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G-62 issue

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Old 06-17-2012, 12:39 PM
  #1
wireman
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Default G-62 issue

After sitting for several years while I recovered the plane, my G-62 was reluctant to run and needed several chokings to finally run continously, I initially chalked it up to being cold blooded and it seemed to run fine after that but I had to richen the high speed jet 1/2 turn to max out RPM. While adding some right thrust I noted leakage around the muffler and found the bolt tang broken. I pulled the cylinder to weld it and found the top of the piston heavly carboned up and the top ring stuck with the second one almost completely stuck, I am amazed it ran as well as it did. After replacing the welded cylinder I can not get the thing to run more than a few seconds after the initial pop from chocking. I have checked the timing, 28 degrees BTC, as well as the hall effect and the module using the neat little tester C&H used to sell and they seem to be fine. New gaskets on the block as well as the carb, different carb, all to no avail, still on runs several seconds of the choked prime and stops. At this point I am at a loss since spark, compression, and fuel all seem to be present. I know I am missing something and hope some of the gurus on this site can offer something else to look at.

thanks for looking
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Old 06-17-2012, 02:04 PM
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Default RE: G-62 issue

Check both of those carbs for stiff diaphragm gaskets. Take the cover off the carb with the four screws. That diaphragm has to be very supple, and it is very common for them to dry out, get stiff, and either cause a "no fuel" or a "flood" condition. Also make sure that the needle isn't stuck. You should be able to blow into the fuel inlet, and no air should pass until you push down on the needle lever under that diaphragm. When you push on the lever, raising the needle, then you should be able to blow through.

If that checks out, then pull the cover off the carb with only one center screw. There is a screen in the carb there that can get clogged. Also, if the fuel pump diaphragm that is on that side is distended very much, it won't pump fuel, nor will it pump fuel if the little flapper valves in that diaphragm are stuck to the carb body.

When I reassemble my carbs, I flood the interior with WD-40 so everything is moist and sealing well for the first start.

This is all assuming you are sure you didn't somehow get your pulse hole clogged that goes to the carb for the fuel pump.

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Old 06-17-2012, 02:39 PM
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Default RE: G-62 issue

It ran well before you intervened with it. Cleaning the piston should not change that.
Since you took the engine apart, check gaskets for proper crankcase pulse hole alignment. Your carb depends on it.
Also check for any gasket leaks or other blocked passages.
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Old 06-18-2012, 02:13 AM
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Default RE: G-62 issue

I agree with Pe, sounds like the pump isn't working. Aside from gaskets, is it possible the carb insulator ison backwards?
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Old 06-18-2012, 05:48 AM
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Default RE: G-62 issue

So far I have done all the above, including complete disassemble of carb and shot carb cleaner through all passages and thru the needle and seat. The diaphram feels pretty good and has fuel in it when I take it apart so it seems to be getting through to there, removed screen and cleaned from the backside and replaced, I cut new gaskets and used the little red tube from a spray can to make sure the pulse hole was not covered while putting the insulationg block back on and made sure the holes lined up for the carb also, guess I better go back and recheck again, about the tenth time I have had it off to check. Compression is excellent and ignition right on so it has to be something in the fuel delivery but I seem to missing it somehow!!!! GRRRR
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Old 06-18-2012, 06:49 AM
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Default RE: G-62 issue

just to be sure; when assembling the carb, on the pump side the gasket is against the carb cover, on the regulator side the gasket is against the carb body.
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Old 06-18-2012, 10:25 AM
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Default RE: G-62 issue

Are you sure the base gasket on the cylinder didn't get "out of whack" when you assembled the engine?? You could possibly have an air leak, or blocked pulse passage there....

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Old 06-18-2012, 12:20 PM
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Default RE: G-62 issue

The other day we had a 62 in a tow plane. Would run, but would cut out on acceleration for take-off.
Sure enough it was the base gasket not lining up properly, so don't be satisfied with your assembly results too quickly.
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Old 06-19-2012, 09:58 AM
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Default RE: G-62 issue


Quote:
ORIGINAL: pe reivers

The other day we had a 62 in a tow plane. Would run, but would cut out on acceleration for take-off.
Sure enough it was the base gasket not lining up properly, so don't be satisfied with your assembly results too quickly.
Reminds me of something I did once

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Old 06-19-2012, 11:33 AM
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Default RE: G-62 issue

Don't cry! It happens to all of us.
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Old 06-21-2012, 03:11 AM
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Default RE: G-62 issue

Well the saga continus, I pulled the cylinder yesterday after work and the gasket was OK, checked the pulse port, OK. Installed all new seals and diaphram in the carb same issue still remains. Choke draws fuel as expected, engine fires for several seconds running up to several thousand RPM and dies, prop it again and it will start and run for several more seconds and then runs out of gas and has to be choke again. I removed the diaphram cover for the needle and manually held down the rocker arm while flipping the engine and fuel squirted out of the needle and seat assy. I then sprayed carb cleaner into the main jet and it sprayed out the venturi. Reassemble everything and try again, same result. In 95 degree heat and total dejection, I gave up and put it back in the trailer. May be time for a new carb as I have totally run out of ideas and patience!! If nothing else, this a great way to vent as the dogs and my wife don't want to here it!!
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Old 06-21-2012, 03:51 AM
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Default RE: G-62 issue

It sounds like it is running the prime off or initial residual fuel. So either the engine can't draw fuel (air leak someplace) or the carb is not letting the fuel get into the engine. Sounds like your carb fixes have the carb cleaned up, so that leaves an air leak some place to find.

