Search found 1204 matches

by barryh
Fri Nov 27, 2020 1:42 pm
Forum: Airhead Q&A's
Topic: Coil types
Replies: 34
Views: 777

Re: Coil types

While the second part of the statement is true, the first isn't. 'Electrical Resistance' describes the resistance to a steady electrical flow imposed by the physical characteristics of the conducting material. Put simply, the resistance of a conductor is a function of it's length, its cross section...
by barryh
Thu Nov 26, 2020 8:58 pm
Forum: Airhead Q&A's
Topic: Coil types
Replies: 34
Views: 777

Re: Coil types

I spoke to Boyer and they said that the Bosch is physically larger than British coils of the same era and the wires are of a heavier gauge resulting in a lower resistance reading and losses, the coils inductance would be higher offsetting the lower resistance, so all is good ,thanks to everyone .Ia...
by barryh
Fri Nov 20, 2020 1:52 pm
Forum: Airhead Q&A's
Topic: Rear main seals
Replies: 11
Views: 326

Re: Rear main seals

I'd replace the breather before the rear main seal. If it's the disc type breather it can be replaced with the reed type or as an option to try first, drill a 1.5mm hole in the disc. Nothing to lose by trying that and It worked for me, all but eliminating the turkey gobbling noise. I presume it work...
by barryh
Wed Nov 18, 2020 6:52 pm
Forum: Airhead Q&A's
Topic: Coil types
Replies: 34
Views: 777

Re: Coil types

Primary resistance of the 313 coil is 0.7 ohms which is why I said earlier the Boyer had done well to survive. You have been running with 0.7 +1.2 = 1.9 ohms or thereabouts. The critical component in the Boyer will be the power transistor. It's normal in electronic circuit design to be very conserva...
by barryh
Wed Nov 18, 2020 11:01 am
Forum: Airhead Q&A's
Topic: Topdon findings and low charging
Replies: 11
Views: 330

Re: Topdon findings and low charging

Just under 14 volts at 3000rpm is ok but hardly optimum especial with modern batteries. I would want at least 14.3 volts although the gel battery should be checked for recommended charging voltage. Traditional gel batteries are not tolerant of overcharging because they must not be allowed to gas but...
by barryh
Sat Nov 14, 2020 8:39 pm
Forum: Airhead Q&A's
Topic: Brembo Caliper Rebuild Bolt Torque Settings?
Replies: 10
Views: 290

Re: Brembo Caliper Rebuild Bolt Torque Settings?

George, Motorworks say the callipers should not be split or they may leak on reassembly. On the dual piston Ate caliper which is very similar to the Brembo, Ate don't even issue a torque setting because they don't want you to take them apart. Nor do they sell the O ring. Mine didn't leak either.
by barryh
Wed Nov 11, 2020 6:37 pm
Forum: Airhead Q&A's
Topic: Coil types
Replies: 34
Views: 777

Re: Coil types

That's explains why your points survived Ok. Instead of having the 8.57 amps mentioned above you only had 6.3 amps which is not that much more than the 5 amps if the coils had both been correct, The theoretical problem with two different coils in series is that they will have different voltage drops...
by barryh
Wed Nov 11, 2020 3:58 pm
Forum: Airhead Q&A's
Topic: Strange flywheel
Replies: 6
Views: 191

Re: Strange flywheel

The early R45/R65 flywheels were heavy but not as heavy as the other airhead heavy flywheels. The diameter of the casting below the ring gear is a fair bit smaller than the other heavy flywheels which is the give away as to why the the above flywheel is an R45/65 as those protruding bosses are neede...
by barryh
Wed Nov 11, 2020 1:17 pm
Forum: Airhead Q&A's
Topic: Strange flywheel
Replies: 6
Views: 191

Re: Strange flywheel

It looks like a 78-80 R45/R65 flywheel. Mine isn't exactly like that but it's very similar. I would have liked to have seen the timing marks.
by barryh
Tue Nov 10, 2020 9:04 pm
Forum: Airhead Q&A's
Topic: Coil types
Replies: 34
Views: 777

Re: Coil types

I've seen the normal points coils quoted as 1.2 ohms and confirmed that by measurement. At a nominal 12 volts, maximum current works out as 5 amps for the 1.2 ohm points coils and 8.57 amps for the 0.7 ohm coils. If I was running points on 0.7 ohm coils I'd be careful to avoid or minimise an ignitio...
by barryh
Tue Nov 10, 2020 7:31 pm
Forum: Airhead Q&A's
Topic: Coil types
Replies: 34
Views: 777

Re: Coil types

That part no does appear to be the 0.7 ohm low resistance coil intended for electronic ignition. Both the points and the Boyer ignition have done well to survive near double the usual current that would have occurred with the correct points coils.
by barryh
Mon Nov 02, 2020 6:31 pm
Forum: Airhead Q&A's
Topic: Testing for parasitic battery drain
Replies: 2
Views: 139

Re: Testing for parasitic battery drain

10.8 microamps is indeed very low and nothing to worry about in terms of discharging the battery. It's a very long time since I measured mine and can't remember if the result was equally low or zero. The only reason I can think of why it wouldn't be zero is some leakage on the diode board.
by barryh
Mon Nov 02, 2020 11:21 am
Forum: Airhead Q&A's
Topic: Gearbox / rear diff oil R100R
Replies: 16
Views: 645

