Andy the main bearings come as separate outer races and gaged rollers which run directedly on the main shafts. The rollers come in about 3 different sizes to allow for wear on the main shafts which you would hope are not too badly oval or scored.

The outer races are removed from the cases by heating the cases (best in an oven to around 200 degrees) I remove the drive side outer race by drilling two small holes in the ally that sits between the race and the sprocket. That way when the case is hot you can easily drive the race out with a nail or similar (I use a pop rivet as the drift)

Ron

PS. if you want to bring the stripped cases and the crank down, I'll help you with it. I have an oven in the workshop.

email (option): ronpier@talk21.com

Hi Ron thanks for the reply and offer of help..after years of messing about with Velocette engines ,especially the later ones that use taper mains and require a 4 thou "nip up" on the cases, I am quite used to "cooking" engines, albeit in the kitchen whilst Maz is out of the house, to get bearings to fit.
Your comments did cause me to look more closely at the parts list and as you rightly point out there is no inner journal with the rollers running directly on the shafts. This does not seem the best arrangement to me but there you go.So hopefully new rollers would surfice as long as not to much wear on the shafts.
I am sure you mentioned once you did a rebore and new piston ( I think it was on a WD/CO ) and had to get the crank re balanced because you where not happy with some vibration ..you dont recall the balance factor you used and was it an improvement ?

email (option): marian.andrew@btopenworld.com

I'd have to ask Ainsley if he remembers the balance factor. He did it twice as I wasn't happy with the first attempt, so he set the balance slightly different. The lack of rubber handlebar mounts and footrest rubbers doesn't help the cause though. Ron

email (option): ronpier@talk21.com

Thanks Ron ..if you can find out that would be helpfull for the future.

email (option): marian.andrew@btopenworld.com

Andy.... Ainsley says we settled on 57%. There will always be vibration, but this gave me the most comfortable setting. My WD/CO and WD/G are both fitted with the dome top pistons from Hitchcock's. These raise the compression from 6.1-1 to 7.1-1. But yours seems to go well enough with however your engine is configured.:+1: Ron

email (option): ronpier@talk21.com

BSA singles of the era use 58%..I've always used 60% after picking up the figure from a well known BSA builder in my area back in the 70s...I've had good results with that...I think a figure in that area is a safe bet for an engine where the factor is unknown...Single cylinder engines are inherently out of balance and will always vibrate, it can only be moved to an area of the rev range which is not used frequently...
It can be made a lot worse by omitting the head steady or running with it loose as it is an integral part of the triangulation of the frame/engine assembly....Badly worn engine plate holes and studs can also have an effect...These things change the frequency at which the engine vibrates 'in sympathy' with the frame...Ian

email (option): ian@wright52.plus.com

Yes Ian, Ainsley balanced my crank to 60% but it was horrible. So I removed and stripped it again and he moved it to 57%. Which I'm more than happy with. The engine had new mains and big end and one of the Bullet dome top pistons, which was a different weight to the original. (I think it was heavier??) I have the tool for aligning the main bearing races.

These RE's don't have a head steady and with no spec written down it was all a bit guesswork. Ron

email (option): ronpier@talk21.com

Thanks for info Ron ....very helpful. I have read about the main bearing tool
....just wondered why this is needed as surely the positioning of the races is fixed by the machined positions in the cases??...or am I missing something ?

email (option): marian.andrew@btopenworld.com

I thought that as well...If the register between the two halves of the crankcase is machined at the same time as the bearing housings and the cases are a good fit together, then the bearings are bound to be in line..That is the method employed on BSA engines and they are good enough to mix crankcase halves without problems....Ian

email (option): ian@wright52.plus.com

The tool is to make sure that the races are pressed in parallel to each other. I also wondered about that myself, but my mate made me the tool so I used it. Ron

email (option): ronpier@talk21.com

Ian, Andy, out of interest, here is the details about the main bearings. Since I was trying to eliminate anything that might aid vibration, I went ahead according to the book. It more than likely made no difference though? Ron

email (option): ronpier@talk21.com

To me it reads like it's an aid to an unskilled fitter who may not push the bushes in square.
I try to "idiot proof" as much as I can.
(especially for me)

Mark

email (option): pes.sales@btconnect.com

The reason I was looking at this Ron is because on the the recent Worcsetershire Rally my WD/CO developed a new and quite loud mechanical noise from the engine. It sounded quite disconcerting...further investigation has revieledthat bizarrley it was mostly the decompressor shaft vibrating against the exhaust tappet and the the alloy cover..you would not think something so small could make a noise so loud...fixed it by putting a very small rubber o ring in the recess in the alloy tappet cover to "wedge" the shaft in place !!

email (option): marian.andrew@btopenworld.com

Ha Ha Well done Andy. A rubber O ring was a cheaper fix than a total strip and new main bearings....You just need to nail that exhaust pipe on better.:hammer_and_wrench: Ron

email (option): ronpier@talk21.com

Never really had this engine apart... I suppose I really should but scared to look! Runs ok though even if its not as quiet mechanically as yours. As long as it lasts another 3 or 400 miles I will be OK :smiley: ....The exhaust has been well and truley fixed curtesy of the correct stud and shouldered nut from Hitchcocks !!

email (option): marian.andrew@btopenworld.com