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Old 08-06-2020, 08:58 AM   #1
Not Yet Wild
Join Date: Jul 2020
Posts: 5
Default G9 airflow problem

Hi I have a G9 I just bought with a weird issue. I'm an auto mechanic but not much experience with these things and its driving me crazy. I've read on here many times that these wont run well without a tight sealed airbox but the issue I'm having seems backwards to everything I know about engines. It had a bad rod bearing when I bought it fixed that and inspected everything else.

When I went to start it it wouldnt run right unless the choke was on. Then I noticed that with the airbox disconnected from the carb it ran pretty good. If I put the airbox hose/snorkel on the carburetor with the other end disconnected from the air box (just the hose on the carb) the engine dies unless I choke it. I also get a popping from the exhaust now and then.

Running better with hose attached and choke tells me the engine is running lean and getting too much air but with an open carb you would think it is getting more air than with a hose attached I feel like I'm in an upside down universe. It seems to me that attaching that hose to the carb would slow down the volume of air coming through or am I wrong does that hose being on create a venturi/velocity like effect and increase the air volume?

Heres some history and data
Bought with a knock in lower end. Put in new rod bearing crank seals and gaskets.

Cylinder and piston within spec. Rings within spec. Didnt touch the valves doing this on a budget and didnt want to wait for parts.

Compression 160
Valves properly adjusted
Went through carb it was already very clean when I took it apart
Hooked up a temporary gravity fed fuel supply to eliminate the pump
Replaced carb spacer
Checked for air leaks with propane and carb cleaner
New spark plug
Removed valve cover and double checked valve clearance
Verified choke plate is not loose or flopping around
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