Thanks Blumbly,
Yes the washers are very thin indeed. Luckily I had a couple from another carby to play with. After a bit of experimentation with various (top) diaphram springs and (under) cam washers, it was amazing to see such great variations in max RPM's. Initially, I had 4,200RPM (too high). After the first adjustment this dropped down to 3,400RPM (too low). After further tinkering it settled at 3,800RPM (just right
) which I'm happy to keep it at. It was a bit like Goldilocks & the three bears but it all ended well I guess. To be fair, I did take your previous advice and swapped the decompressor which marginally reduced the RPM's. Still I appreciated the suggestion and as I had a spare, it didn't hurt to rule it out as a problem part.
The mower is finished and looks/runs great. The only thing is that I swapped the piston over from another powertorque. Being inexperienced with these, I've only since realised that there are differences between the cylinder's transfer ports between the donar & recipient engines. The one pictured, has the later (more oblongish) ports whilst the donar is from an earlier engine with the more ovalish ports. According to my Gregory's manual, The newer port design had an upgraded piston where the piston ring stops where spaced closer together. This piston can be used in any 160cc model but the older type piston cannot. I did put new rings on this mower but now need to get hold of a later piston. The manual says they have "580" stamped on the crown. The original piston was stamped but it looks more like "S-80". Unfortunately this piston is too badly scored for sanding smooth so I'm keeping an eye out for another powertorque - hopefully with the later type piston.
As I said, it runs well but still haven't got the knack of "cold starting" it yet. I adjusted the throttle lever (matchstick gap) and only turn the fuel tap on just before starting. I push the primer bulb slowly x3 and when I kill the engine, I either run it out of fuel or at least tunr the tap off before putting the throttle in the stop position. If I try and start with the throttle in the "start" position, nothing much happens for about 6 or so pulls and even then it coughs and wheezes a bit. If I start it in the run or full throttle position, it usually starts on the second pull but this is usually accompanied by a puff of smoke from the exhaust for the first few seconds then exhaust is clear.
When the engine is warm/hot, I just start it in the run postion and it usually starts first pull. Maybe this is usual behaviour? I see alot of Victa 2 strokes for sale where the ad states "starts first pull". Perhaps this is true or perhaps just a bit of sellers spin. Anyway, it's a great mower. It ploughed through some foot-high grass. My old 4 stroke (Tecumseh) usually starts to die at that point and I have to do the old "wheelie" trick to let it get back to normal revs.
Anyway, enough babbling from me. Thanks for all your help & interest Blumbly & Joe. It's very much appreciated.
