Clinician
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Post by styxfan on Mar 23, 2015 8:25:58 GMT -6
Please Help...
I was having issues with my MC-54-250B not being able to idle (unless it was set at 2K+) so I decided to replace the carb.
Now that the new carb is in, the engine will start and it will idle nicely between 1-1.5K. The problem I'm having now is whenever I give it gas, the engine stalls.
I've checked all hose condition and connections and all looks good. I tried raising the idle and even at a higher idle as soon as I twist the throttle, it dies. I have tried small adjustments of the A/F and no difference. I have even tried the A/F adjustment from all the way closed to all open and every point in between and still she stalls out any time I twist the throttle.
This is so frustrating. It will start and idle fine, but once I give it some gas it stalls out.
Could it be the fuel pump? I did manually check it and it seemed to work OK. Could the fuel pump be intermittent? Is that a thing?
Sad to say I am not an "engine guy" so maybe I'm missing something obvious.
Any ideas as to why I'm stalling out?
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Post by cyborg on Mar 23, 2015 12:05:29 GMT -6
I'd wager a guess that the jets are too small,,, or you have an air leak
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Clinician
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Post by styxfan on Mar 23, 2015 12:10:06 GMT -6
I've checked all hose condition and connections and all looks good. Beside the vac hoses, where else could I have an air leak? The new carb is an exact replacement of the original, but how would I determine if the jets are too small?
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Post by Alleyoop on Mar 23, 2015 12:13:25 GMT -6
Sounds like the carbs fuel ratio mixture has not been adjusted. So the first thing is adjust the Fuel Ratio Mixture, follow this procedure and take your time. On the center stand if no leaks and the proper air and fuel is being delivered you should be able to give the throttle a nice quick twist and it should rev up quick and come down to idle quick. Once you get it to that point then ride it and see how it acts with a LOAD. It may need a minor tweak when under load but nothing drastic. Alleyoop scooterdoc.proboards.com/thread/1499/4ts-carb-tuning
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Post by Alleyoop on Mar 23, 2015 12:19:10 GMT -6
A few pictures of the carb area might help usually if it stalls when you give the throttle a twist it is usually to much air and not enough fuel. Will it take throttle if you slowly twist the throttle? What type of Air Filter does it have on it, a performance air filter or a air box and if so does the air box have a foam filter in it? Alleyoop
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Post by styxfan on Mar 23, 2015 13:55:34 GMT -6
It has the standard air box with foam filter on it. If I really slowly throttle it up, it may catch, but usually not.
I tried posting pics, but I get an error (could be our firewall at work) so I can try later on from home
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Post by Alleyoop on Mar 23, 2015 14:13:21 GMT -6
Have you adjusted the new carb usually if you turn the fuel ratio screw clockwise until it stops and then turn it out 2 1/2 turns counter clockwise they will run pretty good and may need minor tweaking.
Now to find out if the PILOT jet is to small or to big test it out like this: Get it to IDLE then start turning it clockwise IT SHOULD KILL the motor when there is about 1 full turn before it is all the way closed.
1. If it keeps on running after it is closed then the PILOT is to BIG. 2. If you need more than 3 1/2 turns out(COUNTER CLOCKWISE) from the closed position to have it idle good then the PILOT JET is to SMALL.
When you twist the throttle all your doing is opening the butterfly letting in a LOT OF AIR all at once OR NOT ENOUGH(MAKE SURE THE FOAM FILTER IS CLEAN and not restricting air). Alleyoop
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Post by styxfan on Mar 23, 2015 14:27:25 GMT -6
"Now to find out if the PILOT jet is to small or to big test it out like this: Get it to IDLE then start turning it clockwise IT SHOULD KILL the motor when there is about 1 full turn before it is all the way closed."
start turning it clockwise Turning what, the A/F adjustment?
Foam air cleaner was cleaned prior to all this.
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Post by Alleyoop on Mar 23, 2015 14:37:38 GMT -6
"Now to find out if the PILOT jet is to small or to big test it out like this: Get it to IDLE then start turning it clockwise IT SHOULD KILL the motor when there is about 1 full turn before it is all the way closed." start turning it clockwise Turning what, the A/F adjustment? Foam air cleaner was cleaned prior to all this. YES turn the FUEL RATIO screw CLOCKWISE it should kill the motor when it has about 1 full turn before it stops(all the way closed). IF the motor keeps running and not dieing then the PILOT JET IS TO BIG and letting in TO MUCH FUEL. How many miles on the motor and WHEN was the last time the valves were adjusted on that motor? Alleyoop
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Post by Alleyoop on Mar 23, 2015 14:46:30 GMT -6
Is this what your motor looks like ? Take some pictures around the carb and the hoses maybe you have something connected wrong. Alleyoop CLICK ON THE PICTURE TO EXPAND IT TO SEE IT BETTER:
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Post by styxfan on Mar 23, 2015 16:44:54 GMT -6
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Post by styxfan on Mar 23, 2015 16:54:16 GMT -6
About 5400 miles on it currently and last time valves were adjusted was July 2012 at 2300 miles.
Don't want to sound naive but, why would a replacement carb have larger jets than the original?
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Post by Alleyoop on Mar 23, 2015 17:40:12 GMT -6
Ok you have the LINAHI motor which are little harder to adjust the valves. But It may help to first adjust your valves. Usually the Intake will be ok the EXHAUST Valve is the one that usually gets tight due to the heat it takes. The intake stays cooler due to cool fuel and air always hitting the valve. The hoses all look good from what I can see and they are connected correctly. SO TRY turning the fuel screw clockwise and see if it kills the motor when it is about 1 full turn from the closed position. JETS IN CARBS: When you get a new Carb they are aftermarket carbs and not the originals that was set and put pm at the factory. So the jets that the aftermarket carbs all come with are a SHOT IN THE DARK to be honest. The only way to see is to take the carb bowl off and unscrew the jets and HOPEFULLY they are marked a lot of the aftermarket carbs comw with JETS THAT ARE NOT MARKED. Alleyoop
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Post by styxfan on Mar 23, 2015 19:40:05 GMT -6
I still have my old carb so maybe its possible to compare the jets if they are not marked (or are they too small to tell)?
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Post by Alleyoop on Mar 23, 2015 19:55:03 GMT -6
Yes unless they are really small or really big it is hard to tell. But let ask this with the old carb was it running good? Why did you go and buy another carb. With these carbs not to much can go bad on them maybe the ENRICHER or if left for 3+ months without starting them they carbs get gummed up and all they need is to be cleaned out and that is all.
If it was running good with the old carb I would then take the Jets out of the OLD CARB make sure they are clean you can see through the holes and put them in the new carb.
To help you in the future if you keep the scoot in the garage over winter Just start it once every week and let it warm up 15-20 minutes or once every two weeks. And it will always be ready to go when spring and riding weather comes around. Alleyoop
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