Hm100 carb problems
- Thread starter David wulf
- Start date
- Tags carb hm100 problems
Those carburetors are notorious, for the internal passages clogging; especially if the engine had set and not run for a long while.
And there is one passage, that is sealed off by a welch plug; if it is corroded inside, you will never get the engine to run correctly. Trying to take that welch plug out, usually ends in destroying the carb.
We have soaked them, used compressed air, and fine wire probes; and still on some we have never gotten them right.
I believe they are making replacement carbs in China or somewhere; and the people that I talked to, have had success with them.
And there is one passage, that is sealed off by a welch plug; if it is corroded inside, you will never get the engine to run correctly. Trying to take that welch plug out, usually ends in destroying the carb.
We have soaked them, used compressed air, and fine wire probes; and still on some we have never gotten them right.
I believe they are making replacement carbs in China or somewhere; and the people that I talked to, have had success with them.
The only passage that can really plug up is your idle circuit... It is fed from the main jet, there's a port drilled right next to the main jet, in the aluminum, that is a real small tube, then there is a small hole drilled from the main jet to the idle circuit line.... That is the hole that will plug.. The threads being dirty on your main jet can shave off crud and jam it into the feed hole for your idle circuit....
Looking at the inside of the carb, the big aluminum tube that everything works off from, there is a raised rib, running along one side of that main aluminum tube, that is the tunnel where your idle fuel flows... if you look INSIDE of the main aluminum tube, looking in the direction of that raised rib.. You can see the small hole that is drilled from the main tube, into that rib... It is up in there a ways, and penetrates at a 45 degree angle.. if you can't find that hole, that is probably your problem... You can poke it open with a wire or something..
If it has gas in the bowl, it HAS TO RUN at a 1/2 wide open, full speed, speed, because that is all done with the main jet, and you can physically SEE any problems there....
The main jet, the big brass deal, has at least two small holes drilled in the side of the jet.. One is towards the bottom and pretty good sized.. It lets fuel from the bowl, INTO the jet... THEN there will be a VERY small hole, like ONE STRAND of very thin steel wire.. It penetrates the jet about 1/2 way up, and at a 45 degree angle... That hole feeds the idle circuit.....
Check make sure the main jet is ALL OPEN and flowing.. the tiny tiny hole is very important, as it won't run without it...
THEN you can screw the idle fuel metering screw out, stick the red poker tube (comes with carb cleaner) into the hole.. And blast it.... You should be able to see carb cleaner squirting into the throat of the carb, via the two or three port holes before the throttle butterfly...
At the bottom inside the bowl, you should be able to see carb cleaner squirting out the bottom of the main tube where the main jet screws in...
If gas can make it from the bowl to inside the throat of the carb, it should run...
Other things to look for is a worn out throttle shaft.. Allows an air leak to wreck the vacuum pulling fuel into the idle half of the carb...
Fuel settings can be way off....
Best way to start the whole deal off is make sure the bowl is full of gas, screw out both metering screws about 1.5 turns out,... then choke it, hold it wide open and PULL THE HELL out of it.. :laugh: to get it fired off, then start slowing down the running speed and messing with your fuel metering screws..
Looking at the inside of the carb, the big aluminum tube that everything works off from, there is a raised rib, running along one side of that main aluminum tube, that is the tunnel where your idle fuel flows... if you look INSIDE of the main aluminum tube, looking in the direction of that raised rib.. You can see the small hole that is drilled from the main tube, into that rib... It is up in there a ways, and penetrates at a 45 degree angle.. if you can't find that hole, that is probably your problem... You can poke it open with a wire or something..
If it has gas in the bowl, it HAS TO RUN at a 1/2 wide open, full speed, speed, because that is all done with the main jet, and you can physically SEE any problems there....
The main jet, the big brass deal, has at least two small holes drilled in the side of the jet.. One is towards the bottom and pretty good sized.. It lets fuel from the bowl, INTO the jet... THEN there will be a VERY small hole, like ONE STRAND of very thin steel wire.. It penetrates the jet about 1/2 way up, and at a 45 degree angle... That hole feeds the idle circuit.....
Check make sure the main jet is ALL OPEN and flowing.. the tiny tiny hole is very important, as it won't run without it...
THEN you can screw the idle fuel metering screw out, stick the red poker tube (comes with carb cleaner) into the hole.. And blast it.... You should be able to see carb cleaner squirting into the throat of the carb, via the two or three port holes before the throttle butterfly...
At the bottom inside the bowl, you should be able to see carb cleaner squirting out the bottom of the main tube where the main jet screws in...
If gas can make it from the bowl to inside the throat of the carb, it should run...
Other things to look for is a worn out throttle shaft.. Allows an air leak to wreck the vacuum pulling fuel into the idle half of the carb...
Fuel settings can be way off....
Best way to start the whole deal off is make sure the bowl is full of gas, screw out both metering screws about 1.5 turns out,... then choke it, hold it wide open and PULL THE HELL out of it.. :laugh: to get it fired off, then start slowing down the running speed and messing with your fuel metering screws..
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