64 SC Beater

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Dave Erickson
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Posts: 2300
Joined: Sat Oct 26, 2013 9:34 pm
Location: Monterey, CA

Re: 64 SC Beater

#46 Post by Dave Erickson »

The last year did not see a lot of progress on the 64 SC specifically, but I built a new garage with 4-post lift and lots of cabinets to hold parts. It is nearly done, cabinet trim and cabinet doors and the final inspection are all that remain), then I will start organizing all the parts now in boxes and spread around. Now the 64 has a perch above the action in the garage and walking under it every day gets my thoughts back to where they should be, and hopefully progress will be more rapid this year (although maybe not; I just pulled plans to build a guest house and I have some furniture to make that I promised my wife...). I just sent a bunch of parts to be powder-coated (including axle tubes and brake backing plates), but I was not sure about these parts:

rear spring plates
rear heater valves

Were spring plates originally painted, or were they bare steel with just a heavy wax coating? Were the rear heater valves painted or zinc plated and undercoated or ?? Were the clamps painted or plated?

Photos of the area where the shop was built, construction and now:
The 356 lived under a tarp the last 15  years...
The 356 lived under a tarp the last 15 years...
Same view as the first photo, with the 356 in its new home.
Same view as the first photo, with the 356 in its new home.
The Hardy Moment Frame may stop the building from collapsing during an earthquake, but it was the single most expensive component of the construction: more than the lumber, roofing, stucco, ...
The Hardy Moment Frame may stop the building from collapsing during an earthquake, but it was the single most expensive component of the construction: more than the lumber, roofing, stucco, ...

Dave Erickson
356 Fan
Posts: 2300
Joined: Sat Oct 26, 2013 9:34 pm
Location: Monterey, CA

Re: 64 SC Beater

#47 Post by Dave Erickson »

I just had my SC brake calipers rebuilt by Centric, and in general I am quite pleased with the results, but there are some small details that are not quite right. i.e. the bleeder valves and caps are not original Ate, and the small tube that goes between the caliper halves does not have the correct ATF nuts (10mm instead of 11). But these are small details and I know most people would not care. They did an excellent job with the plating and finish. And they did return all the original parts so I can reinstall the original Ate bleeders and tubing. The pistons were the originals, not new, which also was a bit of a surprise.

-Dave
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IMG_4703.jpg

Dave Erickson
356 Fan
Posts: 2300
Joined: Sat Oct 26, 2013 9:34 pm
Location: Monterey, CA

Rebushing Solex 40PII Split Shaft carburetors

#48 Post by Dave Erickson »

Back on the topic of Rebushing Solex 40PII Split Shaft carburetors. This week I am starting on a 40PII rebuilding project. At least a decade ago I bought a bunch of 40PII cores, that have been sitting. Finally finished some other projects so I am back on them. The cores were mostly throttle bodies, not complete carburetors, and they were split half and half between split and solid shaft. My thinking then was to rebush and bore the lot of bodies, then sell them to people who wanted to rebuild 40PII's, but did not have the capability to do the machine work. I will get to the details later.

The split shaft 40PII strictly speaking is not a 356 part. They were a redesign of the solid shaft 40PII that was introduced for the 912. A number of changes were incorporated when the split shaft was introduced. The major changes included A) the split shaft B) dependent idle circuit C) New design mixture adjustment screw D) Additional drillings in the idle circuit E) transition vacuum port for the vacuum retard distributor on the 912 F) Improved throttle shaft bushings G) change in location of the accelerator pump bleeder H) changed jetting (mostly as a result of B). Probably other things, please add anything I have missed. There were a lot of claims when split shaft carbs came out that they improved the idle and transition circuits, and owners were happy about that. However, the split shafts proved problematic, so that over-shadowed the improved running, and gave the 40PII's a bad reputation.

So today was spent rebushing. First task was to remove the bushings, second was to pull the actual bushing out of the outer carrier, then install new bushings and re-install in the carburetor.

