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Hey everyone
I have a 03 exmark laser-z with a kohler ch25s engine. Recently had a bent pushrod, I replaced all the rods and lifters and lapped the valves, the whole 9. All this because the mower would bog down when trying to go full speed. If I let up on the throttle it would rev back up. It will idle perfectly fine full throttle, but the minute I try to go full speed it bogs down. The right cylinder is running great. The left, not so much. When I let the engine just run on the left it slowly stalls out. So, fixing the pushrod issue didn't solve my other problem.
Any ideas on what the issue may be?
The left cylinder definitely has spark, it gave me quite a shock when pulling it off to test it.

Thanks for your help

Sound like your carb is dirty. Time for a good cleaning.

Which side had the bent push rod ?
Pushrods bend because the valve won't move when it tries to push it .
This can be because the valve is sticking in the guide or the guide itself is moving in the head.
If it is a Command engine you need to bleed the hydraulic lifters or they end up with an air lock in there that compresses so does not move the valve.
Do you have the Kohler manual ?

bertsmobile1 said:

Which side had the bent push rod ?
Pushrods bend because the valve won't move when it tries to push it .
This can be because the valve is sticking in the guide or the guide itself is moving in the head.
If it is a Command engine you need to bleed the hydraulic lifters or they end up with an air lock in there that compresses so does not move the valve.
Do you have the Kohler manual ?

Click to expand...

I do have a manual, I bled the lifters before installing. I believe it was the intake side on the left cylinder. All the hydraulic lifters had very little movement compared to the new ones I installed. On that same cylinder the exhaust valve loomed pretty badly burned out, I lapped them very very well, but there could still be a possibility it's not seating right. Could this cause the issue?

BlazNT said:

Sound like your carb is dirty. Time for a good cleaning.

Click to expand...

Cleaned the crap out of it multiple times now. I think I'm going to try a rebuild though