Replace Smog valve cover with Non-smog - concerns

Hi All,

I've got an 1983 kz750 LTD which has had the smog valve cover (i.e one with the reed valves installed at top front) replaced with a standard ( or UK standard without emissions control ports) instead. Having read the below quoted thread, re: a 550, I was concerned as nothing had been done to mine other than swapping the rocker/valve covers - i.e no other holes have been plugged internally. My understanding is that the kz engine is just that - no difference between the UK and US models and therefore, a non-reed ported valve cover is fine to to put on as we have no similar emissions regualtions and the engine is the same internal design regardless. in the thread below there is a parts diagram from Aric - I have basically swapped the upper cover for the lower one in the diagram( albeit for a 83 H4 model)

kzrider.com/index.php?option=com_kunena&...85202&catid=3#185202

Please read this thread as it should demonstrate what I'm talking about better.

WiredGeorge - you say in the above threads that there seems to be internal differences under the valve cover, or am I misunderstanding?
The bike has only been running for 15 minutes in 7 months of owning it as I've been trying to do an extensive restoration and repaint - just getting to the engine gubbins now, hence sudden paranoia!

Any thoughts and advice, gratefully received in advance.
Cheers
Ben ( Nottingham UK)

I know that the emission ports in a 750 twin head have to be blocked to use a non emission cam/valve cover, but I don't know about the 750 four heads.

I'll go look and be right back.


Ok, here's the deal;

If the cam cover you are using has four protrusions that cover up the emission ports (if your 750 head has them), then you're fine.

If you can see four holes in the head, one directly behind each exhaust valve, while the cam/valve cover is in place, then you need to plug those passages.



I have absolutely no idea whether the US and UK spec motors are the same, but I rather doubt it.

The Canadian valve cover I got for my '84 1100 blocks off the exhaust holes that feed the reeds. I'm told that is all that is needed.
I think when I adjust the valves and have the old cover off, I'll plug the holes anyway. Can't hurt.
Stephen

Thanks Steell and Darmahsd,

I'll check tonight as to whether or not there are protusions blocking the holes. There are definately no holes showing with the valve cover in place, but I don't know if the ports are actually blocked under the cover - maybe this doesn't matter? so long as the ports are not exposed and are under the valve cover.I'll report what I find.
Thanks for your help.

Now to sort out the choke that doesn't work. And dead master cylinder.And centre stand dangerously close to the chain. And... ;o

Cheers Ben.

>I have absolutely no idea whether the US and UK spec motors are the same, but I rather doubt it.

Just to clarify, I have a US bike/engine but have put a UK valve cover on it.
Cheers

Just no way for most of us to guess the difference in foreign spec parts and US parts. On a 79/80 KZ1000, there are four openings on the cylinder head that go down to the exhaust port just outside the combustion chamber. These ports are covered by the OEM valve cover and tied to the reed valves. If you use a 77 valve cover, for instance, where the engine never had the open ports the later models did, the ports would be uncovered by the early model valve cover. This would mean cold air (backfires? burnt valves? FLAMES?) would come out the ports. You have to use a 79/80 valve cover on a 79 or 80 cylinder head. I suppose that you could tap the ports and install large bolts with thread lock to block the port and use a standard valve cover but again, I am not real sure because the gasket mating surface and gaskets will have a somewhat different shape. On your bike, I can't say for sure... LOOK AT THE CYLINDER HEAD WITH YOUR PREFERRED VALVE COVER SITTING ON IT. Do you see the round openings and ports going down to the exhaust port off the combustion chamber? These will sit to the front of the valve cover if they are there. If so, use the correct valve cover and if not, don't worry about it.

The Canadian rocker covers for '79-80 MKll's and the KZ1100's do not have the smog ports.We've sold lots of them to US dragbike guys who don't need the ports or the ugly blocks on the covers.

Jack, That is good. Do the Canadian spec valve covers cover the ports that lead down to the exhaust runners on a US spec cylinder head? If not, then the ports must be plugged in some fashion and the valve cover will essentially be a 77/78 valve cover except the well where the cam chain idler sits will be bigger as the later heads had a bigger idler assembly and the earlier valve covers won't fit unless the older idler assembly is also used.

>Do you see the round openings and ports going down to the exhaust port off the combustion chamber? These will sit to the front of the valve cover if they are there. If so, use the correct valve cover and if not, don't worry about it.

Well I can't see 'em so I'm officially stopping worrying.

wiredgeorge wrote:

Jack, That is good. Do the Canadian spec valve covers cover the ports that lead down to the exhaust runners on a US spec cylinder head? If not, then the ports must be plugged in some fashion and the valve cover will essentially be a 77/78 valve cover except the well where the cam chain idler sits will be bigger as the later heads had a bigger idler assembly and the earlier valve covers won't fit unless the older idler assembly is also used.

Don't know,but I'll look at my buddy's bike he just bought from the US,the previous owner had bought a Canuck rocker cover to eliminate the smog ports.I've never had a US casting head apart.

ok, time for a side by side comparasion.
the first cover is off a 77 650.
it has no provisions for the smog set up.
look at the top part of it. see how there are no holes?

[img size=150][/img]

and here is one from canada for a gpz.
it has the block offs on the top.
see the four holes?
they go nowhere, they just block the exhaust.

you must either drill and tap them for a pipe plug or find another way to plug them or they will leak exhaust if you use an early cam cover on a later smog head.
look for a canadian cover. but they are really hard to come by.

hope this clears this up for you.