Bike sputtering at 1/2 throttle

[JTr717]

Hello,

I just purchased 2 brand new pit bikes (SSR 125 DB-X10, Kiehin carb) and I am having problems with only 1 of them. At 1/2 throttle the bike sputters badly. I have done the following so far but still exactly the same problem.
Checked/cleared fuel cap and breather
Checked fuel flowing thru pet****, fuel filter and to the carb
Took apart bowl, removed jets and confirmed that they are clean.
Air filter clean
93 Octane fuel
Adjusted air/fuel screw, started with 2 turns out, tried 2 1/2 turns out and tried only 1 1/2 turns out
Set Idle screw
Checked spark plug
All adjustments were done with engine warmed up for several min.
I am still having same problem at 1/2 throttle, runs ok at low RPM and with throttle wide open
Bad carb? or anything else I can try? I am in Maryland 55 Deg at sea level

Thanks J.T.

 

[JTr717]

After more searching I found some helpful information. Tomorrow I will set the air/fuel mixture screw back to factory (2 turns out) then try adjusting the "C" clip up 1 notch at a time. From what I have read so far this sounds like the next logical step and I believe going "up" on the "C" clip would be the correct direction. Please let me know if I am wrong or if you have another suggestion I can try. I will check back in thanks, J.T.

 

[JTr717]

Moved "C" clip up 1 notch and test rode. Now it sputters when full throttle and runs a little better at 1/2 throttle. There was no washer under the "C" clip not sure if supposed to have one but that could be the culprit so I will try moving "C" clip down several notches to replicate a washer being there and see how it runs tomorrow. Getting to cold out tonight. Please let me know if I am going down the wrong road as far as diagnosis of brand new bike.

 

[KtmJono_777]

Why don't you have a look at the carby on the other bike that is working correctly and replicate it on this one? Match the clip position and ensure it has the same jets installed etc. Also If the bikes are brand new make sure you check the valve clearances. My bike was way out from new.

 

[geoff5]

If your mid range is ok after moving the C clip then you'll need to up on your main jet. Just went through this earlier today with my buddies SSR 110 dx.

 

[JTr717]

Why don't you have a look at the carby on the other bike that is working correctly and replicate it on this one? Match the clip position and ensure it has the same jets installed etc. Also If the bikes are brand new make sure you check the valve clearances. My bike was way out from new.

The other pit bike is my neighbors if he is around today I will take a look at it. As far as valve adjustment I haven't done one in years (last was TRX450R) but if find a how to I will give that a shot as well. Going to adjust the "C" clip some more today to see how it reacts and post my outcome.

 

[JTr717]

If your mid range is ok after moving the C clip then you'll need to up on your main jet. Just went through this earlier today with my buddies SSR 110 dx.

I can go up one more position on the "C" clip so I will give that a shot. As far as it needing a larger main jet can you explain how that needle works? It seems to me (I dont have much experience with carbs) that by moving the "C" clip up it allows the needle to drop further into the main jet blocking more flow so wouldn't I want a smaller main jet or am I way off on the way that works?

 

[JTr717]

Runs better with "C" clip in lowest position but still bogs down on full throttle. Took apart the other bike and found it has a larger main jet "88" mine has "86" assume this is the culprit. Going back to the distributor to try and get a free jet kit for my troubles.