240 Pro sounds lean but it’s not

[fxstbi]

My bike is sounding lean at about 2/3 and up throttle. (It almost sounds like detonation.) I’m running an OKO 26mm carb, 48 pilot and 115 main, needle clip in the second notch from the top. The main is one size bigger than required. I don’t think it’s a carb problem anymore. I checked my timing and it’s right on. I checked my pipe and it appears clear and the muffler is a new Wes. I’m running the stock champion plug. Any ideas or suggestions? 

[technowaldo]

Bin that champion plug for starters fit a ngk 

[lineaway]

 I would go up to a 52 pilot and see if that clears it up. When was the last time it had mains and seals?

[fxstbi]

Unfortunately I don’t have any past history for the bike. Is there any way to check the seals? Perhaps some sort of leak down?  I’ll try the bigger pilot, thanks for the tip. 

[misscrabstick]

As an experiment try some octane booster additive. Fuel these days isn't what it was in this bikes heyday.

[fxstbi]

That’s a good idea and easy to try. Thanks! 

[alberto]

On 12/9/2019 at 8:45 PM, fxstbi said:

My bike is sounding lean at about 2/3 and up throttle. (It almost sounds like detonation.) I’m running an OKO 26mm carb, 48 pilot and 115 main, needle clip in the second notch from the top. The main is one size bigger than required. I don’t think it’s a carb problem anymore. I checked my timing and it’s right on. I checked my pipe and it appears clear and the muffler is a new Wes. I’m running the stock champion plug. Any ideas or suggestions? 

probably you have to change the seals

my oko run with

35 pilot

105 main

jjh 3clip

at least change the ignition seal, so you don't have to open the engine

 

[fxstbi]

Thanks everyone for the replies. After extensive checking and testing I haven’t found anything wrong so I went back to the carb and increased main jet size to 118 and put in a new NGK B6HS plug. It actually runs better! It still has a little lean sounding knock or ping at almost full throttle. I’m going to go up to a 120 main and give it a try. 

I would have never guessed that I would increase jet size so much. Like Alberto indicated above, my bike came with a 105 installed. I was surprised when I was told 112 is the correct size. Thank you all for the help. 

[lineaway]

Change the pilot.

[nigel dabster]

11 hours ago, lineaway said:

Change the pilot.

bit harsh.

[lineaway]

 And Short.

[fxstbi]

Line away, I did go up to a 52 pilot and I have the 118 main in it now with an NGK B6hs plug. After all the testing I’ve done the (what sounds like) detonation is still there. It’s only about half as much but still present. With the 118 it’s not reving out clean at w/o throttle so I might need to step down one there. 
Do you think it could be coil or ignition related or stay with the carb and go up more on the pilot? Any and all advice is greatly appreciated!  

[heffergm]

What octane fuel?

[lineaway]

 So where is the clip for the needle, position wise. Are you using the stock air box? So does this thing wonder up and down depending how warmed up the bike is?

[fxstbi]

The clip is in the second notch from the top. The bike runs and starts great (with the 115 main) with the 118 it doesn’t want to clean out. It falls to idle quickly as soon as I chop the throttle. It just bangs like detonation when the throttle closes. I just read about deceleration knock, “pipe bangs” some call it. I haven’t had an opportunity to research it yet but the one short article I read describes what I think I’m hearing.