I have a 1971 cb100cc. I CANNOT for the life of me get that bike to run, in a sequence. Points gap is set right, advance seems to work good, it's getting fuel and has good spark. But it still will not

Take a close look at the shaft where the lobe is, is there play in the shaft? High mile bikes the bushing or shaft can wear down and not open the points correctly. You did a good job troubleshooting so far.

check the firing order as you may be 180 degrees out in the order.

Hi,
Looks like you need to tune your engine ignition.
Set the right timing , contact point gaps, and ignition advance .
Check also the sparkplug gaps and carburetor.
Hope that helps!

Try this, (old trick from my GTO). You can set the point gap fairly close using a matchbook with cylinder one at top dead center if I remember correctly.
I remember the point gap being around .015 and a match book is around .012.
You will see the points attempt to open if they are not adjusted right. I used my thumb over the spark plug hole to sense approach of cylinder then manually rotated crank and
set the gap with a match book. This got it close enough to run and set the timing properly. Have someone bump the starter to rotate the engine (and remember to have
them hold the clutch in or be in neutral if you have a manual). I hope I remembered
this correctly.

Generic advice for motorcycle contact breakers

I asume that you know where they are, generally behind the flywheel on a two stroke (mostly on left side of motor) a pain to get at. If you have an OverHeadCam 4 stroke (like the KLX 110) you will probably find the points behind a cover on the cylinder head working off the end of the camshaft as the Japanese realised a long time ago that this was a simple and cost efective way to make and service these items.
You will need to find the engine timing marks located on the flywheel
You will need feeler gauges and some basic tools
What to do.
Take out the spark plug
Take off the points cover
Take off the flywheel cover( oil may or may not leak out from this cover) if in doubt lean bike over away from you when you take it off to see if oil is inside casing.
Find timing marks. You should see i guess two marks. one will be "T" for Top Dead Center or T.D.C. (piston at top of bore) one will be "F" for fire (the point at which the spark happens) this will be Before Top Dead Centre B.T.D.C
There will be a mark on the engine casing( often just a line or dash, maybe a small triangle) to line these marks up with. If you cant find it get the piston to the top of the bore(put a pencil or similar down the plug hole to feel the piston coming up),Do this slowly and be sure not to get whatever you have down the plug hole caught up in the valves as they move. If you feel it snag take it out start again.
Get the piston to the top.
Now if you look at your "T" timing mark it should be close to whatever it;s supposed to line up with on the engine casing

First you need to set the gap of the points. Between .012 and .015 of an inch is right for most bikes. If you have the Kawasaki figure for this bike then use it.
In metric 12 to 15 thou would be .0.3 to 0.4 millimeters
(i think sorry i am old, and always use imperial mesurments for stuff like this)
Use a socket on the flywheel nut to rotate the engine in its normal direction. You will see the "T" mark pass the mark on the engine case, Followed by the "F" mark . At this point the points should be fully open.
You need to set the gap . The feeler gauge should be a light sliding fit. It is easy to set the gap to small not noticing that the feeler is pushing the points open.
If in doubt set the gap and tighten the points up. Get a smaller feeler and see that it is loose inside the points. You have to hold the feeler square and slide it in and out gently. Otherwise you will get a false reading.
Often you find that when you tighten the points up the gap will change. This is frustrating. Sometimes you have to allow for it by seting the gap to big or small by trial and error till you get the right gap after you finish tightening the points up.It's a pain to be honest.
I just set them by eye myself. But iv'e been doing them for years, i know what to look for.
Now you have your points set to the right gap you need them to open at the right time. This is when the "F" mark lines up with the timing mark on the engine case.
There are various methods for telling when the points open. This is much more critical on a 2 stroke where a small error can lead to a melted piston!
on a 4 stroke though, there is a much larger margin for error.
Remember the points only open once for every 2 revolutions of the engine.
The cigarete paper method
You need a cigarette paper, as thin as possible, Blue Rizlas are good for this.
Put the paper (or a small torn off bit of it) in between the points Holding the other end of the paper tug it gently . Turn the engine over as the points open the paper will slide out from between them.
This normally takes several attempts. When you are happy with the result then tighten up the points backplate. It may be possible to put the engine in the right place and move the points backplate clockwise and anticlockwise to get the points to open at the right place.
You always need to turn the engine over a couple of times and recheck as often things seem to change a little. Again it is trial and error.
The radio method
Works if your bike has a battery ignition system
Get a portable radio, set it to an empty space on FM turn it up. put it close to the points
Turn on your ignition
Turn over your engine. You should hear a distinct pop or crack from the radio as the points open.
The Multimeter Method
Ignition Off
Meter set to OHMS
Black lead to Earth on bike
Red lead to MOVING side of contact points.
When the points are closed you should get a reading of 0.00 or 0.01 on your meter as you turn the engine over and the points open the reading will go to 999.99 or infinity you get the idea. If you are new to this having an asistant may help as you seem to run out of hands to do things with till you are used to it!
Your points should now be set. They don't tend to stay in adjustment very long. As a i said earlier it's not so critical on a 4 stoke. I mean the closer the better . But as long a you have a close to correct gap at close to the right time you will be fine.
Hope this is enough to get you sorted. It's not easy working out how to write these things for people. It's a job iv'e done so many times on so many vehicles in my life. I just do it automatically. I thought i could knock this answer off in ten minuets. That was an hour or so ago!!

