Almost stumped with a carb issue

[El Camexican]

OK guys, I have made some headway with this thing.

First thing I tried was swapping the known working choke plunger in from my 350x. Still ran the same. But when I swapped my complete carb in, it now runs perfect! I verified that the idle air circuit coming into the choke plunger housing is clean and clear with a small piece of wire, so I know it is getting air. For some reason, the neither choke plunger is stopping fuel from coming up through the enrichment circuit from the bowl. All I can think is that the little raised sealing surface in the bottom of the choke plunger housing has something physically going on with it preventing the needle and rubber face of the plunger from sealing off the fuel. You can see in the pics I included of the choke plunger that it is not damaged. I can't see anything obviously wrong with the base of the housing... This is weird..

But I'm selling him my stock 350x carb and I have a 400ex carb in the soak solution as we speak that will be going into my 350x. His quad will now run perfect, and I am finally doing the 400ex carb upgrade to the 350x... Win-win!

Crap, no pics.. Having trouble with the upload box......

You're a brave guy. I'd test that 400 carb before you commit to selling the good 350 carb. I had a bad experience like that once going from a bank of good 34mm to a bank of 36mm carbs that turned out to be trash.

[RIDE-RED 250r]

Good point, but the carb is in his Fourtrax and the deal is made. These 350 Foutrax carbs don't seem very abundant and he was talking about getting a Chinese ebay carb. I didn't want to see him go down that road and possibly get a junk carb as hit and miss as those chinese knock-offs can be... I think the 400 carb will be ok after a cleaning. It really wasn't too bad to begin with. I've brought back much worse carbs to running condition.


Wanted to note: When I was swapping his old brass into the 350x carb, I did find a few more subtle differences between the two carbs.

1: The 350x carb has a deeper bowl and taller main jet orifice/emulsion tube

2: We all know that the 350x carb uses the same main jets found in the PWK's and other popular Keihins. The Foutrax carb uses the round main jets that take a flathead screwdriver, like the start jet.


Aside from these little differences and routing a longer fuel line, the swap is pretty easy and straight forward.

I had to fatten up the pilot jet from the original #35 to a #45 for some reason. Idle was hanging. Main seemed good sticking with a 140 as found in the original carb.

The old girl runs like a watch now and for it's size it gets up and goes through the gears with surprising authority. Well, not too surprising, it IS a 350x mill after all.

There's my pics. You can see the rubber face of the plunger where the needle is that is supposed to stop the fuel when the choke is off and seated.