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Discussion Starter #1
I'm the new owner of a stock 2002 Bonneville and have got a question.

Engine response to closing the throttle seems awfully abrupt (to me anyway).

Are there any mods that would reduce this effect?

Does shimming the needle jets or removing the air injection system help?

Thanks
 

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Engine response to closing the throttle seems awfully abrupt
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I'm not sure what you mean by abrupt.
Abrupt , fast ,quick, suddenly.
Are you saying it slows down to abrupt. I don't know?

I know the stock set up has a delay in the throttle response.
And rejeting to bigger jets helped by giving it a little
quicker throttle response.
Bill
 

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a mod to the speed of your wrist will slow it down.
or speed it up.
the throttle (like pretty much all throttles) is designed to snap shut when let go of. modify how fast you close it
G
 

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Discussion Starter #4
What I meant by abrupt was that closing the throttle
relatively quickly at low speed causes a sudden decrease in engine speed (expected) and then the whole bike pitches forward on the front forks.

I was expecting a smoother transition from a light to closed throttle.

The effect seems to be amplified by the soft fork springs.

It's probably just me not being used to the bike yet.
 

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It depends on what gear your in. If your at high rev's and
in a low gear she's going to lunge forward when you let
off the throttle.
Bill

[ This message was edited by: bonnevillebilly on 2006-12-04 18:29 ]
 

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If you're talking about "engine breaking" one way to smooth things out is to increase the idle speed. I'm not going to pretend to know the mechanics behind it but ever since I upped my idle speed for the winter months there's less breaking (and popping, etc.) on decel. I normally keep my idle speed fairly low because I love both the popping and not having to jump on the breaks all the time.

Maybe someone more knowledgeable can explain what's going on here? Just a thought.
 

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What is there to explain? You let off the throttle ,you stop
giving the engine gas ,your in gear.
What's going to happen?
Bill
 

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Short version = Don't worry...it's supposed to do that.

Slightly longer version = If it doesn't do that, then you've got problems (or a two-stroke motor). :)
 

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What is there to explain? You let off the throttle ,you stop
Yeah, maybe it is that simple. I guess I was thinking maybe there's something about the bonnie's unique engine config (360 deg, carbs, flywheel, etc.) that makes it more noticeable or pronounced than other scoots.
 

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A lot of it has to do with the gearing.
I depend on the engine helping me slow down.
I noticed a big difference when I switched my front
C.S sprocket from the stock 17T to the 19T.
I had to get used to dropping down a gear to help slow
me down going into a corner.
Bill
 

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Triumph did this so you wouldn't have to wear out the stock brake pads so quickly. Same reason they installed a 17 tooth counter sprocket the first few years. Saves the brake pads for the twisties where the wear and tear is worth it--or so I hear. Kinda hard to find very good twisties out here in the flat lands. :-D 17900 miles and I still have 75% of the original pads left--now tires are another matter...time for the third set.

Larry
 

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Redbird: Hmmmmmmmm.... Sounds like you're stalking the countryside North East of me again!!!!!! That's what I like to hear, is a guy who wears his tires quicker on the sides than in the center, especially here in "flatland"! Your gonna have to train me some on those brake pads though. See ya in a couple days. tommyturbo2
 

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What were you riding before? Engine braking on a twin is more pronounced than on a four. Even more so than a two stroke.
 

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A lot of the difference in how a bike responds to off-throttle has to do with the compression ratio of the particular engine, the size of the engine, and flywheel weight. A new BMW twin with approx 600cc displacement per cylinder and over 12:1 compression decellerates with the throttle closed like you threw out the anchor, especially since the BMW fuel injection shuts off on closed throttle until the engine slows to approx 2000rpm. By comparison, the Bonneville twin is very well mannered.

Think of your engine with the throttle closed at 7000rpm as a giant compressor, which the forward inertia of your bike continues to turn over. Downshift a gear and you're turning the 'compressor' faster, therefore more engine braking.

Bob
 

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Swebb- what you describe sounds very much like you simply need to adjust your throttle cables - probably some slack in them, and you get that sudden surge (or decel.) whenyou get down to the stop or come on off it. My Scrambler's a bit like that, as the cables stretch a little initially, and the slack has to be taken up. Check it anyway - simple fix, you never know - good luck mate - Pat
 

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Swebb: I thought the exact same thing when I first got my Bonnie. Before that I was riding a '70 TS250 (a two-stroke) and the engine decleration was not nearly as pronounced on that bike as it is on the Triumph. I'm sure that's just they way they are. Nothing is wrong with your bike and you don't need to mod anything. The way I overcame this was to just feather the clutch a bit when decelerating. Pull it in a bit, let off the throttle, then slowly let the clutch out again.

[ This message was edited by: Hilts on 2006-12-06 13:44 ]
 

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It ain't all that flat here. There is a curve up North of Guthrie. I been watching those ice patches we still have here though.
I suspect closing the throttle on a big twin will do that. I like my idle set up a bit. I can get it off the enricher quicker on these cold mornings. Plus with the idle set up it will blubber more on decel. And not slow down so fast with throttle off.
I have noticed that I have to pull in the clutch while slow cornering. Otherwise I either have decel or accel. No in between. I was thinking that the throttle cable cam at the carbs should be a diminishing radius. Slow throttle response off idle (large radius) & then all wide open throttle (small radius) with just a little more throttle twist. Progressive. Smaller diameter grips would do that too.
 

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Discussion Starter #18
Thanks for all the feedback and advice.

I haven't ridden much in recent years and need to get used to riding a relatively large twin cylinder bike.

Will also take a look at throttle cable slack.
 

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I have the opposite problem. When I twist the throttle the power comes on more abruptly than I think it should.
I am not new to bikes but new to Triumphs. I just bought a 2006 Bonneville T100. Man, I love this bike! When I bought it, I noticed that there was quite a lag and jerk when I twisted the throttle. No big deal I figured, I will just learn how to finesse the throttle. However, it has been a month and as much as I try to be smooth and controlled, I still get that lag and jerk of power when I give it gas. This makes me nervous when I am in a corner. I go in slow and come out fast. I have to be right-on with the application of the throttle, otherwise it may jerk as the power comes on and that is not what I need.

Is this just how the T100's work and I have to accept it, or is there something I can tweak?

The only mods I know of on this bike was the aftermarket peashooters (that sound awesome) and the removal of the AI, I still need to "look inside" for other potential mods.

Any suggestions?
 

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The Bonneville lurch

My 2009 T100 EFI Bonne does the same thing, it's kind of a lurch forward when in a low gear and closing the throttle. My Harleys were much more gentle coming off speed, so I guess it's a Bonneville thing. It does bug me at times.
 
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