Can't restart bike...what am I missing?

Topper wrote: This still sounds like a fuel supply issue to me, but tell us more about this:

"Can only get it to about 800 RPM's with 1/2-full throttle"

If you give it more throttle at this point does it die? Or do the RPMs go up? Also, what's going on with the choke through all this?

I agree that it sounds like a fuel supply issue. I would do this.

1) After the petcock, disconnect the fuel line from the carbs and run longer tube over to a gas can and open your petcock. Watch the fuel coming out of the end of the tube as it pours into the can. It should be freely pouring. Let it run for a while to make sure it continues to flow freely. This thread has lots on how to properly open your petcock, but believe me, you wouldn't be the first to do this wrong. If fuel isn't freely pouring try different petcock positions until you figure out your petcock. Vacuum assisted petcocks should only pour fuel in the prime "pri" position when the bike is not running.

2) Turn off the petcock and hook the tank hose back up to your carbs. Now attach a longer piece of the tube you used to check the float height to the bottom of one of your carb float bowls. and run that tube over to your gas can. Again, open your petcock. Fuel should be freely running out of this bottom of the float bowl. Again let it run for a while to make sure fuel is freely running. Now check the other carb float bowl.

3) If you have a vacuum assisted petcock and the above check showed free flowing fuel in the "pri" setting, for now just run you bike in the "pri" position so you have no worries about the bike getting fuel. Just remember to turn the petcock off when you are done for the day.

4) Now try to run you bike. If you still have trouble it's not fuel supply.

5) You also say you can only get 800 RPMs at half throttle. That sounds like a vacuum leak in your carb system.
Vacuum assisted petcock: In this case remove the vacuum hose which connects from the petcock to one of your carburetors. No fuel, by the way, should leak out of the vacuum nipple on the petcock. Now plug the vacuum nipple on the carb with with a plug. Your other carb should have the same vacuum nipple with a plug already on it so use a similar vacuum plug. Any auto parts store should have them cheap. Since they are so cheap, I would replace the plug on the other carb. These vacuum nipples are used for balancing your carbs as well so remember where they are for later balancing.
Standard petcock: Check the vacuum nipples on the carbs and replace as needed.
All:Now look around for other potential locations for vacuum leaks, most important on the engine side of the carbs. Are the rubber boots connecting the engine to the carbs cracked and degraded? If they are you need new ones, but as a stop gap you may be able to fill them with silicone calk for a short term fix. Make sure the silicone is dry before attempting to start. Are there other nipples on the carbs that are not plugged? If so plug them.

6) Now running the engine again.

7) Still doesn't work? Well maybe you are flooding. Leave the bike off and on the center or side stand with the petcock open so fuel can freely flow to the engine.. Now go do something else for an hour or two. If you come back and find a puddle of fuel under your bike or fuel in your air box then your float needles aren't fulling seating. Some will tell you that a little leaking is not such a bad thing, but I wouldn't buy it. Get new float needles and seats. I prefer the rubber tipped needles for the best seating. In my opinion you should be able to let your bike sit indefinitely with the petcock open and not drip a drop of fuel from your carbs. In my opinion the only reason it's a bad idea leave your petcock open indefinitely is that gas evaporates from you float bowls causing varnishing. If you leave the petcock open and park your bike for a long time you can evaporate all the gas in the tank through your carbs instead of one float bowl's worth.

Now for a bit of carb adjustment sacrilege. The float bowl level adjustment isn't that critical particularly when running on the center stand. The bike has to go up hill, down hill, and through the twisties. The float adjustment is done to make sure the bike works at top performance in all these conditions. This means when you are running on your center stand you just need to make sure the fuel level is near the top of the float bowl and not flooding. I have never met a Japanese carb that didn't run the pilot screws at 2.5 turns out as the pre adjustment starting place. After you get the bike running, ride it and get the bike good and warmed up. Then adjust all our pilot screws at the same time and always to the same number of turns. After you are warmed up, pop the RPM and drop the throttle. If the the RPM don't snap back to idle you need to adjust. One way, the idle will drop too low. The other way the RPM will slowly drop back to idle speed. Adjust to get the quick snap back to idle. That is how I do it anyway.

good luck.

