Wrist Pin /Gudgeon Pin part 2

rosbullterier · Post by **rosbullterier** » Sat Apr 12, 2008 12:22 am

The Clymer book and information from a Seagull employee stating the gudgeon pin open end is fitted uppermost is worrying me.

I am putting the crank together to reassemble a 170 for which I have had a brass end cap made ( you can see the extent of my concern).

The engine has not been stripped before and my reminder paint blobs show the gudgeon pin open end was facing down . . . How would the factory assembly machine have built it?

And after tightening the big end cap cap bolts to hardish hand tight - there are are some fairly light tight spots. Surely that would signify slight ovality on the crank pin rather than poor cap machining?

StephenRT · Post by **StephenRT** » Sat Apr 12, 2008 7:19 am

If the connecting rod rotated smoothly with the original big end cap fitted then it seems likely that the new cap is the problem.The only way to be sure is to measure the big end journal for ovality and to measure the internal diameter of the connecting rod with the new cap fitted and fully tightened.

redclyffe · Post by **redclyffe** » Sat Apr 12, 2008 9:39 am

could the cap have been machined to go on the other way round?

rosbullterier · Post by **rosbullterier** » Sun Apr 13, 2008 10:37 pm

Tried the original alloy cap and the rod span round perfectly in spite of a real tightening. I assume the brass cap has been made too short and tightens on the pin after tightening the screws.

Should have followed CharlesUK's advice and insisted on Cad machining; its going back tomorrow - I don't look forward to the confrontation!

StephenRT · Post by **StephenRT** » Mon Apr 14, 2008 7:56 am

Connecting rod big ends are usually line bored as a complete assembly of rod and cap to ensure a perfect fit.

rosbullterier · Post by **rosbullterier** » Tue Apr 15, 2008 12:59 am

Stephen I understand and agree. However finding someone to undertake this one off and then not telling him how to do his job is something to contend with.

I returned it this morning. He is is a very nice and venerable chap. He could not understand why it does not fit as he was sure it did when I left.
It is tight rather than slack so there should still be material to remove. I'll pick it up next Friday. Hey ho - Tohatsu's are so ,well, you don't play around with them . . .