So the remaining pistons have now been cleaned of most of the carbon build up. Number 3 piston proved to be quite a mission to get that clean with a simple soft pad, but got there in the end. Piston rings have also been cleaned. Before going back in they're going to need plenty of oil.
Lower crankcase is also looking good from the inside, in preparation for putting the lower half of the engine back together.
Now for a slight complication. Whilst my original plan was to simply take the main journal bearings in my old lower crankcase, and put them in the new lower crankcase, and then use my new piston rods, with my old pistons on the new crankshaft and put it all together - it appears it's not quite that easy, and that's mainly due to the main journal bearings and sizes. In the below picture you can see the codes AAAAB which indicate the crank case inner diameter size, and this has to be cross referenced against a similar code on the crankshaft in order to select the correct size main journal bearing.
Below you can see the codes for the crank shaft (new one), and it's different to my old crankshaft. My old crankshaft had the code L22222. So 2 of my main journal bearings are going to need replacing so that I achieve the correct oil clearance between the crankshaft and main journal bearings. Now looking at my existing lower crank shaft, I have 4 Yellow bearings and 1 Green one which correctly corresponds to the B code in the above picture. So I've just ordered a Pink bearing which corresponds to the code 1 on the crankshaft and code A on the crank case. But....there is another complication. My new lower crank case has different coloured bearings to my old lower crank case. This indicates that either the crankshaft that used to sit in there is a different size to my one or that the upper crankcase that was made alongside my new lower crank case has a different main journal inner diameter than my one. So basically my worry now is that I've got 2 crankcase halves each of which are going to have slightly different inner diameter sizes for the main journals!
In order to account for this issue, I'm going to use plastigauge and measure the oil clearances I have right now. I must do this on both halves of the crank case so when I bolt everything together I'll put some plastigauge on the main journal upper half, and some on the main journal lower half. They both need to be within specs otherwise the main journals will not receive enough lubrication. Preferably I would want both halves to have exactly the same oil clearance so that the crankshaft main journal is not rotating around something that's not completely circular (I know we're only talking hundredths of a millimeter but it really does matter if I want this engine to last a long time).
My other concern was that would be matching incorrect crank pin bearings and piston rods with the crank pins on my new crank shaft. However thankfully all the codes are the same for the crank pins so I don't have to worry about that. When I switch over the pistons an use my old ones I must make sure to measure the piston pins outer diameter and piston rod inner diameter and ensure the clearance is within service limits.
No comments:
Post a Comment