Bore gauge/Mic vs plastigauge.

Having recently started refreshing my Suzuki gsxr600 engine, using a bore gauge I’m happy with all my clearances big end/main (around 0.025mm avg and in spec) but with a final check using plastigauge they all come back at over 0.040mm, around 0.012 over the loose end of spec. Big ends are also now over spec. I also can’t get larger bearings so I feel stuck. How much can you trust plastigauge? Iknow a few experienced builders who use it no end but with so little experience can’t decide on my own. I understand that it’s a tool to use but and measuring tools surly trump a strip of wax but I wondered what people’s thoughts are on this or where my large difference in measured has come from. Thanks

I don't use plastic gauge at all, micrometer only. The reason being is i know a few cases when it showed 0.023 mm clearance but in fact it was much bigger.

Plastigage is a lot better than people give it credit for.

Measuring accurately can be tricky. What bore gauge do you have? Quality varies a lot.

How do you set the bore gauge? Do you use a micrometer? And which one?

Plastigage may not be as precise as expensive measuring tools, but it is reliable and consistent and good enough for measuring clearances unless you are building something extreme.

Regards,

Henrik

Hi henrik, Insize bore gauge (good enough for these guys) and mitutoyo mics. Using a calibrated mic in a stand to set the gauge.

Getting the same results over and over but when using the correct shell sizes specified by the book/crank case marking results were just always super inconsistent and nothing like the clearances expected. Nothing ever showed less than spec which is a good thing but it always had me second guessing.

Maybe down to plastigauge manufacturer or even temperature who knows.

regards

Callum

I didn't even know there was more than one brand of Plastigage.

As long as you're around room temperature, I don't think that will affect it much.

Regards,

Henrik