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Author Topic: 1982 CB750F... The resto-not  (Read 29871 times)

Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #660 on: Aug 07, 2019, 23:33:20 »
Progress.  Picked up all four colours of Plastigage from the local Napa as I had no idea which colour I needed.  Turns out it's green.  Flipped the upper case upside-down and onto a milk crate -



installed the new yellow bearing shells into the lower case -



cleaned the journals and then lowered the crank into the upper case -



cut the plastigage and placed a length across each main journal -



then lowered the lower case onto the upper, making sure not to move the crank while I was at it.  Torqued the crankcase bolts in sequence to spec, then removed them, and then lifted the lower case back off and checked the plastigage -



0.051mm or 0.002".  Right at the looser end of spec, which is what I was expecting/hoping to see given that the bearing shells I chose (the yellows) should be the loosest.  Just to recap, I chose (was advised to use) yellows as I could no longer see the colour on the shells that needed replacing.  2 were showing copper so I decided to change all 5 lower case bearings.

Hoping that means I'm in the clear as far as clearances go on the main journals - tomorrow I'll check the crankpin and con rod clearances.

"I'm telling you Donnie, nuthin' but nuthin' but right"

Offline CrabsAndCylinders

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Re: 1982 CB750F... The resto-not
« Reply #661 on: Aug 08, 2019, 03:05:49 »
Re Tool, Excellent!
Lighter, Quicker, Faster.
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Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #662 on: Aug 08, 2019, 19:20:14 »
Checked the crankpin/con rod clearances, all well within spec.  Time to get this party started.
"I'm telling you Donnie, nuthin' but nuthin' but right"

Offline trek97

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Re: 1982 CB750F... The resto-not
« Reply #663 on: Aug 08, 2019, 19:55:51 »
Checked the crankpin/con rod clearances, all well within spec.  Time to get this party started.

NICE!!!!

Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #664 on: Aug 08, 2019, 20:21:22 »
NICE!!!!
Ha, yeah man - like most things that happen in my garage so far it'll be a first.  Wanted to take my time with this and give myself the best shot of not fucking things up.  That, and it took me ages to get my shit in gear and order the parts I needed.  Still, all my ducks are in a neat little row now so time to quack.
"I'm telling you Donnie, nuthin' but nuthin' but right"

Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #665 on: Aug 15, 2019, 23:18:16 »
Ok well things stalled.  Started rebuilding the primary shaft last week (installed the new rubber dampers, installed the bearings etc) and then found out that I'd lost a tiny pin that anchors a washer to one of the split gears.  I thought the pin was attached but turns out it wasn't - an hour of looking on the floor and a week later after ordering a new one from Honda and this turned up today -



Tiny, but crucial.  You can see where it lives on the right had side of the gear -



Got it installed before i lost it again, and got the shaft rebuilt.  Dropped it in the case, temporarily bolted upper and lower case together and then torqued the bolt in the primary shaft to spec.  You need to wedge a broad screwdriver in between the teeth of the shaft and the case itself here -



in order to torque the thing. 

Primary shaft done.
"I'm telling you Donnie, nuthin' but nuthin' but right"

Offline Jimbonaut

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Re: 1982 CB750F... The resto-not
« Reply #666 on: Aug 15, 2019, 23:43:53 »
Having never completely rebuilt an engine before, my plan is to do so upside-down.  The engine, not me.  I remember how tricky it was to lower the cylinder down onto the piston and rings on my KLR, and that's a single cylinder thumper.  And it probably wasn't even that hard - I just really made a meal of it.  So, I'm pretty sure there's another method that involves installing the pistons - with the con rods already attached to them - into the cylinders, and then mate the con rods to the crank which is itself installed in the upside-down crankcase.

Anyone done this?  Ultimately doable?  Pitfalls I should know about?  Or is this the way everyone does it and I'm just late to the party?   
« Last Edit: Aug 16, 2019, 01:46:15 by Jimbonaut »
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Offline irk miller

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Re: 1982 CB750F... The resto-not
« Reply #667 on: Aug 16, 2019, 07:54:48 »
That's essentially how you install pistons on a small block Chevy and most V8s, with the piston attached to the con rod and slid into the cylinder from the top.  I've never found it overly difficult to slide the cylinders over the pistons, especially since the cylinders have a bevel that helps compress the rings as they go over.  Assembly lube goes a long way toward helping ease the process.  I don't have ring compressors either.  Just my fingertips and the tip of a plastic spudger.

Online Maritime

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Re: 1982 CB750F... The resto-not
« Reply #668 on: Aug 16, 2019, 08:29:38 »
If the bottom end is open you can do it that way fine. when just refreshing the top end Irks method is how you have to do it. Either way good luck, take your time and you'll be fine.
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Offline irk miller

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Re: 1982 CB750F... The resto-not
« Reply #669 on: Aug 16, 2019, 11:50:49 »
I challenge anyone to produce a service manual that says to install the pistons and such that way- top end rebuild only or not.  It's not that hard to do by sliding the cylinders over the pistons.  Just line them up at the same spot in the stroke, block underneath the skirt so they don't move, then start working the cylinders over.  The pistons will be close enough in tolerance that they help keep things from getting too far out of line.  You can slide it down to the top of the first ring, then push the ring in with a spudger and work around the perimeter.  The bevel at the base of the sleeve will help this along. The weight of the cylinder will make the piston slide up into the bore.  Then once all four of the first rings are in, you can tap the cylinder with a dead blow until they get to the middle rings.  Just taps where the weight of the hammer is doing the work, not force from your arms.  It's really not hard and because a 4 cylinder has much smaller pistons, you can't totally compare the experience with a bigger single piston.  I don't see how playing a game of Twister with the case upside down is any better.