Much cooler downpipe

[moizeau]

Been playing with the Zeph11 again. I got it running decent with a lot of help from Al and others on here but always a bit fluffy on low revs pick up under load. Carbs off again (Keihin CVK34), another clean of the pilot circuits. Result was a bit better. Balanced them to within 1 cm of Hg, Played with the Colortune. Very difficult to see, maybe my eyes, maybe because it's got 2 plugs per cylinder so only seeing 1/2 of the combustion? Got it what I think was OK. Running better still but not spot on.

Then got my infrared temp sensor on the downpipes at idle
3 was 120 degs
1 and 4 were 100
2 was 70

So 2 is the same cylinder as I was having most trouble with and put it down to the carb.
What would cause this if not carburation (it may still be)? I have adjusted the mixture screw a lot in both directions and it makes very little difference to the temp.
I'm thinking this may be combustion issue, as in, not a complete burn.

I haven't done a compression check, going to borrow a tester.
I haven't checked the valve cleances, maybe one is too tight?
Anything else?
I have ruled out coils/ignition due to it having 8 plugs and 4 coils.

Thoughts and advice please gents.
Cheers

[Mark W]

Next thing is definitely a compression test,could swap the coils around just to make sure.My 1100 struggled to start when warm and ended up being the induction coil

[moizeau]

Thanks for the reply Mark. The Zeph starts cold with choke or hot without instanly and ticks over fine. I'll try a compression test first, then a leakdown test and see what the results are.
Cheers

[moizeau]

125/1
50/2
145/3
150/4

This is on a cold engine.
Need to try and rig my compressor to the spark plug hole using my cheap compression tester with wierd quick fit fittings and do a leak down test.

[Mark W]

Definitely started to narrow it down,rings,valves or head

[moizeau]

Rigged something up, not very scientific and couldn't be used to do a leakdown test but a way of getting air into the cylinder.

It was leaking but was hard to hear from where then I realised that the vac pipe for the tank tap is cyl 2. Couldn't hear anything but sticking it in my mouth and operating the air gun told my it's leaking from the inlet valve at least. Cam cover off it is then.
Glad I checked with the infrared gun or I'd have just ridden it. It was also a good excuse to buy a compression tester.

[moizeau]

Not the inlet, must have been my imagination or the reed valves are weeping along with the vacuum solenoid clean air thingy and getting back to the pipe in my gob.
Anyway

So 2 inlets are justin and 2 ,justout, his half brother.
No exhausts are in tolerence with no.2 being the illegitimate cousin.

Carbs off again to gain access to the tensioner
Then exhaust cam out, then in then out..shake it all about

[Mark W]

I have taken the tensioner out with the carbs still on but it was bloody difficult to get that long spring back in,it took so long I wish I had taken the carbs off!!!

[moizeau]

With the low seat height there is no room. Managaed to split the cam cover with the coils in place but will probably take them out anyway

[gray]

Just a thought.
Right at the beginning you wondered about ' incomplete burn" . As I remember, the zephyr 11 has 2 spark plugs per cylinder , and i remember reading in a magazine article that having an extra spark plug in the head was to compensate for poor head design. But if 1 of the spark plugs in No 2 cylinder is defective/ loose / stripped its thread in the head that might give poor compression and poor burn on 1 cylinder

[moizeau]

I have taken the tensioner out with the carbs still on but it was bloody difficult to get that long spring back in,it took so long I wish I had taken the carbs off!!!

I have no idea how you mananged that, patience of Jobe of a very full swear box?
One puzzler with the tensioner, the FSM mentions a guide pin. So bolt, washer, spring, guide pin.
Mine hasn't got one and I can't find any reference to one a part from in the FSM.
Did you see one?

Just a thought.
Right at the beginning you wondered about ' incomplete burn" . As I remember, the zephyr 11 has 2 spark plugs per cylinder , and i remember reading in a magazine article that having an extra spark plug in the head was to compensate for poor head design. But if 1 of the spark plugs in No 2 cylinder is defective/ loose / stripped its thread in the head that might give poor compression and poor burn on 1 cylinder

I believe the idea with the twin plugs and the clean air system was to fudge it through emmission laws.
The issue with No.2 was it's exhaust valve was held open.
On first install I went down 5 shim thicknesses and it's still only 0.01 above the lower spec so going down another 2 sizes to get it to the top end of spec

I'm also not going to fit the Clean Air System when it goes back together, just join the 2 outlets from the reed valves together and block to outlets on the carbs.

[Al]

It looks like the late version has an extra part, a rod or perhaps guide pin as they call it. Not present on the early version.

https://images.cmsnl.com/img/products/t ... 1_160a.jpg

AL

[moizeau]

Thanks for clearing that up Al.
Probably to stop the spring trying to tie itself in a knot when you put the end bolt on.

[Mark W]

Well spotted al. Mine is a 98 zephyr 1100 and hasn’t got that rod and I imagine that would make installation a lot easier

[moizeau]

Mark, check your Clean Air System.
On mine the vacuum solenoid is knackered and is always open regardless of how much or little vacuum is applied so the airbox is always feeding air into the exhaust.
The reed valves work but the inner gasket on cyl 1/2 was broken and it was a bit of a mess in there.

When I chucked some air into cyl 2 I thought I heard air flowing in the cam cover but dismissed it as it should be impossible. Having now seen the centre part of the gasket missing.......it was. It was flowing from No.2 across the 'should be blocked off' wall and back out No.1.
Given it all a clean

And now have blocked off the passage ways.

8mm tap, no pre-drilling required, grub screws with 243 loctite