1970 Honda CB 100 Problems Solutions
I’ve replace evrything on this bike, points, stator, wiring harness, coil ignition switch, still no spark. ny ideas?
need to find the timing marks
I am assoming that you are talking about the marks on the points plate.
Before you put the points and point plate on, check the spark advancer for proper function. Twist the point cam and it should snap back to the correct original location.
If not MARK the relationship between the point cam and the advancer base. HINT. you can put it together backwards and the bike will NEVER run!
The points should mount up on the plate with no problems, other than check carefully where the point wire goes onto the insulated bolt and don’t let the terminal end get grounded out on the point base/plate. Point plate and points should install so the points are at about 10-11 o’clock location when the plate is secured to the cylinder head. The point wire enters the point base plate at the far right and runs underneath the point cam to connect with the contact breaker on the left side.
When installing new points, be sure to check and clean the point faces of any grease or oil that is a preservative. Put a drop of oil on the felt and a light coat of point grease (if you can find it anymore at auto parts stores) on the point cam. Because the point rubbing block is new, the little high spots will wear down initially in the first couple of hours of operation, so you will probably have to come back and recheck the gap and timing after some run-in time.
The gap needs to be about .014-.016 checked at the highest point of the point cam. Turn the engine over with a wrench and watch the points open and close, then observe where they are open the widest and check the gap with a flat feeler gauge. If you set them about .016, then they will close down to around .014 or so after they have seated in.
This is how it is done in a perfect world of new, unworn parts.
The inherent difficulty here lies within Honda’s choice to cutaway the cam bearings to facilitate camshaft installation. This area tends to wear rapidly, causing the camshaft (and point cam) to wobble around during rotation, even when the camchain tensioner is fairly snug. If you grab the end of the point cam or camshaft with your fingers, try to move it from side to side/up and down. ANY movement will translate to a change in the point gap, which makes a change in the ignition timing.
If it is really loose, the timing will be difficult to set and the running timing will be erratic. The only way to fix it is to put on a new head and cam and/or POWROLL may still be able to convert the head/cam to a needle bearing design. all a lot of work and expense for a 30 year old tiddler bike.
The timing, once the gap is set properly, is adjusted by moving the point plate back and forth until the points JUST BARELY open when the F flywheel mark is aligned with the pointer mark on the case. You can check this with a 6v test light or a ohmmeter or audible test unit. Recheck the point gap when you move the plate, as it tends to change the gap.
Go back and forth until you have both the proper gap and the correct point opening moment set.
This bike MUST have a fresh 6-volt battery installed to run. It is NOT a magneto ignition.
Hope this helps out. Let us know how it goes.
stuck in gear
The bike has a bent shift fork. This means the engine comes out and must be totally torn down to fix the bad fork. The top end comes apart, the flywheel, electrics, shift shaft, clutch, main drive gear, kick starter. shift drum index wheel assembly all come apart then the gearbox gets split open for access to the shift drum and forks. This is not a job for the home mechanic.
You have a few more problems I had best mention.
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