Topic: I changed the rear tire, now it will not start.

[Salem350F]

I know there are similar post to this, but I started anew thread anyway.

CB-350F 1972

I seemed to have everything running well, then I worked on the drive train, new rear tire brakes, chain & sprockets, after the bike was down for several days I went to start, nothing, I finally got it going but now it will not start again.

Complete tune up done: New points, plugs, ignition wires (I thought these were the culprits), valves set.

Might start with the kicker, electric starter just draws down the battery.

I have a spark and it is not too bad, blue, but no snap

Voltage check: battery (new) 13.4 V,  across the points 10.2 V

I suspect the generating system might not be working.  I got the bike running two nights ago took it out for a 6-mile spin, Ignition seemed to break up @ 7000 rpm.  I will check that out when I get the bike running again.

Another issue seems that the timing will not hold.  I have set the points and timing many, many times because I feel that I am chasing an ignition problem.  There seems to be a lot of play in the point plate when I go to tighten it down it shifts so the exact setting floats around.  Is this common? It seems that I should be close and get it to start and run, but usually I get a few pops but no start.

Carbs. were rebuilt this winter, and when I get it running it runs well up to @ 7000,  idles very well.

I am pretty sure it is a ignition problem, I am especially concerned about the big voltage loss to the open points, I know it is a funky set up through the kill switch, but is @ 2V too much?  Are there any common areas to look for voltage drop problems?  I am planning to go through the wiring with a fine tooth comb tonight.

I have the battery on trickle charge right now, and see if the charge being up there helps me start.

I have gotten to the point where I am going crazy, maybe someone could come up with some ideas to help me?

[bryanj]

Getting both the contact gap and timing spot on is an aquired black art akin to witchcraft hang in there and just make small adjustments with the screws only loosened just enough to move things and you will get there

[Bob Wessner]

As for the timing plate, I've found the same problem and attributed the movement to having loosened the screws too much so when tightening them, there is more "travel time" under the screw. I now just loosen them enough to allow movement of the plates with some effort using the screw driver tip and the pins and slots on the plate. Then retighten the screws when done.

[TwoTired]

I went out and measured my 77 CB550F for grins.  This is a good running, easy starting bike, unless it sits more than a month without operation.
Ignition on (and headlight) 11.40 Volts at battery (engine stopped)
Across open point set 10.16V
So, I lose 1.24 volts through my wiring.  It's all stock and I've never cleaned the connectors...yet.

Using your numbers, you're losing 3.2 volts through your wiring/connectors.
Were I you, I'd check the connectors for corrosion and correct.

FYI.  The voltage at the points will be even lower during electric start when the 300 amp starter motor sucks down the power.

The points plate probably doesn't fit into the mount bosses on your motor very well.  Any lateral or vertical movement of the plate, also changes the point gap and therefore timing.  I've seen plate movement amounts greater than the point gap, making precision adjustment, ahem, challenging.  When this is a problem, I stuff feeler gauges into the plate-to-boss gap to stabilize and eliminate the radial movement of the plate.  Set the points gap, and then timing, lock down the plate and remove the feelers.  Bobs note about just loosening the mount screws just enough to get slippage during adjustment is a good one.

[eldar]

One thing you may want to look at, when you go through the wires, solder what you can instead of using connectors. If you can get away with it of course. You will suffer ZERO voltage drop from soldered connections, unless they were done poorly. You also do not have to worry about a solder coming apart, unless it is done poorly again. Just put heat shrink tubing over one side, solder and wait a few seconds then slide the tube over the joint and the residual heat will usually shrink the tubing enough, if not hold the solder iron UNDER NOT ON the tube and the heat will finish the job. Then a little silicon at the ends will seal everything tight.

Like I said, do this only where you can and there are no problems with it.  I plan on doing this when I can.
one final note, if you are worried about telling if a solder joint is bad, just pull on the wires. If they stay together, the joint is good!

