J’s dirty 30

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.
My coil tester shows the spark jumping a big gap. I cleaned up the carb last night and fired it up earlier. I drove it about 5 minutes before it did its typical thing. It starts sounding strange and bogs out when I give it throttle.
Removing the filter allowed it to start again but adding throttle bogs it down. The spark still jumps a good 3/8” gap.
Lever height is set according to the gauge that came with the spiral diaphragm kit. Pop off pressure is somewhere in the 22-25 psi range, hard to tell on the gauge on my compressor.
I knew it was rich while running because it sounded lethargic and responded to turning the low needle in. The plug looks fouled after that little run. I have left the needles as is to pick up where I left off.
Seandonato73 said:
Needle tip issue is possible, metering lever height would definatly cause the issue. Blow main check would cause the issue.
Click to expand...
What is the main check?
 
Your problem is your insulator is causing the carb to pressurize and is pumping fuel into the engine under pressure. It's a heat related issue and what happens is the heat of the cylinder is migrating to your carb which in turn is causing the pressure to rise in the carb and forcing fuel through the jets. You need a delrin or nylon price sandwiched between 2 gaskets, that I guarantee will solve your issue, I know because I did the same thing and suffered the same symptoms. 1000006770.jpg
 
Rep732 said:
Your problem is your insulator is causing the carb to pressurize and is pumping fuel into the engine under pressure. It's a heat related issue and what happens is the heat of the cylinder is migrating to your carb which in turn is causing the pressure to rise in the carb and forcing fuel through the jets. You need a delrin or nylon price sandwiched between 2 gaskets, that I guarantee will solve your issue, I know because I did the same thing and suffered the same symptoms. View attachment 93277
Click to expand...
Will that thin Teflon gasket between 2 paper gaskets be enough or do I need something thicker
 
Yea you do. I personally prefer the insulators from obr as their delrin insulator between the carb and manifold is about 1/4" thick. I didn't have good luck with the style your running and I ditched the Teflon pieces and that's how I ended up In your situation
 
Rep732 said:
Yea you do. I personally prefer the insulators from obr as their delrin insulator between the carb and manifold is about 1/4" thick. I didn't have good luck with the style your running and I ditched the Teflon pieces and that's how I ended up In your situation
Click to expand...
I will have to go the same route I think.
I spoke with Dave at DDM and he says I ordered the plastic insulator for a g290 not a g320 so no wonder it won’t fit a 38cc.
Here is what I have now:
IMG_5208.jpeg
At the head and intake: the Teflon sandwiched between 2 papers
Between carb and manifold/insulator: Teflon sandwiched between 2 paper gaskets.
 
Dang it started and idled great but the first time I gave it enough throttle to engage the clutch it immediately started running funny.
If words could describe, it would sound like “dunno dunno dunno”, not a “ding da ding ding da ding ding ding”.
 
Dirty30J said:
My coil tester shows the spark jumping a big gap. I cleaned up the carb last night and fired it up earlier. I drove it about 5 minutes before it did its typical thing. It starts sounding strange and bogs out when I give it throttle.
Removing the filter allowed it to start again but adding throttle bogs it down. The spark still jumps a good 3/8” gap.
Lever height is set according to the gauge that came with the spiral diaphragm kit. Pop off pressure is somewhere in the 22-25 psi range, hard to tell on the gauge on my compressor.
I knew it was rich while running because it sounded lethargic and responded to turning the low needle in. The plug looks fouled after that little run. I have left the needles as is to pick up where I left off.

What is the main check?
Click to expand...
Spark isn't the issue then. See #22 on the diagram. It's basically a check valve in the main jet, more so air doesn't go back into the carb, but I've seen blown ones cause all sorts of funny running issues. Basically means new carb, but I'm not sure enough to say anything definitively.
Rep732 said:
It's loaded up, you need to run it at higher rpm with a load on it to clear all the fuel in the crank case. Usually these don't smoke much when the tune is right, the smoke is telling me it's burning alot of excess fuel.
Click to expand...
Good grief pig rich batman!

Screenshot_20240515_063041_Drive.jpg
 
That was one full turn out on both needles on a cold start, it just did the same thing to me today. I went in more leaning it out to where it would bog down and not move while giving it throttle but it did rev up. All the while it’s pouring out smoke. This is confusing, but a new carb is on the way along with a new insulator.
FearlessRC is sending me the carb for free.
 
Back
Top