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Old 06-21-2012, 04:25 AM
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Default RE: G-62 issue

So the carb does pump and fuel flows with the regulating lever depressed. Jets are open.
Will the lever depress when the carb diaphragm is back in place? The lever may be set too low, or: Is the lever forked? The engagement may be binding. In that case just snip off the engaging part from the diaphragm. It is not needed and another trouble source less.
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Old 06-21-2012, 07:18 AM
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Default RE: G-62 issue

For all those other need to knows like myself, where or what is the engagement part of the carb's diaphram?

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Old 06-21-2012, 10:56 AM
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Default RE: G-62 issue

it's on the regulating diaphragm, the one under the pressed steel cover. In some carbs the diaphragm engages the forked metering lever. (The little thingy with the hinge pin that operates the fuel admission needle). This engagement sometimes is not all that neat, causing a binding action or even failure to operate well.
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Old 06-22-2012, 11:26 AM
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Default RE: G-62 issue

When you did the cylinder welding repair, you may have distorted the cylinder.
Just a thought.
You may want to try a known good cylinder (maybe a new one).
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Old 06-22-2012, 01:29 PM
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Default RE: G-62 issue

I seemed to miss the post where wireman mentioned a cylinder welding repair???
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Old 06-22-2012, 01:58 PM
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Default RE: G-62 issue

Post #1, 4th line down.
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Old 06-22-2012, 02:15 PM
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Default RE: G-62 issue

Got it. In that case, a quick check of piston bearing pattern inside the cylinder should give a clue about remaining roundness. If not round anymore a hone job is due, or a new cylinder.
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Old 06-22-2012, 03:10 PM
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Default RE: G-62 issue

I ounce got the metering diaphragm in backwards and the button is not symmetrical so contact with the metering needle wasn't proper... similar results IIRC.
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Old 07-03-2012, 05:05 AM
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Default RE: G-62 issue

Well I finally gave up on getting this to run and asked a friend to return my other G-62 so I can get back in the air and I noticed a big difference in the compression between the engines. I swapped them out and have ordered a new piston and rings from Daves Motors. I now suspect that the excess carbon was actually acting as a seal and removing all of it and unsticking the rings may have lead to leakage rather than sealing. I also order a flexiable cyclinder hone from McMaster Carr as my 3 legged one will not work in this cylinder with all the transdfer ports, etc. Just for drill, before removing the engine I put the carb and insulating block from the running engine on the bad one as the same effect as before, so there is something going on with the lack of compression. Earlier, before repairing the broken tab, when it would start and run a few seconds off chok and then run after the second starting, I suspect the oil created enough of a seal with the excess carbon to get over the hump and run, actually suprisingly well! Parts should be in this week and I will see if the change makes a difference.

thanks for all the inputs
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Old 07-03-2012, 05:52 AM
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Default RE: G-62 issue

Keep the hone out of the cylinder or you are going to be setting on the sidelines again.

The Chrome plated bore in the cylinder doesn't need to be honed. The new rings will seat in the cylinder without honing it.
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Old 07-03-2012, 08:36 AM
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Default RE: G-62 issue

Using a hone in your cylinder is a definite no no, just use some 320 grit emery paper or a Scotch Brite pad to deglase the cylinder bore, that's all you need to do if anything.

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Old 07-05-2012, 04:02 AM
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Default RE: G-62 issue

Thanks for that info, there definitally was a glaze on the cylinder so I took your advice and used 600 grit wet/dry with Marvel Mystery Oil and it looks good. Parts should be here shortly to rebuild top end.
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Old 07-16-2012, 05:48 AM
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Default RE: G-62 issue

Well a new piston and rings, deglazed cylinder, all new gaskets and a carb from a running engine and it was worse than before. double checked the ignition timing and pulled the spark plug looking for a solid spark and it seemed to be fine. While slowly hand propping I would get a solid bump but only a pop when actually trying to start it. In desperation my next move was to put a new spark plug in not expecting anything but Lo it fired right up and is running like my memory says it should! Boy, I did not see that coming from the events that lead up to this whole scenario but I hope my embaressment will help someone else down the road.
Thanks to all for input during this adventure.
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