Phantom Acceleration?

[jay-d]

So, before I put my bike away last Fall, I noticed something really weird. The bike was warmed up, I got up to speed, decelerated the throttle but my RPMS went up, like a surge. I immediately pulled the clutch in and the rpms shot up to like 4,000 and then went back down to idle. It didn't happen again, but curious as to what would cause this surge?

There's about 25,000km on the bike, it's a 2006, never had a tune up. The only maintenance I did was coolant flush.

I'm selling the bike .. but will buy a 8th generation in the near future! Want to make sure it's in good working condition before I sell it.

[Knight]

Are you the original owner? Are you saying the bike has never had maintenance or only just during your ownership? Your post reads as though the bike has never had an oil or brake fluid change, never had cables and pivots lubricated, etc.

What was the bike temperature? Was it cold when this happened?

1) Throttle cable: Pull it and observe the butterfly action. Look for a sticking point. These require periodic adjustment and lubrication, so if you are lucky, the problem will be something like this and stick out like a sore thumb, and doing basic maintenance will fix it.

2) Test the throttle position sensor per the manual. I think you may look for spikes in the voltage, but check the official procedure

3) Test the idle wax unit

4) Clean and test the movement of the starter valves. I don't think this could cause it, but it is something basic to go along with the above.

Unfortunately lack of inspection and maintenance means some problems like this open a can of worms, leaving too many items to have to check before finding the cause.

If all of this turns up negative check that the ECU is secure, that the side stand is staying up and not flopping during deceleration, and any other safety and movement related switches and sensors.

I'm obsessive compulsive but I would worry about selling a bike with this particular issue unless you fully disclosed it to the rider. What if a novice buys this bike and goes briefly out of control due to the issue?

It would be a great selling point to show a receipt that the bike was inspected and adjusted. However, these bikes that get little or no maintenance, there is probably a lot of work that a competent mechanic will want to do to it, and I get the feeling you will be happy to let the bike go and let the next owner refresh it instead.

[checksix]

Check the throttle cable at the handgrip end to ensure there's a little bit of free play?

[jay-d]

Are you the original owner? Are you saying the bike has never had maintenance or only just during your ownership? Your post reads as though the bike has never had an oil or brake fluid change, never had cables and pivots lubricated, etc.

What was the bike temperature? Was it cold when this happened?

1) Throttle cable: Pull it and observe the butterfly action. Look for a sticking point. These require periodic adjustment and lubrication, so if you are lucky, the problem will be something like this and stick out like a sore thumb, and doing basic maintenance will fix it.

2) Test the throttle position sensor per the manual. I think you may look for spikes in the voltage, but check the official procedure

3) Test the idle wax unit

4) Clean and test the movement of the starter valves. I don't think this could cause it, but it is something basic to go along with the above.

Unfortunately lack of inspection and maintenance means some problems like this open a can of worms, leaving too many items to have to check before finding the cause.

If all of this turns up negative check that the ECU is secure, that the side stand is staying up and not flopping during deceleration, and any other safety and movement related switches and sensors.

I'm obsessive compulsive but I would worry about selling a bike with this particular issue unless you fully disclosed it to the rider. What if a novice buys this bike and goes briefly out of control due to the issue?

It would be a great selling point to show a receipt that the bike was inspected and adjusted. However, these bikes that get little or no maintenance, there is probably a lot of work that a competent mechanic will want to do to it, and I get the feeling you will be happy to let the bike go and let the next owner refresh it instead.

hey Knight, you are right, after reading my post it does sound like the bike has never had any maintenance! That's not true at all though, I bought the bike in 2012 with 5,500km and have done regular maintenance, even posted a brake fluid replacement DIY. What I meant to say was the last maintenance I did was the coolant flush, and wondering if the bike requires a tune up soon.

I did remove the tank and all that good stuff to tighten up the coolant hoses last summer, and the throttle was within spec. Once the weather gets warm, I will check those items, I just wasn't sure where to start to be honest.

[Knight]

hey Knight, you are right, after reading my post it does sound like the bike has never had any maintenance! That's not true at all though, I bought the bike in 2012 with 5,500km and have done regular maintenance, even posted a brake fluid replacement DIY. What I meant to say was the last maintenance I did was the coolant flush, and wondering if the bike requires a tune up soon.

I did remove the tank and all that good stuff to tighten up the coolant hoses last summer, and the throttle was within spec. Once the weather gets warm, I will check those items, I just wasn't sure where to start to be honest.

That's a much happier story lol.

One of the guys on the other forum complains about a 4000 rpm surge but he reported that it was his clutch because he is clutching at the time it happens. Maybe that is a red herring. I think it was happening on the start of a trip, aka when cool. I will be curious to hear what you find as this will be helpful for others.

[CandyRedRC46]

I had it happened to me once or twice while coming to a stop with the clutch pulled in. It hasn't happened in years and I had forgotten all about it until you and the other guys posts. It wasn't a big deal, I just let out the clutch a tad and the RPMs dropped back down to normal. I can only think that it could have just been a tiny leak in one of the vacuum lines/boots or a funk wax unit. I never came back, but I have replaced my vacuum lines last year just doing routine maintenance.