Question about breaker points

TeddyG

TeddyG

Hero member
Location
Portland Oregon
Sorry guys- yet more endless questions about my 750 that I'm going over. I'm not versed w/ points and wondering if these are nearly worn out- the contacts @ 1mm thick, and not sure about the wear marks on the shaft and the layer of grease that's on it. Also the 2 blocks that ride on the shaft- are those getting worn out?
One of the mounting plate screws was bodged and broken at the slot.points.png
 
not pretty, but should still work OK (something you can come back to later) ... so as long as you're getting a 'break' call it good
 
In general the points setup is very reliable and durable and lends itself well to roadside diagnosis and fix - if it's working and you've got the timing set then leave it alone - don't be tempted by electronic ignition until you (we collectively) can no longer find points and condensors that do the job!
 
My take is with the button start your ok with points, kick start with points = a world of hurt with contactly deteriorating correct tune. The best thing I ever did to my Bonnie was an EI. I am full of it, being a lazy buggar I love the concept of set and forget so EI always.
 
TeddyG said:
Sorry guys- yet more endless questions about my 750 that I'm going over. I'm not versed w/ points and wondering if these are nearly worn out- the contacts @ 1mm thick, and not sure about the wear marks on the shaft and the layer of grease that's on it. Also the 2 blocks that ride on the shaft- are those getting worn out?
One of the mounting plate screws was bodged and broken at the slot.View attachment 87318
Click to expand...
They look ok, just dirty.
As long as the contact isn't badly pitted, which could indicate a dud condenser, all's fine.
Clean, degrease and then oil lightly the felt to keep the cam oiled.
Paul
 
Best part with points, you can set the spark ignition ( points opening ) with a transistor radio, six transistor radio... yes same vintage as the engine your timing... no its not a joke, i used to a radio on some outback road and timed a closed points ( badly worn buffer block ) Guzzi V50, rough opening period ( the not nearly critical "dwell" ), off station on the radio, listen for the click and that is the RF produced when the primary winding field comes out of saturation. Yes i know test lamp or bulb... we were in the scrub, i was the two wheeled broom wagon...j
 
Pull the points completely apart so that you can properly see their condition, very easy. They can be dressed with a very fine knife sharpening stone, with care to keep the surfaces flat, but clean them thoroughly with no traces of oil at all. It looks like the cam has been run dry and shows some scraping, but it shouldn't matter, just make sure that the felt pad with a bit of grease is contacting the cam, but it shouldn't be bathed in grease. The adjusting screws can be fixed. The points on an SF are as under stressed as just about any ever.
 
Thanks again guys,

I've learned that as long as it works, don't "fix it". Just wanted your opinions and hoping to just leave it as is since the bike did start up. The contacts appear thin but have no pitting and I'll clean the grease off the shaft- just wondering about the shaft pitting. In the meantime I'll try to buy a backup unit.
 
iis_iis said:
Best part with points, you can set the spark ignition ( points opening ) with a transistor radio, six transistor radio... yes same vintage as the engine your timing... no its not a joke, i used to a radio on some outback road and timed a closed points ( badly worn buffer block ) Guzzi V50, rough opening period ( the not nearly critical "dwell" ), off station on the radio, listen for the click and that is the RF produced when the primary winding field comes out of saturation. Yes i know test lamp or bulb... we were in the scrub, i was the two wheeled broom wagon...j
Click to expand...
Did similar when we taught the Cubs Morse code- turns out it is illegal to transmit morse without a licence in UK.🤔
 
Don’t apologise for asking questions 😁
The contacts wear very slowly through spark-erosion, so they get pitted and need occasional dressing to maintain good contact, as per Tippie. Yours don’t look too bad to me for thickness but if you get a replacement set you can compare them, it’s a good spare to have on the shelf anyway.
Fair enough to leave things alone if they’re working, it’s a policy I use often, but if you’ve got time I’d suggest at least checking the timing anyway. Adjusting points needs patience and accuracy and some understanding of the steps and how changes affect other adjustments. It’s a good skill to have in your toolbox 👍
 
Exmoor beast said:
Did similar when we taught the Cubs Morse code- turns out it is illegal to transmit morse without a licence in UK.🤔
Click to expand...
'mazing... i still practice Morse code from time to time, always send faster than i could receive, when cell phones first came out, and i heard the group of sounds when a message came in, as like a message in my ear..dit dit dit, dar dar, dit dit dit S M S... akin to the happy sound of points sparking away...j
 
Centrifugal advance mechanism underneath i would be more concerned in regards to design value operation, easy enough to check with a dial back timing light. While points have their supporters ( am one ) the actual advance curve versus optimum matching advance to cylinder load would be a lottery these days with fuel soups. j
 
....from the WWW, useful graph on what happens with "advance" the wiggly bit at the top of the 40degree timing would be pinking ( its not pinging in automotive engineering ), the piston rattling in the bore at sonic speed. j

1703879244456.png
 
The original Bosch ignition points as used by Laverda can be difficult to find but the points plate can be easily modified to use VW points.

Both my twins still use points and they never have problems except for the occasional failure of the condensor. My 1968 750GT still is running the points it left the factory with 55 years ago.

Also you need to periodically remove the points cam from the auto advance and clean and grease the shaft it pivots on. Most problems with the points ignition on these bikes is from the auto advance wearing out from lack of maintenance.
 
Another long term problem is the felt of the oiling pad wearing exposing the toothed metal blade backbone. That then starts scouring the cam.
Paul
 
Thanks once again guys- it's hard to tell, but the dirty felt wiper appears to still have some thickness where it presses along the shaft- too bad it can't be removed to replace or clean. I'm sure others have tried this, but I did a search for Bosch ZVUB1Z1Z stamped on the plate, but nothing appears since it's been discontinued.

1200ts- not sure what the "auto advance" looks like- I just see a shaft that the two "blocks" and felt pad press against- please elaborate, thank you.
 
All will be revealed when you remove the whole points plate assembly, springs and wobbly bits in their mechanical glory...HTH j.

** would think there would be sticky lubes for the cam lobe these modern times, an oil soaked felt pad was a good idea ( sort of ) in the day.
 
You must log in or register to reply here.
Back
Top