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.

Hi there
Well you have a good BMC there so set the tappets to 12 thou , but check the wear on the rocker bushes first as they have the point of wearing on top and bottom and setting with stact cold some times still rattle so the best way to do them is start run with rocker cover on warm up to thermostat open then remove rocker cover and set throttle to low idle and run andcheck with 12thou push in and out ,if 1 or 2 are noisy
adjust running to 12th.
Points set also to 12thou with points open to any one cylinder and push cam towards the points with your finger and if it opens to 15 (which it will) then set points to 10 as when auto advance opens up 3deg BTDC
the points go to 15 and your spark could give you a problem at pulling power, also auto advance weights in distributor will send points to open up sooner ,reset throttle to 550 rpm and away you go .
Have a good run

The base setting for the point gap is 15 thousandths. Set the left cylinder to .015 and check the timing with a timing light. Adjust the timing for the left side by moving the base plate up or down. Now change the timing light to the right cylinder and check the timing for the left cylinder. Adjust the timing for the left side by changing the points gap if the left base plate can not be adjusted, ( I can't remember if the left plate adjusts or not ). The wires should not be grounded. Check to see if the timing advances as it should when the revs increase. Below is a photo from an 1979 RD400 owners manual. Yours looks the same.

Go to the site below where you can see a parts diagram for your specific bike. You will select the actual brand, year, model, etc., once you go to the site. Part numbers and prices are also shown. You can order parts from this site. In the event no price is shown on a particular part and/or the notation "Not Available" is in the description, the part is not in stock. It looks like they have points for a 1975 RD350 and they should work on your bike. www.babbittsonline.com/pages/parts/viewbybrandand/parts.aspx

Yamaha can tell from the VIN what exact year and model your bike is. Check with them as I don't think the 350 was made in 1979.

I worked on a bunch of these bikes back when they were new and I was working at Mathews Honda in D.M. Iowa. Bear in mind that was 30 years ago. IF I recall correctly. . . . .

First, the points only open and close. Other than that they don't move. The points are adjusted for gap by being moved L and R then locking down in place with a screw.
Assuming you have a good set of points, set the point gaps to 15 thousandths. The timing is set by rotating the base plate the points are mounted on. Behind the plate is a centrifical advance. Get an inductive pickup timing light and hook it up to the battery. Hook the pick up on the left sparkplug wire.
Start the motor and point the light at the top of the gearbox flywheel. Yes, with the cover removed some oil will spit out. This is normal. Rev the bike and you will see the timing marks. You will also see a static timing mark on the casing. Rotate the points base plate to line up the marks. When you let off the gas the flywheel marks should move counter clockwise. If they don't, then remove the points cover and free up the centrifical advance mechanism. You just timed the engine.

The photo will not open in "FixYa". Email it to me at [email protected]. Would you like to know how to synchronize and balance the carbs?
Include your phone number in the email.

Hi! Not knowing what year your H.D. is? and also not knowing whether electronic ignition or Points? Have you taken a look behind the aluminium round plate With Harley Davidson or H.D. on it usually located on the right side of the engine (as you sit on the bike) By the base if the front Cylinder.
If points check/adjust gap, if Electronic? ignition module may need replacing.
Failing all this try new plugs and leads?
Good Luck! I hope this sorts your problem? if so press FixYa blue button.
Merry Christmas!
Paul 'W'
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