Forum bmwbike.com

Hi Mark. Firstly , thanks for the books, They arrived about two weeks after you sent them.
My query is as follows- I am experiencing a heating problem with my R60/2 now that I have
attatched a Tilbrook sidecar (Australian made and came with the bike new in 1964). The
main jets are #110 and the plugs are the correct Bosch's. The plugs read too hot which suggests
that the jets need to go up or I should use a harder grade of plug. In my racing days we used to
drill jets, fill them with solder and re drill etc etc but I notice that you stock jets up to #140.
What would you recommend? The needle jets are 1308's and as far as I know the needles are correct. I have checked the igition timing statically but not with a strob, It accelerates ok in
the lower gears but doesn't like being driven much above about 60 mph in top. Out of interest, are the main jet numbers related to metric drill sizes eg 110 =1.10mm or are they calibrated
in flow rates. I have a range of small drills, numbered and metric should the need arise. Regards, Peter.

Peter,

What clearance do you have between piston skirt and cylinder bore. If you have the solo clearance or less then this may cause overheating when a sidecar is attached. You should have 0.06mm+0.01mm for sidecar riding.

Hi Pierre,

thanks for your reply Pierre, the piston clear.clearances are standard. Since I wroe the

query I have found a couple of reasons for the heating problem. Firstly from Mark I discovered

that the carburetor main jets should be #125 and not #110. Unbeknown to me the chap

I bought the bike off fitted the later carburetors (my bike is 1964 and the carbies are from

the 1966 models on) but put the earlier jets in. In addition to this when I put a strobe light

on the timing was correct at idle but wildly out at revs due to worn cam lobes on the centrifugal

advance unit. I have just ordered new jets and advance unit from Mark so this should do the trick.

If not, I will certainly consider giving the bores a hone to increase clearance as you suggest.

Thanks again, best regards, Peter