Topic: 400/4 No spark -Update

[MDW]

I just rebuilt the carb and prior to that number 4 cylinder wasn't firing. Now I don't have spark going to 1 or 4. What I have done:

 - Tested the capacitors - both appear good
 - Tested the coils for resistance - both at factory spec
 - Replaced the points for 1 & 4 with a new set
 - I swopped the plug caps and that made no difference i.e. caps appear to be fine

What I still need to do:

 - The  timing may be out (using a test light it stays on for the whole cycle of the engine) but the engine was running prior to the carb rebuild (2 weeks ago)
 - The carbs need syncing

I thought tracking down the issue would be simple but so far I have not found it. Any thoughts on what I could try?
Thanks

[mca2]

Check plugs are good, check for 12v at the feeding side of the primary circuit. Check for 12V and the cables going to the breakers with points open. Check for 0V with points closed.

[Deltarider]

Check plugs are good, check for 12v at the feeding side of the primary circuit. Check for 12V and the cables going to the breakers with points open. Check for 0V with points closed.

Don't expect to see 12V at the points. It will be more like 10 - 11V.

[MDW]

Thanks both. I will have a closer look at this today. I saw that I had about 10 volts going into the coil. Hope at is as it should be?

[MDW]

I checked the voltage at the coil and I have 9.8v in the black/white wire, the same at the yellow but 1.3 at the blue. At the condenser/points on cylinders 2/3 I have 9.8v and  on 1/4 1.6v. I looked for obvious signs of problems in the wiring in different places but saw nothing. Any suggestions where I might look or how best to track down the issue (electrics are not my  strong point!). Thanks

[Deltarider]

Clean the surface of points 1+4 very lightly (4 strokes is enough) with a little file as you may find in your nailclipper. You may need some aceton or alcohol. Do not clean with paper like business cards! Repeat measurement. You should read less than 1V across the points when they're closed and around 10V when opened. It takes very little to hamper the points switching. Paper will fill up the little crater and even after having had a plastic card between them for temporary isolating (to prevent frying the coil), you will need to clean them.

[MDW]

Thanks Deltarider I will try this but I isn't the problem related to not having enough voltage going into the 1/4 coil? I read 10 volts at the black wire and yellow but about 1 volt at the blue which goes to the 1/4 coil. The black/white is the live wire as I understand it but if I also have 10 volts on the yellow (2/3 cylinders). Shouldn't I have the same at the blue wire going into the coil?

[MauiK3]

I'm stuck back where you mention the test light staying on, this may indicate a points wire is involved.

[MDW]

Yes, I cannot explain that unless I have something not connected properly. Please see the attached photo. Everything looks right to me, but maybe a more experienced eye will notice something?

[scottly]

Put a piece of paper between the 1/4 points contacts. Do you still read 1.3 v?

[MDW]

Responding to Deltarider and scottly  - I got voltage readings at the points circled in the photo. So for 1/4:

Breakers/points fully closed - 10v at the blue wire and <1 volt at the points
Breakers/points fully open  - 10v at the blue wire and <1 volt at the points
Breakers/points just open - 10v at blue wire and 10v at the points

I got the same results for 2/3 except when the points were fully closed I got <1v at the wire and <1v at the points. It was quite tricky to get stable readings on both 1/4 and 2/3. At one stage on 2/3 I was getting 10v at both places even if the breakers were wide open. I got that a couple of times then the next reading seemed to be in line with what I listed above for 1/4. Could there be an intermittent fault? I may need to test this again but the readings for 1/4 seem to be correct.

Also I took readings with a piece of paper between the 1/4 points when they were closed. At the points on one side of the paper I got a reading <1v and the other side 10v which still confuses me!

Can you draw any conclusions from this? Thanks

[scottly]

Does the spring have the insulating washer between it and the tab on the points plate? It sort of looks like it's missing or miss-installed, which is why I suggested putting the paper between the points. Compare the 2/3 points for reference.

[MDW]

Do you mean the spring on the on the points mechanism whether it connects to the points plate in the lower red circle on the photo?

[scottly]

Yes.

[MauiK3]

A common problem

[Don R]

 The thing to remember is the connecting screw, the condenser wire and points wire need to be isolated from ground until the points close.

[MDW]

Scottly, Deltarider etc. Please see the photos. As far as I can see the insulation washers etc. are correctly installed. It looks like I can only post one photo at a time so will add the others in separate posts

[MDW]

#2/3

[MDW]

#4/5

[scottly]

Yes, the insulators now look correct, but look at the side view of 1/4, image 5038. See how the blue condenser wire is connected with the end pointing down, close to the points plate? It looks like there is clearance now, but it should be flipped over like the 2/3 side in image 5039. This wouldn't be the first time this is happened, but it's been quite a while, and I wouldn't have caught it without the last pics.

[Deltarider]

There is also a rare risk that the smallest insulator inside the breakerpoints ia misaligned. See pics for the correct assembly order.

[MauiK3]

Additionally, I had the same issue with worn points plate screw heads, I got new ones, at either Partzilla, Z1 Enterprise or Common Motors, they are M5 x 12 (I think)

[MDW]

Thanks everyone. I will flip blue condenser wire over and start her up to see if 1/4 now fire and I will get back to you with an update!
I also saw Partzilla carries those screws but never got round to ordering them yet

[MDW]

Deltarider, in the photo of the assembly order of the washers/insulators etc, where (which side of the plate mount) does the smallest insulator go? Is it with just one of the larger insulator washers or on the side with the nut etc.? I am not sure mine even has them, or where I would find them if it doesn't. Is there a work around?

