78 KZ650 with some Questions

Hey guys,

I have been lurking for a long time - reading lots and lots of posts. It seems that it is time for my first.

I have a 1978 KZ650B with just under 27,000 miles on it. It was given to me by a friend who left the country a year ago and was in somewhat neglected shape. Over the course of the past winter I have pulled most all of it apart and gotten quite familiar with things. I did a carb cleaning - not rebuild but a major disassembly and soak, clean, etc., replaced all cables, tires, a variety of electrical bits, and what have you. Installed Dyna electronic ignition, 3 ohm coils, new plug wires, NGK resistors, etc. It has an aftermarket 4-1 exhaust that I eBayed and repaired, stock air filter, and the main jets in the carb are marked as 95. It had a 4-1 on it before that was rotted out - so I don't know if the jets have been changed in the past to accomodate the exhaust or not. I left them as they were because it ran alright previously.

Since the re-assembly I have put a little over 500 miles on the bike and enjoy it immensely. The power is great throughout the range, doesn't seem to have any dead spots or hiccups. These bikes just want to pull and pull! Its always had trouble starting with the starter - I think the starter clutch is nearly dead; telltale slippy clanky noises. It also has always had a touch of smoke out of the exhaust before its warmed up. This seems to be more defined if it had a hard time starting after sitting for a week or so, usually needing several kicks.

I changed the oil out twice, each time with a new filter. The first time I used a Valvoline 10-40 motorcycle oil, the second time(current setup) I used 15-40 Rotella T based on some recommendations here on the board and the fact that it was relatively cheap and I didn't anticipate on keeping it in there very long.

The main things that I am concerned about at this point are:

1.) Smoke.

It seems to be smoking pretty much all the time right now - I seem to associate this with the last oil change, but I am possibly just more aware of these things now. Its a light white smoke, with perhaps a very slight touch of blue to it. It is not a lot of smoke or very thick, but enough to bother me about the engine's current condition. It is definitely not a thick stinky oil smoke as I have experienced on several cars in the past...but I wouldn't discount that it may well be oil.

I am in the process of getting hold of a compression tester - I know that this will provide me with far more usable information - I just don't have that yet. It doesn't muddy up plugs too badly, they are a little sooty, but not oily. Inspecting inside the cylinder through the plug hole shows a very polished cylinder wall surface, typical crusty black carbon buidup on top of the piston, and a small bit around the edges of the valves.

Could the different oil be giving me grief with the smoke? Nothing is burping up into the airbox - the filter is clean. I imagine the valves could stand to be adjusted, as I don't know when they would have last been serviced. There is a bit of top end chatter...

2.) Idle.

The bike is really cold blooded and requires a pretty full choke on most all but the hottest days. I typically put on the full choke, turn the throttle screw in a bit, and give her 2-3 kicks and it will start right up. It will run at about 3k, then warm up a bit and jump up to 4-5k at which point I reduce the choke and it comes down accordingly, then I back the throttle screw off a bit, repeat the other steps, etc. until she requires no choke and idles happily at 1800 - 2000 rpm. If I back off the idle screw more, then the engine gets quite grumpy and clattery. At this point I drive off and maybe a half mile down the road at a stop I back the throttle screw off some more. The lowest that it will run happily is 1500 rpm when its fully warmed up.

I imagine/know the the carbs need a good vacuum sync, as they have only been bench synched by me before installation. I notice that the number four cylinder is running a bit hot as well - the paint has burned off the header pipe much more so than on the other three.

Could this also be related to having the wrong size main jets in the carbs?


I'd appreciate your suggestions or prior experiences with the these type of issues. You can just point me to other posts I may have missed or write back a response in detail. I'll attach a few photos for your enjoyment as well..

Thanks,

-Pete


Post edited by: SenorPedro, at: 2007/08/19 21:35

More

and more

Hey welcome to the forum,

You did a nice job on the bike, it looks great.

At first I thought "95's are on the small side for a 650 with a 4-1", but you live in Oregon so if you're at a much higher elevation they may be fine. My stock 78 650 has 102.5's. The main jets varied on different models and years of the 650, I guess Kaw was trying to meet EPA regulations back then. I would think it should have 105's or 107.5's, but the way you say it runs sounds like it's doing all right.

