Checking rotors
Q: I have a Benelli 750 Sei exactly like the one I had in the 1970s. I am rebuilding it. I bought a second one for spare parts. The front rotors that came with the second bike were new, drilled and look great. Do cast iron rotors that are drilled become fatigued or brittle over time? They were stored between parts books very carefully for many years.
Walter Kettler/via email
A: The cast iron shouldn’t suffer from storage, but I’d probably have them inspected if they weren’t drilled from the factory. A good machine shop should be able to Magnaflux them for micro cracks and possibly chamfer the holes if needed.
Got the blues?
Q: Do you know the correct blue color for the 1966 Honda CB160? Thanks.
John/via email
A: The information I could find said that in addition to the Blue/Silver scheme, color options for all the model years of the CB160 were Scarlet Red/Silver, Black/Silver, and White/Silver. The gas tank, frame, forks, headlight bucket, taillight housing and rear shocks were the main color while the fenders and side covers were silver. As for the color codes for the correct blue, check with Marble Motors (marblemotors.com). They will have the correct paint.
Oil filter kit
Q: I like your informative column. I have some questions about the oil filter kit installed on the 1968 Triumph. A: Will this unit work on a 1968 BSA A65? B: Is the oil pump powerful enough for the oil filter? C: Is the bypass spring in the oil filter set to the pressure the oil pump supplies? Thank you for your info.
Jim Justice/via email
A: Those are good questions. I contacted Brian St. John at Legend Cycle who supplied the kit from and he replied quickly.
“I haven’t tried to fit the oil filter kit to an A65 and I don’t have one here right now to test it on but I do know the frame tube diameter is only 1-1/8-inch. The filter body is designed to clamp on a 1-1/2-inch diameter tube. I have reducers that take it down to 1-3/8-inch diameter to fit the Triumph 350 and 500 frames but that’s all.
The oil pump is plenty powerful enough for the filter. Given the low bypass pressures of the filters it doesn’t take much to push the oil through the filter. For example, if the bypass valve on the WIX filter opens at 8psi, the pressure required to push the oil through the filter material would be less than 8psi. The bypass valve in the Fram filter is 13psi. The bypass valve in the WIX filter is 8-11psi. So there is no fear of the oil flow being interrupted even if the filter gets plugged.”
Major meltdown
Q: I had a major meltdown in the alternator of my Norton Commando MkIII. Apparently there was not enough clearance, and the rotor rubbed the alternator until everything heated up and seized. I’ve cleaned it up and replaced the rotor and stator. I have a reasonable gap all the way around except in one half inch spot, which does not move when the rear wheel is turned. I have hit the assembly many times, as per instructions, and nothing happens. Do you have any advice?
Margie Siegal/via email
A: I don’t know who started that whole hit the alternator bit, or the bend the mounting studs bit, both of which can break the casting of the case if done with vigor. The current accepted cure is to enlarge the holes in the alternator so that you get some wiggle room that way. That can be difficult to achieve in a home workshop as the laminated alternators tend to grab a drill bit and delaminate. If you’ve got a rat tail file that’s the right size that might work better than trying to drill it out.
Energy transfer ignition
Q: I’ve had my 1966 Triumph 650 TT with the energy transfer ignition since 1975. I’ve had it apart a few times. This time I rebuilt it and replaced all the worn parts and then some. I don’t ever remember timing the rotor to top dead center. In the past I have just put a new primary chain on and off you go. It always ran well and was powerful. This time I bought a new rotor that was not drilled. I followed the known procedure. At top dead center close to 9 o’clock I looked at the phase mark on the rotor and it lined up with the pin and instructions from JRC Engineering . I drilled a hole, set the timing, and got a fair spark. When I kick it, it just backfires out the exhaust. What I did notice though is at top dead center my crankshaft splines are not the same as in the pictures in the manual. It’s closer to 10 o’clock. Can you tell me what is wrong?
Brit Hemenway/via email
A: If it’s consistently backfiring, I’d guess that you have somehow reversed the coils, so they are firing on the exhaust stroke. Starting with the wires under the points plate, make sure the rear set is connected to the yellow/black wire and the front set is connected to the white/black wire. If that’s correct, then swap the left and right spark plug leads on the plugs and see if it will start. The alternator rotor shouldn’t affect the timing, just the strength of the spark produced by the coils. The rotor is positioned so that the AC voltage curve is at its peak when the points open. Too soon or too late on the curve and you get a weaker spark. Way too early or late and you get no spark.
Send questions and feedback to keithsgarage@motorcycleclassics.com.
