I think by now that most of you will be well aware of my fixation with rod little end truth, but I thought I would just harp back to it again as I have just had another glaring example.
As I usually have quite a long delivery, I try to help owners in difficulties by offering a one day service to strip, inspect, measure and make a report with recommendations. The owner is present to see how it is all done and gain confidence from seeing it all come apart. I then sell any spares necessary and as I have a working arrangement with Eddie Shermer who can turn jobs round faster than I, Eddie then takes over the job. If the owner wants a top spec job and can wait and afford it, then it stays with me.
A new owner bought a 55 Brum Scott which looked very nice (They usually do — on the outside) Within a few days of ownership a disturbing noise arose while at speed.
For those of you that take our free newsletter, we did a replay of “Autopsy of a Flyer” article which went through the stripping and examination process. If you do not receive the newsletter, then why not?, it’s free and has some helpful info. (End of commercial) As I have pointed out before, you should look out for “Blueing” of the rod. If is blue at the top, then the axis of the little end bush is on a slope and the rod is wagging side to side in use, which causes much unhappiness to the big end. If the blueing is at the bottom, ie big end area, then the axis of the little end bush has a twist error which results in the rod having to twist in use against the roller plates. Now if you have both, then, my lucky man, you have a full house! However, there is Blueing and Blueing! The modest normal variety where the errors are only just plain bad, is a pretty iridescent blue, but there is a “Super” variety where the errors are such that the perpetrator should be shot and if he is not dead, he should be shot again! In this case the errors are so extreme that so much heat is built up that the oil mist is baked on the effected areas, so instead of the iridescent blue colour, we get a grey hard deposit. You would have to be completely lacking in compassion not to feel some sympathy for the hopeful recent owner as I fished out the RH crank in two pieces. I told him that he was a lucky man that the sector of crank that had broken out was so large that it was contained within its clearance diameter and has not made a break for freedom through the side of the crankchamber, as evidence showed had happened already on the LH side.
I explained that the long stroke Scott cranks had a finite fatigue life and that if, in addition to giving the engine some “Stick” the errors in the rod LE bush alignment were such as to stress the engine considerably more, then it was hardly surprising that the cranks cried enough. I explained that a Scott engine in good condition is a great pleasure and that he now required to dig a little deep into his financial courage to buy new high strength cranks and recon rods etc. What man has done before, man can do again and with the benefit of seeing and learning, then unless he is a fool, he should be able to do better. Ah, of course, I measured the errors in the rod little end. stoning the inside datum face and clamping to a special precision ground toolmakers angle plate with a good fit pin through the bush, we clocked either side of the bush. Parallel error 0.009!” Twist error 0.009″
Conclusion. Inspect the appearance of the rods periodically and if you see signs of bluing, investigate immediately, especially if you are using original long stroke cranks that may be near the end of their fatigue life. This is not to Damn what is a fine basic design, but just to be aware of the realities of life. In the past owners who were very good men often did their best to repair their bikes with limited resources and experience, but then, as Marina points out, being a good man is not a profession! Enjoy your lives and enjoy your Scotts. Kindest Regards Roger