I would throughly clean the carb completely. If you can give it a ultrasonic cleaning that would be best. After that, buy yourself a high quality carb rebuild kit. Shindy kits are usually pretty good. I’d start with that then go from there.

The fuel pumps on these atvs are not high pressure pumps. When working the pump typically pulsates fuel not continuously flows it. Your fuel petcock based on your model is the non vacuum type, On/Off/Res. These fuel petcocks unlike the vacuum style doesn’t shut the fuel supply off automatically whenever the engine is shut off. Thus requiring you to shut the fuel supply off manually. With that style fuel petcock, they are solely gravity fed. So pulling the fuel line off before the pump should simply cause it to flow out.

First thing I would do however is drain the gas tank and refill it with fresh fuel. After that thoroughly clean and rebuild the carb. In those 5 years I’m pretty confident the fuel in the tank has gone bad, and the jets, seat, and other runbber components have most likely dried out. Which is probably what causing the majority of your problems. And welcome to the Forum.

5 Posts
Discussion Starter · #3 ·
Thanks for reply,
I have been into a lot of carburetors and cleanliness is next to Godliness.
I looked at everything but i did not know the float level setting so I left it as it was.
I am pretty sure the carb is right or close. Cutting torch tip cleaners, assortment of tiny brushes and carb cleaner were used.
EXCEPT: I did not know the correct turns out for that fuel metering jet on the bottom
of the carb. It sounds like i have to figure out how to turn that bottom screw out some...preferably while it is running.
I have maybe just the right tool for that
It did not seem like the fuel pump was putting out a lot. Was wondering if it was starving itself.
thanks gary
1 - 3 of 3 Posts