A ⅜-16 tap was used:
IMG_3614.jpeg
However, these carbs are 60+ years old. at least half of the bushings started spinning when the tap was in about 2 threads. After pulling them it was clear that the retaining compound had failed. The bushings are two piece, with an outer carrier and an inner bushing. The inner bushing is pressed in place, but the carrier is a loose fit, held in place with a retaining compound that is '60's technology. So it is even easier to remove the bushings by driving them out with a punch and hammer. I made a small driver that was 7.75 mm in diameter with an 11 mm shoulder, so it would fit in the bushing and clear the carb body.
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That made the job of removing the bushings easy. But, for those bushings that I was able to tap without spinning the outer carrier, I made a puller to extract the inner sleeve. For the bushings that were driven out whole, I needed a way to hold the outer carrier, so that I could tap it and extract the sleeve. I could have put them in the lathe and drilled out the sleeve, but that proved to be unnecessary. I used a 5C collet block to hold the bushing, and it worked fine. However, if you don't have a collet block, drilling the sleeve with a drill just under the sleeve diameter would make it easy to remove.
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The puller body was just a piece of scrap. It had an i.d. large enough for the sleeve to go through and small enough to block the carrier.
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Only 2-3 threads are needed to pull the sleeve.

This shows the 4 carriers after extracting the sleeves:
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A ball hone was used to clean the bores in the carburetor and inside the carrier:
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Attachments
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Dave Erickson
356 Fan
Posts: 2300
Joined: Sat Oct 26, 2013 9:34 pm
Location: Monterey, CA

Rebushing Solex 40PII Split Shaft carburetors

#49 Post by Dave Erickson »

Bushings for 40PII's used to come in carb kits, way back when. The bushings shown will work in both solid and split shaft carbs, but the solid shaft carbs only use outer bushings (the throttle shaft runs in the carb metal on the inside).
IMG_3613.jpeg
Pressing the sleeves into the carriers used a vise. The round bronze piece is just scrap that matched the curve on the end of the carrier. The green retaining compound is Loctite 680. It sets up fast, so you need to work quick and position it correctly, otherwise it is coming back out.
IMG_3637.jpeg
Pressed together:
IMG_3639.jpeg
Trimming the excess on the lathe:
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Cleaned and ready to install
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The bushings were installed proud of the carb throat. They will get cut flush when the carb is bored to the first oversize.
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Ready to ream.
IMG_3648.jpeg

User avatar
Martin Benade
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Location: Cleveland, Ohio

Re: 64 SC Beater

#50 Post by Martin Benade »

What is the purpose of the two parts for bushings?
Cleveland Ohio
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Dave Erickson
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Joined: Sat Oct 26, 2013 9:34 pm
Location: Monterey, CA

Re: 64 SC Beater

#51 Post by Dave Erickson »

That is an open question. My speculation is that the sleeves were intended to be removable and easily replaceable without removing the outer carrier. I can envision pullers that would do such a job, but only if the carrier was held in place with relatively new retaining compound (that was not 60 years old). Removing the inner sleeves and leaving the carriers intact is challenging because the sleeves would need to be removed into the gap between the barrels. If the tool had an expanding collet, it might work. If that was the original intent, it would allow replacement of the sleeves without the need to re-machine the throats of the carburetor.

One thing I forgot to mention above: the carriers varied in outside diameter. All of them were sized to accept sleeves with a 10mm outside diameter, but the outside carriers were larger than the inners, and there were at least two sizes of outside and inside carriers. I needed four collets to handle the range of sizes I ran into.

Jurgen Amtmann
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Location: La Luz, NM 88337

Re: 64 SC Beater

#52 Post by Jurgen Amtmann »

Dave, I don't usually go to the Projects page, but the 64 SC Beater title caught my eye. I have an original 64 C that I bought in Germany. But that is not why I'm writing. I've had a number of classic BMW R bikes and recognized your R /2 (50, 60 69 ?) bikes all of which I've had and enjoyed back in the days. Then came the /5, /6 and 7 where I stopped. I'm sure that you finished yours. Regards, Jürgen

Dave Erickson
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Posts: 2300
Joined: Sat Oct 26, 2013 9:34 pm
Location: Monterey, CA

Re: 64 SC Beater

#53 Post by Dave Erickson »

Ah, Jürgen, the R60 in the photo is in the same state as it was when the photo was taken. It seems I have slowed down in the last few years. Hope to get to it eventually.

Jurgen Amtmann
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Joined: Mon Nov 18, 2019 12:38 pm
Location: La Luz, NM 88337

Re: 64 SC Beater

#54 Post by Jurgen Amtmann »

Dave, I wish that I still had my R69, it was a fun bike. The /6,7,10's were more capable, but not the same. I, too, am very slow on my 64C, I creak when under the dash. Jürgen

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Phil Planck
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Location: NE Michigan, lower penn.

Re: 64 SC Beater

#55 Post by Phil Planck »

Good carb info Dave. Looking forward to more
Phil Planck

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