R26 camshaft setting check

[BSA Bob]

Is there a method of checking for the correct camshaft setting on an R26 without dismantling?
I have a manual describing this on an R27 but I don't fully understand it.
I'm sure there's something about this on the Forum but I can't find it.
Hoping someone can help.

[BSA Bob]

[4Taktix]

Hi Bob,
the description for R27 is not transferable for R26 !
R27 has advanced valve-timing due to a different cam / Cam-sprocket.
To phrase it simple: Both valves have to be opened the equal amount at piston in TDC.
For usual this is described in the manuals by putting a ruler on the top ends of both pushrods and check for
horizontal orientation. So you'd have to remove the rockers and headbolts.
Not sure if this can be eyeballed sufficiently with mounted rockers & Bolts. Worth a try at least.
You can only take the TDC-marking for reference, if it is verified the flywheel ( and the TDC-marking ) sits in correct position on the crankshaft.
( Piston-stop & degree-dial on the crank front end )

Regards,
Sascha

[BSA Bob]

Thanks for the reply, Sascha.
I've tried to eyeball movement of the pushrods, but this is difficult & no guarantee of any accuracy.
The bike is a good starter, idles well & runs well at medium speeds but is reluctant to wind out. In trying to improve on this I thought I might start with the camshaft check but for now I'll assume it's OK & go on with other  tests.
Bob.

[Kees]

The opening and closing points of the valves are mentioned in the workshop manual in degrees, at 2mm valve lash!

So, set the valve lash at 2 mm. Mount a degree wheel on the front of the crankshaft with a pointer. Index the pointer at TDC at 0 degrees. Then get the values from the manual. Rotate the crankshaft slowly in the normal direction and feel when the valves open and close. You can feel them by (trying to) rotating the pushrods. Don't fret over a few degrees difference here or there, this method is precise enough to recognize if the chain skipped a tooth or not.

[rolf.soler]

If that is the case, it's most likely just suboptimal settings of carb and ignition. Optimal settings bring a massive increase of power and speed. My R27 went up from 90 km/h vmax to 120 km/h just by gradual improvements of ignition settings, carb adjustment, with a lot of trial running, always the same stretch on the motorway, with different jets and more or less early ignition. It's individual, but most machines run best with a main jet one or two numbers larger than the recommended one and early ignition at around 40° (38-42°)
Another reason might be low compression, that is easily checked with a compression tester, or in a garage. screw it in, open throttle fully, push fast (run) in 2nd gear and read pressure. Should be around 7 bar
For the camshaft position, does the description in the workshop manual R26/R27 not explain well enough ? the quadrilingual manual (downloadable here) gives instructions for R27 AND for R26 (which are different). There is always the possibility to check the valve opening and closing times with a degree disc

[rolf.soler]

...sascha was faster re valve timing...

[BSA Bob]

Thanks again for the replies.
Kees & Rolf, I've looked at the R26 manual on the Forum. I have a very similar manual in English. Both these manuals refer to checking the R27 camshaft with 2mm valve lash. But I can't find any mention of doing this with the R26. Am I missing something?
I agree that my bike probably just needs fine tuning as Rolf describes.

[Heiko]

Hi Bob,

English:



Page 66 - 68

[Borgward]

https://bmw-einzylinder.de/forum/index.php?topic=16732.msg235707#msg235707

Hubi

[BSA Bob]

Hi Heiko & Borgward, thanks for joining in to help me.
Yes, that's the manual I'm looking at & I have a very similar one in English. My concern is that the instructions for checking the cam are only in the R27 section on p66. The R26 instructions don't mention it. Do you think it's possible to use the R27 instructions to check the R26? Obviously you'd use the R26 settings.
And thanks for the degree disc & link, Borgward.

[Borgward]

Bob,
you are right, at this point the manual considers only the R27. For the R26 you can use the instructions if you take in account that unlike the R27, the R26 has a symmetric valve timing and therefore the balancing takes place exactly at T.D.C.

Hubi

[BSA Bob]

I've used my new degree disc to check the camshaft & this is what I found. The numbers might be out by a couple of degrees but they're quite close.
I set the valve lash to 2mm on the compression stroke.

intake opens   13 degrees after TDC
intake closes  36 degrees  after BDC


exhaust opens   25 degrees before BDC
exhaust closes  5 degrees before TDC

How do these numbers compare with other camshafts?

[4Taktix]

this might help:

[Kees]

Workshop manual:

Intake open 6 after TDC
Intake close 34 after BDC

Exhaust open 34 before BDC
Exhast close 6 before TDC

So, you are a few degrees out here or there but this seems correct. Those are probably just measuring errors. Or your camshaft is worn. But you didn't skip a tooth on the timing chain.

