What's wrong with this picture? R50S

[Carl]

Originally Posted by RecycledRS

Very nice work!
Its called an R50S but the bore and stroke work out to 896cc. If true I think he may well get much more than 70 hp.

I must be missing where the bore and stroke increase on that engine is 896cc. From the pics it does not seem like the geometry and positional placement of the cylinder to engine case interface has been modified to have an increased bore to make it just south of a liter engine.

The site has this: Bohrung 70mm Hub 64mm 500ccm. Visually the pistons look like a large bore and w/ a shorter stroke. So is it a 1/2 liter or 1 liter engine? Time for an e-mail to the builder.

Carl

[RecycledRS]

Using the translator built in to Firefox, the first page of the site lists the bore as 64mm and stroke as 70mm (64*700= 448cc per side). Maybe something lost in the translation? Bill.

[bmwrench]

Originally Posted by Houseoffubar

How do you install the roller bearing crankshaft into the case with the rods already installed?

That's how "/2" engines are assembled. The crank and rods go into the crankshaft tunnel, then the assembly gets rotated onto its back, then finally goes vertical to drop through the rear bearing counter bore. Just to add pleasure to the job, the case has to be hot enough for the rear bearing to drop in.

[Houseoffubar]

Thanks Wrench! I could not see how they would fit. I've never seen a /2 motor up close, I will need to fix that!

[O.C.F.RIDER]

I'll tell ya what's wrong with those pictures.............
they weren't taken in MY garage!

That thing is sweet.

[ericrat]

Originally Posted by RecycledRS

Using the translator built in to Firefox, the first page of the site lists the bore as 64mm and stroke as 70mm (64*700= 448cc per side). Maybe something lost in the translation? Bill.

You forgot to use the radius (as opposed to the diameter) in your calculation. Actually that is a little under stock. Reference here, http://w6rec.com/duane/bmw/engine.htm. Let me google that, http://lmgtfy.com/?q=(64%2F2)+squared+*+pi+*+70+*+2. Come out to about 450cc total. I wonder if there is a 450cc class, or if that is from using a stock piston from a modern bike? Piston sure doesn't look stock.

A wonderful bit of work. I am in awe. Do you think that is a whole custom head casting? I have had dreams of boring a four inch whole through the middle of an R50 head, shrinking in a big piece of billet and starting over. These thing keep we awake at night. Somehow, I don't think I would get this through tech as a "vintage modification".

Thanks for posting!

[SlackerSteve]

maybe the undersize thing is for racing class rules to make up for the unfair advantage of the 4valve heads.

[crazydrummerdude]

Originally Posted by ericrat

Do you think that is a whole custom head casting? I have had dreams of boring a four inch whole through the middle of an R50 head, shrinking in a big piece of billet and starting over.

A local aluminum foundry would probably love to have the business. There's one in St Louis that will cast anything you want in any quantity you want.

[RecycledRS]

Originally Posted by ericrat

You forgot to use the radius (as opposed to the diameter) in your calculation. Actually that is a little under stock. Reference here, http://w6rec.com/duane/bmw/engine.htm. Let me google that, http://lmgtfy.com/?q=(64%2F2)+squared+*+pi+*+70+*+2. Come out to about 450cc total. I wonder if there is a 450cc class, or if that is from using a stock piston from a modern bike? Piston sure doesn't look stock.

A wonderful bit of work. I am in awe. Do you think that is a whole custom head casting? I have had dreams of boring a four inch whole through the middle of an R50 head, shrinking in a big piece of billet and starting over. These thing keep we awake at night. Somehow, I don't think I would get this through tech as a "vintage modification".

Thanks for posting!

Ooops. Of course your right, god I'm gett'in old.

[Carl]

Carefully and closely inspect those heads. They have many secondary ops done to them after they were cast. It appears to include gasket surfaces, combustion chambers, exhaust threads and most probably the plug threads, valve guide bores, valve seat c'bores and rocker arm features. Plus, there is the sourcing of the valve train parts. Then there are the secondary ops to complete (inserting seats and guides, seat cutting and/or grinding) the assembly of the heads w/ the valve parts.

You'll be spinning your wheels by attempting to modify a stock set of R50/60heads to do what they have done. I'd recommend you have lots of time and money before starting from scratch.

Carl

[Carl]

Vierified by the builder:

• ~500cc engine
• The builder did the machining himself in-house
• The pistons are Suzuki 750 GXR Bj.91
• Engine will spin to 10000/min

I like his design approach.

Carl

[danedg]

Originally Posted by Houseoffubar

How do you install the roller bearing crankshaft into the case with the rods already installed?

bearing to the back, webs down, rods up...
...tip into the crank housing and feed the rods up through the cam housing...
once in place....the rods will protrude through the respective cylinder housings...

there's a few pictures of the process on the smuggy below


...and a fresh stock head....


There's NO way you're gonna fit 4 valves in this thing....
Like Carl said... totally custom from scratch

[ericrat]

Originally Posted by Carl

...many secondary ops done to them after they were cast.

That is, I am sure, an understatement

You'll be spinning your wheels by attempting to modify a stock set of R50/60heads to do what they have done. I'd recommend you have lots of time and money before starting from scratch.

Carl

Well this is racing after all. Insert standard jokes here, you know how to make a little money racing? Start with a whole lot of money.

Notice the intake ports are not angled in toward the rider, but parallel to the frame. The exhaust ports are angled out a bit. Really lovely. I wonder about the "window panes" in the case around the flywheel, beside "holes is faster". The castelated flywheel either.

I wonder if he would share his cam specs.

Eric

[Carl]

Originally Posted by ericrat

That is, I am sure, an understatement

Eric

Not really, you can count the secondary ops from when the raw casting was completed.

Originally Posted by ericrat

That is, I am sure, an understatement


I wonder if he would share his cam specs.

Eric

He sent me a batch of specs. Will need to check on which ones are definite shareware bits.

Originally Posted by ericrat

I wonder about the "window panes" in the case around the flywheel, beside "holes is faster". The castelated flywheel either.

Eric

Lightened flywheel and relieved case. The case mods are for cooling/breathing/disc dust removal

Carl

[s.c.m.]

Originally Posted by ericrat

Come out to about 450cc total. I wonder if there is a 450cc class, or if that is from using a stock piston from a modern bike? Piston sure doesn't look stock.

"Bohrung" means "bore", so the displacement calculates
(7cm)²* Pi/4 * 6.4cm * 2 = 246.3 cm³ * 2 = 492,6 cm³


Best regards
Sven