Crankshaft lightening and balancing

[ChrisK]

Looking for some tips on who could make up a race crank for me for my T500. Basically, I want the crank to have some serious meat taken out of it and balanced. I know Chris Applebee in England can do the job but the Aussie $ is not looking too good against the GBP at the moment. Is there anyone in the US that specialises in this work?

[tz375]

I'm not so sure you want to do that, but if you do decide to go ahead, just press the crank apart and machine it. Then get it pressed back together. There are enough people in OZ that can do that. I don't know about WA but in New South and Vic there are shops that can do what you need.

I don't think they were dynamically balanced from the factory, and since they are a 180 degree crank they arguably don't need to be unless you have a resonance at a particular rpm that you want to move.

Back in the day, Ron Grant used to machine them down and fit case stuffers but with modern pipes that may no longer be the most appropriate solution.

Is your desire to do that coming from previous 4 stroke race experience or something you read?

[Cyzygy]

ChrisK,
The Aussie $ isn't looking too good against the green back either:-( There are some very talented motorcycle engineers in Perth who could do this, two that come to mind are Ray Easson Motorcycle Engineering and Bullet Racing Engineering, one north of the river and one south.
Bob

[ChrisK]

I'm not so sure you want to do that, but if you do decide to go ahead, just press the crank apart and machine it. Then get it pressed back together. There are enough people in OZ that can do that. I don't know about WA but in New South and Vic there are shops that can do what you need.

I don't think they were dynamically balanced from the factory, and since they are a 180 degree crank they arguably don't need to be unless you have a resonance at a particular rpm that you want to move.

Back in the day, Ron Grant used to machine them down and fit case stuffers but with modern pipes that may no longer be the most appropriate solution.

Is your desire to do that coming from previous 4 stroke race experience or something you read?

There's a school of thought that the mass of the original crank is detrimental to rapid rev build up in racing situations and there are a few guys that have reduced that mass to good effect I believe. I'm familiar with the stuffers and yes, that is old school technology when crankcase compression was seen to be the way to HP. Mostly resulted in very narrow power bands. Nowadays the scavenging of the pipes and ports is much better. Apparently, the dynamic balancing has quite an effect on what could be a pretty shaky motor. Here's a link to Chris Applebee's vid where they are balancing a GT750 crank. https://www.youtube.com/watch?v=lynL7IUGXLQ" onclick="window.open(this.href);return false; also an example of his work on a similar crank http://www.astrax.co.uk/bikes/gt750_crankshaft.html" onclick="window.open(this.href);return false; to extensively lighten it.

[ChrisK]

ChrisK,
The Aussie $ isn't looking too good against the green back either:-( There are some very talented motorcycle engineers in Perth who could do this, two that come to mind are Ray Easson Motorcycle Engineering and Bullet Racing Engineering, one north of the river and one south.
Bob

Thanks Bob. Yes, I started off with Ray as I know he does excellent work but he doesn't have the gear to be able to lighten and balance, only rebuild the standard one. Will follow up Bullet. Also have been trying to get hold of Graeme Selwood in Darwin who, according to some of the racing fraternity on the East Coast, is one of very fews guys left that do this work properly, but all my efforts in the last few months have unfortunately gone unanswered. I do have another local contact from ex racer and bike builder from my era, Peter Senior, so I will follow that up as well. I would obviously like to keep the work local but if the expertise and equipment is not here then I will have to go the expensive route, offshore.

[Craig380]

Please note that I have no practical experience of racing anything other than a bicycle, but I recall reading an interview with Barry Sheene talking about his days of riding and developing the TR750 racers.

He mentioned that the factory experimented at Daytona with a lightweight crank that had smaller flywheels in an attempt to get it to rev quicker. Apparently in this form, in Sheene's words "it wouldn't pull up the (Daytona) banking and was slower", so they reverted to the original 'heavyweight' crank.