I have a suzuki quad runner, it’ll start but dies right away I cleaned carb and have 122 psi for compression. What could it be?

 

Lots of different Quad Runners from 50cc two strokes to 500cc 4 strokes. Try a new plug as you never know, it could be a dud plug, but carb is still the most likely problem. With 50s the float set too low will stop much fuel getting into carb so, when you start it up fuel already in there gets used, but the float needle doesn't allow enough through to keep running. Once it stops, enough drips through to get it started again. The fuel filter, or tap can also do the same trick, as can a blocked tank breather, though it usually takes a while to stop with that.

 

You could also add a spark tester inline to see if you are losing spark as it dies or if it keeps sparking.

These inline testers make that easy and they are cheap at places like harbor freight.

 

Yeah I have good spark and it doesn’t stop at all unless I let off the starter button, if I stay on the starter button it would run but burn the starter out haha. I know I have fuel and pressure and all vacuum lines are clear and tank valve is clear also

 

compression is too low. should be minimum 171 psi. do a rebuild with good cross hatching on the cylinder and lap your valves and youll be good to go

 

Never seen a quad yet with 170psi, most have about 110 to 130psi.

 

If you only have spark while cranking, you have a wiring or CDI issue.

Read about this before but cannot remember the cause. Whether it be CDI, or if it was a neutral switch or something. Have to open the manual and start doing pinpoint testing I suppose.

 

not sure which quad runner you have but if its an LT230s they require 171 to 228 psi of compression. They did not have auto decomps built in like most modern engines on the cam. if it has a manual decomp you may not have enough compression for it to run properly

 

228psi is aprox 15 to 1 compression ratio, that is closer to diesel engines. In comparison, a mid 1980s Honda 200cc quad had a ratio of 7.8 to 1