OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Hand and Power Tolls Power Tools GMC 750W Generator

ok so i was reading through the thread Max Gara had on the same generator, and i came across this site while looking for solutions to the generator running.

ok so a friend of mine Ian has a GMC 750w genny, and he has the exact same issues he was thinking it was the coil and so i said i will take a look,
so it has a coil and a cdi module and a stator so it seems like its adopting the same set up as a motorcycle so i checked all ignitions areas even removed the flywheel and no issues has nice spark, checked and cleaned carb, no issues there checked and cleaned muffler yes was caked up with oil and carbon but i had it running for half an hour before it stopped working which i was amazed it actually would run with no work to it at first. well anyway so i checked the tank nope no issues i cleaned the sediment bowl that near the tap nope had a little bit of dust and rust flakes but no issues as it had run before i dug into it deeply. i had the front panel off no issues there the switch works as it should.

had the head off some carbon but no issues and thus reinstalled after cleaning,
tried different plugs still the same it would fire for a couple of seconds and then stop..

this is where it gets funny, so i had some atf in a squirty bottle so i though ok squirt some down the carb and well it was a little smoky but it would wanna run but still not continue to run... so dumb fool me forgot i got a compression tester. did the compression test 95psi... so did a google and see what is ok for a two stroke... and well well 120-150psi so she is down quite low, its low enough according to a google search to barely want to run if it can run. ok so i never took notice of the bore at the time as the motor looks like its only done so many hours and looked in a reasonable condition... well yeah maybe not the case so id say its done a fair few hours and the rings are at the rooted stage, so him mucking with the ignition would prove useless and a waste of money.

so i got the bad news to tell him about it, now cause its such a long time since it was made im gonna bet you cant get a set of rings. so watch this space i have a few more tricks i can try to get it to run once again.

i hope that max gara is still on here he can follow in on this topic, i dont like to walk away from a engine until ive exhausted all my possibilities im around 12hrs of mucking with it so far so each arvo for about 4 hrs i work on it.

but off the subject i have got another motor he gave me to keep a 5hp briggs and that will not wanna stay running and leaks badly around the updraft carb so im putting my money down that its a compression issue as well as everything seems fine on that engine.

Tony.

well so i had a look and the bore is polished like a very shiny coin with a mirror finish so i gave it a slight hone with a plastic makita abrasive disc and it sort of made it a bit dull with hone marks and gave a head a bit of a sand with some wet and dry on a very flat surface and it made no difference to the compression of about 95 still, and i gave it a few tugs fires but wont stay running so with the glazed bore and the amount of oil in the muffler i think she has done many many hours and is fucked basically i reckon a set of new rings and a bit more of a hone and she may run ok for sometime but i think she has done her time, so im gonna ask Ian how many hours he thinks its done im thinking now he most likely got it already used from someone else and ran it for a while before it failed to wanna run see he assumed it was the ignition but i have tested and checked and it has a very good spark.... im pointing to glazed bore not enough compression she has done her hours and needs a major job like hone and new rings or a rebore with larger piston, but i think parts are long gone for it unless i was to source a piston of the same size from somewhere else thats at the 63cc size but i think its possible but not worth the costs.

Hi Tony,
Just curious, that would you use a 750 watt genny for?

got no idea its not very high in power output, i think its one of those cheap generators from back around the mid 2000's i reckon it was to power a caravan that had a portable fridge etc.

Was given one of those. Previous owner had only used it a few times and the tab on the fuel tap had snapped off.Seemed OK otherwise, started and ran briefly with a squirt of fuel into the carb. The thread on the tap was odd, couldn't find anything to fit.

Masters had gone under by then but found out a place on Sydney Road in Melbourne had acquired their GMC spare parts and bought a tap.

https://gpttools.com.au/about-us/

Once running it was next to useless as a generator, very low power which cut in and out, gave it to an electrician.