coalburner

My Feedback: (1)

Zenoah G62 carb problems, not drawing fuel

I own and run many G62's, a great engine for my giant scale sport flyin.
Recently at a swap meet, I bid 10.00 for a box containing 2 zenoah engines for "parts". they looked unused for years and covered with grime. To my surprised the g62 looked in pretty good condition after i cleaned it up. Compression felt good and I put a new champion plug on and a brand new hda 48 carb bought from dave's discount motors. I used the original insulator block and the 2 carb gaskets that were on the engine. It fired after 4-5 flips and ran at 7000 rpm with an APC 22x10. Wow, what a buy!
Now for the problem and past problems that I am very curious to get help in solving. I have rebuilt many small engine carbs successfully using the parts that come with the various rebuild kits. This carb and another hda 48 carb i am having trouble with. I used all the parts in the kits with the exception of a few small parts. I changed, the large screen, metering needle, rocker arm, pivot pin, diaphram and gasket, pump membrane and gasket. I soaked the stripped carb body in kerosene, blew out every port possible with compressed and carb cleaner, pressed out the brass check valve and cleaned, removed the welsch plug and blew out the tiny ports and installed the new aluminum plug. I used silicon fuel line and blew thru all ports with my mouth to feel for airflow and be able to adjust sensitivity of the hi and lo needles. I checked the carb body and covers for cracks. I did this operation twice using 2 rebuild kits and also tried using the original rocker arm. The only part not replaced was the spring because the rebuild kits that I have did not come with one. I paid close attention to the installation sequence of the parts and made sure the height of the rocker arm was level with the carb surface and pulse port was aligned during reassembly. Even used new insulator block gaskets for the second rebuild.

Problems is the carb is still not drawing fuel when my finger is over choke. Tried to get fuel into the carb after cranking and flipping engine, no go. I sprayed a little engine starter fluid into carb and the engine fired for a second on one flip.

The quick and easy fix is the replace the carb for fifty bucks, but I am sure there must be an answer to this. I must have missed something during the rebuild.

I would be greatly appreciative for your input to my carb mystery.

w8ye

My Feedback: (16)

If you could try a different carb and the engine runs, you will know it is the carb. Otherwise the problem is in the manifold or impulse path?

kmeyers

Not that you missed anything, but, fuel is pumped. Several actions make this: inlet open to fuel tank, suction on opposite side of fuel pump chamber, flapper opens allows fuel into chamber, pressure on opposite side of fuel pump chamber, inlet flapper closes and exit flapper allows fuel pressure to push fuel to metering side if the needle is in the up (none seated) position. This process continues while the piston goes up and down providing the pressure pulses.

No fuel pumping:
Check that insulator block, carb and gaskets are lined up with the crankcase pressure port.
Check for clean screen.
Check for gasket and pump assembled correct.
Check needle assembly for proper action.
Check diaphram for stiffness, gasket and metal button for proper assembly.
Check all through holes that are involved in this process for dirt, old gasket material, gasket sealer and proper alignment with the crankcase.

So the pump diaphram goes against the carb body and its gasket goes against the pump cover.

The diaphram gasket goes against the carb body and the diaphram goes against its cover.

This is where I would look.

Truckracer

My Feedback: (19)

A thumb choked carb should pull fuel from the tank even if the pump isn't working as long as all the parts are assembled correctly and there are no obstructions to fuel flow.

As suggested by W8YE, I'd run the engine with a known good carb. If all goes well, you know the problem is the carb in question and not the spacer, pulse passages, gaskets, etc. Once we know the carb is the problem, as Kmeyers suggested, its time to look at how the carb was assembled. You mentioned the check valve was removed. Was it inspected carefully and will it allow fuel to pass? I've seen metering needles that were too long for some carb bodies. If one of these was installed, no fuel could pass. Please let us know what you find.

coalburner

My Feedback: (1)

Thanks for the replies.
I did everything mentioned, that's what is puzzling about this carb problem.

coalburner

My Feedback: (1)

Here is a picture of the engine with a new carb and new snuffler muffler. As I said earlier, I'm using the old insulator block and the 2 old gaskets on the insulator block. Runs great on the test stand. I am sure the problem is in the old carburator. I just disassembled it and put it back together again to make sure the sequence is correct. With the thumb choking the carb, I still cannot draw fuel from the tank. Both needles are opened about 4-5 turns and I'm at WOT when choking. Earlier, when i pressed out the brass check valve, I soaked it in kerosene and then blew some carb cleaner in it for good measure. when it was died, i blew thru is lightly by mouth. It works, definitely a one way valve with the slightess amount of pressure to open the valve. The engine runs good as shown, just still really curious as to why I'm not drawing fuel.

kmeyers

10 dollar bid. I have to go to more swap meets!