1975 H1 center cylinder not firing

[Grant]

Sometimes things befuddle me. I have this fairly nice H1F that I actually licensed and put insurance and plates on. I had started it last year and it ran, not perfect but that should only have been a morning to sort it out............WRONG!
Symptoms are the left cylinder runs fine, the right cylinder runs but doesn't have the exhaust puffs that the left does, the center cylinder on the road will fire about every 500 to 1000' for one or two strokes and the bike surges forward so I pulled the plugs darkened the garage, took the plugs out and laid them on the cylinders. The plugs were brand new B9HS and showed some carbon on the left and right plugs and the center was wet with no carbon. Removed the altenator/timing cover and used a drill and spun the crank with the ignition key on. All three cylinders seem to spark blue the same over a certain speed, which I can achieve with kicking or the drill. Okay, I have spark so the next thing was to switch the left and center carbs, this made no difference. I believe that only leaves timing. My question is can timing be out that much on that bolted plate where nothing was found loose?
Or any other suggestions?

[kawonda750]

I find that it is usually carb setting that do that. Make sure they are synched so that all slides move at the same time. Clean the plugs so all fire well, set air screws and then play with the idle screws.

[kawonda750]

Of course, check your timing first to confirm it is on. Then proceed with carbs.

[Jim]

The part about occasionally firing for a short time doesn't sound carburetor related, and swapping carbs with no change confirmed that. Timing wouldn't jump around to cause the center plug to occasionally fire, since with that system the timing is the same for all three cylinders.

Since plugs are much harder to fire under the pressure in the cylinder, I still suspect a spark problem of some sort. With that ignition system, a lot is in common with all three cylinders. The exceptions are the carbon brushes in the alternator, the wiring from the coils to those brushes, the three coils, the plug wires and the plugs themselves.

[Grant]

I swapped a coil complete with plug lead and cap with another 1975 H1 and didn't seem to get any better running. Though.......I took the bike out on highway 402 and opened it up, it sort of looked like a horizontal NASA launch with a smoke plume to be proud of, I revved it pretty high and got up to 60 mph/100kph with still no good running from the center cylinder. I'll dump the gas and pull the tank again and swap the center coil and wires with the left and see if that makes a difference.
If I let the bike idle and pull up the center carb slide anywhere from a 1/8th inch to 1/2" there is just no corresponding motor rev?
I've never owned a 500 that I had on the road so am not sure as to what to expect, but I did watch and hear several youtube videos and this bike doesn't sound like any of them. Does anyone know of a good triple mechanic in southern Ontario?

[Walms]

Depending where you live, Rick Yates in Ayr ON
Or Curtis up in Peterborough
Both board members, Rick is the creator of this board.

[Walms]

Have you done all the ignition checks?

[Walms]

Fwiw, I've chased a similar problem on my 500 for what seems to be for 2 years, all the iggy checks were done but it wasn't until a couple of weeks ago when I put on my magnifiers that I saw that I had a bad solder connection on the centre pickup on the stator.
The Paris rally, RB's rally etc. I was looking elsewhere for the issue.
It's a frustrating thing for sure!
In my case, the iggy started breaking up at 4.5k but seemed to get better on the pipe but not clean... definitely pulled out a bit of hair on that one! Even left the bike for a month this summer because I was sick and tired of it! Lol

[sf]

Not to hijack this thread.... that's great news Andrew perfect timing this weekend supposed to be a nice one.

[Walms]

Thanks, it wasn't my intent either, just pointing out it can be frustrating to sort these things.
Also, swapping carbs is an easy thing to try.
Basically you want to shift this dead cylinder to another. If swapping coils and leads, then carbs doesn't help, double check the compression on the cylinders... that's all I have, the resource site has all the iggy checks for each model on there.

[Grant]

Well, I've swapped carbs with both the rh and lh sides, no improvement. I've taken the complete stator system from another 75H1 and tried it, no improvement. I swapped the regulator/A/B boards with the same result. Just in case someone was playing with the plug wires, I swapped the leads and couldn't get the bike to even fire up.

I have never had seals go bad on a triple before (just lucky I guess) would this be a sympton of bad seals, the lh cylinder fires perfectly, the rh fires but has lots of smoke but no good exhaust pressure? The center doesn't fire at all.

[Jim]

Try grounding all three coil negative wires to the frame temporarily instead of being plugged into the alternator's distributor. If all three fire when you do that, the problem is with the distributor or the wiring to it.

[Mitch E]

Bring it by my place sometime grant and we can swap ignition and see what happens

[shiloh]

Oct 2, 2017 10:19:35 GMT -5 Jim said:

Try grounding all three coil negative wires to the frame temporarily instead of being plugged into the alternator's distributor. If all three fire when you do that, the problem is with the distributor or the wiring to it.

+1 to what Jim has noted.
When I was building my h2 i had similar issues, it was in the wiring.
Thats your next logical step.
Good luck, keep us posted.