David Mc
New member
- Joined
- Feb 5, 2012
- Messages
- 22
- Tractor
- NEW HOLLAND TN75S,KUBOTA z121,KUBOTA KG222
Great thread on the Chinese clones of the Yanmar L100 guys. Thought that I would chime in with my experiences with the 186F(SE) as I am now looking down the barrel of a complete rebuild (looks like compression is shot). The generator this thing runs died after 2 years (only about 150hrs) and the engine has just packed it in after a couple of issues.
1. First issue was that the rocker shaft, which was mounted with 2x m8 bolts on the early versions of these engines, was re-designed by its Chinese manufacturers who reasoned that one M10 bolt could do anything that 2 x m8's could do - wrong! replacing 2 symmetrically loaded bolts with a single bolt which is subjected to a large cycling load, encourages the bolt to work loose, then fatigue and break (conveniently right at the interface line with the cylinder head.) This was initially repaired after some judicious drilling and removal of the broken bolt stem with a torx adaptor (don't get me started on EZYOUTs - they are the bane of mankind). Bolt was replaced with a grade 8.8 (high strength) bolt, loctited in position, resulting in a repeat of the original performance about 30hours later. Second attempt, the original bolt and head were drilled and tapped to suit a stainless steel helicoil which now secures a 12mm grade 8.8 bolt (this does do what the 2 m8 bolts from the former design did).
2. Issue 2 - engine just petered out and stopped whilst running under light load about 75 hours later. Checked fuel supply, cleaned and checked fuel injection nozzle and tried a squirt of diesel starter (ether) - nothing. Suspected blown head gasket, so removed cylinder head to reveal heavy carbonisation on the crown of the piston and throughout the combustion chamber. Decided to pull the valves and check the stems, seats and guides for wear or carbon deposits that may have contributed to the valves not seating. Ever pulled valves out of a head that was not fitted with valve stem seals? I have - this one. I guess this is where the Chinese shave another couple of bucks off the cost of building these things. Priced a couple of Yanmar stem seals ($15 each), so did a bit of research for 3 weeks and eventually located some Viton seals - perfect fit and about half the price of the Yanmar rubber seals. Head gasket is solid copper, so I miked it, checked for flatness and consistency, reinstalled the reconditioned head and torqued the head bolts as per the Yanmar manual. Meticulously recreated some sundry gaskets for the bonnet, intake and exhaust, changed the oil and still no start.
Current options are to just bench the engine and use it for spares, purchasing a replacement for around $600 or spend about $200 on parts and refurbish the thing myself - properly. Even though the second option involves more work, I am leaning towards it as I don't want a repeat of the cylinder head issues I experienced with the current engine. What is the consensus amongst everyone?
1. First issue was that the rocker shaft, which was mounted with 2x m8 bolts on the early versions of these engines, was re-designed by its Chinese manufacturers who reasoned that one M10 bolt could do anything that 2 x m8's could do - wrong! replacing 2 symmetrically loaded bolts with a single bolt which is subjected to a large cycling load, encourages the bolt to work loose, then fatigue and break (conveniently right at the interface line with the cylinder head.) This was initially repaired after some judicious drilling and removal of the broken bolt stem with a torx adaptor (don't get me started on EZYOUTs - they are the bane of mankind). Bolt was replaced with a grade 8.8 (high strength) bolt, loctited in position, resulting in a repeat of the original performance about 30hours later. Second attempt, the original bolt and head were drilled and tapped to suit a stainless steel helicoil which now secures a 12mm grade 8.8 bolt (this does do what the 2 m8 bolts from the former design did).
2. Issue 2 - engine just petered out and stopped whilst running under light load about 75 hours later. Checked fuel supply, cleaned and checked fuel injection nozzle and tried a squirt of diesel starter (ether) - nothing. Suspected blown head gasket, so removed cylinder head to reveal heavy carbonisation on the crown of the piston and throughout the combustion chamber. Decided to pull the valves and check the stems, seats and guides for wear or carbon deposits that may have contributed to the valves not seating. Ever pulled valves out of a head that was not fitted with valve stem seals? I have - this one. I guess this is where the Chinese shave another couple of bucks off the cost of building these things. Priced a couple of Yanmar stem seals ($15 each), so did a bit of research for 3 weeks and eventually located some Viton seals - perfect fit and about half the price of the Yanmar rubber seals. Head gasket is solid copper, so I miked it, checked for flatness and consistency, reinstalled the reconditioned head and torqued the head bolts as per the Yanmar manual. Meticulously recreated some sundry gaskets for the bonnet, intake and exhaust, changed the oil and still no start.
Current options are to just bench the engine and use it for spares, purchasing a replacement for around $600 or spend about $200 on parts and refurbish the thing myself - properly. Even though the second option involves more work, I am leaning towards it as I don't want a repeat of the cylinder head issues I experienced with the current engine. What is the consensus amongst everyone?