So I managed to recheck valve clearance and points gap this evening before it got pitch black. Couldn't get to the timing but I'm pretty sure it's right. I'll check it again when there is daylight, without rain.

In terms of the petcock. I had a clear tube hooked up to both carbs. With the bike running, the float levels maintained their levels. I'll take a closer look eat them again when weather and daylight permit.

I've attempted to find another petcock in the event that mine is insufficient. '77 kz400 d4 has two options for a petcock. I can't seem to find a NOS replacement for my existing petcock. I can only find the other option which I believe to be too large of spacing for mounting holes. I'll keep looking although I'm pretty certain my petcock is functioning properly. I'll check per jakedude's recommendation when I have time.

One more thought on fuel supply. Perhaps your tank breather is plugged. If it is, as fuel drains from your tank it will create a vacuum and the fuel will stop. The checks I mentioned should catch this. You might however simply run the bike with the fuel cap lose or off while you are getting the other aspects of getting the bike running properly. On my KZ1000p the tank breather is in the cap. I don't know where yours is. If it doesn't run any different with the cap lose or off your breather is fine.

It's been suggested before that I should run it with the gas cap off because of the possibility of what you describe. In the past ice done this. However, I had forgotten to do it this last time. However, the bike is acting the same exact way as before so I doubt I would have got a different outcome. However, I'll be sure to do it next time I run the bike.

Ok... Please bare with me.

I'm not sure exactly how to ask what I'm wondering. Nor do I know what it would mean (although I think I have an idea.) I was doing a little reading on KZ400.com and noticed something that was in the manual, which I remember seeing.

If you refer to the image below, you will see the instructions to checking the valve clearance. According to this and the service manual, once TDC is reached, continue to spin the crank "approx[imately] 1/4 turn until the T mark...aligns with the index pointer on the primary cover..."That makes perfectly good sense to me, pretty easy. However, when I've preformed this step, what should have been approx. 1/4 turn (say ~90 degrees) to reach T was more like 10-20 degrees. That's somewhere around 1/32 to 1/16 of a turn. Much less than what I see in the photo below and the manual I'm working with.



Is it possible the relationship between the camshaft notch and the index point on the engine head isn't set properly? According to the video below, the sprocket can only go on one way. So that would mean the relationship between the camshaft notch and camshaft sprocket are always correct. My thought is that maybe the camshaft notch was not set properly by someone that was previously in there.



I'm not seeing the video I was mentioning. It can be seen here.

Does or would this make any sense?

I suppose I might try to ask this another way. Is it possible to have the cylinders at their highest point (TDC) yet have the Timing Advancer Assemble in an incorrect position?

Nduetime,
Many of us have been where you are so don't worry about any of us losing patience.

I don't own your bike model so I can't be much help on your valve adjustment, but there has been good advice in this thread, particularly from 650ed, and Patton.

I think you should step back and reevaluate your situation. For your bike to run you need fuel, spark, compression and reasonable timing. Check in that order. Follow the old adage "keep it simple stupid." Always start with the simple and cheap fixes. Your bike does run even if it is for just a short time. Don't give up, you are almost there.

Take a look at this link for the 1974-1977 KZ400.

home.online.no/~ivbekkel/Workshop%20manu...al%20Page%201-72.pdf

I think you will find better instructions (see images below). Notice it mentions going 1/4 turn counterclockwise from when the inlet valve opens and closes not from TDC. Remember - the inlet valve closes well before the piston reaches top dead center. Otherwise the piston would not compress the air/fuel mixture. Ed

I see the difference now...it's after the inlet valve has opened and closed, not necessarily the piston. Right?

Nduetime wrote: I see the difference now...it's after the inlet valve has opened and closed, not necessarily the piston. Right?

Exactly. Ed

650ed wrote:

Nduetime wrote: I see the difference now...it's after the inlet valve has opened and closed, not necessarily the piston. Right?

Exactly. Ed

I'm such a tool! Thank you for clarifying that.

-b.