Not fully understanding Big End Bearings & colour codes.

[waffey]

Ted, apologise for jumping on your thread but looks like we are in the same place.

Oddjob, I've struggled to ID any markings on the crank except one which looks to be A1. So I'm stuck and not sure what i should do next. I have a Parkside micrometre but I'm doubting it as it reads for example 32.18 but if I read the the manual I should be looking for that extra 0 i.e. 32.018. Discussed with my friend and he question the tolerance in the manual. I cant see any real colours on the bearings either....

Anyhow, I now think I need to take the crank and conrods to a local engineering firm to get measurements then i can work out the correct bearings i.e. if the crank pin is 32.018 and the conrod allowance is 35.016 then a need a GREEN bearing??

[Nurse Julie]

Waffey. The tolerance scale in the manual is correct. Your micrometer isn't fine enough to get the correct critical readings.

[K2-K6]

A micrometer with vernier scale is required for finer resolution

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https://www.wonkeedonkeetools.co.uk/micrometers/how-does-the-scale-of-a-metric-micrometer-work

Link shows it used in practice.

[K2-K6]

Although the above picture is inaccurate as the thimble scale shows 0.284 ish and the vernier shows 0.009 

You'd think they'd get the illustration right if they are going to demonstrate it wouldn't you 

[waffey]

Just as I thought, I'll take it to an engineering firm for measurement.

thanks all

[waffey]

Oddjob, I did try, sat in the sun, in the shade, petrol all over, magnifying class, photos I just cant see them.

Why is it never easy!

[waffey]

Oddjob,

do i assume these markings on the conrods refer to the bearings i.e. 3c= GREEN, therefore I just need to verify clearance before replacing them?

[McCabe-Thiele (Ted)]

I believe the C  is just the weight code - 3 gives you the Con rod allowance on the left of the tables- now you need to measure the corresponding crankshaft jounal to find out the Crank pin allowance to find the correct colour code in the tables. Others will confirm if my understanding is correct.

Just to confuse the tables for Mains & Big ends are arranged differently so check the con rod table.

[waffey]

thanks Ted

[McCabe-Thiele (Ted)]

Just tried the Plasigauge on my crank mains I have the bearings as follows.
Crankcase Code CAABA

1-Black, 2-Green, 3-Green, 4-Brown, 5-Green.

All 5 mains are reading the same at 0.0015 thu / 0.038mm  on Plastigauge chart after torquing up the mains bolts.

That to me looks like 38 micons all round so am happy with the new shell colours.

Next I will be checking the big ends.