Hello,

I just bought a 1998 Honda 300ex. Looks like it was used/abused by its previous owners.

Here are the details. It has a K&N air filter, no holes in airbox, and a Supertrapp exhaust.

It does not run worth a crap! I can get it to start at about 3/4 or 1/2 choke, and it will run if I rev it up there. It will run for about 30 seconds, then does not want to idle, and it backfires.

I know that the fuel tank vent is fine, and it appears to be getting gas OK.

I cleaned the carb today, and it did not help. Here more details:

It has a 130 main jet in it. Not sure on the pilot jet. The air mixture screw appeared to be ALL the way in! I turned it two turns out, and that did not help.

I do not know what slot the needle is in.

Does anyone have any suggestions to help!

Thanks

 

Backfire usually indicates a lean condition! Are you sure the previous owner ever rejetted after the mods?

Bad idle that improves with the choke on, indicates a clogged pilot jet or leak in the intake. Lots of folks say they "cleaned" the carb, but all they actually did is spray some cleaner around and overlook the pilot jet. Pilot jets are cheap, just get a replacement. Fact that the screw is all the way in, fits the pattern as well (they tried to make up for the lean condition that way).

No doubt, it is in need of a valve adjustment ASAP!

 

Hello,

Thanks for the reply!

I have continued to work on the quad, and what I found is as follows:

1.) No gasket at the head in the head pipe. Thankfully, both studs came out of the head (one easy, one not so easy, but both are super rusty and one is broken). I will replace them, along with the exhaust gasket.

2.) It does have a 130 main jet in it. Stock is 122, so I am pretty certain the previous owner did rejet.

I plan on getting a jet kit and jetting approriately.

Any other suggestions!?

Thanks!

 

Hello again,

I just adjusted the valves to what the forum stated was 0.100mm (0.004 inches).

The intakes were a bit snug, and the exhausts were a little loose.

I have the quad torn apart, but I will post back results.

Again, I am open to any ideas on the jetting!

Thanks...

 

I rejetted back to stock with an OEM-style jet kit, and put on a factory exhaust.

Runs great now!

Thanks!

dgilfillen