Running hot after 24mm oko install

[stipe]

So after a long overdue ride here is the report.

With the oko installed i noticed a few different things when riding, firstly when im full throttling in say 3rd i can actually feel and hear the bike cutting out at high rpms. Secondly there seems to be a fair bit of back firing going on with the bike when reving and lastly whilst adjusting the air mixture screw ive noticed that with the screw completely in the bike still runs and is still rideable (when im pretty sure its not meant to be).

Found the bike would lift in first when snapping the throttle much the same as the molkt but would only lift sometimes whilst shifting in second.

What do you guys think i should do? Go up in pilot and down in main?

 

[my67xr]

Yeah, go up one one the Pilot jet (#36 in it now ?), then tune it to suit.
If it run's best with the mixture screw less than 1.5 turn's out, fit the next size up pilot
The main jetting might be ok once the pilot circuit is sorted, what main is in it?

Have you checked for vacuum leak's at the carby/rubber adapter join, and manifold to head ?
Start the bike warm it up and spray some wd40/degreaser etc on the join's, listen for any change's in the idle, it the does change then there is a leak there.

 

[stipe]

Its got a 100 main in it and 36 pilot. Ill up the pilot and ill check the leaks.

 

[stipe]

Chucked the 38 pilot in it and tightened up the exhaust manifold, also added a 1/4 turn throttle. Noticed the bike idles a little better now but wont start up with the choke on. Is this an issue at all? ill get the bike started and need to throttle a little until it gets warmed up a tad. Whats your opinons?

 

[my67xr]

Have you adjusted the mixture screw to suit the new #38 pilot jet ?

 

[stipe]

Yeah i think ill get it best as i can. still noticed that when the revs were a little up whilst tuning if the screw was all the way in the bike wasnt sputtering or anything...

 

[my67xr]

Starting without the choke is ok, i have my bike set up the same way.
You'll only need it if it's under 10° C

The mixture screw should be about 1 - 1.75 turn's out when it's set at the best position.

So with the #38 pilot jet in, it still run's fastest/smoothest with the mixture screw wound in fully ?
If so, you could go up to a #40 pilot or maybe even a #42, and then try winding the mixture back out to get it idling nice.


With it cutting out at high rpm's, does it sort of start spluttering then die ?
If so, it sound's like the main jetting is too rich when the powerjet come's in.


Tuning the powerjet can get expensive, you'd need about 8 or so new main jet's to play around with and get it spot on. (guessing a #78, #80, #82, #84, #86, #88, #90, #92, #94 )

You could try pulling the small hose at the back of the carby between the bowl and the power jet at the top, and push a 4mm-5mm ball bearing into the hose, then refit the hose to the barb on the powerjet.
This will block off the powerjet circuit, and will give the carby a leaner mixture in the top end (wot), and try that out.
Another way to block off the powerjet circuit would be to remove the hose and fit a couple of block off rubber cap's onto the barb's (like what's used on some automotive carby's, and vacuum line's etc)

 

[Trains]

You can also just screw a small bolt into the tubing. Will also do the same thing as a ball bearing

Sent from my HTC_0P6B6 using Tapatalk

 

[stipe]

i think ill go up to a 40 pilot and see what happens. If i block the powerjet will i be loosing any performance?

 

[my67xr]

Nah, the main jetting sound's too big to be able to run the powerjet too.
If it's cutting out at high rpm's it sound's like it's flooding to me

You could try giving it a run at wot, and let it stall/die, then get off and pull the spark plug out straight away and check if the tip of the spark plug is all black.
If it is, then that confirm's it being too rich once the powerjet come's in.

Oko only used the powerjet on a couple of carby's, the 24mm and some 28mm's, i reckon the PJ carby's are more suited to 2 stroke bike's.

 

[stipe]

And of course i get that one... haha. Yeah found that when opening the throttle it would rev out then hit a point towards the top where it would sputter a little then continue to try and rev through. so ill go down one from #100 to a #98.

 

[my67xr]

You could also try raising the clip on the needle to the 2nd notch down from top, that'll lean it a bit in the mid range.
But i think you'll need to go down in your main jet a bit more than a #98

 

[stipe]

Will have to order more in then. What would you recommend? #95?

 

[my67xr]

I would try it without the power jet connected first.
But see post #27 above

 

[stipe]

where can i buy the exact caps that i need to block it off? Cheers

 

[my67xr]

Most car part's shop's sell them, Burnson's, Repco, Autobahn, they are used them on carby's etc
Master's have them for $2 a pack- 3mm Champion Rubber Cap 3mm - Masters Home Improvement
4mm Champion Rubber Cap 4mm - Masters Home Improvement
Just don't use silicon cap's they swell with petrol and will fall off.