A Dolmar PS421 is my small job saw. It had a 0.375 (3/8) pitch low profile chain, 6 tooth star sprocket and 16 inch narrow-nosed Oregon Double Guard bar. I recently converted it to a 0.325 pitch narrow kerf chain, 7 pin rim sprocket and 16 inch wide-nosed Oregon SpeedCut bar. There are previous AS threads that generally cover this conversion and I found them useful. I also appreciated the extra info I got from AS supporting member Franny K. Here are some details and photos to help others who may want to do this conversion. The most challenging part of this conversion was finding the right washer to fit on the output shaft under the rim system's drum. It is needed because the center hole on the star sprocket drum is extended inwards past the bearing with a fixed bushing. It provides inward clearance for the two oil pump drive stubs on the edge of the drum, first pic. The center hole of the rim system drum is not extended inwards with a fixed bushing. Without the washer the oil pump drive stubs on the rim drum rub on the case. I heard and felt those stubs rubbing on the case when I test fit and hand spun the rim drum. I tried a hardware store washer but it was too thick to add the thrust washer and the e-clip to the end of the output shaft. I found a thin washer that worked from my Olympic saw parts. The dimensions are 18.4 mm OD, 10.7 mm ID and 0.8 mm thick, second pic. But now the OEM e-clip was too thick to fit into the now narrower groove on the end of the output shaft with the washer in place, third pic. My hardware store had a 3/8 inch e-clip that was 0.9 mm thick and it worked, fourth pic. This Oregon SpeedCut bar is a K095 mount. It has small diagonal channels that feed oil directly into its chain groove. Those diagonal channels did not quite reach the oil output channel on the powerhead. I used a Dremel with a small conical stone to extend the channels and a 3/8 inch welsh plug closed the open hole, fifth pic. Oregon Bar is 160TXLBK095 or 584410, Chain is 95TXL066G. Dolmar drum and rim are from a PS-5105, Drum is 1447655 and Rim is 181224040.
