Forum bmwbike.com

The "handbuch" for my 1937 R6 (also covers the R5) states that the sparkplugs should be Bosch W240T1. BMW Profiles - Motorcycles from Munich 1923-1969 says the R6 should use W175 T1 and the R5 should use W225 T1. Does anyone know which is correct? Does the Bosch number denote temperature range? Is a Bosch cross reference chart available?

What is the correct gap? The handbuch doesn't say. I'm running about .025" (±.6mm).

The plugs that are installed are Beru (from France) and they read a little hot.
The numbers on them are "7A" stamped on the metal and "719" baked in the porcelaine.
I would like to try some cooler plugs. I will also try some larger jets in the carbs (I have Bings instead of Amals).

Any information wuold be greatly appreciated.

Best regards,

Bruce

hallo,
for what firm you need a croos reference list( old Bosch to new, or old Bosch to others)?
These old Bosch numbers were a temperature range.
Do you(your R6) have a magnetic ignition? or battery(I think battery)
Magnetic: gap 0.4mm-0.5mm
Battery : " 0.6
Nevertheless: I would trust the Handbuch
rolf

Hi Rolf,

Thanks for the response. I would like to know the new Bosch (no resistor) numbers for the old W175T1 and the W210T1.

Do you know the Bosch spark plug "code"?

All the prewar bikes R5-R71 use battery ignition. Strangely, the R5/R6 Handbuch does not give a gap for the sparkplug.

Best regards,

Bruce

Hey Bruce,
the new Bosch has another (and wider )range, par example: W4AC=W225T1-250T1
W: the same
4 : see above (5=195-220,3=255-275, all roundabout), the new numbers works in an other direction: HIGH new number-LOW old number.
A=T1(C =T2)
C= copper Elektrode(I do not know in english)
Par example: W260 T2=W3CC .
Is that what you want to know with the code?
or do you want know what the old numbers
means(240 etc.)?
You need a gap of 0.5-0.6mm, o.6 give a stronger spark,0.5 made it easier for your ignition.
Short: you need a W5AC or a W6AC, you have to try it out(by driving)
greetings
rolf

Thanks Rolf.