Mitch's 74 Basket Case

htown16

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Decided to do a build thread on my 74 850 rebuild like I did on my 72. Here's a link to that one.
mitch-basket-case-t4616.html
Bought this one about a year and half ago and have been plugging away at since then.
This was the what was included in the initial purchase. Frame, bottom end, cylinders and pistons, gearbox and several boxes of parts including oil tank and some other bits. All matching numbers.
Mitch's 74 Basket Case

First item was to locate a cylinder head. Baxter's had one and I had them go ahead and do a rebuild on it before sending it to me.
Mitch's 74 Basket Case

I raided my parts bins and did a mock up. Fortunately, I had all this stuff from my parts scrounging over the years.
Mitch's 74 Basket Case

The black tank in the above picture is a fiberglass junker. I had a repop steel tank and painted it in Duplicolor metalspecks blue with Spraymax 2K clearcoat. Came out looking pretty good for a spray bomb job.
Mitch's 74 Basket Case

More to follow
 
Engine coming apart.
Cylinders were in decent shape. Standard bore and even showing some crosshatching. Evidence is pointing to this being a low milage engine with a long storage in a damp climate. There was some evidence of rust where the piston rings had sat. Note the broken fin. Someone had probably tried to pry the head off. I found a guy that welds cast iron industrial pieces and he brazed it back on for me. Was into motorcycles and didn't even charge me.
Mitch's 74 Basket Case

Pistons were in good shape no scuffing. However this piston had one of the compression rings that was absolutely stuck in it. No amount of soaking or heat would break it loose. Since I was probably going to damage the piston getting it out I decided to go with new pistons +.20 and clean up the rust damage in the cylinder walls. Got in a new set of JCC/Cyclecraft with Hastings rings. They're what I used in my 750 and have so far worked out well.
Mitch's 74 Basket Case

Damage on end of cam due to moisture in points cavity. I'm going to attempt to repair this with a Speedi-sleeve as the cam is otherwise in excellent shape.
Mitch's 74 Basket Case

Here's the bottom end coming apart. The crank worm-drive and cam nut were absolute pains. I had to get some impact sockets from the UK and use my impact wrench on them along with heat and penetrating oil. Even then I had to let the wrench hammer on them a while. The cam nut will need replaced. Thankfully a member on here loaned me a cut away timing cover so the pinion shaft is still tight. The cam gear needed a puller to come off but the crank pinion gear pulled off by hand with no puller, go figure. The cases also were a bear to split. Took a lot of pounding with a wood block and hammer but they finally parted with no damage.
Mitch's 74 Basket Case

More to come.
 
That series of cases are the easiest to install a reed valve on, right where that pipe is at the back of the timing cover. Tap two holes for mounting, and one for the breather, and screw it on from the outside.
 
Yep, definitely a reed valve. Have the Mike's XS 650 type on my 750 and it has minimal leaks.
 
Cam lobes look good with minimal wear, lifters also looked good. If I can repair the damage done in the seal area the cam should be good to go.
Mitch's 74 Basket Case

Flywheel had some rust on it, like water had sat in the bottom of the crankcase. Fortunately it was below the level of any machined surfaces and did only surface damage. The main bearings, which are Superblends were also apparently above the water and had enough oil on them that they look pristine. New crank hardware on order.
Mitch's 74 Basket Case

Crankshaft cheeks also have some surface rust but journals look in really good shape. Very little sludge in the trap.
Mitch's 74 Basket Case

Timing side journal
Mitch's 74 Basket Case

Drive side journal
Mitch's 74 Basket Case

Big End bearing show minimal wear. Again I think this is a low mile engine. Crank journals mic out to right on standard spec with no ovality.
Mitch's 74 Basket Case

I was tempted to put these bearing back in but have a new standard set on order. Hope I never have to split the cases again.
 
Same with me on the JPS rod bearing shells- they looked new, but they're getting new ones anyway.

Yours is looking very nice and clean. I also have the same issue with surface rust on the bottom of the flywheel.
 
Anytime the rods are pulled apart the slipper bearings should be replaced wheather they need it or not in my opinion, they aren't that expensive and knowing that they are new.

Ashley
 
ashman said:
Anytime the rods are pulled apart the slipper bearings should be replaced wheather they need it or not in my opinion, they aren't that expensive and knowing that they are new.

I sure haven't figured out why they cost twice as much as almost identical bits for Triumph big twins...
 
The flywheel was before I took a wire brush to it. It looks a lot better now.
 
With the holidays over, I finally have gotten some shop time in.
Crank back together with new Andover hardware.
Mitch's 74 Basket Case

Rods back on with new standard bearings.
Mitch's 74 Basket Case
 
Cam had some rust damage. I measured where the seal runs on another engine and it is .15" out from the end of the threads. You can faintly make out the track of the seal. Fortunately most of the damage is beyound that. I filled the damage with some JB Weld Steelstik. The cam lobes look pristine so it's going back in.
Mitch's 74 Basket Case
 
Excellent - I'm at a similar stage with my 850 - just waiting for the cam to come back from being reground. I do most other stuff myself, so the wait is killing me!
 
Cleaned the cases and inspected the main bearings, superblends in excellent condition. Cases went back together easily using Hondabond4 sealent. New cam chain because of all the heat and pounding it took to get the old cam nut off. New cam nut and oil pump drive tightened using a cut away timing cover.
Mitch's 74 Basket Case

I feel like I dodged a bullet on the bottom end. I knew the engine had water in it, but the only rust was on the bottom of the flywheel. If it wasn't for the water I would not have taken it apart as all indications are this is a really low mileage bike.
Note cheapo depot engine stand that is super sturdy.
 
Always nice to get a project rolling after a break. Once you get on a roll, it moves quickly.
 
On to the gearbox. First thing to do was remove the dreaded 6203 layshaft bearing. Which actually looks in good shape. But out it comes.
Mitch's 74 Basket Case

New roller layshaft bearing in, also replaced the main shaft bearing as it felt a bit "crunchy".
Mitch's 74 Basket Case
 
Main shaft gear set
Mitch's 74 Basket Case

Layshaft set
Mitch's 74 Basket Case

Gears are beautiful, absolutely no spalling. Only a very minor amount of sludge in the bottom of the box and per usual the top of the shift mechanism was rusty.
 
Everything assembled
Mitch's 74 Basket Case

checking the end float on the layshaft because of the roller bearing replacement per Old Brits. It measured .055 first go around. Added two .020 rear isolactic shims and now it measures around .010 which Old Brits sets as the top limit. It's not completely torqued down so should be fine. Pretty hard to measure that small amount of movement pushing the shaft back and forth. However, the .055 was real consistent and I measured each shim so should be pretty close. If you do this you need to enlarge the ID of the isolastic shim to clear the radius on the base of the kick starter shaft. I used a drum grinder bit in my Dremel.
Mitch's 74 Basket Case
 
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