Also I flipped the blue condenser wire. I haven't tried to run the engine yet but when checking the timing with a 12 volt bulb I notice the bulb is lit for almost the entire cycle of the engine. It goes out a good way before 1/4 is supposed to fire. Obviously this is not right but what are the consequences? The engine was running before when it also had this issue. Thanks

[scottly]

The smallest insulator goes inside the hole in the plate. It keeps the screw from grounding out on the plate.
The light should turn on when the points open at the F mark; the spark happens when the points open. The light should go out when the crankshaft rotates approximately 1/2 turn, or 180 degrees, when the points close. The time when the points are closed is called "dwell", and is also approximately 180 degrees of crankshaft rotation. During this time, the ignition coil is charging up, getting ready for the next spark when the points open. If the point gap is too big, it will shorten the amout of time the points are closed, giving the coil less time to recharge, which can affect the strength of the spark at higher RPM. Since the light is turning off and on now, it looks like the original problem is fixed. Like Maui suggested, you should get new screws, because yours look pretty buggered up.
The lower screw that holds the main points plate to the engine is missing a plain washer like the other 2 screws have.

[MDW]

I checked of the insulation washer that insulate the screw and both points have them. I checked and reset the timing (after buggering up the buggered screw even more and had to find a temporary replacement!). I started her up and all cylinders fired except #4. I checked the spark plug gap of #4 which was correct. I took spark plug #3 and put it in cylinder #4 and put #4 spark plug in cylinder 3. I started her again and all cylinders fired (i.e. all exhaust pipes got hot whereas before #4 didn't change temperature). I would say that after swopping the spark plugs that #3 exhaust felt a little less hot than the other pipes to the touch. I do need to sync the carbs but have no idea why all 4 cylinders would fire after swopping the spark plugs around. Any ideas?

[scottly]

Was the #4 plug fouled or wet with gas?

[bryanj]

Fit 4 NEW plugs

[HondaMan]

Hmmm...could it be a counterfeit sparkplug problem?
I've found those with both the NGKs and the NDs. They cause misfire, if they work at all.

[MDW]

The plugs were new last year. I bought them (NKG) from David Silver. I would say it was slightly wet, but hard to tell. As mentioned, I need to sync the carbs and should now be able to do that as all cylinders are firing. What is a "counterfeit problem"?. I may fish out the old plugs and see it one of them works better. However, I want to start it up again, sync carbs and see if I notice anything different.

[Bodi]

Look up "fake NGP plugs" or similar. There have been a lot of counterfeit NGK and Denso plugs from ebay or website sellers. A trusted store or site (like DSS) is unlikely to have them. There are pics of real and fake ones: the box and plug differences are usually pretty obvious side-by-side like font colour & size, text placement... but the fakes do look pretty good to an untrained eye. And the protection tubes are usually different or missing.

[scottly]

I would say it was slightly wet, but hard to tell.

The #4 cylinder may have been slightly flooded from the process of trouble-shooting the ignition problem. Since it's working now, I wouldn't worry about it.

[MDW]

Thanks

I hope to get to the syncing in the next couple of days and will report what I find.
I am pretty sure the NKG plugs are OEM but I will take another look just in case.

[MDW]

I started syncing the carbs using a Carbtune Pro device. Had some issues to find a stable idle and had to readjust the idle screw several times during the process. I also had issues when tightening the lock nuts on the adjuster screws as it sometimes sent the carbs out of tune again. The Haynes manual says the tune must be in the 16 - 24 cmhg range and no more than 3 cmhg difference between the carbs. I just about got them aligned at 16-18. I also found that when I restarted the engine it needed a quick blast of full choke, even when hot. I have the fuel/air mix at 2 turns out. I also noticed what looked like condensation tripping out of the joint between the downpipes and silencer.

[Mark1976]

I started syncing the carbs using a Carbtune Pro device. Had some issues to find a stable idle and had to readjust the idle screw several times during the process. I also had issues when tightening the lock nuts on the adjuster screws as it sometimes sent the carbs out of tune again. The Haynes manual says the tune must be in the 16 - 24 cmhg range and no more than 3 cmhg difference between the carbs. I just about got them aligned at 16-18. I also found that when I restarted the engine it needed a quick blast of full choke, even when hot. I have the fuel/air mix at 2 turns out. I also noticed what looked like condensation tripping out of the joint between the downpipes and silencer.

  Most of what you mentioned is common, getting them evened out and keeping the idle adjustment screw in the middle of its range is the important part. The adjusters can be and are sensitive when snugging down, just remember they don't require as much tension as you might imagine. Doing the sync with the bike fully up to operating temp is essential.
   The mixture screws are set at 2 turns out +/- 1/2 a turn as per the manual. So while you can try turning in the mixture screw in a 1/4 of a turn (richer), you'll need to do it with the carbtune attached as it could (will) change your sync. That may or may not improve your hot start up.
   Having to use the choke on start up isn't uncommon, as long as once its hot, it returns to idle without hanging and it doesn't stumble on take off or when changing gears. If you haven't, ride it around a bit and see what ya have.

[MDW]

Just a note of thanks to those on this thread. I now have her running reliably, holding idle and no low end hesitation. I do have an issue with vibrations which I will post separately about.