SOHC.co.uk Forums > CB350/400

Big end bearing help

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Dolomite_:

--- Quote from: Bryanj on April 11, 2024, 09:00:38 PM ---I think you are missreading the plastigauge chart or the micrometer ifvit was the gap you say you would probably feel play

--- End quote ---

I'll give it another go tomorrow. The measurements for the mains went fine, unless it was just one of those days today.

McCabe-Thiele (Ted):
When you check the big end bearings iirc the two slots for the bearing shells are on the same side plus the weight code marks will then be in alignment. Have you fitted the big end cap the wrong way round when taking the Plasitgauge readings.

For reasons that seem contrary to common sense the axis for mains & big ends are transposed the number code for mains are on the vertical axis with the letters on the horizontal axis.  For the big ends (con rods)mits letters vertically numbers horizontal.

My big end tollerances were all pretty much the same at 25 microns each a lot tighter than the mains clearances that were 38 microns. I had Green shells in all four of my big ends the codes on my crank were mostly illegible.

Dolomite_:
measured again and the clearance looks like its more along the lines of 0.038mm 0.050mm 0.050mm 0.025mm. I might order a set of black and see what that shows.

Deano400:
Not sure going to Black is going to help.
You’ve posted two sets of readings and got different results, so not consistent readings.
Set 1         0.050mm 0.050mm 0.050mm 0.038mm
Set 2         0.038mm 0.050mm 0.050mm 0.025mm
Are you giving everything a clean between readings? No remanence of oil, plastigauge or anything else that may affect your results.
Conrod and cap aligned with the C and 2 always matching?
Conrod installed with shell tabs to the exhaust side?
Torquing progressively on both bolts i.e. not torquing one up then the other?

Dolomite_:
I took 2 measurements each time. Cleaned them in between and made sure it was the correct direction. I've ordered some blacks anyway as I need to do an order at DSS. Just need to wait for that and some more plastigauge. I'll take pictures next time too.

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