You didn’t kill any bottom ends with those 75cc jugs did you? They were pushing 190-200 lbs. I know Shane’s 71cc was 225 or so after break in and it was probably the best running one I ever built with a stock piston.
Never had problems. I figured they broke at 190-200psi once I go some good run time into them.
That's perfect. When I took them up north for winter work then I just primed them each morning and do the filter at the same time. They get tight in the winter from sitting out. First spark and they flashed every time. I actually got in the habit of doing it year round. The way I tune the low, my saws have always been a little harder to start in the morning only.
I am comfortable with 1200 hours on the bottom end. I base it at 5 1/2 run time a day. I went to 1300 on one of yours even know I had a brand new saw to swap it on.
Only had two clutch sides go in 20 years of 371/372. My 'helper' took fuel out of the jug for my side- by -side and I didn't notice for a while.
Finished the few days left in the shift and after Christmas break I tried to warm it up and it got tight and stalled a few times.
Whole engine went in the garbage. I wouldn't take a chance on the crank.
On the Simonized I cooked the top in a about 3 months work. I didn't realize I had the cooling fins stuffed. I ran it in 38C (100F) and cooked it in Nov at -36. When it ceased the debris were burning hard.
Friend I worked for at the time of the Simonized top end ran gas station brand oil too which I hate to us. After that I supplied my own oil. I put on a BB and the main bearing went at about 120 days from new. About 700 h. That was in 2007 so that was with the so called better bearings.
Both top ends were 190-200 I would think but obviously there was issues with heat and oil.
225 psi..that's crazy man. I heard that. The only time I ever did a compression test was on two cylinders that I put on. It was the cylinder before your 51.4. It was a 52 BB on one saw and on the other a dome 50 window that I copied Simon's mild intake work. I believe it was an open skirt single ring that Simon had on mine. Anyway Jonny mildly worked the intake and exhaust on the BB.
I put them together dry and the BB was 170 & the dome 50m was 150psi.
The 50mm was way stronger in the wood right away. The 'stock' style piston needs a lot more PSI than the short skirt.
There is no place for them on the coast at 170ish until they break properly. At least with 52mm and the 51.4mm. When you are balls deep they can't sit on their torque and 'break centripetal' and plug the bar grooves and tip. Problem is in the big cedar snags too. Slabs sit down on the bar and the pressure walks the chain out from the bar easy getting the same results.
I have ran a lot of ported 50mm off the bench on the coast and they perform on day one on a broken saw and they my only be 170ish. That's what I think anyway? It all could have been a dream or a bad trip?
