apollo 125cc trouble with idle

[Digler]

Ok, I have a 125cc Apollo I got it from a guy in trade. When I saw it the guy told me that it had to warm up before it would idle at a normal rpm. When I got home and started playing around on it to warm it up, it would never idle at a normal rpm. I thought it might be the carb needed to be cleaned. I cleaned the carb, put it back together and it does the same thing. I checked to make sure the carb was put together correctly and it iswhat the bike is doing is once it starts the idle raises and lowers on its own. Sort of like I'm giving it throttle but i'm not. Also the rpm's are very high. I tried lowering the idle screw to a normal rpm and it just dies out when I decrease the idle. I thought it might be the air/fuel mixture adjustment but not sure what to do. Any ideas what I can try? Thanks

 

[my67xr]

hi, welcome to Miniriders,



test it out for vacuum leaks too before you take it off .
start the bike and let it idle, then spray some carby cleaner/wd40/degreaser over all the joins where the carby meets the insulator/spacer, insulator/spacer to manifold and manifold to head.
it the idle changes in any way, then there is your leak.

the manifold and carby mounting faces can easily warp if you tighten the bolts too much too.
so get some 320g w&d paper and put it on a block, then rub it across the mounting faces.
it should mark the faces evenly, but most will show that the bolt holes are higher than the rest of the face.

if it needs it,
rub the paper/block across the face until it is flat, it may take a few passes to flatten it out again.
use some decent gasket paper (approx 1.6mm thick), and make another couple of gaskets for it too if you can.




when you pulled the carby down to clean it, did you remove the Pilot and Main jets from the carby and check that you could see through them ?
if you look into the carby where the smaller Pilot jet has come from, there should be a pin hole that goes through to the main bore of the carb, sometimes these can block up too.
and blow some compressed air in through the 2 or 3 small gallerys on the air filter side of the carby, while the jets are out, to check they aren't blocked up

once you get it idling better,
re-adjust the idle speed screw, it will probably work better once the carby is cleaned


another thing to check is the valve /rocker clearances
when they come from the factory they are only roughly set up, usually with very little clearance or none at all.
the pitbikes need .003" clearance on the intake valve, and .004" on the exhaust.

click on this link to see how to check the valve clearances-
http://www.youtube.com/watch?v=hZjdJcIYdWo



post up your results, if you need any more help.

 

[GooseMan]

+reps for that very helpful write up there craig, good job.:thumbup:
ANd as he said first check for a leak where the carby meets the engine by spraying anything flammable onto the joins. Good luck let us know how it goes, and welcome to miniriders.

 

[Digler]

Ok, I checked for leaks first and instantly found a leak in the spacer. Fixed that and tried getting the idle set and it idles perfect now. It has however uncovered another problem. When i took it for a test ride, when I gave it throttle it would backfire and sputter. It seems as though the main jet isn't working correctly. I thought it might be because I had the idle to low but raised it some and it did the same thing. Also when I cleaned the carb, I didn't remove any of the jets but I did spray carb cleaner through all of the ports and they seemed to all be cleaned out. Any ideas again would help greatly.

 

[my67xr]

if it sputters/backfires etc when you give it a blip on the throttle, it sounds like the Pilot jet is still/partly blocked

what carby are you running ?

 

[Digler]

Its not sputtering when I blip the throttle its when I put it in gear and get going. I get rolling then it starts acting up. Not sure what carb it is. I'll try and send a picture

 

[my67xr]

so next thing to do is pull the carby off , strip it down and clean the jets then

 

[my67xr]

have you replaced the spark plug too?
put a new NGK one in if you havent already.
also check any joins/connections in the wiring , spray them with wd spray, it may not have a good contact somewhere.

 

[Digler]

So I stripped the carb all the way down. Soaked it in cleaner for the night the sprayed it with carb cleaner. All the holes are clean. I changed the spark plug and it is still sputtering and backfiring when I try and speed up. I was wondering is there an adjustment to the main jet in the carb. Also I saw the marking on the carb that said jing ke.

 

[my67xr]

so it's basically like these carbys,




the Pilot circuit still sounds blocked up?
so you blew compressed air in though all the ports on the intake side of the carby ? (where the air filter mounts)


have you checked that fuel is going through into the carby, no blocked fuel filter or dirt in the needle and seat ?
and that the float height is correct ?
use some clear plastic tube on the drain/overflow tube on the bottom of the fuel bowl, and open the screw
the level is measured from the top of the fuel in the tube, to the top of the fuel bowl.

