Triumphrat

HankQ · 10-10-2005

Hey all, I have been out for awhile working on my rebuild. Anyway, during rebuild of my 72' Daytona 500 I came to the realization that my bike has no small end bushes. The manual I have--Haynes workshop for 500 twins 1958 thru73--would have me check them by inserting the grudgeon pin and checking for a sliding fit. It also states that a new bush usually has to be reamed. Fair enough, except that I have no bushes. The grudgeon pin fits, rather tightly, directly through the connecting rod. In addition, my Triumph parts replacement guide specific to my bike has no small end bushes listed. I have a J.R Nelsons development history of 500 twins, but can't seem to locate any information on discontinuation of small end bushes in the sections on engine mods. Does anyone know when Triumph stopped using the small end bush on the 500? But more importantly, should my grudgeon pin be a snug/tight fit directly through the connecting rod? Seems to me it should be a little looser in order to move as freely as the pston on the grudgeon does. I'm curious as I originally took the bike apart due to a scored piston. After cleaning it up and readying it for the macine shop I noticed that it had already been taken to 0.04 over. Seems to me like there have been a lot of rebores on an engine that looks great otherwise. Thanks, Hank.

jimballard · 10-10-2005

Well, Hank,

I consulted my 1970 factory parts manual, which covers both 650 and 500 models, and it appears that you're right. The 650 model has bushings and the 500 shows only the plain rods. I would, however, check with one of the British experts just to be sure, just in case a mistake was made when the book was printed. It does seem a bit odd, now doesn't it?

Hope this helps you: Jim

HankQ · 10-12-2005

Thanks Jim, FYI I consulted my Triunmph restoration book and it stated that the 500s (t100r etc.) began using bushless small ends in the connecting rods in 69'. The information was in the section on connecting rods and not small end bushes, which was where I had originally looked. I know that other bikes, like the BSA Bantam, have kits to place roller bushes in small ends that are bushless. I don't know if it is necessary in my case or even reccomended, as anything affecting the weight of the connecting rods or cranks can be a problem. It still seems odd as you said. I've e-mailed a few of the known 500 experts in England to find out their take on it. I'll let you know how it pans out. Hank

panda · 10-13-2005

the 'snug fit' gudgeon pins were in my '61 t100.
theory is the gudgeon pin should be chilled, and is then a push fit into the small end. in use the actual movent is in the piston side bearings. eg the gudgeon pin stays still in teh small end, but moves in teh bores of the piston.

incidentally, do not worry about my keyboards dyslexia with 'the'

this means you should -never- have to re bush the conrod, although you might need to change a piston.. a good tip..

chamfer the inside edges of the front piston skirt, so the oil gets deflected towards the piston crown, thereby supplying more oil to these bearings. note to keep both pistons the same weight.