JeanBaptiste
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- Joined
- Aug 19, 2025
- Threads
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Hello all,
First of all, thank you very much for sharing & helping each others so much - it is always nice to see people trying to help others.
Secondly, please excuse my bad english - western french guy here.
I used to run a Kaaz lawn mower equipped with a Kawasaki FJ151v / AC52 engine. It ran pretty well for almost 10 years. When I tried to run it again last spring, it appeared to run badly, despite it was running like a charm at the end of year 2024. Here are the symptoms:
- starting is not a problem, hot or cold,
- there is a power issue, as the engine seems not to run as powerful as before,
- you can hear the engine is not running smoothly, there are like misfires or similar things, almost like a car's launch control system,
- the engine seems to run not as high in rpm as before,
- the sparkplug becomes fouled with dry carbon deposit in like 30 sec, no traces of oil here,
- the combustion chamber was coated with carbon deposit, but a slight layer, not chunks,
- a light, grey smoke is visible at the exhaust, that wasn't here before,
- the crankcase pressure seems higher than usual/designed: when you popped the oil gage cap off and put it down on its threaded interface, without screwing it, you can see it dancing around by the pressure oscillations in the crankcase. Checked the venting system with the elastomeric valve on top of the crankcase, seems to be in good condition.
The oil level is good, the oil has been changed at least 2 times with brand new & fresh oil.
What has been done and did not solve the problem:
- changed the original carb for a chinese equivalent - no result,
- new sparkplug, fresh gasoline of course,
- adjusted the valve clearance to original specs (but the original setting was already good, so no excessive wear detected here)
- changed all piston rings, no result - the cylinder is in good shape, still some crossed-pattern traces of the original honing process visible,
- the decompressor/starter mechanism (decreasing the compression ratio) seems to be free and fully functional, although I do not have a specific method to check it while the engine is running
A year or two before, the carb needle valve was stuck open and gasoline poured into the engine's oil, increasing the oil level up to the point of the engine was smoking badly. But at that time, draining/changing the oil and replacing the faulty needle valve solved the problem.
I'm thinking of the valves guides becoming loose, but this engine hasn't been used so much - maybe 100 hours at max? so I would be surprised of having worned valves guide.
It seems another guy had similar issues on a Kawasaki 180FJ engine here back in 2022, but the thread does not indicate if he succeeded in solving the problem.
Big thanks for any help.
Best,
J.B.
First of all, thank you very much for sharing & helping each others so much - it is always nice to see people trying to help others.
Secondly, please excuse my bad english - western french guy here.
I used to run a Kaaz lawn mower equipped with a Kawasaki FJ151v / AC52 engine. It ran pretty well for almost 10 years. When I tried to run it again last spring, it appeared to run badly, despite it was running like a charm at the end of year 2024. Here are the symptoms:
- starting is not a problem, hot or cold,
- there is a power issue, as the engine seems not to run as powerful as before,
- you can hear the engine is not running smoothly, there are like misfires or similar things, almost like a car's launch control system,
- the engine seems to run not as high in rpm as before,
- the sparkplug becomes fouled with dry carbon deposit in like 30 sec, no traces of oil here,
- the combustion chamber was coated with carbon deposit, but a slight layer, not chunks,
- a light, grey smoke is visible at the exhaust, that wasn't here before,
- the crankcase pressure seems higher than usual/designed: when you popped the oil gage cap off and put it down on its threaded interface, without screwing it, you can see it dancing around by the pressure oscillations in the crankcase. Checked the venting system with the elastomeric valve on top of the crankcase, seems to be in good condition.
The oil level is good, the oil has been changed at least 2 times with brand new & fresh oil.
What has been done and did not solve the problem:
- changed the original carb for a chinese equivalent - no result,
- new sparkplug, fresh gasoline of course,
- adjusted the valve clearance to original specs (but the original setting was already good, so no excessive wear detected here)
- changed all piston rings, no result - the cylinder is in good shape, still some crossed-pattern traces of the original honing process visible,
- the decompressor/starter mechanism (decreasing the compression ratio) seems to be free and fully functional, although I do not have a specific method to check it while the engine is running
A year or two before, the carb needle valve was stuck open and gasoline poured into the engine's oil, increasing the oil level up to the point of the engine was smoking badly. But at that time, draining/changing the oil and replacing the faulty needle valve solved the problem.
I'm thinking of the valves guides becoming loose, but this engine hasn't been used so much - maybe 100 hours at max? so I would be surprised of having worned valves guide.
It seems another guy had similar issues on a Kawasaki 180FJ engine here back in 2022, but the thread does not indicate if he succeeded in solving the problem.
Big thanks for any help.
Best,
J.B.
