Compression release made easy?

curtisfox · Feb 24, 2021

Here is the build of it https://motorbicycling.com/threads/excalibur-09.37011/ lot of lesions to be learned here, on this fantastic build.........Curt

Mr.B. · Feb 25, 2021

Chrisc1978 said:
I realize this is a very old post, not sure exactly how I got here, but I'm glad I did and got to see the pic you posted of your bike. That is definitely very high up on my list of cool bikes. It's beautiful on a few levels. I love the long handle, is that to engage the drive belt? Early on I was faced with the decision of how I should set up 2 different brakes and a clutch because while I suppose I could pull the clutch and use a finger to engage my front brake, it just looks sloppy having 2 levers on the handlebars. I don't care for the dual lever either because I like having the option to increase front brake pressure a bit more as I slow down, but not in the rear. I toyed with the idea of a suicide brake handle for the rear brake, it would look so awesome.... But alas, my excitement was short lived when it quickly dawned on me that I don't posses the necessary 3rd hand to operate my brake lever on the right so I'm right back where I started if I do that. I digress, you have a pretty cool conversation piece there. That engine will most likely outlast my next 5. The frame is such a perfect match for such an awesome piece of history. I love old engines, I suppose that's how I got here come to think of it. Someone mentioned a compression release valve and it got me thinking of old engines my Grandfather would tinker with. They started with a crank in some cases and the compression was tight to say the least. If she misfired in the slightest she'd kick that crank back at you like a mule and you'd better be ready to let go of it and stand back because those things would snap an arm bone like a toothpick. Sad really, 50 years from now my son won't see very many engines left from my time (not that there's many worth keeping for that long), but I'll bet there will still be a few like yours still plugging along. Sorry for the long post, just wanted to give you credit for an awesome build. A lot of idiots would call it trash, but I think between the bike and the engine, there are some stories there, a lot of them. That's class and a perfect use of some historical artifacts that may have gone to waste if left in someone else's hands.

Wow, this an old post but thank you for the kind words, Curtis too!

Yes the long handle is linked to a lever that presses a idler pulley into the drive belt (basically a simple slip clutch). It has a semi-circle ratchet plate on the tank side and a spring loaded button at the end of the handle to disengage it. The right hand brake lever is the throttle so I can always have at least one hand on the handle bars.

To answer the unanswered question from the original post at one point i drilled and tapped the cylinder head and installed an old brass gas light petcock to work as a compression relief. But unfortunately the engine was still too stiff to pedal start and the valve leaked a little oil. So i eventually just put a plug back in the hole.

I believe that most actual period CR values lift the exhaust valve and i bet that would work, but that's more engineering than i wanna do!

I still have the bike and ride it 7-800 miles an season, including an annual long distance ride of 70 some miles in one pop! (the Scare Crow run)

Thanks again.

curtisfox · Feb 25, 2021

I believe that most actual period CR values lift the exhaust valve. This is what Kohler has in the big singles, but also have electric star, don't think you would ever pedal start one.
You are welcome Mr.B yours bike is a big inspiration, and guide on my build. Now to get back on mine...........Curt

wrench · Feb 25, 2021

Mr.B. said:
Wow, this an old post but thank you for the kind words, Curtis too!

Yes the long handle is linked to a lever that presses a idler pulley into the drive belt (basically a simple slip clutch). It has a semi-circle ratchet plate on the tank side and a spring loaded button at the end of the handle to disengage it. The right hand brake lever is the throttle so I can always have at least one hand on the handle bars.

To answer the unanswered question from the original post at one point i drilled and tapped the cylinder head and installed an old brass gas light petcock to work as a compression relief. But unfortunately the engine was still too stiff to pedal start and the valve leaked a little oil. So i eventually just put a plug back in the hole.

I believe that most actual period CR values lift the exhaust valve and i bet that would work, but that's more engineering than i wanna do!

I still have the bike and ride it 7-800 miles an season, including an annual long distance ride of 70 some miles in one pop! (the Scare Crow run)

Thanks again.

I know your build was 9 years ago. But sounds like ya still might want a C/R valve
The push button compression release is automatic push button.
When the engine fires the compression closes the C/R valve it's spring loaded.
It requires another hole drilled & taped in the head the same size as a 10mm S/P.
The C/R valve seals just like a S/P with a crush washer seal.

You already drilled a hole for a failed attempt with an old brass gas light petcock.

If ya ever want to delete the C/R push button valve Just plug the hole with a 10mm bolt
Slip a S/P crush washer on the 10mm bolt first for a good seal.
Of course the 10mm bolt will have to be cut to length.

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Compression release made easy?

curtisfox

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Mr.B.

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curtisfox

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wrench

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