Milwaukee Midget

[PorkPie]

the Blue Flame is well protected here in Sinsheim....

Under Pork Pie's watchful eyes, I have no doubt. 

....with so friends you need no enemies.....

[Milwaukee Midget]

A quick addition - Mr. Overland used to be a director at the Henry Ford Museum, is very familiar with the Goldenrod, knew my friend Dr. Martin Jack Rosenblum, the first official Harley-Davidson historian, and falls into the "hell-of-a-nice-guy" category.

I hope our paths cross again.

[PorkPie]

the Blue Flame is well protected here in Sinsheim....

Under Pork Pie's watchful eyes, I have no doubt. 

....with so friends you need no enemies.....

...for better understanding....if someone in Germany says.....I have no doubt he means normally the opposite.......

[Milwaukee Midget]

"Well, that explains it", he said, wiping the egg from his face once again . . .

DSCN0170 by Chris Conrad, on Flickr

That's busted.  Here's how it's supposed to look -

DSCN0172 by Chris Conrad, on Flickr
DSCN0171 by Chris Conrad, on Flickr

So I went and did my "go-zin-tas" on this.

I was using a 948 Bugeye master and slave cylinder combination ("Frogeye" for those across the pond). Both the master cylinder and slave cylinder are .875" diameter, yielding a one-to-one ratio. So for every ounce of fluid forced out of the master cylinder, the slave cylinder receives one ounce of fluid. Therefore, for every inch of travel the master cylinder was depressed, a corresponding inch of extension was achieved to actuate the clutch fork.

The 1275 clutch arrangement is different. The master cylinder bore is .70" diameter and the slave cylinder is 1.0 - a .7-to-one ratio. So one inch of travel of the master cylinder translates to .7 inches of travel from the slave.

Why the difference? The 1275 utilizes a diaphragm style pressure plate - the 948 Sprite, a 3 finger arrangement -photo courtesy of Moss Motors - just don't tell them they extended me this courtesy . . .

190-963_2 by Chris Conrad, on Flickr

I was pushing about 40% more fluid into the system than the mechanicals were able to handle, and that's why the clutch failed.

I'll be figuring out the engine management a little later this winter.

[salt27]

It appears you made a good call on pulling the plug at World of Speed.

  Don

[manta22]

Good analysis, Chris.

[WOODY@DDLLC]

MM, if you had that much over-travel you might want to check the corresponding thrust face on the crankshaft! 
Don't axe me how I know! 

[Milwaukee Midget]

MM, if you had that much over-travel you might want to check the corresponding thrust face on the crankshaft! 
Don't axe me how I know! 

Woody, I will put a dial indicator on it when I get it in the basement - that's a thought I would not have thought of without being prompted.

Some day, I might actually get good at this. So far, I've never developed enough power to be too dangerous.

[Jack Gifford]

I'm glad you identified the culprit.
You were actually further off than you realize. A .700" diameter master cylinder will only move a 1" diameter slave 0.490". [Area, thus volume, varies as the square of the diameter.]

[Interested Observer]

Further, the stroke of each has not been addressed.  How much travel is required at the slave and how much is available at the master?  Would a pedal stop be of any use?

[Milwaukee Midget]

Stainless suggested a pedal stop when I began suspecting this problem a few weeks ago.
I'm fairly convinced that simply returning to the original configuration will fix the problem - all the original dimensions of the mechanism remain the same - but as Jack just pointed out, and to paraphrase a Fordboy quote, sometimes I'm unlucky at math. 

[Milwaukee Midget]

Further, the stroke of each has not been addressed.  How much travel is required at the slave and how much is available at the master?  Would a pedal stop be of any use?

More directly to your point, I've never been clear on, nor for that matter, ever seen a spec as to what an appropriate amount of release for a Spridget clutch assembly actually is.

I CAN say with a degree of certainty that on September 12, I had too much, and I know why.

It's a tough measure - access with a feeler gauge would be virtually impossible, and while it could be calculated, I know the standard 1275 arrangement works with the appropriate parts.

[Stainless1]

Chris, we fight the same problem with the lakester with every motor change... our automotive master moves way too much juice for the old motorcycle slave.
That's why the pedal limit... and we have an fine adjustment on the master push rod to help.  I usually adjust the clutch to ensure it just releases... With the motor shut off, I adjust for release, from where the trans does not to where it will turn... if it drags when I start the motor, then I give it another half turn till I get full release...
OK the differences... we have wet multi disk, yours is dry single... but I think your adjustment can be simplified the same way.

[Milwaukee Midget]

Bob,  I agree, and I can create some adjustment capability in the pushrod for the 1275 setup.

I talked a number of years back with T. C. Christianson in Kenosha, and he had a similar approach to setting the clutch on the twin-Norton powered Hogslayer drag bike.

It's akin to tuning a guitar by ear vs. using a tuning fork, but carrying the metaphor a bit further, it does require starting with the proper gauge string.

[manta22]

Chris, you could put the Midget in 1st gear and crank the engine over with the starter. Push in the clutch to the point where the car stops rolling forward and that's where your clutch stop needs to be. QED