New Kei Hin Carbs ??? By kiwibilt (Read 2,037 times)

[kiwibilt]

Aloha,
I've just started working for a company that imports Chinese 50cc 4 stroke (GY6) scooters for sale & rental, & I am responsible for their assembly, maintenance & repair. They have a large fleet of which the older models are approaching 300 to 450 km. All of these scooters run like s**t. And I'm having difficulty figuring out how to tune them correctly. I am hoping I may get some definitive answers here.
1) What is the correct valve clearance ?. The owners manual shipped with the scooters says .3 mm, & the dealer in LA says .03 mm.
2)The Kei Hin carbs on the new models have NO idle /air adjustment. I was trained to adjust CV carbs by attaching the throttle cable after setting up the correct idle/air mixture adjustment then backing off the idle screw to obtain correct idle. The cable adjustment at the carb was only used to maintain tension on the throttle arm, & the adjustment at the throttle end was used to remove throttle free play (if the cables not stretched). I'm finding that after setting the carbs up this way~
a) they will not restart without pumping the throttle
b)the engine dies if you wind it out then release the throttle
It seems like you need to use the cable adjustment at the throttle end to keep them running, or max out the idle screw on the carb.
The carbs seem to be getting adequate fuel through the petcock/regulator, but they keep cutting out & lack power from idle to mid range, with occasional backfiring. Should I just stock a load of rebuild kits, or should I convince my employer to replace the carb with a better/tuneable version.
3)What is the rated output of these ignition coils & can I test them with my multimeter
4)Can the timing be adjusted, & has anyone heard of the static timing preset at the factory being incorrect or "shifting" after 300 to 450 km.
5)Where is the best place to find a service manual for these bikes (in English LOL).
Thanks in advance for any advice & as I have a busy holiday period ahead, I truly appreciate your prompt response.
PS...All these scooters are run at sea level to 1000 feet in a tropical environment.

[kiwibilt]

Just found a service manual
www.chinesescooterreference.com/pdf/50_150cc_gy6_shop_manual.pdf

[Alleyoop]

Dec 13, 2012 22:44:25 GMT -6 kiwibilt said:

Aloha,
I've just started working for a company that imports Chinese 50cc 4 stroke (GY6) scooters for sale & rental, & I am responsible for their assembly, maintenance & repair. They have a large fleet of which the older models are approaching 300 to 450 km. All of these scooters run like s**t. And I'm having difficulty figuring out how to tune them correctly. I am hoping I may get some definitive answers here.
1) What is the correct valve clearance ?. The owners manual shipped with the scooters says .3 mm, & the dealer in LA says .03 mm.
2)The Kei Hin carbs on the new models have NO idle /air adjustment. I was trained to adjust CV carbs by attaching the throttle cable after setting up the correct idle/air mixture adjustment then backing off the idle screw to obtain correct idle. The cable adjustment at the carb was only used to maintain tension on the throttle arm, & the adjustment at the throttle end was used to remove throttle free play (if the cables not stretched). I'm finding that after setting the carbs up this way~
a) they will not restart without pumping the throttle
b)the engine dies if you wind it out then release the throttle
It seems like you need to use the cable adjustment at the throttle end to keep them running, or max out the idle screw on the carb.
The carbs seem to be getting adequate fuel through the petcock/regulator, but they keep cutting out & lack power from idle to mid range, with occasional backfiring. Should I just stock a load of rebuild kits, or should I convince my employer to replace the carb with a better/tuneable version.
3)What is the rated output of these ignition coils & can I test them with my multimeter
4)Can the timing be adjusted, & has anyone heard of the static timing preset at the factory being incorrect or "shifting" after 300 to 450 km.
5)Where is the best place to find a service manual for these bikes (in English LOL).
Thanks in advance for any advice & as I have a busy holiday period ahead, I truly appreciate your prompt response.
PS...All these scooters are run at sea level to 1000 feet in a tropical environment.

Hi and welcome, 300-400KM is not a lot of miles that is only 180-250miles that is still pretty new the motor isn't even broken in at those miles.

Q1.
1) What is the correct valve clearance ?. The owners manual shipped with the scooters says .3 mm, & the dealer in LA says .03 mm.
A1. 50cc 4 stroke, adjust both valves to .003 inchs, if they CLATTER to much set the Intake to .002 inchs and leave the Exhaust at .003 inchs. The Exhaust is the one that tightens up with the extreme heat it takes.

Q2. Carbs with the Mixture Screw Plugged.
A2.You can drill the plug out use a 1/16 drill and just drill about 1/8 in get a screw and screw it in the hole and work the plug out. Then you will be able to get at the Fuel Ratio screw.

ON some even the screw behind it will NOT HAVE A SLOT to turn it with in those situations you will have to try and make a slit to fit a small screwdriver to get it out. Once out then you can cut a slot so a screwdriver will fit.

If you cannot get at it or can't drill the plug the best deal is an AFTERMARKET carb they are cheap and work just as good.

