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KZ440A Odd Starting Issue 15 Oct 2018 14:29 #792335

  • gavroyer
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I'm having an odd problem getting my 1980 KZ440A LTD started first thing in the morning. It doesn't seem to matter what I do or where I set the choke, it will not start. Furthermore, I can only get it to pop out the exhaust if the choke is off/down, I hold the throttle open, and then let it snap shut. This causes the bike to pop a few times, and if I do this enough, eventually it'll start going enough to run on its own very poorly, where if I let it sit for a while it'll eventually be warm enough to run fine. If the bike is warm/warm-ish (cool enough that I can put my bare hand on the head without burning, but warm to the touch), it'll start up much easier without any fiddling with the choke/throttle. And any time I use the choke to start it warm, it fires right up immediately.

The start of this problem seems to coincide with replacing the carburetor boots/holders (the carb -> head ones) with new ones, as the old ones were leaky causing the bike to run very lean. This was confirmed with a can of carb cleaner sprayed on them, which caused the telltale idle rise. Prior to this replacement, the bike started up fine with the choke and would not start without it, although it would need to sit for a minute or so before I would be able to ride it and it did still exhibit typical lean-condition symptoms (high idle when warm, failure to return to the set idle point, popping from the exhaust on deceleration, etc). It was only after I replaced the boots that this problem got really bad.

My dad mentioned it might be the spark, but normally I've heard that coils work better cool and get less reliable when hot. I did replace the spark plugs (B7ES) a couple weeks ago (unrelated to this issue). And it seems odd that changing the choke would cause a difference in the behaviour too. I did try leaning the pilot jets all the way, put them at the standard 2.5 turns out, and the backed them out to the end of the adjustment range, all with no discernible change in the starting.

Another friend suggested it might possibly be the valve clearance. Does that seem likely?

EDIT: One other thing I just thought about is that it doesn't seem to matter if I set the petcock to PRI first for a few seconds or not. And when I come to the bike usually it's been sitting for less than a day (usually just overnight) and there shouldn't have been much evaporation in that amount of time anyway, right? Last time I could, I also pulled a plug after a few minutes of cranking and while there was a bit of gas on it, it certainly wasn't soaked or anything, so I don't think the mixture is off too much.

Thanks in advance!
1980 KZ440-A1 LTD

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Last edit: by gavroyer. Reason: Added details

KZ440A Odd Starting Issue 15 Oct 2018 16:21 #792341

  • JR
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1. Set the petcock to PRI and count 10 elephants or time 10 seconds and try again.

2. Routine checking the valves is often neglected. Tight valves can lead to low compression and compression is necessary for engine to fire.

3. If you have old style mechanical points then check timing.

If bike runs fine when warmed up then 2 and 3 are not real likely causes but should be checked as part of routine maintenance.

Drain the carbs into a clear container and see if you have sediment which may be clogging the pilot jets.

Do you have a manual ?

Good luck
1980 kz750E1, Delkevic exhaust

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KZ440A Odd Starting Issue 16 Oct 2018 15:49 #792401

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Points are clean and gapped; they were last checked about a month ago when the starter was rebuilt.

Setting the petcock to PRI doesn't seem to help. I've tried everything with the petcock including setting it to PRI and walking away for a few minutes.
1980 KZ440-A1 LTD

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KZ440A Odd Starting Issue 16 Oct 2018 17:01 #792404

  • Scirocco
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Remove the petcock and look if the internals and/or the filter screens are clogged with rust particles that reduce the fuel flow.
You can try to use a plastic bottle as a temporary fuel tank to get a good fuel flow to the carbs for the engine start procedre.

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KZ440A Odd Starting Issue 16 Oct 2018 17:17 #792408

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You can try to use a plastic bottle as a temporary fuel tank to get a good fuel flow to the carbs for the engine start procedre.

Good idea.

Just a further thought.
Not sure what carbs you have. Does the choke operate an enricher or does it operate a choke flap/choke butterfly on the airbox side of the carb ?

If its a choke flap/butterfly system can you hear the click or snap as it goes from the horizontal position to the vertical ? Happened to me. I was moving the choke lever but the butterfly was not moving.. Interference by fuel line with the linkage. Perhaps something was disturbed when you removed the carbs to replace the boots ?
1980 kz750E1, Delkevic exhaust

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Last edit: by JR.

KZ440A Odd Starting Issue 27 Oct 2018 23:13 #792913

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The carbs are stock carbs (Keihin CV32s iirc). They have butterfly valve chokes, not enricheners. The choke wasn't moving all the way vertical; the tab was too far to the left and it got caught on one of the bolts. However, now the problem is even odder. If I apply the choke, even with the bike warm, the bike will not start at all unless I crack the throttle a lot, and even then it'll only run on one cylinder, so you need to keep the RPMs up around 2-3k to keep it from stalling. And I have to hold the throttle open just a hair to get it to start when it's hot.

So far, here are the things I've fixed/done to try and get the bike starting properly:

1) New spark plugs
2) Points were cleaned, and gap was checked (found to be in-spec)
3) Carb > Head boots were leaky, so were replaced
4) Carbs have been disassembled, cleaned, and reassembled
5) Valve clearance was checked and adjusted to spec (0.008 in).
6) Carbs were synchronized
7) Inline filter was replaced, new fuel line from tank to filter to carbs
8) New vacuum line for the petcock

The chokes do close completely when the flap is up, and they move in sync. They also open to perfectly horizontal when the flap is down. I'll double check the current cold-start behaviour tomorrow morning, since I did get the carbs synced today and that has significantly improved the idle. But I'm not terribly optimistic that the choke mechanism will work correctly with the engine cold if it doesn't let the bike start hot either.
1980 KZ440-A1 LTD

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