Down under, an idiot and a 400F

[neevo]

Anyone used Plastigauge before? Looking to buy some to reinstall the original bearings to measure and see if I can just replace them with new ones.

I got this for Christmas:



... which means I now have a Haynes, Clymer and Honda manual. Should get me through the rebuild

Looking in the Clymer is has a max clearance of 0.003" or 0.08mm, I assume this means I need the green Plastigauge (0.001 - 0.003")?

 

[crazypj]

Hi Ed,
I used to teach using Plastigauge, it's pretty simple if something of a PITA to keep stuff lined up when doing main bearings
Rods are easy as you do them one at a time
Just make sure everything is de-greased and you don't rotate or 'rock' rods on crankpins while torquing them down
shoot me a PM if you want more help

 

[swan]

It's pretty simple if something of a PITA to keep stuff lined up when doing main bearings
Rods are easy as you do them one at a time
Just make sure everything is de-greased and you don't rotate or 'rock' rods on crankpins while torquing them down.

+1 to this, keep everything clean and oil free, tighten down to spec and then check the results:

 

[o1marc]

I think it should be used every time you change bearings or have done any work on the crank or cams. I quit working for a guy who build Detroit Diesel engines for buses. He put in a rebuilt crank and it was too tight and bond up as soon as the motor was fired. I asked if he plastigaged it, he said no. They replaced the crank and he put it right in and I asked if he checked it this time with plastigage. He said again he hadn't. I told him I could no longer work with him if he was going to get pissed and start throwing tools if he insisted on doing it wrong, especially after having an issue and then setting himself up for failure a second time. It was always like that. There was "The right way, the wrong way, and then there was Bear's way" and that wasn't always right.

 

[neevo]

Thanks all!!! Turns out I have 3 crank bearings (C) and two (B), luckily the C's are cheaper on David Silver Spares

I have ordered some green Plastigauge to measure up how in spec the old bearings are and then look to replace with new ones. I am also going to push the button on a Vesrah gasket kit, does anyone know what is in these kits? Specifically does it include the following?

Cylinder Head Oil Control Valve Rubber Gasket (x?)

I am also going to bite the bullet and replace all these parts with new, DSS has some great prices on aftermarket cam chain tensioner blades so I will go with those, otherwise I will be using genuine Honda Parts:

1. Crank Bearings x10
2. Big End Bearings x8
3. Cam Chain Blades x2
4. Primary Chain x1

+1 to this, keep everything clean and oil free, tighten down to spec and then check the results:

Swan I assume the measurement is done without case gasket, does adding the gasket on final button up change the bearing clearance at all?

 

[swan]

In my experience, Vesrah kits are complete including the all the small rubber oil seals.

There is no gasket between the crank halves of a CB400F and typically a slight smear 3 Bond or Yamabond liquid gasket is used. I do not use this when measuring with plastic gauge.

New cam chain, guide, tensioner and all new bearings, expensive, but very nice. You will have essentially a new motor.

 

[neevo]

Thanks Swan. I meant liquid gasket for the case halves, thanks for answering that for me.

Not wrong on the motor expense! I would hate to put an old part back in though and it go bang!

 

[swan]

Better than new!

I am cooking up another CB400F, my 5th one. This is a stock restoration and plan to sell it it in the spring. This week I rebuilt the motor, measured everything, honed cylinders, new rings and installed a new cam chain. All the black bits come back from powder coat in two days. I will do a quick restoration thread on the bike soon.

 

[neevo]

You've got a problem with the 400's! Is that motor painted or blasted?

 

[swan]

Flipping Hondas supports my real addiction, vintage British bikes.

Painted and heat treated VHT Duplicolor 1615 aluminum paint.


Before

 

[neevo]

So my Plastigauge turned up this evening, and the temptation was too much to get the crank out and measure it up. I took the rods off the crank, making sure to keep them in order, the crank was stripped down and the engine cases were taken off the stand temporarily, so that I can get the crank in the cases to test the clearance on the original bearings:

I also got the original case bolts out and gave them a scrub in some turps, and if its not too loud, I may whack them through the brass wheel quickly before bolting them into the cases:

To measure the crank bearings I was going to put the crank in and bolt the cases together using these main 10 bolts. I assume that's going to be fine to measure the crank bearing clearances as its essentially the main bolts around the crank and should be enough to get it to tightness spec:

 

[neevo]

Bolts came up really well on the bench grinder/brass wheel. Nice and shiny, which hopefully means clean, as opposed to the fact I'vejust taken the coating off them on the brass wheel!!

