Honda-SOHC

Could this be an effect of ethanol in our petrol?

I may have found the smoking gun. The head gaskets weren't cleaned or wiped when I took the head off, they went straight into the parts tray.

First photo is the left side, you can see oil going from the stud, top right in the photo, across the gasket (and under the head) to #2 cylinder (the lower one )



This photo you can see a similar trail, from the front right stud to cylinder #4.



2 and 4 are my two 'wet' cylinders.

The oil feed to the cams comes up the rear outer studs. There don't seem to be O rings to stop it leaking in the parts book.

One of these things is not like the other....



I'm not sure if I should be worrying about the two pistons with NO carbon, or the two that have coked up that much in only 375 miles. Either way its not right, I'm glad I pulled the head off, I'm sure it wouldn't have lived a long and happy life like that. As far as I can tell I didn't have an air leak from the inlets, everything was tight, the rubbers are new. The plugs were pretty much like the pistons, pale and weak looking on #2 and #4, sooty on the other two.





Until I borrow some calipers, I can't accurately measure the bore to piston clearances. The piston thrust faces are lightly polished, as are the honing marks in the bores.

I'm wondering about the head gaskets. I had been intending to retorque the heads at 500 miles when I did a service, but when I took the head off I was surprised how untight the head nuts were, it didn't take much force to undo them. could the gasket have 'settled'? could oil and/or air have been getting into the bores around the gasket? That could explain both the air and oil where it shouldn't be? Air could get into the 'clean' cylinders (there was a whistle but I assumed it to be induction noise from the airbox), and or oil from the feed studs into the bores. Or it could just be the valve seals, which seemed to be hard and not a great fit around the valves, which had black burned oil deposits on them (they were new).

By the way, Saturdays test ride has produced my first Notice of intended Prosecution for speeding in many years. I saw the van, but too late, it must have been set to long distance looking down the hill I was coming up. At 42mph in a (deserted) 30mph limit, I just qualify for a Speed Awareness course, I looked up the limit and it is up to and including 42mph. Hopefully, it is up to plod's discretion.

I’ll do photos tomorrow but I have the head and barrels off now. Nothing obvious found, though #2 and #4 pistons were unusually clean despite my efforts to ensure no air leaks and balanced carbs, matching the plug readings. Can air be getting down the valve guides if the seals are shot?

First I checked the valve clearances. 7 were in spec, one was 1 thou out at .006. The valve seals are black and quite hard. They weren’t ripped but not a tight fit on the valve. I’d rather find something obvious but it is what it is. The valves, despite being new have black deposit on the stems, so I guess that’s excess oil.

Bores and pistons are new, the pistons are marked as plus 0.5mm. Stock bore measurement is 66mm, mine measure 66.50 which seems spot on. The pistons are ART, which I believe is OEM.

I seem to have lost one of the idler damper rubbers which is worrying, I’ve drained the oil and I’ll drop the sump pan tomorrow to see if it’s made it’s way down there.

Ok I will, it’s looking like the problems are with pot #2. #1 exhaust port is dry, #2 is wet through. As the pipes are linked it seems possible that pot 2 is chucking out oil that gets into #1 exhaust. I notice that due to the way the engine leans forward there are substantial pools of oil around the exhaust valves. The plugs for the middle two pots look lean (is that normal?) it certainly doesn’t look as if #2 was burning all that oil. I’m sure it will all be obvious when the head and barrels are off, I just hope it’s a small thing and not a disaster.

I’m almost ready to take the cams out and whip the head off, but I want to record the valve clearances first. As well as giving me an idea if I need to buy some shims, it may also give me an idea of how well the engine was put together.

Do you know if it was re bored?

Yes, no documentary proof (of anything) but I could see brand new pistons and valves when I shone a torch down the plugholes. I would expect a lot of smoke if it were burning that amounts of oil, there is none at all, just the oil in the pipes.

Well my running in was going well, 350 miles in a week after getting the Z1A back on the road after a long sleep as an unfinished project. The bike is running perfect (apart from a poor tickover when hot sometimes) but I think my valve oil seals are shot.

Saturday I did 100 miles running round the Peak district, I met a lot of people who have had a zed at some time in the past. When I got home, I noticed, to my horror, a load of oil in the ends of #1 and #2 pipes. Also, the oil level had dropped from Max to Min in only 100 miles, a bit steep. When I started from cold, I noticed a puff of blue smoke, but absolutely none during riding. I hoped it was due to overfilling - I had topped up to the top mark in the sight glass, however I would expect some oil in the airbox, and there was none.

Sunday I didn't top her up, I cleaned out the pipe ends with paper and brake cleaner, and went for a test ride. This was the result:



The upside is that those two pipes will never rust from the inside. I should watch for drivers behind me putting on their wash / wipe. Its also on the rim, chainguard and the back and front of the number plate.

I'm guessing that, as the engine was rebuilt an unknown time ago, that the valve oil seals have perished and failed. When I stop on a ride I use the sidestand, which probably pools oil on that side too. If it were bores or rings, I'd expect smoke and oiled plugs if it were using that much oil. the fact it's not oiling plugs makes me think specifically exhaust valve seals, the oil is going straight into the pipes without being burned.

I've seen the Suzuki Viton seals recommended on the Z1OC forum, I'll order a set, also I need a Vesrah top end gasket set, can anyone point me at ones which have the split head gasket (typical Ebay blaggers are advertising sets with single head gaskets as fitting all 900s), if not I can get a full set from Z Power. Never had the head of one of these before, I have a shop manual, but there may be questions. I'll check the valve clearances before I take the head off, to see how accurate they were and give me a heads up if I need extra shims.