G2 stock airbox is trashed, and intake hose is gone - but cart runs fine?!

[ShawnQ]

So I recently picked up this G2 cart. I have been reading up on it a bit, and everything I have read says there needs to be an air tight seal on the intake box/tube so the crankcase pulse can operate the diaphragm fuel pump. Makes sense.

However, my intake box has no straps, the lid is warped from the previous owner causing a fire by attempting to pour gas into carb, and the intake tube itself is missing about the last 3" so it is not even connected to the carb. So, basically, the carb itself is open to the air.

With all of that said, the cart will make about 20mph (on 4" lift and 22" tires). It did backfire a bit when I had the straight pipe exhaust that it came with...but putting a temporary lawnmower muffler on it got rid of the backfire.

So, how is this thing running fairly decent without the intake sealed up? I don't get it...

Any input?

Thanks,
Shawn

[Mike Mac]

Just lucky I guess!!

[TheNewGuy]

I would say the carb must have been re-jetted to run with no air filter and no muffler.

[ShawnQ]

Originally Posted by TheNewGuy

I would say the carb must have been re-jetted to run with no air filter and no muffler.

I was thinking the same.

I plan to look into the jet size today.

[Shepard]

I replaced my air cleaner system to a uni-filter -- vented the crankcase into the rubber portion of the filter. Replaced the carb and insulator + gaskets at the same time for about 56.00 dollars for all parts. The carb is not been rejetted. It runs perfectly after I adjusted the low speed screw. 20-22 mph with 20 inch tires @ 3350 rpm. Oil the air filter -- this will create a slit resistance to the air flow.

[ShawnQ]

I put an air filter on it today. It didn't run quite as well at first. It still made 20mph but that was at the rev limiter.

However, when I got home it wouldn't run. I'm thinking the plug may have fouled due to excessive fuel. I haven't torn into it yet but I'll check it out.

I assume the previous owner probably drilled the jet or re-jetted so it would run without a filter (for some unknown reason).

Will update

[smallblock450sl]

Originally Posted by Shepard

I replaced my air cleaner system to a uni-filter -- vented the crankcase into the rubber portion of the filter. Replaced the carb and insulator + gaskets at the same time for about 56.00 dollars for all parts. The carb is not been rejetted. It runs perfectly after I adjusted the low speed screw. 20-22 mph with 20 inch tires @ 3350 rpm. Oil the air filter -- this will create a slit resistance to the air flow.

Just for clarification, what is "low speed screw"?

[sho305]

Idle mixture on side of carb? Some will run with nothing on the carb because (I think) the open carb does not flow air well the carb flows more with a tube or hose on it or at least a velocity stack.

The pulse runs off the block and has nothing to do with the airbox, but the breather goes there and can drip oil sometimes especially if you have a lot of blowby.

I have a clone now but I jetted my stock engine to run with no silencer on the airbox. I just hogged the main a little with a torch tip cleaner until it ran good. I never used the choke on that cart in the summer, and did the same thing with my clone drilled it out. Also make sure you use the G16 plug I think, its the bprs2 ngk. Lot more resistant to fouling and yamaha recommends it for G2/9.