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Discussion Starter · #1 ·
Anybody have a ticking sound in the carbs when the bike is warming up?

If I put my finger on the throttle linkage (synchronization screw), you can feel it pulsing/ticking. Like the butterfly is opening/closing and hitting the "cylinder walls" (venturi walls) indside the carb. What causes that?

Is it the vacuum of the engine trying to suck the butterfly open? Maybe the vacuum isn't high enough when it's warming up to hold the butterfly slightly open and that's why it gets better after warming up?
 

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Bomber,
I am puzzled by this one....:dunno:
 

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Maintenance Overlord
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h'mmm

One can only hypothesise here.

At warm up combustion is less than perfect and cylinders maybe unevenly loaded. One may expect some uneveness in engine speed propogating an inbalance in the engine intake system, the variation of absolute pressure (vacuum in this case) acting on the the carb butterfly and linkages.

I will check zr7 next time at start up, we are now into our winter, Day temp around 21C say 70F, it has been going down to a miserable13C say 55F at night

h'mmm

[email protected], ava good day
 

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Re: h'mmm

graeme gould said:
it has been going down to a miserable13C say 55F at night
[email protected], ava good day
Someone needs to come and ride in Canada in the early spring....
13C miserable!!! :Wow1: :Wow1:
I beg your pardon...
 

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Discussion Starter · #5 ·
I found this on the web. Mikuni's site to be exact. I know we have Keihin carbs, but same difference. If the following is indeed what's happening, do you think this could wear out the needle or needle jet faster?

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1) Slide rattle:

Most HSR carburetors make a soft "ticking" noise at idle. This ticking is the result of the normal pulsing of the air in the intake system. This pulsing is caused by piston and cam action. The ticking is not a sign of wear or incorrect tolerances. It is normal.

During the intake cycle, when an intake valve is open and the piston is moving down, a partial vacuum is formed in the cylinder, intake manifold and behind the carburetor's throttle valve. The normal pressure on the out-side of the carburetor's slide then pushes the throttle valve back in the carburetor body. This movement can cause a "click".

Near the end of the intake cycle and below a critical rpm, which varies with cam design, a positive pressure forms in the cylinder, intake manifold and behind the throttle valve. This positive pressure forces the throttle valve forward in the carburetor body. This movement can cause another click.

So, the throttle valve being "pushed and pulled" by the variations in manifold pressure at low (idle) rpm results in some ticking. As soon as the throttle is opened and the throttle valve is raised, the ticking stops.

Cams that have been designed for high rpm performance usually close the intake valves much later (in crankshaft degrees) than the stock cams. The later the intake valves close, the greater the pressure on the back of the throttle valve and the louder the ticking may become.

Exhaust systems with no baffles, like long open straight pipes, also tend to increase the reverse pressure on the throttle valve.

By the way, it is the late closing of intake valves that cause "reversion" in high performance engines. Reversion is the word most commonly used to describe the fog of air/fuel ejected from the mouth of the carburetor when the throttle is opened at low rpm. Reversion disappears when the engine rpm becomes high enough that the intake valves close before the piston can push air/fuel mixture back through them.

Factors that affect slide rattle:

1) Cam design --- the later the intake valves close (in crankshaft degrees) the higher the rpm before reversion and therefore slide rattle stops.
2) Exhaust systems without baffles, particularly long, straight open pipes, increase reversion pressure.
3) Windshields, fairings and unrestricted air cleaners (like the Screamin' Eagle) echo any noise coming from the intake system.
4) Throttle valve to carburetor body clearance. There is some minor variation in the amount of play between the throttle valve and carb body. A "loose" throttle valve and a "big" cam can combine to make the normal ticking sound louder.
 

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Bomber,
I have been thinking a lot about your ticking noise since you posted about it. The explanation that you found makes sense, however, I would think that the rattling of the slide would eventually cause some wear on the needle. Is it possible that the slides are worn and thus rattling in their cages?
 

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Discussion Starter · #8 ·
I'm sure that's possible. However, I only have about 12k miles on it.

Also, consider this....if I put my finger on the throttle linkage (the synchronization screw), I can "feel" the clicking VERY strongly. I think that this linkage is attached directly to the butterfly...right?

So I guess the virbrations could be transmitted from the slide to the linkage, but the screw is the only place you can feel it.

Thanks for the brain power!
 

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Discussion Starter · #9 ·
This noise is getting worse. It's most noticable now from a slightly cracked throttle to about 1/2 throttle (or at least thats as long as I can hear it over my exhaust).

I am beginning to think my slides are worn out. Is 14.5k a common lifespan for a slide?

Is there any danger in swapping a couple of the slide around between carbs to see if that changes anything?

Anybody else have worn out slides?
 

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50,000 miles and no worn out slides here.
 

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Saluts Bomber,
I am really surprised by this problem. I don't think that anyone here has ever experienced anything like it, furthermore, I can't recall ever having heard of such a problem on any Japanese slide carburator, be it Keihin, CVS or whatever. I don't know what to make of it! I would think that swapping slides would be a reasonable thing to do. All slides have the same part number.

André
 

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i went out to look at my carbs today and try to notice any ticking i feel vibration but cna't tell if that is ticking i hear or what? i guess my ears suck....i have 45k on my carbs no problems here...
 

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Andre Lalonde said:
Someone needs to come and ride in Canada in the early spring....
13C miserable!!! :Wow1: :Wow1:
I beg your pardon...

Quite right Andre! Already it's been down to 8C for my morning ride, and I'm ashamed to say that I plugged in my electric vest for that one. I'm getting old. Then again it was -8C coming home from a Toronto trip last year. That my friends is stupidly cold on a bike. Can't feel anything, and I mean anything, cold. :eek:

In GG's defense though, I know a lot of riders around here who stop riding and start complaining at about 25C as it's "too hot". :stfu:
 

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craig, i'll ride with you at -8, did toronto to kingston 2 years ago i think it was -10, electric vest, arm chaps and legs plus the heated grips makes a world of dif.
 

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Got the electric vest, just the usual quilted one as I couldn't afford the nice one that allowed you to add arm chaps. I do want the heated grips though. Do you have the permanent ones or the "hot hands" wrap-arounds that velcro on? For cold weather trips this fall I'm thinking about battery heated hunting socks.
 

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Discussion Starter · #16 ·
Well, I moved the slides around, and it still 'ticks'.

My dad thinks it COULD be the screws that hold the butterflies onto the linkage are loose. I never thought about that and it seems plausible...what do you think....worth pulling the carbs to check them?
 

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Johnny Blue Lightnin'
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I thought you accepted that it was normal. Or do you just like to tinker?
 

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Johnny Blue Lightnin'
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I have never noticed it from mine but I have never tried to either. With the frankenpipe exhaust I have ight now I doubt I could hear it. Next time I start it I'll listen and try to feel it. I assumed it was the noise as described by your post from the Mikuni sight. It makes perfect sense to me.
 
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