[eldar]

Any spot you can lower voltage drop will help your system.

[Salem350F]

Thanks for all the advice!!

Well, I am back in the house after several frustrating hours in the garage.  I made 2 steps forward and 2 steps back.   I found my voltage drop problem.  I was nosing around with connections and found the white nylon plug with the 4 wires to the ignition switch was very warm to the touch.  I pulled apart the plug and found a lot of green crud in there. I scrapped off the crud and then used contact cleaner on it got the voltage up to 11.1V.  I set the gap and timing again trying to minimize the wiggle.  Everything was dead on with the gap and just using a static light.

I couple of kicks and I got it running!  It wouldn’t idle though running around 2500RPM.  I though this would be a good time to check the charging system; I got 14.1V at the battery so at least that is not a problem.  I noticed my throttle cables were not adjusted to allow the stop to sit against the screw. I took it for a road test and could barely climb the hill near my house.  Back in the garage and a dinner break.

After returning from dinner. I adjusted the cables and got the proper bounce and resting against the stop.  Fired up on the first kick.  I hooked up my strobe timing light to fine tune things.  That is when I ran into trouble.  The timing was advanced I would say 3/8 of an inch ahead of the mark, I ran out of adjustment to bring the timing in.  I remember someone saying to open the points a little more to give yourself more room.

I set the points at .017 reset the static timing, triple checking everything after tightening screws and following advice given about tapping with a screwdriver. 

Now I am back to kicking in the 80- degree weather and sweating instead of riding.  No start.

I noticed there were some center punch marks on the advance mechanism so I set to those no luck, I have tried everything, the engine will not run if it is set up to the marks with gaps anywhere between .012 and .017. advance and retarding the timing nothing except a lot of sweat.

I am ready to throw in the towel and get a electronic ignition, but I am worried that the overall timing of the engine might be off, I have had it running and it does seem to run fine but not start, if I get it to start, it runs poorly. 

Any further suggestions and help will be greatly appreciated

[eldar]

Ok now for your timing. Set your points plate in the middle. Now set your points gap. remember to make sure you have the cam set on the timing marks! Now once you have the points gap set, work on static timing. Now you bike may be a bit diferent BUT you should have some kind of fire mark before the timing mark. Your points should open just as you hit this mark. To make this easier, take out the plugs so you do not have to fight the compression. As you hit this fire mark your static light should either go out OR turn on. This sets static timing.

Now start the bike, this should happen easily now. Once warmed up, hook up a timing light. Aim the light at the timing marks, this works best in shaded conditions. The light should turn on right at the fire mark at IDLE. Now increase revs as you do this, there should be ANOTHER set of marks. These are your advance marks. Your timing should increase to these marks as you increase RPMs. If this all works ok, then your timing should be good. If even after you set the static, you have issues, then you have other problems.

This should give you a good start I hope.

[Salem350F]

Again thanks for everyone’s input:

Update: I followed everyone’s advice and melded it together.  I got the bike running again tonight, poorly.  I have fiddled with the dwell meter and the strobe light;  when I get it running it has little power, the points(new)  bounce allover the place.  If I set it as per the Clymer manual for dwell the point gaps are tiny, and the timing is advanced, everything breaks up and doesn’t produce much power.  If I set it up to the factory marks it doesn’t start.  There are two center punch marks that some PO must have put on the advance mechanism, if I set the timing to those it starts and runs

I gave up for tonight, but I am right now ordering a Newtronics electronic ignition.  There is so much slop in the stock ignition system I think it will take a couple of miracles to get everything to fall into harmony at the same time.  I know that it will run, idles well, but no top end.  I am going to fiddle with the points and timing while it is running so I can tune it by ear, and wait for the Newtronics system.

Newtronics system is @$155.00 delivered from the UK.

I will report on how it works.

Thanks for your help

[Salem350F]

Newtronics is from Australia, not the UK, Sorry.