Why is my pit bike doing this??

[ThisGuy]

I deep cleaned my carb because it was acting like this. When I put it back on, it was still acting like that. Why??? Please list any reason it could be. I am experienced with pit bikes but not an expert. [video=youtube_share;eRgaX7qlCZY]http://youtu.be/eRgaX7qlCZY [/video]

 

[my67xr]

have you tried raising the idle speed a little ?
the screw with the spring on the side of the carby, it lines up central with the carby slide
turn it in half a turn and see what it does



it could also possibly have an air/vacuum leak ?
start the bike and let it run, with a touch of throttle if you need
then spray some wd40/degreaser over all the carby joints, and carby to manifold, manifold to head
if the idle changes in any way, then there is a leak there.
might get away with tightening the bolts/screws ?




otherwise i would be guessing that the Pilot jet is a bit blocked up ?
it's the smaller jet screwed into the base of the carby, towards the intake manifold side
pull it out and clean the hole through the middle, and the holes that go across the jet too.
check where it screws into, at the bottom of the threads there's a tiny hole, you should be able to see light into the carby bore too
try poking a strand of wire from a wire brush or the like through it.
then reassemble the carb and try it out.



p.s. your exhaust is very loose, don't forget to tighten it, 2x nuts under the head

 

[ThisGuy]

have you tried raising the idle speed a little ?
the screw with the spring on the side of the carby, it lines up central with the carby slide
turn it in half a turn and see what it does


it could also possibly have an air/vacuum leak ?
start the bike and let it run, with a touch of throttle if you need
then spray some wd40/degreaser over all the carby joints, and carby to manifold, manifold to head
if the idle changes in any way, then there is a leak there.
might get away with tightening the bolts/screws ?




otherwise i would be guessing that the Pilot jet is a bit blocked up ?
it's the smaller jet screwed into the base of the carby, towards the intake manifold side
pull it out and clean the hole through the middle, and the holes that go across the jet too.
check where it screws into, at the bottom of the threads there's a tiny hole, you should be able to see light into the carby bore too
try poking a strand of wire from a wire brush or the like through it.
then reassemble the carb and try it out.



p.s. your exhaust is very loose, don't forget to tighten it, 2x nuts under the head

Ill try the idle screw, as for the leak, can I use carb cleaner? Ran out of wd40. And I had a blocked pilot jet, I took a needle and cleared it. I see light through it but its a small. I don't know if its still blocked or restricted because the carb cleaner was going through it. And as for the exhaust, I was actuly taking it off because I stripped one of the huts so I can't tighten it anymore. I was trying to figure out how to remove it. Good this be an electrical issue? Like a misfire? Old spark plug? Wires not grounded properly?

 

[my67xr]

yeah carby cleaner will work too.


but if your Pilot jet was blocked, the hole could still be restricted
when fuel evaporates it can leave a clear/yellowish gum behind, it is hardly visible against the brass jets
i would try poking a bit of wire though the hole again,
did you check the side holes in that Pilot jet too?
and the tiny hole at the bottom of the threads where it screws into the carby.

 

[my67xr]

with your stripped nut,
try putting a big flat bladed screwdriver between the nut, and the head,
and put a bit of pressure on the nut forcing it away from the head as you try undoing the nut.

 

[ThisGuy]

Heres the deal...

I sprayed the intake and even the whole carb just to make sure that I sprayed it and the rpm did not pick up. Dont think its a leak. I took out the plug to see if I got a spark, i did. I adjusted the idle screw, still did the same thing. I adjusted the fuel screw. Nothing happened. My last thing to check it the pilot jet. But how would I know if its slightly restricted? When I cleaned it 2 days ago it was blocked then I put a needle in it and then the spray went through. I thought I was done from there. Im lost now. Dont know what else it could be.

 

[my67xr]

ok,
so no idle speed change when spraying it means that there are no vacuum leaks, that's good.



the Mixture/Fuel screw basically controls how much fuel goes through the Pilot jet.
so with it not doing anything when you adjust it, means that there must be a blockage in the jet, the hole in the base of the carby, or somewhere in the Pilot jet circuit.


you say you have cleaned out the pilot jet,
but are there small holes that go across the Pilot jet after the threads ? like with this jet-

you might be able to see through it, but it still may be restricted with some gum/varnish type build up in it.

have you done the things i mentioned in post's #2 and #4 ?



also, what carby are we talking about ?

