Runaway Idle ???

I have fielded many posts on this Forum over the last 6 months and Everyone has been very, very helpful !

I purchased a non-running 77' KZ1000A a while back and finally have it running after going thru the carbs. completely and setting everything Statically for the points and timing. Even using the old set of points, original coils and plug wires, and old plugs and it fired right up to my surprise,

Not really any unusual noise, but reset the fuel mixture screws ( 1 turn out ) and installed New plugs. Seemed to idle smoother.

Anyway, I have started it several times over the last couple of weeks with the help of jumper cables off my honda Fit and no problems.

Today after I started it and let it warm up for a few minutes, I shut it off then restarted it again after a minute or two.

Here's where the Problem occurred. Gave it a little throttle, then all of a sudden it would not return to idle and began take off with it's Rev's. Had to turn off the ignition key? Throttle is working fine with. the carbs. Restarted again, engine started to run away again with the engine RPM?

Not sure what is going on? It did backfire once when I was trying to start it, but hasn't done that before? Any advice you Guys may have in pointing in the right direction?

For it to start Originally a few weeks ago for the First time and idle the way it did, it would tell me that I had the points and timing set pretty close per FSM.

The only thing that I have changed was fuel mixture setting from 1 1/2 out to 1 turn out and installed new plugs. Carbs. set per FSM and operate fine.

Could this problem be Heat related? It was a little warmer today and I did notice what appeared to be a little smoke coming off the motor?

I pulled the Gas tank and inspected underneath. Couldn't see any apparent thing that jumped right out at me. Felt the Harness, plug wires and coils. Nothing felt abnormal?

Did you buy a battery? If the charging system is struggling charging a bad battery, nothing will work right. Runaway throttle? What kind of carbs do you have on it now? Is one slide sticking? What do the plugs look like. They tell a lot about what's happening in a engine.
Steve

Steve, I appreciate you helping me out on the Carb. forum too.

No, I haven't bought a New battery yet. Have to wait a little for the finances still. I didn't think it would be a problem jumping off my car battery and keeping my car running while the bike is running as well? Maybe it does?

The carbs. are the Stock VM26's the bike came with. And pulling off the dual air pods and looking at the slides, everything looks good?

As I said in the carb. section, turning in the fuel mixture screws did Help. Plugs looks so much better than before when they were dark when the fuel mixture screws where set at 1 1/2 turns out.

Plugs are a light golden brown.

Runaway throttle, When i restarted the bike again with the jumper cables hooked up and my car idling, the acceleration or throttle on the bike just suddenly increased without touching the throttle on the bike?

Ouch! NEVER jump start the bike form another vehicle that has the engine running. That can very quickly destroy the bike's electrical system. I wouldn't think it has anything to do with the run away idle, but don't do it.

For the idle problem check the throttle cables. You can unhook them at the carbs and if the problem persists it is not due to the cables. Then check the carb holders for vacuum leaks. Here's how:

Make sure the vacuum caps are tight on the carb holder nipples.

Warm the engine up to normal operating temperature.

Temporarily set the idle as low as possible without stalling the engine. It should be down below 1000 rpm. The lower the better because when it is set low the carb slides are closed (or nearly closed) and this raises the vacuum level in the carb holders. The combination of the increased carb holder vacuum level and the very low idle amplifies the effect of the leak test.

Once the idle is set low, spray carb cleaner around each of the carb holders where they bolt to the cylinder head and where the carbs attach to them. If there are leaks, the vacuum in the carb holders will suck the carb cleaner in and this will affect the idle. It may cause the engine to stall. If the leaks are at the carb holder / cylinder head mating surface you need to replace the holders. If the leak is where the carbs attach to the holders you may be able to tighten the clamps enough to seal the leak. Some folks use starter fluid or other substances for the test, but carb cleaner works best as it doesn’t evaporate too quickly like ether and leaves no residue on the engine like WD40.

If you do need new holders just bite the bullet and buy them. Trying to seal things up with some kind of sealant or goop will only lead to frustration as it will at best only last a short time. Ed

Ed's right but if the carb boots are hard at the mating surface (that's were they start to harden) you can use Permatex for a temporary fix. I know parts are not cheap but mistakes can cost a lot more. I buy my batteries at High tech. Battery solutions on line. Mine cost under $45 delivered. Do disconnect the cables to make sure they aren't the problem.
Steve

Oh, peanut butter color is what I all ways look for on plugs. Good job there.
Steve

Ed, and Steve, I'll check all the areas that you suggested. The carb. boots are the Original but didn't seem to be in to bad of shape but who knows.

Got caught up in the excitement starting the bike, so was using jumper cables. Will scrape together the funds for New battery and carb. boots.

If not already done, would assure that the ignition timing advancer is properly functioning, and isn't stuck in the advanced position.

The advancer might need lubrication of the weight arm pivots (perhaps accessible through the timing inspection window).




The advancer should not look like this:



Good Fortune!

kzdcw wrote: Ed, and Steve, I'll check all the areas that you suggested. The carb. boots are the Original but didn't seem to be in to bad of shape but who knows.

Got caught up in the excitement starting the bike, so was using jumper cables. Will scrape together the funds for New battery and carb. boots.

My original carb holders looked perfect, but what I found were very fine cracks on the mating surface of them where they press against the cylinder head. These cracks could not be seen with the carb holders bolted in place, but the test described above made it obvious that they were leaking. When I removed the old carb holders I was amazed at how fine and shallow the cracks were, and yet the new carb holders made a world of difference. Ed

My thinking about the advancer being stuck in advanced position is because the racing idle didn't appear until the engine was revved, whereby the weight arms likely spread to advance the ignition timing (as they are supposed to), but the return springs of normal strength weren't strong enough to return the weight arms to the retarded idle position due to corrosion or lack of lubrication.

The advancer being stuck in advanced position could possibly have also contributed to the mentioned backfire.

Wouldn't normally expect the racing idle to otherwise so instantly occur, unless possibly the carbs were fitted without the air box, and unsupported at the air intake side, whereby weight of the carbs was sufficient to crack or tear the old hard deteriorated carb holders.

Would also assure that the carbs are nestled completely inside the carb holders, and that each of the four clamps where the carbs attach to the carb holders is snug.

Good Fortune!

I agree that the advancer is a likely suspect, and I would check it out carefully, clean it, and lube it to ensure it is operating smoothly.

The carb holders can do flaky things as well and sometimes can be very inconsistent. Mine would act differently from time to time which I suspect had to do with the effect of temperature changes as the engine reached operating temperature. Ed

YUP.