Author Topic: The rotary disc valves seem to be stamped incorrectly  (Read 4447 times)

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Offline edward

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The rotary disc valves seem to be stamped incorrectly
« on: July 27, 2014, 12:48:20 AM »
   I have attached pictures to illustrate my dilemma. The rotary disc valves seem to be stamped incorrectly according to the manual. My discs seem to be out of sync 180 degrees either way I assemble them.
   Has anyone seen this? How should I proceed?

Offline Bill Black

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Re: The rotary disc valves seem to be stamped incorrectly
« Reply #1 on: July 27, 2014, 04:04:45 PM »
I took a few pics of the split crank ....





they show the alignment of the pin in the crank and the disc valve ......
1995 Grinnall Scorpion
1989 BMW K100rs
1983 Yamaha TT600
1972 Sanglas 400
1967 BSA C25T
1966 Bridgestone 175 dualtwin

Offline Bill Black

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Re: The rotary disc valves seem to be stamped incorrectly
« Reply #2 on: July 27, 2014, 04:08:55 PM »
I think the crank rotates clockwise so the disc valve timing is actually ok , the pin does not correspond with BDC of the crank on that side so the disc opening is after BDC .... ? , sorry for the fuzzy dinosaur phone pics 
Regards Bill
1995 Grinnall Scorpion
1989 BMW K100rs
1983 Yamaha TT600
1972 Sanglas 400
1967 BSA C25T
1966 Bridgestone 175 dualtwin

Offline Bill Black

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Re: The rotary disc valves seem to be stamped incorrectly
« Reply #3 on: July 27, 2014, 04:12:04 PM »
In your Pic you have the L aligned with the pin and should be fine .....
Regards
Bill
« Last Edit: July 27, 2014, 04:15:34 PM by Bill Black »
1995 Grinnall Scorpion
1989 BMW K100rs
1983 Yamaha TT600
1972 Sanglas 400
1967 BSA C25T
1966 Bridgestone 175 dualtwin

Offline edward

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Re: The rotary disc valves seem to be stamped incorrectly
« Reply #4 on: July 28, 2014, 12:09:16 AM »
The manual shows the disc to have the (R) and (L) stamped opposite of what I have, 4 of them in front of me, and they are all stamped opposite of what the manual shows. Which way should I set the disc for? The way the manual shows OR the way they are stamped?

Offline edward

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Re: The rotary disc valves seem to be stamped incorrectly
« Reply #5 on: July 28, 2014, 12:19:14 AM »
Yours look to be stamped backwards too from the way the manual is printed. Going back to my first picture, it seems 180 degrees out of phase. I have never worked with these engine before so I maybe wrong but, in the picture it looks like with the piston in the down position shouldn't the hole going to the chamber be exposed?

Offline edward

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Re: The rotary disc valves seem to be stamped incorrectly
« Reply #6 on: July 28, 2014, 12:21:30 AM »
Thanks for the quick reply! Going back to my first picture, it seems 180 degrees out of phase. I have never worked with these engine before so I maybe wrong but, in the picture it looks like with the piston in the down position shouldn't the hole going to the chamber be exposed?

Offline disc_valve

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Re: The rotary disc valves seem to be stamped incorrectly
« Reply #7 on: July 28, 2014, 05:47:32 AM »
I've not noticed this on ny 175 motor, bu't worry too much about which valve mark is which. Just align the valve mark to the crankshaft pin and check that the valve is covering the inlet port when the piston on that side is at bottom dead centre. If not, simply turn the valve by 180 degrees. the valve needs to be closing the port at bdc to provide somevaccuum in the crankcase as the piston rises.

On an aside, the 350 motor seems to have this confusion built in, as it has only one mark on the valve. If you assemble a GTR otor "by the book", you'll end up with both valves pointing the same way - they need to be 180 prt to match the crank throws. Don't ask  how I found this out - but it's REALLY annoying when it will only run on one cyclinder and you have to partially strip the motor again to fix the problem!

Graham

Offline edward

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Re: The rotary disc valves seem to be stamped incorrectly
« Reply #8 on: May 04, 2015, 11:07:32 AM »
What is the best way to check the vacuum?  Does the rotary disc have to be perfectly sealed around the metal gear?
 
---"Just align the valve mark to the crankshaft pin and check that the valve is covering the inlet port when the piston on that side is at bottom dead centre. If not, simply turn the valve by 180 degrees. the valve needs to be closing the port at bdc to provide some vacuum in the crankcase as the piston rises."
            --- Graham

 


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