Bottom End Assembly - Help Me Out Please!

So I'm helping out a little guy with his CR80. Somehow or another some straight gas ended up in his tank and he fried his rod bearings. I've been helping him with the rebuild but now we're running into a problem with the assembly and can't figure out what's happening...Hopefully the wealth of knowledge here on TT can help me out.

When I assemble the cases and torque the bolts to spec, the shift drum locks up. If I loosen the bolts, it will spin freely. I think when I torque the bolts, it's drawing the case surface into contact with the end of the shift drum, preventing it from rotating easily.

I have a parts breakdown and all pieces seem to be in their place. When I manually run through the gears (before case assembly) it shifts smoothly through every gear.

Is it common to require two base gaskets when reassembling? I'm sure another gasket will do the trick to offer more clearance for the drum, but maybe I'm looking past something.

If you can, please help me (and the little guy) out.



Check that the transmission gears have the right spacers washers in the correct position between the gears. You may have an issue with the shift forks binding against the transmission when you tighten up the cases. :cry:

A thurst washer is in the wrong location or a spacer was substituted for a washer? If it uses a gasket, the total stacked clearance should not of changed. If you have to add a second gasket, something is wrong. And its not fixing it, just hiding it and the problem, may rear its ugly mug in the form of broken parts. Thrust washers come in variuos sizes, but it shouldnt of changed. With straight gas, I suspect you only changed crankshaft, nothing in the gearbox.

I know this one. I've seen the exact problem. Look very carefully at the transmission bearing especially the bearings on the sprocket side. Check to see that ALL of the bearing are COMPLETELY seated in the case. Obvioulsy even a few thousands will make a big problem. Five thousands would bind up assembly easily. I've seen a bearing move just a little while handling and reassembling ( tapping on things ). I assume that all of the bearing, spacers and thrust washers are installed correctly.

Motionsickness has this one pegged right. We had the exact same problem with my son's 97 CR80R. It was actually one of the dowel pins that index the case halves together. We had it in the wrong hole, and while you could tighten everything down and couldn't see a gap betweent he cases, a .001 feeler gage would slide in. The cases were tweaking under the load of tightening the bolts, which would bind up the shifter drum and shaft. It also made the crank feel kinda funny.

We also had a problem with the inner drum (the piece that you have to remove to get the bearing off of the shifter drum). It wasn't fully seated, so when we put the rest of the shift mechanism together, the roller was pressing hard against the side of the inner drum and wouldn't let anything turn.

That's what happens when you wait morae than a day or two to put the thing back kinda forget the details. (This one was apart for a month while we shipped the cylinder off to Eric Gorr for a big bore kit)

As a sort of solution, I'v started to document disassembly, orientation f parts etc. of a project with a cheap digital camera that I picked up at Pep Boys for $39.00. I have an old K6-450 PC hooked up in the garage to play MP3's, connect to Thumpertalk and the YoT websites, and view those pictures. It' really saved my ass in putting the wife's minivan motor back together and getting all the emissions and electrical connections right!

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