- Joined
- Mar 23, 2019
- Messages
- 16
A little story of woe that might be filed under the "what the %^&* were they thinking?"
I purchased a non runner mk3 a couple of years ago, just before I moved from Florida back to California. I finally tore in to the bike a month or so ago starting with a complete dismantling....
The first indication that things may not be quite as they seemed came with the discovery that the swing-arm was from an early 750. Ok, no biggy, can swap that.
Then I took a look at the tranny. It has the correct outer cover and the cross shaft. But strangely, so neutral switch. Opened it up and I find it's an Atlas case with an Atlas main-shaft. Complete with a slightly different end of shaft treatment that the Atlas has. So that needs to be changed, along with the case. Ok, this is mounting. Now we start on the main course.
The engine....drum roll
Off comes the head. Funny, I don't recall elongated slots in the through holes to mount to the barrel. Hmm....ah I get it, someone decided to use a 750 head and "make" it fit. Ok, more bodgery, surely that has to be it, doesn't it?
Nope. Let's crack open the cases shall we. Hmm, I wasn't aware that masking tape wrapped around a journal was a recommended way of getting an interference fit. Since the journal could still rotate they clearly hadn't used enough of it. And speaking of the journal, why were there fine grinding marks on one of the outer faces? There were no marks on either the case or the flywheel so someone had paid some attention to the bearing for some reason. At this point I'm faced with what I think is a totally trashed motor. Donning my Sherlock Holmes hat I couldn't get my head around the masking tape. The bore in the case seemed smooth with no evidence of a bearing ripping it up. So, I made a note of the bearing number on the journal and went to research a bit. What did I find? An imperial main bearing. Which has a smaller OD than the metric one that is supposed to be there. It was also wider, hence the grinding marks.
Oh crap, the inner race is also smaller, so did they grind the crank as well? Nope, the inner race they used was the metric one, the crank hadn't been buggered. That was the first bit of good news. The next bit was that when I offered up a good metric bearing to the case it didn't just drop in, not even "just the tip". So the case looks use-able. Now I know that when we buy old bikes we expect there to be some hidden problems, but these were really well hidden. Being philosophical about this, I will end up with a nice shiny head, a nice overhauled tranny, lots of new internals and everything back to being good with the world.
Now I have to track down a head, decide if I go std bore or 920 with some of those nice alloy barrels and if I go std cam. I also have to decide what grade of masking tape to use to fit my main bearings....
I purchased a non runner mk3 a couple of years ago, just before I moved from Florida back to California. I finally tore in to the bike a month or so ago starting with a complete dismantling....
The first indication that things may not be quite as they seemed came with the discovery that the swing-arm was from an early 750. Ok, no biggy, can swap that.
Then I took a look at the tranny. It has the correct outer cover and the cross shaft. But strangely, so neutral switch. Opened it up and I find it's an Atlas case with an Atlas main-shaft. Complete with a slightly different end of shaft treatment that the Atlas has. So that needs to be changed, along with the case. Ok, this is mounting. Now we start on the main course.
The engine....drum roll
Off comes the head. Funny, I don't recall elongated slots in the through holes to mount to the barrel. Hmm....ah I get it, someone decided to use a 750 head and "make" it fit. Ok, more bodgery, surely that has to be it, doesn't it?
Nope. Let's crack open the cases shall we. Hmm, I wasn't aware that masking tape wrapped around a journal was a recommended way of getting an interference fit. Since the journal could still rotate they clearly hadn't used enough of it. And speaking of the journal, why were there fine grinding marks on one of the outer faces? There were no marks on either the case or the flywheel so someone had paid some attention to the bearing for some reason. At this point I'm faced with what I think is a totally trashed motor. Donning my Sherlock Holmes hat I couldn't get my head around the masking tape. The bore in the case seemed smooth with no evidence of a bearing ripping it up. So, I made a note of the bearing number on the journal and went to research a bit. What did I find? An imperial main bearing. Which has a smaller OD than the metric one that is supposed to be there. It was also wider, hence the grinding marks.
Oh crap, the inner race is also smaller, so did they grind the crank as well? Nope, the inner race they used was the metric one, the crank hadn't been buggered. That was the first bit of good news. The next bit was that when I offered up a good metric bearing to the case it didn't just drop in, not even "just the tip". So the case looks use-able. Now I know that when we buy old bikes we expect there to be some hidden problems, but these were really well hidden. Being philosophical about this, I will end up with a nice shiny head, a nice overhauled tranny, lots of new internals and everything back to being good with the world.
Now I have to track down a head, decide if I go std bore or 920 with some of those nice alloy barrels and if I go std cam. I also have to decide what grade of masking tape to use to fit my main bearings....