carburetor is popping 26mm oko flatty

[lifelessurf]

hey , can some one help me with this problem. i just bought a 26mm flatslide oko carby i put it on, (the main is 100 and the needle is jjh). i installed the carby the bike idled fine but kept popping i moved the clip on the needle up one notch but i couldnt get the bike to run smooth from 1/4 to 1/2 throttle. i then moved it down 2 which is 2nd from the bottom bike went fine but it was still popping and not running that well. also it was running really hot. that hot the pipe glowed a orangy red colour right on the bend of the header pipe. ive got a yx 160 if that helps... anyone got any suggestions i played around with the air mixture screw it makes it run a bit better but still keeps popping also when it pops smoke comes out the air filter

HELP!

 

[krazed0451]

What's your secondary Jet?

The main shouldn't be effecting it at idle...

 

[pbk]

use 102 main jet, 36 pilot needle in either middle notch or one up from middle and mixture 1 to 2 turns out be done with it

and also when its running really hot with the exhaust glowing it means its running lean

if i got a $1 from every oko carb thread i would be a millionaire!

 

[lifelessurf]

i bought it from dhz so im assuming its a 36, since the bike went fine from close throttle to redline i didnt think it would be the idle jet...? i was reading some more forums on cars and bikes and alot of people from similar problems say its the main jet, that its too lean i have got the clip on the 2nd last notch maybe 100 main is too lean?

 

[krazed0451]

Not for the first half of throttle... Would pay to check your valves and for air leaks (gaskets etc) too

 

[lifelessurf]

thanks pbk ill go buy a 102 jet on monday ill let you know you all know by tuesday hopefully

 

[krazed0451]

Check valves/gaskets first...

 

[lifelessurf]

to your respnose krazed i bought a yx 160 engine brand new i checked all bolts n nuts so it shouldnt be a air leak its had 1 hr ridin time

 

[pbk]

where abouts are you from as general area as altitude can affect your carby

and i can just about gurantee you that 102 will fix the problem or at least help

 

[lifelessurf]

im from cessnock u mite have been at the races today i noticed your from the central coast.... im prity sure sea level is around 100m

 

[krazed0451]

to your respnose krazed i bought a yx 160 engine brand new i checked all bolts n nuts so it shouldnt be a air leak its had 1 hr ridin time

That's nice... But you have changed carby, so there may be a leak at the mount.

If you haven't done your valves, do them now. None of these new China engines seem to have them correct out of the box.

http://www.miniriders.com.au/motor-tutorials/24965-how-set-valve-clearances-horizontal-engines.html

Also, use the search function, there are heaps of threads with similar problems... Get the basics out of the way before you go out buying parts expecting them to fix your problem.

As I stated, the main jet isn't even in use at idle, and will have minimal use for the first half of the throttle. If it revs cleanly through the rest of the range it's unlikely to be your main jet. Check your mixture too, as mentioned, you may just be running it too lean.

 

[lifelessurf]

im going to ask a stupid question but when you say check your mixture thats the air mixture screw right??? which plays along with the idle screw?

 

[krazed0451]

Nail on the head... There's a few threads on carby tuning in the tech section.

First things first though, do your valves!

 

[pbk]

the screw with a spring behind is idle scew

the one that is to the right and down a bit is your mixture scew so screw it all the way in and wind it out 1 turn and play with it from there and a just a word of caution dont keeping winding it like your tigthening up a screw or bolt wind it and stop just when it grabs

 

[sean01]

ok there was a thread with a very similar problem just a couple of days ago...
turned out the oring in the manifold adapter wasnt installed right and gave an air leak..

the jetting you have should be enough to get it running fine tho it will be a little lean right at the top of the rev range.. glowing pipe is definitely lean.
and the main jet will have no effect on idle quality, actually you can remove the main completely and it will show the same performance at and just off idle.
a 102 main is heaps big enough and a 36 pilot is perfect...needle clip second from bottom works up here (brisbane).

and if you havent do so yet, adjust your valve clearances... new engine or not makes no difference..

 

[lifelessurf]

ok there was a thread with a very similar problem just a couple of days ago...
turned out the oring in the manifold adapter wasnt installed right and gave an air leak..

the jetting you have should be enough to get it running fine tho it will be a little lean right at the top of the rev range.. glowing pipe is definitely lean.
and the main jet will have no effect on idle quality, actually you can remove the main completely and it will show the same performance at and just off idle.
a 102 main is heaps big enough and a 36 pilot is perfect...needle clip second from bottom works up here (brisbane).

and if you havent do so yet, adjust your valve clearances... new engine or not makes no difference..

just with the o ring issue.. my exhaust only has the lip of the pipe going into the head and the ring that the 2 bolts go through to hold the pipe against the head... am i missing a gasket to the header pipe??? ive never run a pitbike with one before just bare metal on metal header pipe to head

 

[krazed0451]

You'll need an exhaust gasket... That could be (and most likely is) your problem right there!

What Sean is referring to is the o-ring in the adapter where the carby mounts to the inlet manifold

 

[lifelessurf]

lol ill put that on the list

ill do my valves tomorrow ive got a 102 main jet on the way and is it ok to use a copper washer as my exhaust gasket?? i checked dhz and they use copper washers? ill just have to find the right diameter

 

[grnman]

yep use a copper one that is fine. oh and by not running an exhaust gasket can assist in making your engine lean. if you address all the issue posted in this thread you should be fine.

 

[lifelessurf]

hey everyone ive been workin on the bike and this is what ive done, i done the valve clearance they were definately too tight i saw a video on youtube sayin that the top valve should 0.004 and exhaust valve 0.006 so i did that instead of 0.003 top n 0.004 bottom. i then tightened up the o ring on the adapter which attaches the carby to the manifold. which had a small gap on each side so i siliconed around the edges of the pipe to fix any leaks. i didnt do the exhaust gasket because i didnt think it really needed it from previous experience with engines ive had an engine doesnt actually need a exhaust at all so i thought a small leak would not come into this type of problem.anyway i started the bike and it sounded a bit lumpier and the carby dont pop any more nor does it run as hot as it was before which had the pipe glowing red. i started working on the idle screw and air screw to get it idling right. i got it on the road went through 1st 2nd then about half way through 3rd it just stop reving up engine was still running but not accelerating i then moved the clip on the needle down to 4th notch from the bottom it made no difference i then moved it down to 5th notch the very bottom it still did nothing so im assuming it is the main jet since this jet has alot to do with power delivery from 3/4 to full throttle as i said before it is running a 100 main so im going to put a 102 maybe even a 104 on wednesday.... anyone have any suggestions of what it could be other than that im so close to getting this carby right just want to say thanks aswell to the guys that have helped me out yesterday on this thread, very grateful.