Engine hunting at 100kph (Fixed)

i_happen · August 21, 2009, 04:14:58 AM

I have a reasonably new 09 GS500 and at night while at 100 the bike seems to hunt a bit with the rev's. Its ok when the weather is warmer (above 10-15 Celcius) but below 10 it hunts. Feels like a loss in power then it comes back. When the engine is cold and the choke is off it is fine. It's only after about 10 minutes at 100 the prob starts. Does anyone have any idea's before I take it back again to the shop. I have drained the carbies a few times and its clean.
Thanks in advance for any advice
Regards Brian

The Buddha · August 21, 2009, 04:38:49 AM

That is called lean surge ... Poit it to the throttle position ... like dont say 100kph, say at 1/2 throttle in gears 4-5-6 it surges and I'll tell you exactly what to adjust. However you could use a +1 all around if its all stock.
Cool.
Buddha.

bill14224 · August 21, 2009, 08:31:30 AM

I would agree with Buddha except for one thing. Lean condition tends to improve as the engine warms-up, but you have a lean condition coming on as the engine warms. I would check the PAIR system (pulse secondary air system) and make sure it's connected properly, as well as the rest of the vacuum lines. Any vacuum leak will make your bike run leaner than it should and can cause surge. It sounds to me like you have a vacuum leak that's getting worse as the engine warms, or perhaps the PAIR system is leaning things out excessively on the exhaust side as it gets hot as it sits on top of the engine. You can plug the lines to it off and see what happens without hurting anything except destroying our planet with greenhouse gases. If the planet suddenly warms-up and we all begin to boil, please put the lines back on.

But, since the bike is under warranty I'd make the dealer find the problem. Good luck, and keep us posted. I'm curious about this one.

kml.krk · August 21, 2009, 12:41:30 PM

depending on how restrictive the inspection is in your place, you may want to get rid off PAIR system. there are people on this board who have done that successfully.
But if there is possibility that you will not pass inspection with PAIR removed then leave it alone and find other solutions (mentioned by previous posters)

good luck and keep us informed

The Buddha · August 21, 2009, 09:37:17 PM

Quote from: bill14224 on August 21, 2009, 08:31:30 AM
I would agree with Buddha except for one thing. Lean condition tends to improve as the engine warms-up, but you have a lean condition coming on as the engine warms. I would check the PAIR system (pulse secondary air system) and make sure it's connected properly, as well as the rest of the vacuum lines. Any vacuum leak will make your bike run leaner than it should and can cause surge. It sounds to me like you have a vacuum leak that's getting worse as the engine warms, or perhaps the PAIR system is leaning things out excessively on the exhaust side as it gets hot as it sits on top of the engine. You can plug the lines to it off and see what happens without hurting anything except destroying our planet with greenhouse gases. If the planet suddenly warms-up and we all begin to boil, please put the lines back on.

But, since the bike is under warranty I'd make the dealer find the problem. Good luck, and keep us posted. I'm curious about this one.

Not quite always. Lean condition improves as weather warms up. For sure.
Air cooled bikes make very vastly varying levels of vacuum when warm vs cold. I will not count on anything improving when hot, as the motor starts to draw, a lean condition will seriously show its head.
But the rest of his assesment should be checked, I am useless when it comes to PAIR crap, I threw mine in the trash the day I went to buy the bike ... on all bikes.
Cool.
Buddha.

i_happen · August 25, 2009, 08:58:49 PM

Ok. The bike has been fixed. According to the shop the problem was a loose connection causing an imbalance between the carbies. He said the fact I run a high octane fuel helped mask the issue for a while. It's only when I put in a standard fuel the issue made the bike really bad. So right now it's all fixed.
Thanks everyone for your input.

kml.krk · August 26, 2009, 04:33:02 PM

Quote from: i_happen on August 25, 2009, 08:58:49 PM
[...]He said the fact I run a high octane fuel helped mask the issue for a while. [...]

did you dare to ask him WHY? because I see no logical explanation to his explanation...

Chanse · August 26, 2009, 08:10:43 PM

agreed, I think they may have screwed something up previously and caught it when you brought it back... that or it was something insanely samll and they wanted an excuse to charge you an extra hour or two of labor.... I hate shops and stealerships.

i_happen · August 29, 2009, 04:06:12 AM

The work on the bike was free of charge. The guy at the counter indicated the guy that worked on it was having fun filling out Suzuki's claims paperwork. He was in the middle of a bit of a sh1t fight when I picked up the bike as the phone system and computer system was out and others were trying to find out how much they owed for work they had done. He knew mine was free of charge. The problem first appeared before the first ever service on the bike but was gone after the service. It was fine for the next 400k's but came back really quickly. The loose connection was the mechanical linkage were the syncronisation screw is. The guy said it was the plate on the end of the butterfly shaft. He said it wasn't "pressed" onto the shaft enough and because it was loose the whole assembly was replaced. I have since looked at the service manual and it actually adds up. With this plate becoming more loose with usage the symptoms would and did get worse. After the first service they would have adjusted the carby balance and covered up the problem. The shops story matches the issue and the symptoms.
Thanks again for everyone's input

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Engine hunting at 100kph (Fixed)