I think it may be hard to tell if the mixture is correct if it's burning a lot of oil at the same time. But you say the plugs are "sooty, not oily" so I am not sure what to offer in the way of advice. Well let me take that back.

Check the voltage to the coils and see if you get 12v or more. If you get less than 12v then that can leave you with sooty plugs. It's good to have new ignition components too, nice choice there.
What plugs does it have? NGK7ES or the 8's? If you have 8's then try 7's, they run hotter and may correct the soot issue.

Check the compression on a warm engine, then add a teaspoon of oil to each cylinder and run the compression test again. Notice if it goes up a whole bunch then the rings may be worn. If it doesn't go up at all then check and adjust the valves and check compression again.

Usually smoke at startup that goes away indicates worn valve stem seals. You have to pull the head to fix them.

Really nice bike man, hardly looks like it was neglected. With your idle problem, it sounds like the carbs might need cleaning and might I prescribe my cure to you? I use gumout carb cleaner that cleans carbs and and intake valves and increases compression and you feel the difference. OKC kent is right with that stuff you may have to check such as piston rings,oil seals and guides on the valves. Bad oil with alot of junk in it can actually wreck a good bike, like 80 grit sand paper on a shiny paint job. If you want a simple fix for now switch to 20w-40

Since it has sat up for a long time, the rings may be stuck, meaning the oil ring, and its letting too much oil on the cyl walls, it might free up some with running, hard to tell.

The bikes are cold running untl they get warmed up, normal

The bikes will get a cam chain rattle if the carbs are not in sync, and this could be part of the idle issue also

Have you checked to see if the carb holders are leaking and allowing air to be sucked in at low idle? Ed

SenorPedro wrote:

. . .1978 KZ650B with just under 27,000 miles on it. .

I think the starter clutch is nearly dead; telltale slippy clanky noises . . . hard time starting after sitting for a week or so, usually needing several kicks.

1.) Smoke.

it may well be oil.

2.) Idle.

The bike is really cold blooded and requires a pretty full choke on most all but the hottest days . . . The lowest that it will run happily is 1500 rpm when its fully warmed up.

Ideas:

Smoke . . .

Valve seals.

When they deteriorate, they allow oil to seep between the valve guide and valve stem, causing smoke. A compression test will probably tell you that you are getting good compression. The better the comopression, the more vacuum is going to be available to pull oil past bad seals. Other than pulling the head and valve train to get access to the seals, it is a nuisance, mostly.

Idle. . .

Your pilot circuit is not right somewhere most likely.

It looks like you have the same carbs as I do, with a fuel metering screw in the front of the bowl, under the carb. They meter fuel, not air. The further you turn them out, the more fuel they will admit.

Try turning out one at a time, and notice your idle speed.

The manual says to turn them out until the idle speed doesn't pick up any more. You might have to readjust your idle speed a couple times to bring it back into line.

I was able to readjust mine to get a smooth hot idle at 800 rpm.

And instantaneous ignition, no matter how long the bike sits between rides.

Thanks for all of your input guys, its helpful and good to know that you like the way its looking.

Still have to get the sidecovers back from the painter - he melted the first one! Gauges also need to come down a bit, etc.

Anyway, I got ahold of a compression tester today and checked out all the cylinders. Bike was warmed up, switched to "off", and throttle was held open while kicking vigorously.

I saw number one come up to 110, then let the gauge back down, kicked some more...thinking "ok, low compression. Thats it. Bummer." Kicked some more. Picked the gauge up - 200, kept kicking, kept kicking, finally topping out at a whopping 220psi!

The results for all cylinders are as follows:

1 - 220 psi
2 - 210 psi
3 - 210 psi
4 - 220 psi

So, it seems to me that the valve stem seals and piston rings are in pretty fine condition. The Clymer tells me that 180 +/- 15 is the target. Is it possible that my carbueration system is so jacked up that its smoking?

I took a pic of a plug - it is typical of all four. Kind of sooty, not oily, seems like maybe its running far too rich? Time to check some more things out I guess...

Post edited by: SenorPedro, at: 2007/08/20 21:50

Plug

I am having picture problems...

Post edited by: SenorPedro, at: 2007/08/20 21:54

on a compression test, you want it to turn over 3 times for your reading.
sooty plugs can be ignition as well as carb related, you might try wgs coil mod, to help.

a good carb sync job will help also

This coil mod sounds like a very good step in the right direction...