R90/6 project

[Tim Shepherd]

WOW, nicely done Sam!

[Sam LP]

Hello, a quick update on my slow progress with the R90/6: Jim Cray collected my bike yesterday to give it a look over and prepare it for the UK MOT test (certificate of roadworthiness). I left the air-box off as Jim will be re-jetting and synching the carbs and I'll fit the front mudguard when I have finished modifying the bracket. Sam

[bbelk]

The oil tank is moving on all I need to do is to plumb in the hard lines to connect the exhaust sucker valves (red and green knobs) to the reed (under that cone at the top right of the first picture) and make all other connections: exhaust sucker lines to exhaust pipes, oil returns to sump,etc. and make a lid for the tank.
Cheers. Sam

This is new to me. What does the oil system do for you? Does it have some volume to it? Extra cooling?

Brad

[Sam LP]

Hello Brad,
The oil system is based on the idea that a slight vacuum in the crankcase allows the pistons to descend without costing so much power, deals with leaks which can be caused by excessive crankcase pressure and returns oil which is blown out of the breather. It is based on work done by Udo Geitl in the 1970's (I believe CC Products based most of their business on Udo's developments) and latterly on Jim Cray's race bikes and on what I have read on the Euro spares forum (article here: http://www.eurospares.com/sucker.htm). It has a lower chamber which adds to the crankcase volume, the air exiting through a reed valve array (from a Suzuki RGV 250) which allows the crankcase pressure to pump down fairly quickly towards a low vacuum. Return lines are fitted to deal with oil blown out of the engine breather. I have also added in the exhaust sucker system, talked about in the Euro Spares forum, mainly as an experiment, hence the valves taken from a gas torch which mean I can adjust or remove the "suck" from the system. I have a vacuum gauge which I will fit in the tank tool-box for testing and setting the system. If and when I have a good setting, I will disconnect the gauge and leave the knobs as they are set. I realise that it would have been much more simple to have used a later crankcase, or not to have done this at all. I like the mechanical fiddling around as much as I like the riding, and both make me happy. I plan to swing the balance towards riding for the next year though. Sam

[bbelk]

Hello Brad,
The oil system is based on the idea that a slight vacuum in the crankcase ........... Sam

Thanks for the great response. I did some of the reading and it looks like an interesting project. I don't think I will ever be that ambitious, but I really admire the front fork/brake work.

Good luck with it all.

Brad

[Sam LP]

Thanks for the encouragement Brad. The front fork/brake work is Jim Cray's. He is a really good engineer and tuner. Charles (chasbmw) has had work done by him too. Sam

[Chuey]

Sam, that oil/vacuum system is really nicely done. As Brad said, so is the fork. I too, like to fiddle as much as ride. They both give me pleasure. Actually, I think it is that way for most of the guys here on Boxerworks.

Edit: On my Cafe' Racer I made a system to connect the crankcase breather to the pod air cleaners instead of just running it out to the atmosphere or into a catch can. I was hoping it would have some of the crankcase pressure advantages you made your system for. Is that on the right track?

Chuey

[Sam LP]

Hello Chuey, I am sorry I didn't reply, I didn't see your edit until now - nine months later..

The intake suck must work in a similar way to that of the exhaust, using the exhaust to pump down the crankcase means that the engine doesn't have to burn the oil mist though.

I opened this page as the R90/6 has been back on the road for a couple of months now. It is great to be riding again. The engine breather box (that I made with the help of a great welding friend) seems to work really well. The reed valve pumps the crankcase down, and any oil ejected out of the breather can return to the sump. I also fitted a separate reed valve, two variable/shut-off valves (the green and red knobs) and two lines to the exhaust headers to make an exhaust sucker. I haven't tested this system yet, but will do over the next couple of weeks. Photos below.


http://www.flickr.com/photos/38434100@N00/7875415072

http://www.flickr.com/photos/38434100@N00/7875418172

http://www.flickr.com/photos/38434100@N00/7875416010

http://www.flickr.com/photos/38434100@N00/7875416948