install cam technical question

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schrader7032
Posts: 7871
Joined: Fri Oct 27, 2006 3:00 am
Location: San Antonio, TX

Re: install cam technical question

Post by schrader7032 »

Guenther Wuest is certainly one of the gurus, so you're in good hands!

I know very little about performance enhancements for engines, but you mentioned something that made me wonder. You say you're putting in a mild cam. One thing that I've read about is the R60/5 and R60/6 bikes at 9.5:1 compression also had a mild cam and they were very prone to pinging. (Mild cams to me means they have a more shallow rise/fall of the lobes, keeping the valves closed longer resulting in more compression.) Ways of dealing with that was base gaskets or use of electronic ignition which controlled the advance curve to reduce pinging. I suppose dual plugging was an answer but was an expensive one at the time. Dual plugging requires further manipulation of the advance. You can't let the engine get advanced too early otherwise it will ping. One way to prevent this was to build in a mechanical stop on the advance unit...this allowed for keeping the original timing at idle. Another way was to forgo the idle timing and having the points open at very nearly TDC, which would allow for the regular advance curve but it terminated early.

But if Guenther has a way around these things, that will help out!
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

jstewart
Posts: 17
Joined: Wed Jun 09, 2021 3:30 pm

Re: install cam technical question

Post by jstewart »

The ignition system is being changed along with the dual plugging of the heads. There is a specific advance curve built into the ignition module for dual plugged heads which uses a gentler advance curve with less total advance. This is because of the faster flame propagation in the chamber. Actually it is my understanding the BMW OEM performance cams (320 & 336) use more duration with the same lift which gives you gentler cam ramps and more overlap. I will verify this with Guenther but I believe I am right. Guenther worked for BMW when the R90s came out and he believes the test bikes here in the states were sent over for magazine tests with the 336 cam installed. 8-)

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srankin
Posts: 351
Joined: Fri Jul 14, 2017 8:45 pm
Location: Spencerport, NY USA

Re: install cam technical question

Post by srankin »

Well, it seems you have the situation in hand. It will be interesting for you to write about how things turn out.
While you may not have gone in the same direction I would have, I give you large credit for finding someone to guide you along the path who knows what he is doing.

Let us know how things work out. St.
Owner of a 84, R80RT and 78, R100RS

jstewart
Posts: 17
Joined: Wed Jun 09, 2021 3:30 pm

Re: install cam technical question

Post by jstewart »

Well guys things are moving along nicely. There have been delays caused by getting parts from overseas. Covic19 has really messed with supply chains here and in Europe. Guenther is finished with the transmission and we are now waiting on bearings for the engine. Because I could I elected to have Guenther completely re-bearing the engine and transmission and properly set the thrust clearances. The R100 heads are off having the seats replaced for lead free gas, dual plugging, replacement of the 42mm intake valves with 44mm OEM valves and some minor porting work. We should get the engine and transmission back in the frame this Saturday. Pistons and cylinders from Germany are going through US customs and shipment to me by usps. Don't know how long this will take as there are over a quarter of a million packages backlogged from overseas in the usps system for delivery. :o

jstewart
Posts: 17
Joined: Wed Jun 09, 2021 3:30 pm

Re: install cam technical question

Post by jstewart »

We had a marriage ceremony yesterday installing the motor in the frame. Still waiting on the new cylinders and pistons from Siebenrock in Germany and the heads from Max BMW. Plan on installing the re-bearing clutch with new clutch tomorrow. Thanks to everyone here who have patiently answered questions. :D

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