[4Taktix]

but something is odd - at least from my point of view.
Just compare the delta:

   Manual      BSA-Bob      Delta
IO   6° a.TDC    13° a.TDC   7° later
IC   34°a.BDC   36° a.BDC   2° later
EO   34°b.BDC   25° b.BDC   9° later
EC   6° b.TDC   5°  b.TDC   1° later

or else compare the open sectors.
according manual inlet and also exhaust open for 208° both.
Bobs figures add up to 203° for Inlet and 200° for exhaust.

[4Taktix]

I'd adjust the valve-lash until inlet opens at 6° after TDC and measure again.
The same for the exhaust - adjust lash until exhaust opens 34° before BDC and measure.
If your deviation comes from some wearing in the whole valve-train, the above procedure should result in figures
closer to the factory values. Or point out your timing chain skipped one tooth ...
By the way: Even with the tensioner your cam flicks back and forth while cranking the engine slowly by hand.
Depending if a valve is about to open or to close, either the upper or the lower chain strand is stretched.
This might also falsify the readings.

[strichzwojan]

Hi Bob,
you wrote, that the motor is "reluctant to rev out" or so...

Maybe you should consider, that the muffler is a poor aftermarket model. This is quite common with the silencers of the 25/0  and 25/2 models.
Its a huge difference in reving out, when these mufflers are properly modified (Forum-recommendation).

Jan

[BSA Bob]

Thanks for all the comments. It's interesting that the valves close quite close to the figures in the manual But both open late. I hadn't thought about the cam flicking as the engine's turned over, the sort of thing that's quite obvious once it's been explained to you.
For now I've reset the tappets to normal while I consider my next move.
I'll mount the degree disc on a DVD of work practices from my previous employer- finally found a use for it- & will do a more accurate check.
And the bike would benefit from systematic checking of the settings. As for the muffler, I don't know a great deal about what it actually is. I bought it new from Peter Ondrak (in Munich I think) in the 1970s. It's very quiet .

[4Taktix]

When you're done with the timing-checks and everything there is as supposed to be,
you could do a simple test to find out, if your muffler is the limiter.
Just a testride completely without muffler.
( take on old rag or gloves with you, to pick up the sizzling hot muffler,
> THAT YOU LOST ACCIDENTALLY AT THE ROADSIDE DITCH <    )

[BSA Bob]

Having put things back to normal, I took Hildy for a test run. I retained the muffler which was just as well because I got tailed by a motorcycle cop for a while.
But to business.
The points had closed up a bit, I reset them & must have set a bigger gap than previously. The strobe shows the F  about 2.5mm above the crankcase mark , about 1.5 degrees advanced.
The bike starts easily, doesn't kick back & feels snappier, more eager to gain speed. Just in case, I kept to 80kph on the test run but I'll try a bit harder next time.
What do people think of this amount of advance? I see there's currently a big discussion about 50 degrees over in the electrical forum.
Best wishes to all.

[4Taktix]

Hi Bob,
the "50 degree"-case is a one off. It is not yet assured, that this is a false reading or real 50°.
I'd start from the factory-recommended 42° advance.
Now you're on 43,5° - this can work, but you should listen closely for engine pinging,
particularly under high load. ( uphill + high gear + low to medium revs + throttle )
Many members here tend to have a bit less then 42° - F-mark barely visible at the lower edge of the window.
But there is no general patent remedy - you got to carve out by testrides.
( Same stretch, same clothes, same wind, same fuel, same posture a.s.o. )
Yes - this is laborious - even more if you take into consideration that carb-setup influences required
ignition-timing and vice versa.
In general 80kph is way below R26 capabilities.
It should go at least 100 kph to 105 - if you don't weigh in like a Sumo-Wrestler 

Regards,
Sascha

[BSA Bob]

Hi Sascha
I've thought about your comments. 43.5 advance is within the 2 degree tolerance specified in the manual, but I note what you say about running with slightly retarded ignition.
I hope Rolf Soler reads this, I'm confused about his post. Rolf says machines often run well with "early" ignition & then gives the figure 40 degrees.
I think my best option is to take the timing back to standard & investigate from there.
I've no intention of thrashing this bike, I like an 80kph cruising speed but it would be good to have it properly tuned.

[strichzwojan]

It should go at least 100 kph to 105 - if you don't weigh in like a Sumo-Wrestler 

Regards,
Sascha

Even then! But the acceleration might be a little poor.

[4Taktix]

Good morning Bob,
you should read this thread:
https://bmw-einzylinder.de/forum/index.php?topic=10471.msg182981#msg182981
related to R25/3, but transfereable for R26 and a good example how far you can go with advance.
and: english   

[BSA Bob]

Thank you Sascha.
I retimed the bike to standard 42 today & will try it out at full speed. But there's heavy rain forecast so I don't know when that will be.
I notice the R25 record bike started at 3 degrees additional advance. But I'm not interested in pushing my bike's limits.