12/15/14
DT1
I tried out a '72 DT2MX head on the flat tracker this weekend. It is the big one to the left. It is supposed to up the compression, possibly into detonation territory, but seems good so far.
12/13/14
DT1 MX project
I got the six engine case bearings, buying them all on ebay. These should be the same for all the '68-'73 DT and RT engines. The main crank bearings are Yamaha part number 93306-30630-00 and are no longer available, so I bought two Nachi 6306 open C3 bearings.
The smaller left side transmission bearing is Yamaha part number 93315-22004-00, and the bigger one is 93306-30506-00. Both are still available from Yamaha, and I went with OEM on these.
The smaller right side transmission bearing is Yamaha part number 93306-20306-00 and is still available, so I got an OEM bearing for this. The single shield larger right side transmission bearing is Yamaha part number 93306-20503-00, and it is no longer available, so I bought an NSK 6205ZC3. For all six bearings it came to about $107 shipped.
I put the bearings in the freezer ahead of time, and all but one of the circlips goes in the cases first. I warmed the cases in the oven to 200 degrees F. It seems like the bigger the bearing the more likely it will just drop right in, and the smaller ones need a little help. I have sockets ready to help drive them in if needed. Be sure to clean the sockets first, especially the inside, since you don't want any grit to fall on the bearings.
I'll be getting ready to assemble the bottom end of the engine.
The smaller left side transmission bearing is Yamaha part number 93315-22004-00, and the bigger one is 93306-30506-00. Both are still available from Yamaha, and I went with OEM on these.
The smaller right side transmission bearing is Yamaha part number 93306-20306-00 and is still available, so I got an OEM bearing for this. The single shield larger right side transmission bearing is Yamaha part number 93306-20503-00, and it is no longer available, so I bought an NSK 6205ZC3. For all six bearings it came to about $107 shipped.
I put the bearings in the freezer ahead of time, and all but one of the circlips goes in the cases first. I warmed the cases in the oven to 200 degrees F. It seems like the bigger the bearing the more likely it will just drop right in, and the smaller ones need a little help. I have sockets ready to help drive them in if needed. Be sure to clean the sockets first, especially the inside, since you don't want any grit to fall on the bearings.
I'll be getting ready to assemble the bottom end of the engine.
12/6/14
DT1 MX project
The bearings are ordered, so I'm getting some of the other parts ready. I removed the transmission from the engine with the damaged cases, and need to clean and inspect it for the new engine. After removing the transmission, make sure all of the shims and there. Sometimes they will stick to the bearings in the cases.
Here is the countershaft ready to clean.
I lay everything out in the order it came off the shaft, putting the side down in the direction it came off the shaft. On an old 2 stroke the transmission will likely be the cleanest part of the bike inside or out, so doesn't take much to clean. I used dish soap in hot water and a toothbrush. Cleaning is where you'll usually notice any excessive wear or damage.
After the parts are cleaned I lay them out to get ready to reassemble. I print out a parts diagram, this one from Boats.net where I get most of my OEM parts, and label everything to make sure it is all there and in the right order. Use oil anywhere metal touches metal when reassembling.
Here is the countershaft back together.
The rest of the transmission is cleaned and ready to drop in.
Here is the countershaft ready to clean.
I lay everything out in the order it came off the shaft, putting the side down in the direction it came off the shaft. On an old 2 stroke the transmission will likely be the cleanest part of the bike inside or out, so doesn't take much to clean. I used dish soap in hot water and a toothbrush. Cleaning is where you'll usually notice any excessive wear or damage.
After the parts are cleaned I lay them out to get ready to reassemble. I print out a parts diagram, this one from Boats.net where I get most of my OEM parts, and label everything to make sure it is all there and in the right order. Use oil anywhere metal touches metal when reassembling.
Here is the countershaft back together.
The rest of the transmission is cleaned and ready to drop in.
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