EC300 2018 Knock on steady revs 🤦*♂️🤦*♂️

[fabiopaulo]

Hi, i have a GasGas EC300 2018 and when i go with steady throttle, lets say, 1/2 throttle i heard a knock sometimes, not a sequential One like a rod bearing, knock knock knock, it sounds different, but it really pisses me off. When on stand and you rev it until half throttle it does the same. When idle it sounds pretty normal and when i go full throttle its good too. some friends said that is normal on 2 Strokes but i don't think so.. do you have any idea? Usual problem? Use RON98, mixture @50:1. The top and bottom end are new, 10hours.

 

[gasgasman]

Every GasGas that I've owned has that noise.

 

[blitz11]

Chain slap? This was a characteristic of the older GG models. Sound comes from down low (swingarm), so it can be masked as engine noise.

Power valve making a transition at 1/2 throttle (but this is engine speed dependent)? You said new top end? Possible that something came loose in the PV mechanism, and the power valve is flapping around? That could cause a rattle.

 

[fabiopaulo]

Chain slap? This was a characteristic of the older GG models. Sound comes from down low (swingarm), so it can be masked as engine noise.

Power valve making a transition at 1/2 throttle (but this is engine speed dependent)? You said new top end? Possible that something came loose in the PV mechanism, and the power valve is flapping around? That could cause a rattle.

Chain is on spec.and it happens when i have the bike on stand, it definitely came from the motor. Already checked the PV and its ok, nothing loose..

 

[fabiopaulo]

Every GasGas that I've owned has that noise.

Theres nothing that i can do to stop it?

 

[gasgasman]

Not really.
Can you post a video with the noise?

 

[Jacob 'Berg]

It could be pipe bang from unburnt fuel in the expansion chamber. But this usually occurs on deceleration, or rolling off of the throttle.

It could also be noise from the clutch assembly. I agree with gasgasman that all of the Gas Gas bikes I have owned make some knocking noises, which typically goes away when you pull the clutch lever in. I notice it most at idle, but hear this when rolling on the throttle as you describe.

I would not worry about it unless you are showing signs of pre-detonation or that the bike is running lean.

Post up a video..

 

[Stoby]

bad engine

Been on gassers for many years familiar with noises . Seems to be lots of issues with 18 up bikes .Mine has a bottom end knock havent pulled it yet but i believe they did a crappy job building or cheaped out on something on the newer bikes . Don't trust it .

 

[Gasser Nate]

Check the flywheel nut. Mine was loctited but was not done up tight against the flywheel. There was also a recall on the right hand crank nut.
Failing that you may have too much compression and need some head modifications. Mine was knocking under load slightly no matter how it was jetted. The head was machined to lower the squish and drop as much compression as possible. Smooth predictable power now with next to no spooge.

 

[webmaster]

The chain buffer (slider thingy) on the swingarm is made of a very hard plastic. And so at a given rpm/load the chain can load and unload to slap against - this is even with the chain adjusted correctly.

If you are right at the threshold where the pv valve with open/close, then it can flop between open and close and be heard.

jeff

 

[Jacob 'Berg]

OP said that he hears the noise when revving the bike on stand, so likely not chain slap. A video would likely help determine the root cause.

 

[fabiopaulo]

I will do a video next week. I think that the knocking could be beacause of the N1EF needle. I want to try other jetting. i read a lot of posts but don't know were to go. Here in my area(Portugal) we don't have to much elevation, is about 0-500m and i have all types of terrain, woods, deep sand and fast open roads. I see some riders using: pilot 42, NECW #3, main 175, AS 1.5 could be the right one for me?

 

[fabiopaulo]

OP said that he hears the noise when revving the bike on stand, so likely not chain slap. A video would likely help determine the root cause.

I hope you can hear the knock on 00:06 and 00:17 until the end... Thks in advance
https://youtu.be/6JaEs8JFaeI

 

[fabiopaulo]

Check the flywheel nut. Mine was loctited but was not done up tight against the flywheel. There was also a recall on the right hand crank nut.
Failing that you may have too much compression and need some head modifications. Mine was knocking under load slightly no matter how it was jetted. The head was machined to lower the squish and drop as much compression as possible. Smooth predictable power now with next to no spooge.

This knock could bem the flywheel nut? Thanks
https://youtu.be/6JaEs8JFaeI

 

[Gasser Nate]

Quite possibly, but after looking at your video I would be fixing all the bits that are flapping around first...

 

[blitz11]

Loose motor mounts? As was said, lot's of flappy parts.

 

[Doc Brown]

Every GasGas that I've owned has that noise.

Same here. 4 bikes two 18's and two 19's they all had it. Made me crazy but now living with it.

I think it is pipe bang, most of the time it appears when going steady and slowly or inadvertently close the throttle just a tiny bit. Bang! Sounds like a hard knock and comes from the cylinder outlet area.

I tried this for hours and it also appears when going downhill with closed throttle or just after the throttle has been closed. I first thought that pieces of branches or stones hit the bike on its plastic bash plate but it appeared always on the same spot of a 15 minute lap.

In the meantime I can live with it, but I can remember that I was really pissed off when I first heard it and was unable to find it though I spent hours and hours....

 

[Jakobi]

Same here. 4 bikes two 18's and two 19's they all had it. Made me crazy but now living with it.

I think it is pipe bang, most of the time it appears when going steady and slowly or inadvertently close the throttle just a tiny bit. Bang! Sounds like a hard knock and comes from the cylinder outlet area.

I tried this for hours and it also appears when going downhill with closed throttle or just after the throttle has been closed. I first thought that pieces of branches or stones hit the bike on its plastic bash plate but it appeared always on the same spot of a 15 minute lap.

In the meantime I can live with it, but I can remember that I was really pissed off when I first heard it and was unable to find it though I spent hours and hours....

Certainly get it at under this scenario.. What I have found will reduce it is running your idle as low as possible.

 

[5valve]

Did you resolve it?
I had a knock on certain revs, 18 bike also, riding bike in slow terrain, so no overreving, 65hrs total engine, with new piston 2 hrs.
Well, knock suddenly increased at some slow descent and stalled the bike.
Didnt try to start it, had it vanned home.
Dismantled, saw some scoring on cylinder wall, which just yesterday went away with honing.
Culprit, so it seems, but have yet to make me a crankcase puller, is the main bearing failure.

May I also say, that I lowered the needle by 1 on N2ZJ, and reduced the pilot 45 to 42 prior to ride, since plug was black from previous ride.

When returned, it was quite whitish, and vent was coming on much too soon during the ride.

So leaner condition and failing bearing kind of coexisted and lead overheating and destruction.

 

[fabiopaulo]

Did you resolve it?
I had a knock on certain revs, 18 bike also, riding bike in slow terrain, so no overreving, 65hrs total engine, with new piston 2 hrs.
Well, knock suddenly increased at some slow descent and stalled the bike.
Didnt try to start it, had it vanned home.
Dismantled, saw some scoring on cylinder wall, which just yesterday went away with honing.
Culprit, so it seems, but have yet to make me a crankcase puller, is the main bearing failure.

May I also say, that I lowered the needle by 1 on N2ZJ, and reduced the pilot 45 to 42 prior to ride, since plug was black from previous ride.

When returned, it was quite whitish, and vent was coming on much too soon during the ride.

So leaner condition and failing bearing kind of coexisted and lead overheating and destruction.

No i didn't. I will try to reduce squish, don't know how yet. Maybe trying a S3 Power head or something like that