Reading the Z head

[Kool_Biker]

When I removed the head of my Z, following its 175 Km self destruct, this is what its combustion chamber tops looked like:

P1070042.jpg

I noticed that 2 & 5 exhaust valves seemed to be running appreciably hotter than the rest, and wonder if this is incidental or trying to tell me something about carburation. Prior to switching off and dismantling the head the bike was run statically and revved for quite a few minutes.

Cheers, Aris

[daves79x]

Aris:
The different colored valves on 2 and 5 probably means something, but not sure it's a worry. I've really never had the opportunity or inclination to view a head that way. Is there some other reason you suspect the carbs may not be 100%? I know you referenced possible ignition and carb fiddling yet to be done on the bike. I'm sure you've checked all the usual suspects(compression, air leaks). Do the carbs sync well with gauges (assuming you've done that)? Idle smooth? Does the bike 'lug down' to maybe 1500-2000 rpm in top gear and accelerate away smoothly (although not very briskly) from there? I don't remember a whole lot about your description of rebuilding the carbs. Did you note anything really unusual while in that process? I know you pulled the pilot jets. Did you confirm all slide/dome combos operated smoothly? An oft overlooked job is to clean the tower on the slide and the corresponding receptacle in the dome and be absolutely sure they operate smoothly.

Also, as you know, 2 and 5 are connected electrically as well. Possibly why you referenced ignition issues. From your description, your bike seems to be as well sorted as 99% of the running CBXs are. But I know you are looking for that last couple of %! Keep us posted!

Dave

[Kool_Biker]

All good stuff Dave, especially the thing about 2 & 5 sharing the same ignition circuit.
I am absolutely not stressed about it, but thought I would ask any way ... after all it was a very sick bike (remember??) back then.

Having said that, I have 3 problems yet to solve:
1. There is a misfire between 2K and 3k, not always, but can get from almost imperceptible to annoying some times (sounds like pinging) - this I will solve.
2. There are 3 or 4 cc of fuel coming out of the carb overflow tubes and onto the garage floor, EVERY time after I take her out for a spin - again I know this I will solve
3. There is more vibration (above 5.5K or so) coming from the engine than I would have expected from a fully balanced 6 - this could be (more) serious and something to look at later.

For now, I have lowered the engine, removed the valve cover and looked at the cams, with all looking good exception for the alignment of the inlet cam (easy to fix). Also valve clearances, as measured, are what I would expect from a running in engine - again, few swaps, easy.

But I have removed the carbs as well (of course I am a masochist), and plan to clean them again as I have my suspicions; my tank was quite dirty 1000 Km ago (it is now clean) ... So I will give the carbs a careful look over in the process.

It is amazing how I can do all this with my eyes close ...

Cheers, Aris

[preston]

You could have the 2-5 ignightor going out ( as Daver had mentioned the 2-5 ignition linked) You wvwn mentioned a misfire--- Look at the ignition closer in my opinion seeing 2 and 5 combustion chambers and the reading.

Preston

[Kool_Biker]

You are right Preston, and it is definitely in my radar.
But how do you test for 'an ignitor going out'?
Below is a 'before' and 'after' pic of my ignitors - any tel tale signs at all?

DSC02846_1.jpg

I was always wondering why one of the 3 ignitors is 'stepped' but never gave it much thought.
Aris

[daves79x]

Aris:
Looks like the stepped one may have been replaced - it can be done. Any splicing of wires? The only way I know to check is to swap with another one, which you probably don't have laying around. And they aren't the easiest part to change. I or someone closer could loan you one to try.

Dave

[NobleHops]

<coughDYNAIGNITIONcough>



N.

[EMS]

I have replaced the ones in my '79 with the later design from the Prolink. These are the red shrink wrap types and they are "leak-safe" according to Honda. You have to make a pigtail to adapt to the wiring, but it is fairly easy. With the pigtail, I was also able to relocate the OKIs into another place that gets more airflow.

[Kool_Biker]

Aris:
Looks like the stepped one may have been replaced - it can be done. Any splicing of wires? The only way I know to check is to swap with another one, which you probably don't have laying around. And they aren't the easiest part to change. I or someone closer could loan you one to try.

Dave

Thanks Dave, much appreciated.

Right now I am concluding my 1K Km service. Once I put the bike back on the road, and assuming the 'misfire' problem persists, I will look deeper into it.

Best, Aris

[Kool_Biker]

You could have the 2-5 ignightor going out ( as Daver had mentioned the 2-5 ignition linked) You wvwn mentioned a misfire--- Look at the ignition closer in my opinion seeing 2 and 5 combustion chambers and the reading.

Preston

How do these ignition units 'go out', other than failing outright?
If anyone has the experience: Do they deteriorate, do they give some advance signals?
I had a look at their (presumed) schematic in the 79' shop manual. Seeing some of the caps utilised I could see ways they would deteriorate and begin to go gradually rather than go out in one go.

SCAN0001 - Version 2 (1).jpg

Thanks, Aris