Dolmar PS-401 muffler mods?
- Thread starter Hoosier
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cuttinscott
Addicted to ArboristSite
Just take the muffler off and look at the outlet on the front there will be a tang protruding from the left side remove this tang and clean the opening to look like the right side and thats all the muffler needs to wake the saw up
Scott
JermB
New Member
Hey Scott, can the same apply to the 5100s. I love my saw but if it makes it hotter why not...
excess650
Addicted to ArboristSite
Brad did the muffler mod on a PS-401 and was rewarded with 1200 rpm up to 13,200. See this thread:
http://www.arboristsite.com/showthread.php?t=82169&highlight=dolmar+401
My own saw, in Makita blue, wouldn't quite make 13K with the tab removed from the exhaust port as previously mentioned. Enlarging the port didn't help either. I pulled the muffler and noted the exhaust port at the piston side of the cylinder was just slightly larger than my outlet, so should have been good. My modified outlet is close to double the OEM size. The muffler itself has a pair of inner baffles. One is the perforated spacer that keeps the muffler from collapsing, and the other has the screened outlet, and fits inside the outer cover. When I pulled this baffle, it appeared to me that there was restriction in the bottom corner between the screen and final outlet. I decided to remove this inner baffle (with screen) and see how the saw would react. Basically, this was a mod similar to a Husqvarna "empty can" muffler with no screen. After the saw was warmed up, I tweaked the carb and could get 14,200 with the occasional lean scream to 14,600, so proved my point, the inner baffle was the bottleneck. I wanted to retain a screen, so looked the inner baffle over and decided to drill holes at the top and cover with screen. This would allow exhaust to flow both from the bottom and top through the baffle and towards the final outlet on the top, left, front. (3) 3/8" holes were drilled, screen installed, and the saw was warmed up and retuned. It would still turn over 14K with the screens in the modded baffle, idles fine, and throttle response is excellent. I need to put the saw into wood and see if the H needs tweaked. I'm hoping that its happy around 13,500, and that will be a fair improvement over the 12K stock recommendation.
http://www.arboristsite.com/showthread.php?t=82169&highlight=dolmar+401
My own saw, in Makita blue, wouldn't quite make 13K with the tab removed from the exhaust port as previously mentioned. Enlarging the port didn't help either. I pulled the muffler and noted the exhaust port at the piston side of the cylinder was just slightly larger than my outlet, so should have been good. My modified outlet is close to double the OEM size. The muffler itself has a pair of inner baffles. One is the perforated spacer that keeps the muffler from collapsing, and the other has the screened outlet, and fits inside the outer cover. When I pulled this baffle, it appeared to me that there was restriction in the bottom corner between the screen and final outlet. I decided to remove this inner baffle (with screen) and see how the saw would react. Basically, this was a mod similar to a Husqvarna "empty can" muffler with no screen. After the saw was warmed up, I tweaked the carb and could get 14,200 with the occasional lean scream to 14,600, so proved my point, the inner baffle was the bottleneck. I wanted to retain a screen, so looked the inner baffle over and decided to drill holes at the top and cover with screen. This would allow exhaust to flow both from the bottom and top through the baffle and towards the final outlet on the top, left, front. (3) 3/8" holes were drilled, screen installed, and the saw was warmed up and retuned. It would still turn over 14K with the screens in the modded baffle, idles fine, and throttle response is excellent. I need to put the saw into wood and see if the H needs tweaked. I'm hoping that its happy around 13,500, and that will be a fair improvement over the 12K stock recommendation.
excess650
Addicted to ArboristSite
muffler mod update: I put the saw into wood today with a fresh 16" 91VX chain, and tuned to where the saw felt strongest. This mod DEFINITELY made a BIG difference, and the saw wants to run when tuned between 13,500 and 14K. I had the full length of the bar buried and was able to lean on the saw more that I thought possible for 39cc.
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