Q3. What is the rated output of the coils.
A3.The output of the coils can kill you, they are in the thousands.
Your volt meter doesn't go that high you can only test the ohms and that is not definite either. I would check what the CDI is putting out to the COIL which will be in the 18VAC or higher.

Q4. Can the timing be set or is it static.
A4. The timing is static set by the woodruff Key on the crankshaft and the Flywheel and the CAMSHAFT when the rockers are both off the came lobes. You can buy CDIs that have a fixed advanced timing which gives you a little more power.
Q5. where is the best place to find manuals in english.
A5. Here in the states(HAHA). But you have to look for them some manuals are on this forum and other forums as well.

And by the way the THROTTLE should have a little play about 1/4 of an inch it should spring back and stop where you set your IDLE SPEED SCREW thst is what stops the butterfly from completely closeing all the way and killing the motor. You back off the IDLE SPEED SCREW then adjust the throttle cable so you have 1/4 of an inch BEFORE IT ACTUALLY STARTS TO PULL AND TURN the THROTTLE CONTROL WHEEL. You then turn the IDLE SPEED SCREW CLOCKWISE and WATCH THE CONTROL WHEEL it must move about 1/16-1/8 of an inch. You can fine tune the Idle once the motor starts.

Also here is how to adjust your FUEL RATIO MIXTURE Screw:

First Start up the Scoot and let it warm up At Least 5 minutes so the ENRICHER cuts off the Extra Fuel.



YOU WANT TO GET THE HIGHEST IDLE OUT OF THE FUEL RATIO MIXTURE:


So from where it is currently set FIRST TRY richening it up more:

1. Turn it 1/4 turn Counter Clockwise and wait about 10 seconds to allow the motor to catch up with the new setting. LISTEN or look at your tach:
a. If the IDLE GOES UP REPEAT #1, UNTIL the IDLE does not change or drops a little THEN TURN THE SCREW CLOCKWISE 1/8 and that should be the highest IDLE from the Fuel Ratio Mixture and go to #3.

**** IF ON THE FIRST 1/4 TURN COUNTER CLOCKWISE THE IDLE GOES DOWN OR DOES NOTHING, TURN IT CLOCKWISE 1/4 TURN TO GET IT BACK TO WHERE IT WAS AND GO TO #2****

2. Turn it 1/4 turn Clockwise and wait about 10 seconds to allow the motor to catch up with the new setting. LISTEN or look at your tach:
a. If the IDLE GOES UP REPEAT #2, UNTIL the IDLE does not change or drops a little THEN TURN THE SCREW COUNTER CLOCKWISE 1/8 and that should be the highest IDLE from the Fuel Ratio Mixture and go to #3.

3. If the idle is TO HIGH NOW LOWER the IDLE USING the IDLE SPEED SCREW so that your REAR WHEEL JUST WANTS TO TURN... Go to #4.

4. Now give the Throttle a quick twist and let go, the Motor should Rev up nice with no sputtering or hesitation and come back down to where you set the idle.

*** IF TURNING THE FUEL RATIO SCREW Clockwise or Counter Clockwise DOES NOTHING Then the Pilot Jet AND OR ITS PASSAGE ARE Clogged and you will have to clean the Jet and CLEAR OUT THE PASSAGE. And go through the Procedure again***

Alleyoop

[kiwibilt]

Thanks Alleyoop,
I just downloaded a manual, but the info you provided on accessing the mixture screw wil be very helpfull. Im going to check the static timing as a matter of course now, but these bikes just seem to run lean after a while. It will also be handy to check the resistance of the coil/CDI/auto choke etc. The previous mechanic simply replaced parts in a process of elimination, so I have a bunch of spares that probably still function fine.
Would the altitude these bikes run at have anything to do with there lean condition ?.
Mahalo

[Alleyoop]

Yes altitude and cooler dense air will make them run lean. As far as testing ENRICHERS they are easy to test, just hook each one to a 12v battery and the PLUNGER should start to EXTEND out about 1/4 of and inch within about 3-5 minutes and when disconnected from the power source as they cool they will start to retract.

Just remember if you have to take the head off and CAM out for any reason, FIRST bring it up to TOP DEAD CENTER align your CAM SPROCKET as if your going to Adjust the VALVES then PUT a MARK ON THE A CHAIN LINK AND THE CAM Then mark the FLYWHEEL where the pointer is pointing at. This way when you put it back together you will be RIGHT ON with the timeing and not off a tooth either way.
Alleyoop

[tvnacman]

I just had a bought with a 50cc 4T , Pull the spark plug and look at it . I could not get a good idle or accel.

There is a PDI that you can follow .
The main things are spark plug avalve adjustments and vac leaks .