 

[my67xr]

these pics are of a Keihin copy carby, same as the Jing Ke , this is the small port where the Pilot jets' fuel travels through, to provide enough for idle - 1/4 throttle
if it is blocked then the bike will be hard to start and wont rev easily, popping and carrying on etc



at the intake end/filter end of the carby, the ports feeds air into the fuel bowl to pressurise it
one port is for slow speed, the other is for high speed

the slow speed port travels past the idle mixture screw on it's way to the pilot jet.
if some dirt has got in there before the mixture screw, the Pilot jet may not be getting the correct amount of air, or maybe none at all.

so when blowing compressed air into the ports, try to make sure you can feel air blowing out of the mixture screws' hole in the carby body.
then refit the screw and feel the pilot jet port as you blow air through the intake end port again.

 

[my67xr]

and another thing that may be causing it to run bad is a warped fuel bowl sealing face too
it might pay you to check that while it is apart ?

 

[Digler]

I sprayed carb cleaner both ways through every jet and port thats in the carb. You are correct my carb is just like the ones you have pictured. I will measure the float once I get some clear tube. The bike no longer has a problem with the idle. It idles great now. The first 1/4 of the throttle seems to work great also. Thats the only time i can get a throttle response. After the 1/4 when i am trying to ride it is when it is sputtering and backfiring. Also, when I took all the jets out they were tightened down so is there no adjustments for them or when they are tightened down they are good?

 

[my67xr]

ok, thanks
yeah the jets are not adjustable, they just need to be nipped up to hold them in.



the idle circuit sounds like it is good/clear then.
is your mixture screws' adjustment about 1- 2 turns out from being done up ?



from what you've said, i agree, i would be looking at the main jet.
when it was out, did you also remove the main jet/needle jet tube? the long tube that the main jet screws into
i have noticed they can use 2 different types of needle jet tubes,
one has a hex head near the main jet, with very tiny holes in the extension, left one in my pic
the other type has 2x flats machined into it, this type has bigger holes in the extension, shown on the right in my pic.
the second type is less likely to block the 20 holes

these 20 tiny holes are there so the air mixes with the fuel as it is drawn though into the carby.
if say half of these 20 holes are blocked it will cause dramas with the air/fuel mix and wont run correctly.
with less air in the mix, it is heavier and harder to draw up into the tube to go into the carby/engine
i would be double checking the tiny holes are all open.






the needle height in the slide is adjustable, this is a fine adjustment of the main jet
standard they are setup in the middle position of the 5 slots.
you could try lowering the clip on the needle and see if that helps it out a bit.
it will make it a touch richer (and visa-versa, raising the clip will lean it out)
if richening it helps, you might want to try a bigger main jet, the china carbys we get here usually run a #70 or even #75 main jet
take your jet down to the local motorcycle shop and see if they have one a bit bigger, they will cost under $10 ea, try a #75 or #80
fit that in and try it out again.
the main jets used can have 2 different sized heads too, one is 10mm across the other is 8mm,
as long as the thread is the correct size (3.5mm across?) then both types of jets will work

 

[Digler]

Alright I finally found some clear tube. I checked the float level like you said and the fuel is even with the top of the fuel bowl in the tube. I'm guessing this isn't good, how do I adjust this?

 

[my67xr]

you will be better off keeping this thread going to solve your problem, and not starting another.
otherwise you will get replies everywhere and not know where you are up to.



you will need to pull the carby off again.
then remove the fuel bowl, turn the carby upside down and see where the float sits
take a picture it may help you to remember how it sits/goes back together.

slide the floats' pin out through one side,
now with the float out you will see the metal bracket that holds the floats and the centre tab that closes the needle and seat.
notice that there will be a small dot in the middle of the centre tab, this is where the pin from the needle and seat/fuel inlet valve sits, and leaves a mark.
if you forget which way up the float sits then knowing this may help you out.

the angle at which the little centre tab sits, when compared to the parts that branch out to the floats, will control the height of the fuel level in the carbys' fuel bowl
so to drop the fuel level, you will need to bend the tab upwards a little
then refit the float and measure it.

i will get some pics up for you shortly.

 

[my67xr]

this is the approximate angle the float should be sitting at with the carby upside down




and the approximate angle of the little centre tab on the float

 

[my67xr]

so to lower your float level,
looking at that tab that sits against the needle/seats' pin, your's will need to be bent down compared to my second picture.
lift the float up and support it, then push the centre tab down a touch (maybe 2mm) with a flat bladed screwdriver.
then let the float drop back towards the carby again and check the angle it sits at.

i will reassemble my carby aqain in a while and take some more pics, showing it full of fuel and showing the level with the clear tubing method.
normally the level will be around 3/4 of the height of the fuel bowl.