Z1 as a project?

[MrDavo]

Hi Roy, I just checked the breather before starting to dismantle. There is a little oil in there, not enough to go up into the air box but enough to show it works.

I’m guessing that I’m going to need to take the barrels off, if only to check that the ring gaps aren’t all lined up!

[royhall]

You may as well, once the heads off the barrels are nothing. May as well check it all while your at it. Who rebuilt the engine? RapSuperbikes did the top end of my GS1000 before I bought it and it was like it had been done by the kids as a day nursery project. I mean 8 thou clearance on the bores, 2 more and I could of got the next size pistons in.

[Laverda Dave]

I had the same situation in my CB250RSA. It drank oil but it didn't smoke. After the inevitable blow up when it was being ridden by the o/h on the M40 the subsequent strip down revealed the rebore had been messed up despite me telling the 'engineer' of the piston to bore clearance and the ring gap. He decided to do his own thing and overbored the cylinder so it wouldn't seize up as a result of overheating. It would have been nice if he had told me what he had done!
If I were you Dave I would check the piston to bore clearance whilst the barrels are off and especially if you don't know who did the rebore.

[MrDavo]

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.

[royhall]

Sometimes these 11th hour problems just make you want to chuck the bike in the back of the garage and throw a blanket over it. I'm sure this is how most "Barn Find" bikes end up there. Good luck with the search Dave, a bit of perseverance will pay off..

[AshimotoK0]

Bummer Dave .. did the P.O. give you any details on what had been done to the engine? Hopefully it will be something simple ... always nice to have a peek inside any engine of unknown build by a PO/'expert  ' and put away any doubts you might have. I would imagine the bottom end will be pretty bullet proof, being a pressed together roller bearing crank. The only Kwak experience I had was owning a Z650B1 that I bought when my yellow 400F2 got nicked. I noticed that Z1 specialist restorers of Z1's RWHS in Market Drayton have started selling quite a few Z650's recently. That
 4-into-2 original exhaust on that model is certainly a rocking-hose-poo item if ever there was one though.

Loving this rebuild and so glad we persuaded you to do a build log on here it. I bet you don't see any  Honda-4 rebuilds on the Z1 forum!

[MrDavo]

An unfortunate consequence of this being an ‘unfinished project’ for the last two owners at least, information becomes third hand at best. Very little info or documents, a 2015 bill from Hagons in the box with the rear wheel led my cyber stalking powers to the last but one owner working for a Japanese bank in the City and living in Canvey Island, but that’s it, I haven’t been in touch. But I know it was a project at least 6 years ago, probably a lot longer.

I was told that the engine was rebuilt by someone who was ‘ex BSB’ but he could have made the tea for all I know. How long ago is anyone’s guess, although imported and UK registered in 1995 it hasn’t come up as on the road since Swansea started publishing records, not sure which year that started.

Anyway when I get in there (I was tempted to whip the head off before putting the engine in last year, but took a calculated risk) I should know if it’s right or not. The puff of blue smoke on startup makes me think its exhaust valve seals. My 911 does that, I'm sure for the same reason, but they are 36 year old seals, as far as I know.

A pair of topless photos I took last night. Nothing much to report other than all very clean with no signs of scuffing on the cams.

[Bryanj]

Looks clean,  there is a special tool for shim changing and if you are going to lap the valves you may need one
HINT
Dont get anal about valve clearance there is a max and minclearance, use two feelers and as long as the small one slides in and the big one dont thats good enough

[royhall]

Amazing how much that looks like my GS1000. Suzuki eh!! I thought they would have been happy with all the knocked off two stroke technology but no, it appears they like stealing from all quarters. That said the Suzuki is a cheaper made version and inferior.

[Laverda Dave]

Looks clean,  there is a special tool for shim changing and if you are going to lap the valves you may need one
HINT
Dont get anal about valve clearance there is a max and minclearance, use two feelers and as long as the small one slides in and the big one dont thats good enough

Strangely enough I had to get two new inlet valve shims for the Z400J after rebuilding the motor. I gave all the valves a very light lapping in but this was to get rid of a very light carbon deposit (I could have used my finger nail to get it off really). Considering the motor only has a genuine 420 miles on it I didn't think it would need any reshimming. After I put it all back together I found No.1 and No.3 inlets were 3 and 2 thou under the specified clearance of 10-15 thou. The remaining 6 valves were mid point between min and max.

[royhall]

15 thou sounds like a big gap. Are you sure. The GS1000 is 1 to 3 thou?

[Bryanj]

From memory the 650 has under bucket small shims where 90 and suzuki have over bucket big shims

[kevski]

Dave the plugs showing lean makes it appear like the problem is above, valve guide seal could be shot, not on or guide badly worn, before removing cam caps strap down the cams as these are notorious for stripping the cap threads, also these normally get small cracks between the spark plug holes and the valve seats and are very rarely anything drastic, if the motor was rebuilt at some stage there should not be a need to lap the valves in, i will hedge my bets here and would not be surprised if it's a guide seal problem.

[Laverda Dave]

15 thou sounds like a big gap. Are you sure. The GS1000 is 1 to 3 thou?

I'm getting my measurements mixed up again Roy!
Inlet is between 0.10-0.15, two of mine were at 0.7 & 0.8 and so were a bit on the tight side.

[MrDavo]

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.