Backfire when throttle closed

[Easy Rider]

Originally Posted by dan_

How do I know where my idle should be set? I prolly have it set to low because It kinda has that low thump thump.. but not really ya know?

Tough call when you don't have a lot of experience. Best I can tell you is turn it up a little at a time until it just starts to smooth out a bit and the individual thumps are hard to distinguish.

This is a case of not knowing what is enough until you find the point where it is TOO much.
If you get the feeling that the engine is racing a bit, then it is probably too high.

May God forgive me.......think about a gasoline lawn mower. Most of them idle nice and smooth when set right. For some strange reason, your GZ should sound about the same when it is set at the right speed. :whistle:

[flainn]

You've just got to love that lawnmower sound! Sure beats a sewing machine though.

[dan_]

Is it bad to have the idle set to low? I mean the guys already say it sounds like a lawn mower.. but none of them have bikes so its prolly all jealousy..

[alanmcorcoran]

Mine stalls... a lot. but it didn't do this for the first 2500 miles or so. I'm not sure if the idle is too low, or the carburetor is effed up or there is crap in my gas tank. I'm going to try the seafoam for a few tanks and see if there is any improvement.

It actually is hard to re-start once it stalls. I've had to take the choke off becaase it get's flooded. I now have to kind of keep the throttle on a little as I'm slowing down for lights and stops. I've also become an expert at push starts. Unless I'm going up hill, I use the push start to conserve the battery. And I'm doing it in second gear now.

And this is after a near $300 3K "service." Nice to know motorcycle dealers are just as inept at servicing carbureators ascar dealers are. Glad the Strat has fuel injection. At least until those get effed up, too.

[Easy Rider]

Originally Posted by dan_

Is it bad to have the idle set to low? .

Bad as in hard on the bike....no.

Shifting is usually smoother if it is set right and getting off the line is easier 'cause you don't need as much throttle.

[Easy Rider]

Originally Posted by alanmcorcoran

I now have to kind of keep the throttle on a little as I'm slowing down for lights and stops.

THAT is exactly what the idle speed adjustment DOES.

You are probably keeping the choke on longer than you need to just to bring the idle speed up.

I was amazed at how low the shop had set mine; I think I cranked the knob about TWO FULL TURNS......but the engine was still cold so I'll probably have to back it off a bit next spring.

Seafoam won't hurt but, please, tweek up your idle speed. You will be much happier.

[BusyWeb]

Originally Posted by Easy Rider

THAT is exactly what the idle speed adjustment DOES.

You are probably keeping the choke on longer than you need to just to bring the idle speed up.

I was amazed at how low the shop had set mine; I think I cranked the knob about TWO FULL TURNS......but the engine was still cold so I'll probably have to back it off a bit next spring.

Seafoam won't hurt but, please, tweek up your idle speed. You will be much happier.

Here is my experiences about engine idle speed.
With my DIY(ha ha ha...) RPM meter, I could measure pretty accurate gz engine speed.
(TIP: you can measure RPM with digital multimeter which equipped with frequency measurment
HZ >> 1 HZ = 60 RPM >> point to the ignitor negative cable)
Service manual says about 1300 is for the GZ. (measuer when engine is warm/hot)
Surprisingly, around 1300 is far low for my GZ, sounds really slow engine running.
However GZ runs well enough without stalling, if I do give more care on the throttling at stop.
Which means that gz seems not very happy with it at the lower speed.
I tried to put rpm to 1800 -2000 idle speed, gz sounds little hurry but not much.
And lower speed jerking problem is gone, and more smoother gear shifting for me.
One thing though, engine temperature goes little higher when I riding in city environment...
Frequent stop and start at lower speed...
That's all for my experience/opinion, as Mr. Easy had to do for the idle speed.

[Water Warrior 2]

I would wonder about proper oil pressure and oil circulation with a low idle.

[alanmcorcoran]

Originally Posted by BusyWeb

With my ... RPM meter, I could measure pretty accurate gz engine speed.
Service manual says about 1300 is for the GZ. (measuer when engine is warm/hot)
Surprisingly, around 1300 is far low for my GZ, sounds really slow engine running.
However GZ runs well enough without stalling, if I do give more care on the throttling at stop.
Which means that gz seems not very happy with it at the lower speed.
I tried to put rpm to 1800 -2000 idle speed, gz sounds little hurry but not much.
And lower speed jerking problem is gone, and more smoother gear shifting for me.
One thing though, engine temperature goes little higher when I riding in city environment...
Frequent stop and start at lower speed...

Hey, Mr. Web. This is probably the most scientific analysis of this issue I have seen. Thanks. Here is my theory about the idle speed: When the bike is brand new or the carburetor, piston and spark plug are in 100% perfect working condition, the bike will idle fine at 1300. If there is any gunk in the carb, on the plug, in the cylinder, or grit/sand in the fuel line, or crap in the gas tank, the conditions are going to be less than ideal and the bike is going to stall until it is heated up but good.

I don't like a high idle because the bike tends to "drive itself", runs hotter like Busy said, and uses more gas. But I also get very annoyed with the stalls - it's very distracting, is hell on the battery and is dangerous, because about half my attention now is dedicated to effing with the controls at stops so it doesn't stall.

When I drove taxi's we had a few old Chryslers in the fleet (this was pre-FI) and they had this irritating tendency to stall when you accelerated from a stop. They'd hesitate, cough, then, down she'd go. No matter how many times we had them serviced, they basically sucked. The typical solution was to crank the idle up so you could do about 20 mph without ever touching the gas - at a stop light, you had to "hold your horses." This of course, wasted gas and used up brakes faster. Not to mention irritated the piss out of you. But the mechanics we had could not fix it.

I find that a really good mechanic that actually knows what he is doing and works for a trustworthy outfit is a rare commodity these days. The problem is that like a lot of American business models, the people that do the actual service get paid the least. The guys that write up the order, the "manager", the owners and the landlord all get paid the lion share of the service fee so the service person with half a brain tends to migrate into something more lucrative. I often feel the guys that are working on my bike are the ones that are too dumb to migrate. They are also not skilled or experienced enough to expertly service the bike. They are probably also under pressure to close tickets in an unrealistic amount of time and do the bare minimum on a routine "service."

If I felt I could take the bike somewhere with a master mechanic and he could truly "service" the carburation system I think I'd be happy with the 1300 idle, but, in all likelihood, I'll probably just crank mine up and learn to live with it.

[Easy Rider]

Originally Posted by BusyWeb

[Here is my experiences about engine idle speed.
With my DIY(ha ha ha...) RPM meter, I could measure pretty accurate gz engine speed.
(TIP: you can measure RPM with digital multimeter which equipped with frequency measurment
HZ >> 1 HZ = 60 RPM >> point to the ignitor negative cable)

This is just wild speculation (at this point) mind you but I have a theory about that.

It seems to me that the proper "real" tach to get for the GZ is a "double fire" model, the same as is used for V-twins that fire the plug TWICE on each revolution. If that is true, your DIY solution might be reading twice the real RPM and you might actually be setting yours about 1,000 RPM, which is about where I think it should be set. In all my riding, I have never set an idle speed as high as the "book" recommends.

If true, that illustrates the problem perfectly. Setting the idle where it should be just sounds and feels way to fast for most people. Then there are those who seem to prefer to keep re-starting and push starting when it only take about 3 seconds to adjust it........mmmmm...A.C. ???

I know there are (or were) a couple of folks on here with tach's. Wonder where they have their idle set ?? (Off to do a couple of searches).

Edit: Sarris.....5th_bike.......help me out here, please ??