Post by ericr on Feb 1, 2020 0:42:20 GMT
A recap of my thread from the old site-
My 73 Oly 340, the first sled I bought back in 2006 when I got back in to sleds after years down south (i'm still there, I just go home to ride them) where was I anyway I owned this since 2006 and rode it nearly yearly- other than chassis maintenance and a few plugs/fuel line, I never really did anything with it. Always ran well and I guesstimate I put about 500 miles on it which considering I come north once a year for a week is pretty good!
January 2019 it started running badly once warm- if you backed off below half throttle, it would bog, barf gas out the carb throat. The carb was opened up and nothing wrong was found. On a summer trip in that year, I pulled the mill and took it home as we drive up from Georgia where I live. I have more time and place to go in to an engine there.
Up on the bench it went. Had 110 psi compression cold. I stripped the tin to the short block, used block off plates and did a pressure test- sure enough, the clutch side seal and case half gasket was leaking badly.
I then pulled the heads and cylinders- lo and behold mis matched pistons. There was an L ring piston that once the Elko number was deciphered turned out to be for a later fan cooled TNT application, and an original Oly piston in the recoil side. And it was installed backwards, with the stamping AUS (out, exhaust) facing the intake port- the ring locating pin had been running right in the center of the port as well. Other than some light scratching, the cylinders were in great shape and measured within spec.
I cleaned the 46 years of assorted goo off, took it down to the crank, the bearings all rolled nicely. I ended up getting two NOS pistons with rings from Goose (www.reproductionvintageparts.com) and put it together again.
I replaced the seals and gaskets obviously, re pressure tested when done to good result, a fresh fan belt and some new rope in the rewind and away it went. I didn't even have to re gap the points after re installing the ignition, other than verifying it was on the marks per the service manual.
I put it in a tub, bolted it to a piece of plywood, filled the tub with spray foam filled trash bags, sandwiched another piece of ply on top and sent it back to Minnesota to meet me when I got there. That cost more than the pistons and gaskets...
I uncrated it after my arrival, and had it bolted in and running in about an hour- I shipped the outer primary and muffler in a separate box. It has a Comet "Powerblock" clutch I found out. Very smooth and quiet compared to a stocker. I ran it on a 30 plus mile run over mostly un groomed heavily moguled up trails...the sled held up fine but my knees and quads no so much!
My 73 Oly 340, the first sled I bought back in 2006 when I got back in to sleds after years down south (i'm still there, I just go home to ride them) where was I anyway I owned this since 2006 and rode it nearly yearly- other than chassis maintenance and a few plugs/fuel line, I never really did anything with it. Always ran well and I guesstimate I put about 500 miles on it which considering I come north once a year for a week is pretty good!
January 2019 it started running badly once warm- if you backed off below half throttle, it would bog, barf gas out the carb throat. The carb was opened up and nothing wrong was found. On a summer trip in that year, I pulled the mill and took it home as we drive up from Georgia where I live. I have more time and place to go in to an engine there.
Up on the bench it went. Had 110 psi compression cold. I stripped the tin to the short block, used block off plates and did a pressure test- sure enough, the clutch side seal and case half gasket was leaking badly.
I then pulled the heads and cylinders- lo and behold mis matched pistons. There was an L ring piston that once the Elko number was deciphered turned out to be for a later fan cooled TNT application, and an original Oly piston in the recoil side. And it was installed backwards, with the stamping AUS (out, exhaust) facing the intake port- the ring locating pin had been running right in the center of the port as well. Other than some light scratching, the cylinders were in great shape and measured within spec. I cleaned the 46 years of assorted goo off, took it down to the crank, the bearings all rolled nicely. I ended up getting two NOS pistons with rings from Goose (www.reproductionvintageparts.com) and put it together again.
I replaced the seals and gaskets obviously, re pressure tested when done to good result, a fresh fan belt and some new rope in the rewind and away it went. I didn't even have to re gap the points after re installing the ignition, other than verifying it was on the marks per the service manual.
I put it in a tub, bolted it to a piece of plywood, filled the tub with spray foam filled trash bags, sandwiched another piece of ply on top and sent it back to Minnesota to meet me when I got there. That cost more than the pistons and gaskets...
I uncrated it after my arrival, and had it bolted in and running in about an hour- I shipped the outer primary and muffler in a separate box. It has a Comet "Powerblock" clutch I found out. Very smooth and quiet compared to a stocker. I ran it on a 30 plus mile run over mostly un groomed heavily moguled up trails...the sled held up fine but my knees and quads no so much!