 

[ThisGuy]

I stuck the needle through the holes on the side and it went through and nothing came on the needle. And yes I did what you said in posts 2 and 4

 

[ThisGuy]

And it's a 19mm carb. With a cable choke. Didn't come with a cable though. Bought it off of eBay.

 

[my67xr]

ok,
take the air filter off and try squirting your carby cleaner through the small hole to the left,
the one just inside the carby mouth (the hole at about 7-8 o'clock)

i would take the mixture screw and pilot jet out while you do it
there's a blockage inside that Pilot circuit port somewhere

reassemble it and refit it.
then try it out.

 

[ThisGuy]

ok,
take the air filter off and try squirting your carby cleaner through the small hole to the left,
the one just inside the carby mouth (the hole at about 7-8 o'clock)

i would take the mixture screw and pilot jet out while you do it
there's a blockage inside that Pilot circuit port somewhere

reassemble it and refit it.
then try it out.

The fuel screw gets taken out? Doesn't it make it run rich?

 

[my67xr]

yeah it needs to be taken out to clean the Pilot Circuit.
if you don't take it out, then spray some carby cleaner into the port, then it may just stay blocked, or it could move more dirt along in the port.

when you spray your carby cleaner into the smaller hole on the air filter side, it will travel through that port, past the mixture screw hole, and into the pilot jet hole.
if there is dirt/dust etc in that port somewhere it will come out one of the holes along the way.

you need to refit it before you try and start the bike though
just screw it all the way in, then back out 2 full turns
that setting should be close on what it needs to start/idle

once it is running, then it can be adjusted from there.

 

[ThisGuy]

yeah it needs to be taken out to clean the Pilot Circuit.
if you don't take it out, then spray some carby cleaner into the port, then it may just stay blocked, or it could move more dirt along in the port.

when you spray your carby cleaner into the smaller hole on the air filter side, it will travel through that port, past the mixture screw hole, and into the pilot jet hole.
if there is dirt/dust etc in that port somewhere it will come out one of the holes along the way.

you need to refit it before you try and start the bike though
just screw it all the way in, then back out 2 full turns
that setting should be close on what it needs to start/idle

once it is running, then it can be adjusted from there.

Okay I took out the mixture screw and removed the carb, but when I sprayed the cleaner in the left hole it shot out the mixture screw hole. I dont know if that is what its supposed to do but it did it. One thing i didnt do because I read your reply late is start it with the screw back inside. I left it out and tried to start it and it wouldnt start.

 

[my67xr]

nah it wont run without the mixture screw, it'll be too lean.
but the Pilot circuit has a blockage, so it sounds like it's not between the port and screw.

spray it again, and this time put your finger over the mixture screw hole
hopefully it will flush out whatever is stuck in there.
the spray should come out the pilot jet hole in the carby

 

[ThisGuy]

Do I clean the bowl out before I start it or it doesnt matter?

 

[my67xr]

yeah, if there's dirt etc that comes out into it.

 

[ThisGuy]

Remember how I told you I had a cable choke? Well I pull on the part where the cable is supposed to go and it started up instantly. Quick question...Is the choke on or off when the butterfly flap is open? Like when you can see down the throat of the carb is the choke on?

 

[my67xr]

no, that is choke off, when you can see the slide in the carby (butterfly horizontal)

 

[ThisGuy]

no, that is choke off, when you can see the slide in the carby (butterfly horizontal)

So when the flap is closed it runs starts and idles perfectly...Where do we go from here? Am I supposed to let it start and run for a while with it closed. I havent started the bike in a long time and when I tried to start it it didnt start. It only starts with the flap closed.

 

[my67xr]

so now you need to set the mixture screw.

turn the mixture screw in, so it is 1 full turn out, then start the bike
raise the idle speed a bit, slightly higher than normal.
now turn the mixture screw in or out a 1/4 turn at a time, to raise the engines' rpms
then you can fine tune it to find the sweetest spot for the mixture screw, adjust it 1/8 turn at a time.
you want to make the bike run at it's highest/smoothest rpm when adjusting the mixture screw.

once you are happy with it, turn the idle speed back down to a normal speed
you are done