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Author Topic: I stepped in it - XS750/896 build  (Read 4182 times)

Offline Frenchtom

  • Posts: 19
Re: I stepped in it - XS750/896 build
« Reply #40 on: Jul 08, 2018, 20:03:02 »
Hi Doc and thanks so much for posting this, its the exact kind of info I am looking for and the kind of work I am interested in trying.
Tom
1963 Honda Sport Cub
1977 Yamaha XS896

Billet: about as creative as duct tape

Offline Frenchtom

  • Posts: 19
Re: I stepped in it - XS750/896 build
« Reply #41 on: Aug 13, 2018, 10:22:08 »
Its been a while but i have some more progress.  I got the engine case split and the crank removed.  It was not as bad as I thought but was not exactly easy either.  The engine was had a fair share of crud, rust and water which I plan to thoroughly clean out.  One of the crank journals had some shiny spots on it that I need to inspect closer for any damage, the rest were fine.  I have not pulled the rods yet but will do that on the next update.  You can see in one of the pictures all of the silicone paste that was squeezed into the engine and trapped within the oil pump pickup.  I am going to test the crank for balance and see how close to perfect I can get it if its not already there.
Tom
1963 Honda Sport Cub
1977 Yamaha XS896

Billet: about as creative as duct tape

Offline datadavid

  • Posts: 1375
Re: I stepped in it - XS750/896 build
« Reply #42 on: Aug 16, 2018, 17:07:01 »
Those lines on the bearing surface are 100% caused by metal debris. I would take it to a good machinist for an expert opinion. Might stay good for the engines lifespan, might be close to failure. Hard to tell without micrometers..

Offline der_nanno

  • Posts: 428
  • Faster!
    • Greasy Greg
Re: I stepped in it - XS750/896 build
« Reply #43 on: Aug 17, 2018, 10:43:09 »
By far not a good machinist (at least not in my own opinion), but the big question is: can you feel them with your fingernail? If yes: buggered.
Real freedom starts with the freedom of thought.

My Blog:
http://greasygreg.blogspot.co.at

My Mule TR1.1 build here on DTT:
http://www.dotheton.com/forum/index.php?topic=75458.0

My Turbo TR1.1 (XV1000) build here on DTT:
http://www.dotheton.com/forum/index.php?topic=72571

My XS Triple Sidecar build here on DTT:
http://www.dotheton.com/forum/index.php?topic=74211

Offline datadavid

  • Posts: 1375
Re: I stepped in it - XS750/896 build
« Reply #44 on: Aug 18, 2018, 04:47:26 »
By far not a good machinist (at least not in my own opinion), but the big question is: can you feel them with your fingernail? If yes: buggered.
Thats right, any scoring and you will need regrinding. Problem with these engines is bearing shells dont come in oversizes, instead there are five sets of thicker and thinner shells in very small increments(cant recall exActly how small) but if you are lucky and crank is ground on the large side it may be possible to grind down to fit the thickest bearing shells.
Other expensive options are one-off bearing shells or plasma spraying the journal.

Offline der_nanno

  • Posts: 428
  • Faster!
    • Greasy Greg
Re: I stepped in it - XS750/896 build
« Reply #45 on: Aug 18, 2018, 09:09:06 »
A good engine refurbishing shop, should know (or have a list with dimensions) of automotive bearing shells to be converted for use on a Triple. For example from personal experience I know that Ford Cologne bearing shells can be shortened a bit and then used as oversize shells on Dnepr cranks...
Real freedom starts with the freedom of thought.

My Blog:
http://greasygreg.blogspot.co.at

My Mule TR1.1 build here on DTT:
http://www.dotheton.com/forum/index.php?topic=75458.0

My Turbo TR1.1 (XV1000) build here on DTT:
http://www.dotheton.com/forum/index.php?topic=72571

My XS Triple Sidecar build here on DTT:
http://www.dotheton.com/forum/index.php?topic=74211

Offline datadavid

  • Posts: 1375
Re: I stepped in it - XS750/896 build
« Reply #46 on: Aug 18, 2018, 09:21:19 »
I have a spare crank and bearing shell kit, even easier..!
A good engine refurbishing shop, should know (or have a list with dimensions) of automotive bearing shells to be converted for use on a Triple. For example from personal experience I know that Ford Cologne bearing shells can be shortened a bit and then used as oversize shells on Dnepr cranks...

Offline Frenchtom

  • Posts: 19
Re: I stepped in it - XS750/896 build
« Reply #47 on: Sep 04, 2018, 20:43:16 »
A little more progress.  I got the engine stripped down quite a bit further and cleaned everything twice.  I'll hit it all a third time with some disc brake cleaner.  I also got the pistons and connecting rods balanced to within a half gram of each other. 

I took a closer look at my crank and the scored journal.  The mating bearing surface has scoring as well so I will pull the crank from my spare engine and see which one is on the best condition.  If its the second crank I will be sure to pull the bearings and transfer them to the new engine.  If not I'll see how much machining the first crank needs.  When I put everything together I will use plasti-gauge and make sure the clearances are correct and buy new bearings accordingly.
Tom
1963 Honda Sport Cub
1977 Yamaha XS896

Billet: about as creative as duct tape

Offline datadavid

  • Posts: 1375
Re: I stepped in it - XS750/896 build
« Reply #48 on: Sep 14, 2018, 10:54:25 »
If you have the same numbers between bearing and crank on both engines bearings should be the same tolerances. I have a main bearing set where i used the black bearing set iirc, could sell you some if need be.

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