Originally Posted by Gary_Shay

I'm in the process of designing a completely new fuel delivery system that will work on almost any carb, including stock glow carburetors.
I've tested the system and it worked amazing. But this was a bench setup and I've not gotten all the components shipped to me yet for what will actually go into the planes but I've done the math.
This new design I came up with eliminatea so much hassle when dealing with gas engines that is often a turn off to many modelers. It will almost completely eliminate maintenance of the carburetor and allow for precise even flow at all times.
I hope to have this system up and running and tested by mid summer. Hopefully we will never need a walbro carburetor again.
The testing I've done so far has made this engine run better than any engine I've seen yet. Superb idle, instantaneous throttle response and rapid return to idle.
Simple fuel line routing, no longer need 3' of vent line to combat siphoning affect when rolling inverted, and you'll be able to mount the fuel tank anywhere on the plane... even the tail. Hahahaa.

I think I'll be able to get all the components needed for around $10. Mostly off the shelf items I hope. I believe it'll be revolutionary and rid us of so dang much hassle.

I'm excited about it !!!!

Math is power. Now you've got me excited.

Thank you,Gary_ Shay for good information ! I am interested to see what you come up with your fuel system.

My parts still haven't arrived yet because I had an issue from the warehouse, so, I decided to try a few new things to see if I could get the thing running better the way it's plumbed.
I got it better than factory plumbed but still not perfect like I want it. I couldn't get the idle down to 1550 for extended periods (2 minutes) but at 1750 it idled for around 5 minutes but wanted to load up a little more than I like and was slightly rich in the midrange, but still 50% better than it comes from the factory.
What I did was made 2 new gaskets for the carb mount (see photo below) that were thicker than original gaskets and cut a notch that opened directly into the intake manifold. Believe it or not, it will run with this setup alone, without the crankcase tube, but at idle it has a hard time drawing fuel from the tank because the diaphragm pump doesn't function other than when the intake valve opens and without the spring in the carb like I showed earlier in this post, which helps the offset pressure differential it runs out of fuel in the carb.
But, when I run it with the original plumbing line from the crankcase, the crankcase pressure equalized the offset and ran well at idle as well. Plus, if crankcase oil builds up and moves towards the carburetor like it does, the oil gets drawn into the intake manifold prior to getting into the carburetor because as the intake valve is starting to open, the positive crankcase pressure pushes pressure into the manifold, I like that part.

The issue I had with the factory plumbing is that it over pressurized the carburetor and would even cause the carburetor to leak because it would exceed the popoff pressure of the metering valve and it even busted the original gasket (I posted a picture of it in an earlier post)

It runs well enough with this setup that I would put it in a plane now (but I'm going to hold off until my parts arrive) and i feel that the engine will perform well enough to keep most people happy with it.

Are you using Walbro wt 1022 carburetor ?
Mine is wt 962.

Can you machine that face to accept an O-ring?

Anything new here?

Finally got mine mounted on a Phoenix Stuka ready to go. I ran a tank thru it on a test stand more than a year ago. On the Stuka, it fired right up and ran really well in any position.

Before and after I ran it, I noticed some side play in the 5-11 clock position. Is this something to worry about? or wait until it becomes a problem then deal with it?

Looking forward to hear the results

I understand this thread has been quiet for some time, however I have a question or two.


I did read about pump issue as described by Gary Shay.

That aside, would I be correct in saying this engine has no crankcase breather? and that it should? and without one it will not run reliably for this this reason alone. Wouldn't the build up of oil and pressure not only enter the pump but be forced out the front bearing?

If factory run and it arrived with dry rockers:
1)It was factory tested dry and some damaged must have occurred? Even if only very minor this would lead to longevity issues?
2)No oil is getting to rockers during operation?

If I was to use the separate pump, would it not also fill with oil and excess pressure resulting in same issue as described by Gary?

For use in a Cub, would a small catch can between engine and carb work to collect the oil and still provide pulses to pump?

TIA
poss

I read about a post (might be posted by Gary_shay somewhere), about using walbro WT-456 for the 4-stroke, its different since it has a return spring on the pump diaphragm.
I have googled about it and find minimal information about the spring, can someone measure the spring? I can have it made here, and would like to give it a shot to the new gf30 i just got.
Measurements of OD, spring steel diameter, how many coil and the height of compress and uncompressed state.

TIA

I need to do some more research, but from what I gather the NGH GF38 runs fine, and looking at HK parts uses the same carb. I see there is provision on both the GF30 backplate and intake manifold for extra nipples, so I believe it could be easily modified to be plumbed the same as the 38cc engine. I wonder if this modification would help? Nipples are a few bucks, I already have necessary drill and tap.

My engine shipped today.

Based on Gary's comments I can't help but think it simply needs a crankcase breather.

Originally Posted by Gary_Shay

That's why other manufacturers vent oil either into the air or back into the intake manifold itself. If you research the 38cc you'll notice the intake manifold has 2 nipples mounted in it to eliminate this very problem. Why the 30cc didn't follow this design is beyond me.

Originally Posted by Gary_Shay

The issue I had with the factory plumbing is that it over pressurized the carburetor and would even cause the carburetor to leak because it would exceed the popoff pressure of the metering valve and it even busted the original gasket.

Put a vent on the 30cc engine and it will be the same as the 38cc engine??????????? It does not even have to be connected to intake manifold. Or am I missing something????????????

The breather is like on the newst os engines 4 strokes.

There is a hole in the rocker box that goes into the intake at the intake valve......so pressure and lubrication is forced up into the rocker box, and vented back into the engine

Thanks for that info, I was aware of that setup on other engines, no one mentioned it for this one (that I have seen).

If that is the case why does Gary say the pump is getting over pressured????

Can you tell me if your carb has a spring or not???????

Walbro provide 2 series of butterfly valve diaphragm carburetors for 14cc to 50cc engines, the WA and WT series and the mirror image models of the same carbs, WTA and WTEA.

WA has no pump spring, WT has a pump spring. The carb used on both the 30cc and 38cc engine is a WT series carb according to the specs.

http://www.walbro.com/wp-content/upl...arbs_PS_EN.pdf

http://www.walbro.com/wp-content/upl...1/WTseries.pdf

http://www.walbro.com/wp-content/upl...1/WAseries.pdf