Re: Gearbox / rear diff oil R100R

I'm not having any significant leaks that I'm aware of using a semi synthetic 75w90 and that's with all original 1978 seals. There can be a huge difference in cold temperature viscosity between 80w90 and 75W90. To give some specific figures at 0 Deg C: Shell 80W90 2882 cSt Castrol 75W90 750 cSt The ...
by barryh
Sun Nov 01, 2020 7:35 pm
Forum: Airhead Q&A's
Topic: Gearbox / rear diff oil R100R
Replies: 16
Views: 645

Re: Gearbox / rear diff oil R100R

The only semi-synthetic 80w90 I've used in the past is Total transmission 80W90. More often these days a semi synthetic gear oil will be 75W90 which will give the same protection at running temperature but will cause less drag when cold. Castrol universal 75W90 is a semi synthetic that's easy enough...
by barryh
Wed Oct 28, 2020 9:11 am
Forum: Airhead Q&A's
Topic: Cam follower ...
Replies: 9
Views: 271

Re: Cam follower ...

The axial play should be little more than the oil film thickness. When I did mine I couldn't quite get a .0015" feeler gauge in all of the way. The rocker block supports are spigoted on the heads so there is not much scope for squeezing them together but what they shouldn't do is move after you have...
by barryh
Tue Oct 27, 2020 12:17 pm
Forum: Airhead Q&A's
Topic: Cam follower ...
Replies: 9
Views: 271

Re: Cam follower ...

Did you check the axial play on the rocker arm. Too much clearance can make the tappets sound noisy.
by barryh
Sun Oct 18, 2020 12:28 pm
Forum: Airhead Q&A's
Topic: Changing Fork Oil Viscosity
Replies: 72
Views: 1966

Re: Changing Fork Oil Viscosity

The pertinent thing about temperature is that fork oil is marketed with the viscosity at 100 deg C which the oil never reaches. The viscosity at 40 C is better guide and even if the oil should exceed that figure it will still be nearer to reality than 100 C. In my experience of getting what are rela...
by barryh
Sun Oct 11, 2020 10:03 am
Forum: Airhead Q&A's
Topic: Changing Fork Oil Viscosity
Replies: 72
Views: 1966

Re: Changing Fork Oil Viscosity

The nearest I could find to original BMW R65LS 1984 specs for fork oil is Motex 2.5w. I also use the thinnest 5W oil I can find in the R65 type forks. Direct comparisons in oil viscosity can't really be made with older airheads as the damping mechanism is quite different and the fork spring rates m...
by barryh
Sat Oct 10, 2020 4:46 pm
Forum: Airhead Q&A's
Topic: Pre or post 1980 snowflakes
Replies: 12
Views: 513

Re: Pre or post 1980 snowflakes

Wasn't there was a change in brake shoe width from 1980 to 81 at least for some models.
by barryh
Sun Sep 27, 2020 1:03 pm
Forum: Airhead Q&A's
Topic: Advice on fuel consumption
Replies: 63
Views: 2096

Re: Advice on fuel consumption

Parasitic drag is the enemy. Panniers, wing mirrors and slab fronted screens all unfortunately cause drag. While I personally do not like the RS fairing I believe it is quite efficient? It really is time that motorbikes were better aerodynamically AndyB I posted this graph recently with a dotted li...
by barryh
Sat Sep 26, 2020 12:27 pm
Forum: Airhead Q&A's
Topic: Advice on fuel consumption
Replies: 63
Views: 2096

Re: Advice on fuel consumption

On the R90S if I kept to a steady 70mph I would expect between 50 and 55mpg. That's more like what a good airhead should do and any airhead should be capable of that figure if fed with the correct mixture. I know gearing makes a difference but RS models excepted they all need to produce much the sa...
by barryh
Fri Sep 25, 2020 9:22 am
Forum: Airhead Q&A's
Topic: Advice on fuel consumption
Replies: 63
Views: 2096

Re: Advice on fuel consumption

“marked on a small gusset on the carb“

Can anyone say more about where to find this?

This picture was taken for a different purpose and it it's not your model of carb but it's the only one I have showing the location of the model number.

The plugs indicate it's running very rich.
Model.jpg
by barryh
Thu Sep 24, 2020 6:56 pm
Forum: Airhead Q&A's
Topic: Actual and Quoted Power Outputs
Replies: 6
Views: 360

Re: Actual and Quoted Power Outputs

Whatever the power loss is between flywheel and the rear wheel I think we can agree it's substantial. If we assume it's 20% that won't be too far off the mark. So that turns a 50 hp airhead into 40 hp at the wheel with 10 hp dissipated as heat in the transmission system. That's 7.46 kW of heat which...
by barryh
Thu Sep 24, 2020 8:59 am
Forum: Airhead Q&A's
Topic: Advice on fuel consumption
Replies: 63
Views: 2096

Re: Advice on fuel consumption

I would have thought anything in the 30's mpg on a is far too low on a long run even with the snake pass thrown in. To give an example at the other extreme I've seen a touring average of 60 mpg claimed by a very reliable source. Mike Fishwick of the UK BMW club advocates dropping the the needle one ...
by barryh
Wed Sep 23, 2020 5:24 pm
Forum: Airhead Q&A's
Topic: Advice on fuel consumption
Replies: 63
Views: 2096

Re: Advice on fuel consumption

Hi Neal, With respect you are asking the vast majority of us to do some maths before we can answer, as we haven't a clue about fuel consumption in km/l. Rightly or wrongly fuel consumption in the UK is usually expressed in MPG. Needle jets do wear and to a a smaller extent needles can wear if they h...

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