OldFart1

I have a Zenoah G26 (magneto version) on my 1/4 scale clip wing Monocoupe. Took it to the field yesterday for the maiden flight - didn't happen

Motor refuses to idle down. Didn't run the tach on the "lowest possible idle", but well past "fast taxi speed". It appears that it's not drawing fuel at lower RPMS (buddy of mine picked it up, it will idle better nose down"

I think I'm going to replace the carb (motor came to me used, have no idea on it's history). I'll probably rebuild this one and keep it in the spare parts box.

What carb do I want? I googled "Zenoah G26 carb" and came up with a whole list

w8ye

My Feedback: (16)

You'll do about as well here

http://www.horizonhobby.com/Products...=ZENT207581000

Walbro WT-645

OldFart1

Are those as good as the "old" 540's?

w8ye

My Feedback: (16)

The G23 just before they came out with the G26 had a WA-167 carb but it is only 7/16" venturi carb. It had a high speed check valve nozzle and worked nice.

Some G26 engines have a WT-813 and it is 12.7 mm and has the high speed check valve nozzle and no choke

The WT-645 has a choke but no check valve nozzle. it is also 12.7 mm

You can also use the WT-643 & WT-644 The WT-643 has a primer bulb

the WT-540 is obsolete and is replaced by the WT-834 and it is too large for the G-26 at 13.49mm

The repair kit for these is the K10-WAT

Checklst

You might check the insulator block and insulator gasket, before purchasing new...............Make sure the pressure port hole is free and clear of debris and it on properly, and has no cracks........This insulator block can give you a hard time on idle speeds, tune, and starting if it not right.

Just a thought before new carb............but new is good also.

Jezmo

One other remote idea, if the carb has been turned over in order to make the throttle easier to hook up then the fuel pump signal hole is not lined up. That is a hole that passes through the phenolic insulator block from the crankcase to the carb in order to operate the fuel pump. If the hole in the carb that goes to the fuel pump diaphragm isn't lined up with the hole in the spacer then the pump won't work and can cause problems similar to yours. May not be it but worth a look.

OldFart1

Hasn't been turned over - but it does have the aftermarket "angled" adaptor - I'll check. I know it worked with that adaptor when I had it on my SuperCub - but replaced the adaptor when I moved the motor to the Monocoupe - might have messed it up.

RBACONS

My Feedback: (3)

I, too, have a G26 that came to me used and has started giving me problems. It initally ran great (smooth, good idle, good transition, good top end, plenty of power) but suddenly started having issues running at full throttle. If I dial my throttle end point adjustment down to restrict how far the carb opens, the engine will run well enough to venture putting the plane in the air. But without limiting the throttle, the engine dies at the last 10-20% of the throttle movement. Seems it just starves for fuel. Richening the engine helps somewhat but doesn't cure the problem. BTW, the carb is a WT-645. I did change out the fuel tank and all of the plumbing to eliminate any issues there, to no avail. Any suggestions short of buying a replacement carb?

Tony

w8ye

My Feedback: (16)

You will find a filter screen inside the carb. You get to it by taking the pump cover off.

This screen may be full of lint from a filter sock.

RBACONS

My Feedback: (3)

Just a follow-up. I pulled the carb last night. Although I didn't find anything obvious, I thoroughly cleaned the carb with carb cleaner, flushed out all of the ports, removed the needles and flushed them, and cleaned the screen even though it appeared fine. On re-assembly, I remembered reading a post somewhere about tack gluing the gasket in place on the carb to ensure the holes in the gasket lined up properly with the pulse port hole on the spacer block. On inspection, it was obvious that there was enough play in the gasket that it would never line up properly just by chance so I did tack glue it down. Reset both needles to 1 1/4 turns out and fired it up. Ran like a champ. Bottom line is I have no idea what fixed it but "when in doubt, clean it out".

BBreck

I'm also having a problem with a G26, I've rotated the carb and used the additional carb mount and hooked the linkage up and the carb seems to idle fine but when opening the carb 1/4 it seems to run at 1/2 throttle and at 1/2 throttle it seems like its running full out yet the linkage is only showing half open....if I push it past 1/2 throttle it shuts down? Any suggestions?

Antique

My Feedback: (4)

The arm is on the shaft wroing...Set it so the threads of the center screw show when the throttle is closed, looking into the carb when it's on the cylinder..

BBreck

I've checked it, the threads are showing when it's closed (or at idle), at full open you can see the screw head on the other side of the flap. I've pulled the cab off and will make sure the gasket is'nt covering up the holes between the carb and the block....I'll try and run it up without the linkage attached to the servo and see what happens.

OldFart1

Solved (my) problem - had the damn "rotation" insulator block on upside down. Idles real slow now

BBreck

OK, I've put the carb back on and adjusted the low idle mix and leaned it out so it's running properly but I'm still gittin the half throttle stall, I've tried to adjust the high Idle needle and it does absolutly nothing. I've taken off both sides of the carb and cleaned out the screen (one small piece of junk nothing that was big enough to restrict the flow) and put it all back together and still the same old problem....if it's run past 1/2 it cuts off but if you drop it back to Idle it will catch itself and still idle and run up to half again.

w8ye

My Feedback: (16)

Sounds as though the carb is running from suction and that the pump is still not working

BBreck

would it still maintain half throttle speed on suction only?, it' will run up to half and maintain half speed, just quit once over that half way point. Thinking now it might be the float needle setting since I'm not getting anything above half. is there an easy way to test the pump?

w8ye

My Feedback: (16)

TKG says they will run up to half way on suction only.

If you removed the regulator diaphragm and needle/seat, the pump should pump fuel out the needle area of the regulator by rocking the prop back and forth in the free turning area from compression to compression of the piston.

I would first confirm the crankcase pressure-vacuum signal path is continuous to the carb pump diaphragm first.

BBreck

thanks, I'll give it a try and thanks to all for the suggestions