Constant speed with small throttle opening.

KevG

KevG

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The problem is I seem to have a barely perceptable "shunting" ,like the throttle is being modulated, at around 30-40 Mph in Top or fifth gear,very annoying in towns! anyone else had this? Bike is 2006 GSA 5000 Mls.
Thanks for any help.

Kev
 
That sounds normal to me, you're just running the engine relatively slowly, so you'll feel the the judders more. I tend to use 3rd at those sort of speeds. Forth if I'm feeling lazy.

TobyS
 
Yep me too.3rd 4th gear.Was gonna mention at my 12K service in a couple of weeks.:nenau
 
Some of the early 1150s were referred to as the Surgin' General because of lean surging. Under the right conditions, it's usually noticeable at lower revs in 3rd or 4th with steady throttle openings, as the computer hunts for an optimal mixture ratio. All new bikes, not just BMs, run very lean these days so it's very likely just a wee bit of lean surging that you're experiencing. And 5th and 6th are definitely not appropriate gears for 30/40 mph speeds. http://www.ukgser.com/forums/images/smilies/rob.gif
:rob
 
Sounds like the surging that the 1150's suffered from, although to a lesser degree. My 1200 is a little unsure on small throttle openings, but nothing I can't live with.

(My Ford Focus 2.0 turbodiesel does something very similar.)

I have heard that ensuring the throttle bodies were well balanced can help.
 
This is a known about, well documented 'characteristic of the oil heads. It has progressively gotten better over the model years. The early 1100s were potential nightmares - you just got used to it and rode around it (at low speed the bikes would actually accelerate all on their own!). If I concentrate I reckon I can notice it on my 1200 as well, but it is very small. No problem with your bike though........just drop a gear - I figure that 4th or even 3rd is best for 30mph.
 
Yep - wot they said. For smooth running I keep mine in the gear that corresponds to the first number on the speedo... 3rd gear for 30+, 4th for 40+ etc.

The lean settings plus clonky shaft drive make it difficult to run in a high gear at low speeds.
 
Has it always done this or is it something new?

You are asking a fair bit from the bike to plod around in top at those speeds but provided you are very delicate with the throttle and you are on the flat, it will just chuff along OK, though it's a bit pointless and leaves you in too high a gear to easily accelerate out of trouble if required.

As the others say, the throttle balance is critical and your symptoms are classic for out of sync' bodies so if it's doing it now but didn't before then this would be the first thing to look at.
 
"......around 30-40 Mph in Top..." As it CAN manage almost 130 mph in top perhaps you are expecting a little too much flexibility from your poor old bike?
 
RickG said:
you in too high a gear to easily accelerate out of trouble if required.

As the others say, the throttle balance is critical and your symptoms are classic for out of sync' bodies so if it's doing it now but didn't before then this would be the first thing to look at.
Click to expand...

I think that the stepper motors maintain the throttle body balance at low revs. My understanding is that the throttle body sync is now no longer as critical as it used to be on the airheads. I know that in the first 25,000 miles on my 1200 I have never had to make an adjustment.
 
Yep I agree about 5th & 6th being the wrong gear for 30mph.

Try an advanced riding course :augie :D
 
As a rule I tend not to drop below 3000 rpm, so 30 is second gear teritory for me. I *think* that's ~3500rpm in second, but I do it on the sound of the engine (spot who's practising for his advanced test :o )
 
Thanks for the input chaps..... I only mentioned the gear I might be in.. it happens in all gears if throttle constant!! I,d been riding in the higher gears as the problem was worse there and I was trying to figure out what it was! (I am a Mechanic by the way) as you do!
Thanks for all suggestions anyway, rest assured I know how to ride it!(I am an EX RAC/ACU Instructer)
Sorry for the confusion.
Anyway took it to Williams today and it was the Throttle sync. Now sorted out problem solved.
All I need to do now is set the rear suspension up correctlly....100Kg rider, as seems too soft and "wallowy" or is that what they're like? I have tried playing with preload etc and not found a sweet spot yet. Damper is working fine. Last bike was a 1987 K75 which I still have, but the GS is a bit different as you can imagine.
Any help appreciated.

Kev
 
Last edited:
Should not be soft - did you find the damper adjustment screw on the bottom of the rear shock? It makes a big difference. I weigh 104 kg and tend to have it set about a third of a turn from maximum setting.
 
Hi Jon

Its not soft, it just seems to wallow a bit?
damper screw is in not sure by how much though. Will check when I get it back, Fuel Pump Controller has failed tonight!


Kev
 
Shcok Solution

Kev, the damper is very likely just fine, it's the spring that's a bit soft and it's easy to sort. See this thread, "Rear Suspension help please" on page 2 under 1200s. Happy to discuss if you want to get in touch.

Note that I changed my sign-in name from Cyclemike to Peak Rider earlier today. An explanation is in the I'm New Here... thread at the top of the forum menu page.

Mike
 
the 1200GSA is softly sprung with little damping, so they wallow.

i never found an acceptable adjustment on mine. a decent shock sorts it.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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