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What a great post. Full of detailed information. See correct information will get you correct answers. I had the same issue with the off idle hesitation and sooty plugs. I have a 1978 KZ1000 stock but for pods, 4 to 1 kerker and Dyan-S. I had rebuild the original VM26's and set levels and played with jets without any change, I recently switched to VM28's with accelerator pump, I just finished the rebuild on them and fired the bike for the first time a few days ago. Still need to vacuum sync and make final tuning. I will be following this post to see how you resolve our similar problem. I will post as I fine tune and hopefully solve the issue. Good luck.

Since my last post I have put 900 miles on my Z1B engine. The engine has 1430 miles on it since it was refurbished (cylinders ball honed and new rings – head fitted with new guides and valves). At 1500 miles I was going to stop the break-in style of riding (acceleration and deceleration) and start normal riding, but at the 1400 mile mark the engine started misfiring. I checked all of the usual suspects in the ignition circuit and all appeared to be in good shape – 12 plus volts across the points – coils, plug wires and caps all had proper resistance readings – plugs taped to head showed decent sparks – ignition timing was off a little, but when that was corrected the engine still misfired – put in another set of points with no improvement in the misfire.

The engine idles normally but starts to misfire between 2000 and 2500 rpm. The misfire is most noticeable up to 5000 rpm and at that rpm any additional throttle has little to no affect on engine speed. I took the advance mechanism off and cleaned it up – it appears to be working normally, and there was no improvement after reinstalling it and riding the bike. For the last 30 miles after each of the 3 check-rides the plugs were removed and checked, cleaned and reinstalled. The plug of number 1 cylinder had carbon on the insulator while the other 3 plugs looked normal after each run. After the last run I did a compression check with the following results: No. 1 – 115 psi, No. 2 – 95 psi, No. 3 – 115 psi, No. 4 – 130 psi. Per the book – spec is 145 psi. After this disappointment we did a leak down test with the following results: No. 1 – 7%, No. 2 – 16%, No. 3 – 7%, No. 4 – 13%. The 16% leakage for the No. 2 cylinder seems consistent with it’s compression reading, but the 13% leakage for the No. 4 cylinder seems inconsistent with it’s compression reading. After gathering this info I took the head off and found quite a bit of carbon build-up on top of the cylinders and around the valves. The carbon fouling problem I had was resolved early in the break-in process, so I believe the carbon build-up occurred in the first 300 miles as the plugs have always looked good since then except for the current issue with the No. 1 plug.

I’m not sure the misfire is related to the condition of the engine, but I want to get the engine (cylinders and valves) in shape before I tackle the misfire issue. The cylinders have been bored 0.5 mm over, so here is where I have my first question for the forum: I understand the cylinder sleeves are replaceable, so should I have the cylinders bored again or just have them replaced? Two mechanics mic’ed the current clearance and both said the engine was at the maximum clearance allowed between cylinders and pistons. To me the safer option would be to have new cylinders installed that have pistons and rings factory fitted to them. Any thoughts? Second question for the forum: I do not want to use machine shop that did the current valve/guide work on the head. I would like to find a shop that specializes in motorcycle engines. I have gone online looking for shops that would accept heads and cylinder blocks delivered to them – do the work – then ship all back to the customer without much luck. Can anyone provide any insight here?

Appreciate any help – thanks.

Brad

You can bore the cylinders another 0.5 mm without any issues. At that point it will be 1015 cc. But the question in my mind is why your compression is so low after the rebuild. Did the cylinders glaze up? Were the rings properly installed? If it was correctly bored and honed, and if you used oversize pistons I'm wondering why piston/cylinder clearance is near maximum recommendation?

You can buy new cylinders...there are a number of sources but I looked at LA Sleeve when I rebuilt my Z1B, although I opted for used rather than new. (So I didn't go with LA Sleeve.)

Try either Pitstop performance, Murdoch racing or APE for the engine work.
All of these are specialists with the Z1 motors and should ship parts in and out as you require as i know they have done in the past.
If you are only 20 thou (0.5mm) oversize then you are currently at 66.5mm and you have another 3.5 mm of material before needing new liners so there's no need to replace them.
That leaves at least 4 more over bores if going up in 1mm increments from 67 to 70 mm.
Go to IMD pistons for stock style replacement pistons and rings.

Also since this thread was started i have begun a choke plunger re-seating service which replaces the worn rubber seats with ethanol resistant VITON.
Worn plunger seats are very likely to be the cause of your rich running if every other avenue has resulted in no change.
I now recommend that the plungers be replaced or re seated before any other jets or carb kits are needlessly fitted when faced with this issue .
At 40 + years old the plunger seats are increasingly becoming the major cause of seemingly unsolvable over fueling, rough running and idling problems.

hardrockminer and zed 1015 - much thanks! Both bring up issues that have been bugging me (glazed cylinders and starter system).

When I remove the cylinder block from the engine I will be checking to see that the rings are properly fitted (correct side of the ring up and gaps in correct positions). However, what does a glazed cylinder wall look like? What causes glazing?

zed1015 I am very interested in your VITON seats - how can I get in touch with you?

Last question - what are the pros and cons of going to something like the Dyna Electronic Ignition system? I would like to eliminate the ignition system as a source of concern - if that's possible

Bald-headed Roach wrote: hardrockminer and zed 1015 - much thanks! Both bring up issues that have been bugging me (glazed cylinders and starter system).

When I remove the cylinder block from the engine I will be checking to see that the rings are properly fitted (correct side of the ring up and gaps in correct positions). However, what does a glazed cylinder wall look like? What causes glazing?

zed1015 I am very interested in your VITON seats - how can I get in touch with you?

Last question - what are the pros and cons of going to something like the Dyna Electronic Ignition system? I would like to eliminate the ignition system as a source of concern - if that's possible

There are no con's fitting a Dyna 'S' ignition.
I have them replacing the points on all my zeds .
They are fit and forget, bigger spark, better starting and performance.
For the best set up fit matching Dyna coils too. either 3 or 5 ohms.
If your cylinders are glazed they will appear shiny/glossy and very smooth with almost a plated look and most of the crosshatching from honing will have gone within the sweep of the rings just like a high mileage bore.
Email me at This email address is being protected from spambots. You need JavaScript enabled to view it. regarding the Viton seats.