John

[kiwibilt]

Im having MAJOR problems with getting these scooters to run...
I have accessed the idle enrichment screw, but it has no effect what so ever. They run fine "out of the box" for maybe 50km & then they start to die going up hills. The scooters my boss is importing now have been sitting since 2011 (he imports them from Canada). Most of them seem to have voltage problems which I guess affects the ignition output (CDI, Coil, etc...). When running, the battery voltage is around 11.8 on my mulimeter & the latest one I assembled has no power from the mag to the auto choke or headlights & tail light (yellow wire). It seems that I can get them to idle & rev out prior to connecting the throttle cable..but once the throttle cable is comnnected & adjusted for free play...they wont wind out & lack power up hill. A mechanic at our dealership in Canada said that plugging the vacuum hose from the right side of intake will make them run richer, but this just makes the one bike I am trying to get run now die. Im ready to go back to basics & check the static timing in relation to the camshaft (at TDC). Can I check the output of the mag ? ( it's AC ?).
At idle, ALL these scooters surge & die, & when you rev them, they cut out, which makes me think the auto choke is malfunctioning (apparently a common problem). With the feeler gauges I have now, I am unable to set the valves tighter than a tight .008 inches...does this make a big difference...even the new bikes come back after 5okm with these same problems.
I take pride in my work..& the better I can get these scooters to run, the more work I will get, as there is nobody else here thart will touch them. I know at 1.9 HP, they are gutless...I just need to get them to run without lacking power & cutting out....Aaargh !!!
I make sure the intake tube is tightened to the head & carb, & also spray starter fluid around the carb to check for vacuum leaks...is there something else I may be missing

[Alleyoop]

All this sounds like fuel delivery problem. Are you sure you do not have any AIR LEAKS by the INTAKE MANIFOLD where it connects to the motor and around the Clamps that hold the CARB as well as the AIR FILTER side. ANY AIR Leaks will make it impossible to tune them.

So take some soapy water and put it in a Spray bottle and Start the scoots and SPRAY INDIVIDUAL areas IF the IDLE changes you found a leak.

Now when you say after you adjust the throttle cable they don't wind out YOU ARE DOING something wrong. With the motor off TURN THE THROTTLE WHEEL all the way open IT ONLY will go so far and mark the WHEEL and ON THE CARB SIDE WHERE IT STOPS. Now connect the throttle cable and adjust so that when you twist the THROTTLE WIDE OPEN the THROTTLE CONTROL WHEEL should open as far as when you turned it by hand and the mark you made.

Can you take a picture of the CARB LEFT SIDE and RIGHT SIDE showing the hoses?
Alleyoop

[kiwibilt]

The "wheel" still maintains full travel after I connect the cable, It just seems to "bog"...just like a chainsaw that needs adjustment.

[Alleyoop]

Whell then it is a fuel mixture problem, has nothing to do with the throttle cable not opening the The Butterfly all the way.

Did you adjust the carb like I posted PRINT IT OUT and follow it, it is very accurate method.

Where does it BOG, starting off or at a higher rpm.
Alleyoop

[Alleyoop]

Also .008 is to wide of a gap even for the 150+ scoots. If you cannot get a set of feelers gauge set that has .003 and .004 then cut a piece out of a SODA can and use that as a feeler gauge. Using that adjust so it slides in and out smooth and easy not tight and that should be right around .003-.004 gap.
Alleyoop

[kiwibilt]

It bogs from mid range to high RPM & adjusting the idle/mixture screw makes NO difference. Im thinking that the CDI or coil is not providing enough voltage to give them enough spark ?. This is determined by the output of the magneto/generator. Can this output be checked
The plug fouls while I am trying to tune it
And it backfires under load

[Alleyoop]

Now are you letting the motor warm up AT LEAST 5 minutes before you start to tune it. If the plug is fouling you have to MUCH FUEL. Are you adjusting the FUEL RATIO SCREW or the IDLE SPEED SCREW TWO DIFFERENT THINGS. The Idle Speed Screw all that does is open the Butterfly a little more for a higher or lower idle.

Let me ask this:

After the Motor is nice and warm and you turn THE FUEL RATIO SCREW in either direction DOES THE IDLE GO UP OR DOWN OR DOES NOTHING. Try it from where the screw is set at TURN IT CLOCKWISE 1/4 of a turn at a time and listen for the IDLE DOES IT GO UP OR DOWN as you turn it 1/4 at a time.
Alleyoop

[Alleyoop]

It is nothing but fuel problem CARB adjustment, nothing to do with the CDI or COIL. If they start and run at idle but have problems bogging it is a fuel to air problem quantity. You are making to much of the problem, they already run they just bog which is a fuel and air mixture problem.

Now on yours the FUEL RATIO SCREW may be plugged IS IT?

This is what the carb should look like on the LEFT SIDE which is where the FUEL RATIO SCREW is at.
Alleyoop



OR IS THIS WHAT IT LOOKS LIKE LOOK AT THE FUEL RATIO SCREW AREA:

[carrie]

Sorry, I didn't know how to properly respond here. I too have a question, as I own a rowdy 150 cc. It's a brand new 2013 with lea than 1k miles, and it keeps stalling! I kept telling my mechanic, and it still hasn't been resolved. I'm thinking it maybe the spark plug, carb, filter clogged, or gas line. Please respond!!!