Crank Finally Measured by Engineering Firm but I'm confused

[waffey]

I must admit now that i'm a little of of my depth.

Firstly I had a local engineering firm measure the crank up but when i look at the manual it looks likes it's too worn. Is that correct?

I also had connecting rods measured with the bearings (at least 3 anyhow!) but i'm not sure where this leads me.

I'm think bolt the connecting rods on, plastigauge for clearance for bearing size???

[McCabe-Thiele (Ted)]

You need to look at the chart in the parts book - I'm a relative beginner but at a glance there's not much wrong with your mains they are all within the maximum tollerance of 32.00 minus 0.03 that would make the minimum diameter allowed as 31.97 mm so all yours look good.

Your big ends are also looking good minimum journal size is 32.00 minus 0.03 mm  so minimum diameter is again 31.97 mm.

Are the journals scored if not you will be able to look in the manual and check your crank case codes & con rod codes to work out what shells you need.

If you look in Ash's dropbox the shell sizes & colour codes are there Page 8- you might be lucky & find some markings on your old shells likewise the crank codes. Mains are fairly easy as the code is stamped on the lower casing at the back.

Subtraction my maths  amended!

[K2-K6]

I've got those above from Honda tolerances at

Crank main bearings left to right on drawing
C C B C C
You'd now need crankcase id to work out main bearing shell's colours.

Crank pins for rods at
5 (-0.001 outside) 5 (-0.003 outside) 5 (exactly on tolerance) 5 (+0.002 inside)  making two of them just outside tolerances.

Rods, I'm curious as the bore is not ordinarily a wear surface (shells are taking the work here) but seem too big.

Will look again at the numbers.

[K2-K6]

"I also had connecting rods measured with the bearings (at least 3 anyhow!) but i'm not sure where this leads me."

Oops, didn't see the proviso "with the bearings" there.

Honda protocol is to measure the rod bores without bearing to then agree bearing thickness to fill that gap between the measurements of pin and hole.

Will look at those big end numbers again to give view.

[K2-K6]

OK, you'd need either the big end shell colours at minimum, and or preferably the measurement of con rod big end bore to determine how to proceed with sizing of any new big end shells.

If there's some Latitude to be had in the machined size of the rods, then that 0.001 and 0.003 error can potentially be accommodated by selecting a shell colour that's wrong in "book terms" but makes up the running tolerance to function correctly.

[McCabe-Thiele (Ted)]

Fwiw if the old shell colour codes have gone and you can't find any markings on the crank my view as a relative novice is try to get hold of a middle of the road shell say Green - fit them and do a Plastigauge measurement - depending on the reading go for a shell that gives you the require clearance/oil film thickness. I was luck as I found Green paint on one main shell and Green on two big end shells so it gave me a starting point.

[waffey]

Thanks K2-K6

bare with me please.

no colour on shells or crank. big end case states BBBCB. assume this is still ok to buy and use.

So i'm going to take the 3 conrods back and get them measured

The conrod table to me looks like it includes the bearing as it's 32 (-0.010 -0.020) as an example, mine are around the 32.

so conrod 4 (32.089 - crank 31.984 = 0.895 then dive by 2 = 0.4475) so i can use C

should of listen in school!

[waffey]

Ted,

great idea, buy one shell green, fit, torque up with plastigauge then measure, move along to the next one.

assume this is what you mean?

[Bryanj]

Why only 3rods? They come with balanced weight codes as a set

[K2-K6]

If the crankcase codes are in the same orientation as the way the crankshaft is noted in the photo, then the shell colours should be;- left to right as photo brown brown green black brown.

Thats for the main crankshaft bearings as it spins in the crankcase.

The 3 rods look like they noted the 4th with "no lining" so three measured with shells in place, and one without as I read the notes from measuring.

[McCabe-Thiele (Ted)]

These are the type of web markings you are looking for. In the photo the left is clearly 1A - you can make out a letter on the adjacent web as leter B not sure if its a 1 or 2 from the photo but it's probably clearer in the flesh. I've lost count as to how mant times I looked at my crank in various light conditions to find them - a light wash in petrol is what worked for me as the white was covered in a layer of brown oil deposits.


.crank web by Macabe Thiele, on Flickr

[McCabe-Thiele (Ted)]

Ted,

great idea, buy one shell green, fit, torque up with plastigauge then measure, move along to the next one.

assume this is what you mean?

Exactly.

[K2-K6]

Because there appears to be some wear on the crankshaft pins (the holes in rod and case don't usually change as it's the shells taking wear) it's more likely to be brown or black shells if you wanted to guess, rather than green.

But accurate measurement of rods is going to give a better picture in the gap existing between it and crank pin to then go with Honda listed choice.

[McCabe-Thiele (Ted)]

I've sent you a PM about  some Green shells.