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Carb Jetting Issue or something else?? 125TC

S

Slammysammy55

Husqvarna
Hello,

I recently rebuilt the top end on my 2024 125 TC, it starts good and can get to idle pretty well until I blip the throttle, it will then rev high and not come back to idle for 5-10 seconds(thinking a lean condition) but then it will start to bog out like it’s getting to much gas, hard to save it even when hitting throttle after that. If i get on and ride it, rides better than before, more torque and sounds crisp. Spark plug looks pretty clean( not white to be lean or to black rich) I switched from a single ring piston to a double ring per the OEM manual but am wondering if maybe i need to adjust the jetting? Not much of an expert so would appreciate any advice anyone has! I did try adjusting the clip position on the jet needle to a lower clip position to get some more gas and obviously cleaned all the jets out and carb as a whole. But didn’t improve much, also adjust the air screw/idle screw didn’t help a ton either way, either would rev up way to high or just die on me, couldn’t find a good sweet spot so just returned to OEM manual specs. Thanks anyone for taking the time to read this! Hopfully someone can help!
 
Slammysammy55 said:
I recently rebuilt the top end on my 2024 125 TC, I switched from a single ring piston to a double ring per the OEM manual but am wondering if maybe i need to adjust the jetting?
Click to expand...
This shouldn't require changes in your carb settings.

Slammysammy55 said:
it starts good and can get to idle pretty well until I blip the throttle, it will then rev high and not come back to idle for 5-10 seconds(thinking a lean condition)
Click to expand...
First off all my experience is with vintage stuff however it sounds like your 125 has the same fuel system (mikuni carb, jet needle, etc) as the older stuff I'm familiar with. With that said, it sounds to me like an air leak between the carb and the cylinder, e.g. the intake manifold. I think you're correct in your diagnosis of a lean condition which could be due to an air leak. In the vintage realm we would do a leak down test to confirm this. If your bike has some sort of electronic fuel management system such as an ECM then maybe something went funky with it at the same time as the top end rebuild.

Slammysammy55 said:
If i get on and ride it, rides better than before, more torque and sounds crisp.
Click to expand...
This leads me to think the leak may be closing as the bike warms up. I've had this happen to me once. If you let the motor cool down to ambient temp does it act the same when starting it a second time?

Slammysammy55 said:
but then it will start to bog out like it’s getting to much gas, hard to save it even when hitting throttle after that.
Click to expand...
Between this comment and the one above, it sounds like its starving for fuel. If your Mikuni has a float bowl did you have the bowl off at any point and if so did the float height possibly get moved?
 
Crash, I really appreciate your fast response, i haven’t had a chance to try some of the things you suggested but you were correct that I have a bad intake manifold, it was cracking when i took the carb off i made sure that there was no light coming through so I thought it was okay till a new one Comes in. I have been very busy but as soon as I try these suggestions I’ll let you know! Thanks again!!
 
Update: I have now replaced the intake flange and the float chamber gasket. Still having the same issue… not sure what to do next. Still starts fine on first kick or 2 then revs up real high like it’s starved for fuel when i have choke on. Turn choke off and it’s okay until i blip the throttle, then it bogs slightly, revs up and then either dies or maybe i can save it with throttle. But it’s boggy. Any suggestions?
 
I didn't notice during my last post that your bike is a newer model with EFI. Nothing more I know of that you can do short of having a mechanic check it out.
 
I actually spent the day working on it, and figured it out!! I had to have taken the carb apart 5-6 times no joke but finally realized the pilot jet was still clogged. I’m a dummy lol but it’s running like a top now, i appreciate you taking the time to respond and helping me out!!
 
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