Running hot after 24mm oko install

[stipe]

Hi guys i just installed the oko flat slide (24mm) in my yx140. After starting her up i noticed that the engine heats up really quickly to a point where it is very hot, more so than it ever had with the stock molkt carb. I did a valve clearance just to make sure but its still running hot. The carb was bought from DHZ with a 100# main and a 36 slow. One other thing i noticed is kinda of ticking noise coming from the air filter. Any ideas?

 

[Trains]

Is it the engine itself running hot or the exhaust? From what ive found Hot exhaust gases means it's running very lean. (Don't quote me on that but that's what ive found). What was the size of the original Carbie on there? The ticking noise might be just engine noise being heard through a more open carbie? just food for thought.

 

[stipe]

It's both the engine and the exhaust that are running very hot now. Before i could touch pretty much the whole engine but everything is just hot now. Original carb must have been a 26mm but i doubt it was 26.

 

[my67xr]

You'll need a #38 Pilot jet for it minimum, maybe a #102 or #105 main jet and adjust your mixture screw to suit.
Are you running it with an oiled, decent foam filter ?

 

[stipe]

Yeah running with the one DHZ sent in the pack. Oiled it as well. If you had to pick 4 main and 4 pilots what would you choose? im thinking of ordering two kits from oko.

 

[my67xr]

DHZ has the jet's for Oko's for $5 ea
Have you checked for vacuum leak's at all the join';s, from carby to adapter, adapter to manifold, manifold to head?
Start the bike and let it warm up,
With it idling spray some degreaser, wd40 etc onto the join's ^^, listen to the engine, if the idle change's in any way then there is a vacuum leak there.


I'd just get the jet's i mentioned above, maybe get a #97.5 main jet too
Just fit the bigger pilot jet first and tune it to suit, give it a ride and see how it feel's might get away with just the bigger pilot.

If it goes alright off idle and rev's ok to mid/high rpm's then fall's flat then fit a bigger main
If it take's off ok and rev's to mid/high rpm's then splutter's then fit a smaller main jet


Are the standard jet's #36/#100 in it now ?
Is this a power jet carby like the one below ?
See the tube running from the fuel bowl up to the power jet on the intake side of the carby ?

 

[stipe]

Yeah thats the one i got.

 

[stipe]

is there any difference that i have that tube and screw there?

 

[my67xr]

It is an Oko Powerjet carby, they are a bit different to tune.
That extra jet at the top of the carby comes into play in the high rpm's and let's a bit extra fuel into the engine.
They are normally jetted a bit leaner in the main jet, around a #90 to give them a bit more power, the power jet supplies the extra fuel to make the equivalent of a #100 at wot

You can remove the powerjet hose from in between the jet and tube of the fuel bowl and block off the port's, and just run it with the main jet that's in it

 

[Trains]

I had one of these carby's and never knew this was a thing! I just blocked mine off!

Sent from my HTC_0P6B6 using Tapatalk

 

[stipe]

i know dhz put in a #100 main so what do you think i should do? how would this effect heating of the engine?

I might drop the main to 95 and jump the pilot to a 38, do i need to touch the power jet at all?

 

[my67xr]

How many turn's out is your mixture screw set at ? And have you tuned the carby to suit your bike ?
if so, what was the procedure you used to tune it ?


If you adjust the mixture screw and can't get it running nice.
I would try it with a #38 pilot, maybe buy a #40 too just in case (DHZ sell's them for $5ea)
Too big on the main jetting and the engine will run cooler, it's lose power and foul spark plug's.
Too lean it'll run hot, burn valve's cook the ring's etc etc
Leave the power jet alone for the minute, i don't think anyone sell's the power jet's in Australia anyway.

Is your air filter oiled ?

 

[stipe]

So what i did was, i installed it and didnt touch anything. The air mixture screw is at the stock setting and it seems to be okay maybe a little bit of hesitation but not much when snapping the throttle. I havent touched any jets yet but i did order a #38 & #40 as well as a #104 and a #98. Air filter is new and oiled.

 

[my67xr]

Try turning the mixture screw in so it's about 1.5 to 1.75 turn's out and see if that help's.
Is it easy to start from cold ?

 

[stipe]

Ill give it a crack later, might re do the valve clearances again. Starts easy but was one kick with my molkt opposed to two or three now. I'm thinking of changing the clearances to .004 inlet and .006 out. Would this be a bad idea?

 

[stipe]

I did the valves again to .004 and .006 engine still runs hot but i do notice when i screw the air fuel screw all the way in the revs rise high and drop when all the way out. i believe its about one and a bit turns out now. Im going to chuck the molkt i had on it back on to see how hot the engine gets with it on.

 

[stipe]

For anyone following this, i changed the carb and got similar results with the engine heating so im not too worried about it any more. One thing i did notice was when i went back to the drawing board, i had realised that i installed the white little piece that keeps the throttle cable seated correctly within the carb wrong. After fixing it i didnt get a chance to install the oko back on but it has me wondering as to whether or not that was causing issues...

 

[my67xr]

When you set up the carby and adjust the mixture,
Warm the bike up, then turn the idle speed screw in to raise the rev's another 800 rpm's or so
Now adjust the mixture screw in or out 1/4 turn at a time and let it settle for 10 second's
Listen the the way the engine is running, you want it running at the smoothest/fastest rev.
Once you think it's close then turn the idle speed screw back out till it's back to a normal idle speed.
Try the bike out after adjusting it.
That should be pretty close to spot on mixture's
Take note of what the bike is doing and at what throttle position if you need to adjust something.
EG, hesitate's off idle, stumble's at 1/4 throttle, feel's sluggish at wide open throttle

If after a ride and you want to adjust the mixture's a bit more, you may need to turn the mixture screw a tiny bit, gtry about 1/8 turn to adjust it from there

 

[china911]

How does the engine behave when riding .Most engines run hot on idle ....mine do ... you may be able to establish if its to lean if you give a run..

 

[stipe]

If i can get the manifold adapter by this weekend, ill give it a good run and come back with an update.