Dry fit in the 10 holes for the crank measurement:

 

[neevo]

Good news!!! My Plastigauge trial was a success. Having figured out a way to put the rods on without them spinning I set to working out the torque values in NM as opposed to the other stuff in the Clymer manual. In the end I went for the smaller end of the torque values and will assume the clearances may come down a little if I crank it up a bit on final install.

I Plastigauged both sides of the rod bearings to make sure the clearance was the same all around.

In the end I came out 0.038mm clearance on both sides of every rod bearing... good news!!!

I also measured the rods and they were D, D, D, C from left to right. I will need to work out what colours these are for reordering.

Spec is anything less than 0.08mm so they are all in spec, the rod bearings look ok too and I suspect I could get away with not replacing them, however I am this far in, so they will be getting replaced anyway. I am pretty sure David Silver Spares carries all the various rob bearings, so replacements shouldn't be hard to get.

On to the crank bearings:

I did these with the motor upside down, as it was easier to drop the crank in. I also did both sides of these bearings against the crank and only ended up with 1 bearing where the readings were the same. I will need some help to understand what this means, I would guess I can average out the clearance and that is my value. I ended up with the following readings across all 5 bearings:

1. Bottom 0.038mm / Top 0.038mm
2. Bottom 0.05mm / Top 0.038mm
3. Bottom 0.05mm / Top 0.038mm
4. Bottom 0.076mm / Top 0.05mm
5. Bottom 0.05mm / Top 0.076mm

I suspect I could go 1 larger on 4 & 5 (C & B respectively), but will need to understand what the next bearing up would be and the effect this would have on the clearance.

All in all a very good evening and I am pleased to say I have cracked my Plastigauge cherry!

 

[swan]

Good work and it always feels good to solve a problem and learn a new skill.

 

[ronnie]

Nice work. I didn't do all of that with the new bearings... Just went with it, haha! Whoops. It should be fine. Haha

Sent from my HTC6500LVW using Tapatalk

 

[neevo]

Can anyone anwer a few specific questions I have:

1. What colour are C & D rod bearings?
2. Where I have 2 different readings for each side of the bearing, do I average them out or take one of them as the reading?

Does anyone know the difference between each bearing shell size for the crank bearings? Trying to work out if I can get the clearance on each bearing the same/similar (the last 2 are a bit further out of spec, eg 0.038mm vs 0.063mm)

 

[crazypj]

There is a chart in the manual that will have A B C D along top and left side just follow from crankcase or rod to crankshaft code (letters are stamped into one of the webs for crankpins and main bearings, 4 for pins, 5 for mains) I'll look it up later and post pic if you can't find it.
The letters will also specify the actual diameter of case bore to thousandth of millimeter
Different readings show either bore or pin isn't round, mic up the pins (you'll need a mic measuring to 1/10,000" or 1/1000mm)

 

[neevo]

Different readings show either bore or pin isn't round, mic up the pins (you'll need a mic measuring to 1/10,000" or 1/1000mm)

Balls! That's not what I wanted to hear. I don't have a mic unfortunately so not sure what I can do there. Could I have done anything wrong on the install? I put the crank bearings back in from a bag I had, maybe I put the wrong ones back in the wrong places as I didn't mark which C/B went where.

I will likely buy the bearings then remeasure to check for "roundness".

I assume these are the rod/crank bearing colours too:

A = Black
B = Brown
C = Green
D = Yellow

 

[neevo]

Also, I received some more piccies of the billet goodness I've ordered (caliper carriers and fender brackets). Its becoming a bit of a sickness as it all looks so good, its fair to say every piece on the bike will become billet at some point:

 

[crazypj]

Them's the charts.
Your looking for numbers on the rods and crank (I forgot they use numbers for rods/pins letters for mains/case)
If anything moved even slightly it will ive a false reading.
Doesn't really matter where the bearings were as long as you didn't swap anything between measurements ('odd' shells would just give tight or loose clearance but it should be consistent 90 or 180 degrees
It may be OK anyway as you still have an oilclearance. If you can't see any extra polishing or marks I would guess you did something 'unknown'
Wish I could afford to do CNC, looks real good and is repeatable, makes my manual made stuff look real crude

For your 0.076mm clearance, you need to find the letters stamped on crankcase (usually at the back below top engine bolt) and the letters stamped on crank