Capt.Radar
New Member
Hi All, I'm new to this forum, having looked many times for useful information..
I have experienced a problem with certain after market cylinders for the Stihl 029 / MS290 and wondered if other users have also had this problem?.
I purchased several 46mm cylinder kits from a local UK supplier and also from one based in Athens, Greece. All have the same defect:
After fitting the cylinder kit the compression is low, getting worse with use, eventually the saw will not idle and loses power.
I have found the problem is the new AM cylinder - the transfer ports are located too close to the intake port and fall into the area where the piston ring gap is located, See attached photos:
I have marked the new AM piston skirt with red pen to show where the ring gaps are located then inserted in the AM cylinder. It’s clear the ring gaps are located right on the edge of the transfer ports!
The distance between the intake port and transfer ports of an original Stihl cylinder is MUCH bigger (see photo), leaving plenty of space for the ring gaps to run against the cylinder wall without catching the ports.
Also note the piston ring ends at the gaps are ‘polished’ due to the wear against the transfer ports (very hard to show this..) after only 2 hours running in this case. Surprisingly, none have broken...
Any comments would be most welcome!
Ray
I have experienced a problem with certain after market cylinders for the Stihl 029 / MS290 and wondered if other users have also had this problem?.
I purchased several 46mm cylinder kits from a local UK supplier and also from one based in Athens, Greece. All have the same defect:
After fitting the cylinder kit the compression is low, getting worse with use, eventually the saw will not idle and loses power.
I have found the problem is the new AM cylinder - the transfer ports are located too close to the intake port and fall into the area where the piston ring gap is located, See attached photos:
I have marked the new AM piston skirt with red pen to show where the ring gaps are located then inserted in the AM cylinder. It’s clear the ring gaps are located right on the edge of the transfer ports!
The distance between the intake port and transfer ports of an original Stihl cylinder is MUCH bigger (see photo), leaving plenty of space for the ring gaps to run against the cylinder wall without catching the ports.
Also note the piston ring ends at the gaps are ‘polished’ due to the wear against the transfer ports (very hard to show this..) after only 2 hours running in this case. Surprisingly, none have broken...
Any comments would be most welcome!
Ray
