Closing the throttle

[Viirin]

I didn't know whether to post this in "general" or "troubleshooting" because i don't know if it's a true problem

When you guys close your throttle to use the engine to slow down do you get much/any backfire?
I get some but i always have so i never really thought of it as anything other than normal but i figured it couldn't hurt to ask

Thanks for any replies

Vii

[Easy Rider]

When you guys close your throttle to use the engine to slow down do you get much/any backfire?

NO. You are only the 2nd person or so to report that condition.......who has a stock, unmodified bike......which I assume is your situation. If you have messed with the muffler or air cleaner, you might just have to live with it or do the "carb mod" detailed on here elsewhere.

It is not a "problem" as such, but might indicate something a little out of the ordinary.

The cause can be as simple as idle speed set too low and making excessive use of engine braking......that is, downshifting at too high a speed.

Other things include loose exhaust pipes at the manifold, a vacume leak around the carbs and carbs that need cleaning.

Last resort would be adjusting the idle mixture screw.....after removing the cap covering it.

I'd suggest starting with carb cleaner, if you haven't already.

[alantf]

I notice that in one of the other threads he said that he had to use the choke to start a European spec GZ. Now he's saying that he's getting a backfire when he shuts the throttle. Do you think that this points to a weak mixture? :??:

[Easy Rider]

Do you think that this points to a weak mixture? :??:

If by "weak" you mean "lean" then yes. :biggrin:

[alantf]

If by "weak" you mean "lean"

weak/rich are the English words for Lean & whatever you Americans call the opposite of lean. :cool:

[Water Warrior 2]

English, the other foreign language on this forum. :lol: It might help if we try to be a little more descriptive in our wording to avoid that "HUH" feeling. Try for a "rich mixture(too much fuel)" or "lean mixture( not enough fuel)". Sometime we will have the complete thought and description in our head but we shorten it in our writing. As Humans we think we are all on the same wave length and words are all the same. Not true. If I go up the road am I headed North or heading for a higher elevation ? Do hope this makes sense because I haven't had my usual multiple cups of coffee yet for the day.

[Viirin]

hmm so you guys think changing mixture could amend "problem" - couldn't hurt to try
You do this by just turning the idle screw right or do you have to get the tools out?
I'll adjust the idle before my ride to work tomorrow and see if it makes a difference, then i should be able to report back

Can this damage the bike? - the lean mixture i mean?

Thanks for all the replies guys

Vii

[blaine]

You are confusing two different settings.The idle screw(big white knob) sets the idle speed.The idle mixture screw is on the bottom of the carb.It may or may not be covered with a metal plug.Turning the screw clockwise richens the mixture.Do a search on how to remove metal plug and finial adjustment. :)

[Viirin]

Oh ok - thanks for clearing that up blaine - any ideas by how much or by what increments i should adjust it?

[5th_bike]

any ideas by how much or by what increments i should adjust it?
I'd first try the carburetor cleaner and if that doesn't help (after using one full tank with it), try and adjust the idle mixture screw - more as a last resort. Feel free to adjust the idle setting (the white knob) whenever you like.

[Viirin]

Added some carb cleaner today after my fill up but i'm starting to think i'm getting too fond of it... actually, for the first time in my short riding life i'm thinking the carb isn't the problem (which is weird considering it's history) but i think by now i have to have one of the cleanest ones out there! still, couldn't hurt to run a bit more though....right?

[blaine]

Oh ok - thanks for clearing that up blaine - any ideas by how much or by what increments i should adjust it?



When you go to adjust,have the bike running,as you slowly turn the screw out you will hear the engine speed up.Once you turn it out to far the engine will start to stumble,(Rich) at this point start to turn the screw back in till engine stumbles.(lean).Set mixture about the middle of the two extremes,where the bike idles best.Do your adjustments slowly,about 1/4 turn at a time.
http://www.postimage.org/templates/images/smiley/sporty/46.gif (http://www.postimage.org/)

Good luck.

[Viirin]

Thats great man - i'll do it as soon as i get a day off...which i think is tomorrow

Thanks for all the help - i'll let you know how it goes

Vii

[Easy Rider]

Thats great man - i'll do it as soon as i get a day off...

You need to be aware that it is not as simple as it might seem.
The mixture adjustment screw faces DOWN and is inside a sleeve, making it hard to see.
You must first pry off a metal cap.
Then you must have a small, skinny screwdriver.....and maybe a mirror.

BEFORE you get into all that, how about explaining that last comment that you now don't believe the carb IS the problem ??
Have your symptoms changed any ? How about a recap of the present situation ?

[Viirin]

No no nothings changed i just frequently clean the carb is all - I get a few pops of backfire (3-5 maybe) when i close the throttle to slow down in 3rd or 2nd that occur roughly 1 or 1.5 seconds after i close it but my bikes always done this i just assumed my bike had a small hole in the air box or something but nothing major. Still if it can be fixed i see no reason not to.

That procedure does seem a little more complicated than i had originally thought though - maybe some more preparation is needed rather than just having a go at it tomorrow morning.

** just to clarify, i'd class the mixture going through the carb as a separate problem to the carb itself - maybe that's just because the normal carb problem involves dirt or gumming up - maybe they're the same thing - i don't really know - apologies for any confusion caused **

[Viirin]

Well after getting that day off and looking at it - i got that familiar feeling of not knowing what i was doing and so i decided to stop before i did any damage - i might ask my local mechanic to have a look at it when i'm getting my brake pads done (should be soon enough) but if it isn't causing any real problem i may not if it's going to cost a fortune in labour

In any case thanks for all the replies and i may have another look at it shortly down the line

Thanks again

Vii