Alan Resinger · Apr 26, 2004 08:14 AM
#0 sourceLAST EDITED ON Apr-26-04 AT 08:16 AM (CDT)
After using the Saito 56 for a couple of years I decided to go to the 72 this year with mixed results. I've done everything the experts suggest but the engine just didn't run that well. After a good break-in, the first flights showed a real need for large amounts of fuel. Using a UHP .275 venturi, the thing wouldn't get through the pattern on a full 6 oz tank. PW told me that I needed the smaller venturi and about 800 more RPM (10000) to get it going properly. In went the smaller venturi and a larger, lower pitch prop. Now I could get through the pattern with 3.25 oz of fuel. Somewhere early on I started to get a lot of black in the exhaust and figured that some wear was taking place as it didn't do it on break-in.
Talking to PW again, he said that one of his 72s did that and the problem proved to be a loose screw that holds the tappet. Checked that and all was ok. Still had black exhaust so I decided to look further. Took the engine apart and couldn't see anything that looked like it was wearing except where the rod seats against the pin on the crank. Carefully reassembled the engine making sure the timing and valves were set correctly but now the won't rev above about 8400.
Any 4 stroke experts out there to make some suggestions?
After using the Saito 56 for a couple of years I decided to go to the 72 this year with mixed results. I've done everything the experts suggest but the engine just didn't run that well. After a good break-in, the first flights showed a real need for large amounts of fuel. Using a UHP .275 venturi, the thing wouldn't get through the pattern on a full 6 oz tank. PW told me that I needed the smaller venturi and about 800 more RPM (10000) to get it going properly. In went the smaller venturi and a larger, lower pitch prop. Now I could get through the pattern with 3.25 oz of fuel. Somewhere early on I started to get a lot of black in the exhaust and figured that some wear was taking place as it didn't do it on break-in.
Talking to PW again, he said that one of his 72s did that and the problem proved to be a loose screw that holds the tappet. Checked that and all was ok. Still had black exhaust so I decided to look further. Took the engine apart and couldn't see anything that looked like it was wearing except where the rod seats against the pin on the crank. Carefully reassembled the engine making sure the timing and valves were set correctly but now the won't rev above about 8400.
Any 4 stroke experts out there to make some suggestions?