New 2010 EC300 Engine Noise (falling revs)

[Jakobi]

Hi all,

Started up my bike today, warmed it up well, few runs around the yard and up and down the street, came back. Refuelled with freshly mixed 98RON and GRO at 50:1. Few more laps around the yard and I pulled up. Noticed a strange sound that happens both in gear and in neutral.

Rev the engine up and let off and it sounds like something vibrates quickly for a while as the revs drop. Idles fine. Revs up, they drop and the sound happens. Only audible on the fall.

Any idea what it could be? It sounds like its coming from the top end/expansion chamber.

Powervalve maybe? Ping?

 

[swazi_matt]

I have the same - sounds more like something is loose and vibrating, not so much as an engine noise - also interested to know where it is because it drives me nuts!

 

[Jakobi]

I have the same - sounds more like something is loose and vibrating, not so much as an engine noise - also interested to know where it is because it drives me nuts!

Mine only just started. It appears to not do it when its cold, and progressively get louder as it warms up. I don't like the sound of it and don't feel confident running the bike while its making the sound. To me it almost sounds like a scraping vibrating sound. Like when someone runs there nails on a black board, but much lower pitched.

I just read this, and wonder if that could be it. I do notice a small area where some spooage is where the pipe and the engine meet.
http://www.gasgasrider.org/forum/showthread.php?t=2058

I feel like I'm spending more time stressing and trying to get this bike right, than I am riding it. Sigh

 

[Jakobi]

Is it okay to reuse the O-rings for the pipe if I take it off? Or do I need new ones?

Meant to be riding in a few days and would like to get this resolved before then.

 

[swazi_matt]

i will also check that.

I have removed my headder a few times to fit sump guards and pipe protection, and doubt you will need to replace the o-rings, they will only be a few months old, but if you do need to make sure you replace them with viton o-rings (for high heat use)

 

[Jakobi]

Thanks Matt.

The bike has all of 400km on the clock and is still under warranty. I haven't had the pipe off yet, but will do it tomorrow to see if I can re-seat it. The sound does sound like its coming from the head/pipe, and is at the revs when everything on the bike vibrates. (ie washers on the retaining pin for the footpegs, etc).

I orginally thought the worst when a new sound popped up.

Whats the easiest way to get the pipe off? Can it be done with the tank and seat on?

Hope this solves both our problems. I'll post back with results tomorrow.

Cheers, Jake

 

[GMP]

The stock high temp silicone orings are not very abrasion resistant and wear from normal vibration. This can allow the pipe to vibrate on the spigot or spigot bolt heads, and varies with engine speed and harmonics. This is especially true if the pipe gets tweaked a bit and does not sit square on the spigot. Viton orings last much longer. I also had a pipe spring that would vibrate on the header once, a small section of rubber hose over it cured it.
The pipe comes right off, two mounting bolts, springs and pull.

The PV rattles some from exhaust pulses as it returns to a closed position as there is free play in the system with the governer in its relaxed (idle or off) position. This is normal, not only on GGs. If rattle is excessive, remove the left PV cover and check that the actuator plate is in contact with the stop bolt head. If not, it could benefit from an adjustment to take up some play.

These bikes are tough, go ride!

 

[Jakobi]

The stock high temp silicone orings are not very abrasion resistant and wear from normal vibration. This can allow the pipe to vibrate on the spigot or spigot bolt heads, and varies with engine speed and harmonics. This is especially true if the pipe gets tweaked a bit and does not sit square on the spigot. Viton orings last much longer. I also had a pipe spring that would vibrate on the header once, a small section of rubber hose over it cured it.
The pipe comes right off, two mounting bolts, springs and pull.

The PV rattles some from exhaust pulses as it returns to a closed position as there is free play in the system with the governer in its relaxed (idle or off) position. This is normal, not only on GGs. If rattle is excessive, remove the left PV cover and check that the actuator plate is in contact with the stop bolt head. If not, it could benefit from an adjustment to take up some play.

These bikes are tough, go ride!

Thanks GMP.

Found another thread - http://www.dirtbikeworld.net/forum/showthread.php?t=49503&highlight=pipe+rattle

Quite sure this is whats happening to mine. Does sound like something vibrating in the pipe and the sound changes as the bike heats up and the metal expands. I wouldn't imagine the PV would do this.

Like mentioned earlier I can see a little spooge coming from the exhaust port, where the pipe appears to be touching it. Will remove the pipe, clean it up, and re fit with the stock O-Rings and some high temp silicone.

Haven't tweaked the pipe on anything so unsure whats caused it.

 

[GMP]

You see spooge because the orings are shot. Silicone is very good for high temp but very poor for abrasion. When you remove the pipe you will see the orings worn flat. Replace with Viton and move on. Silicone RTV is OK for a temp fix, bet really its no big deal to just ride the bike as is until you get some Viton orings.

 

[Jakobi]

You see spooge because the orings are shot. Silicone is very good for high temp but very poor for abrasion. When you remove the pipe you will see the orings worn flat. Replace with Viton and move on. Silicone RTV is OK for a temp fix, bet really its no big deal to just ride the bike as is until you get some Viton orings.

Thanks again. I'd just like to isolate the sound and confirm it actually is the pipe vibrating before taking it out the following day for a 100+km ride.

 

[hannesd]

Thanks again. I'd just like to isolate the sound and confirm it actually is the pipe vibrating before taking it out the following day for a 100+km ride.

if you put your foot on the exhaust and twist the throttle to evoke the vibrations. when those are gone, you'll know it was the exhaust

 

[Jakobi]

Only problem with that approach was that I'm limited for time this morning, so didnt want to identify and then change a hot broken pipe

Found the problem:

Unsure if this was the source of the noise, or just allowed the head of the pipe to contact the exhaust flange, but I should have a new one in my pocket ready to fit and ride come the morning!

Yeww!!

O-rings do not appear to be worn, have cleaned them up and will refit. Do people suggest a bit of grease on them? or perhaps some red silicone?