Deceleration roughness, rattling

[Earwinder]

Hi guys

I recently changed the stock/out of box jetting on my 2013 EC250
stock ( N1EF, 175, 42)

to

Needle N3EH 3rd clip
Mainjet 168
Pilotjet 40

The bike is definitely more willing on acceleration, but I noticed a definite increased roughness on engine deceleration.
It seems more unbalanced and 'rattlely' as the engine decelerates. This happens with bike in neutral on a stand as well as decelerating in gear, approaching a corner.

I don't know much about pinging, detonation, squish clearance, .........

I checked for loose nuts and exhaust mountings.
Bike starts very easy from cold/hot and idles slightly higher than with the stock jetting.

Hopefully this will be an easy fix for all the wise-men of the forum.

Regards

[GMP]

Your lean. First what carb is on the bike? If its the old style AS1 screw top, forget about H dia needles.


Sent from my iPad using Tapatalk HD

[Jakobi]

As Glenn said.. When jetting these bikes theres an order to the chaos
1) Establish the carb model
2) Set the float level (they vary depending on the carb model)
3) Select a needle depending on characteristics you want (this will also vary depending on carb models)
4) When installing the needle start in the middle clip. Drop the slide height down to a couple mm. (make sure the idle screw isn't turned all the way in).
5) Set the air screw between 1.5 and 2 turns out and then change pilot jets until the bike will start and idle well. (Have engine come up to temp before expecting this to work)
6) Work on clip position for best response close to 3/4. (May require a change of needle again to fine tune)
7) Dial the main jet down with plug chops for WOT

Thats a tried and true method. I could go into much more detail about needle selection, and thats kind of a topic on its own.

Just curious, are you riding at elevation? Or is it a 36mm carb? That main is about 10 sizes smaller than expected. 178 would be my typical starting point. Or did you get the idea from a JD jetting guide sheet? They have a misprint.

[(F5)]

which is how mine sounded till I did the youtube mod

http://www.gasgasrider.org/forum/showthread.php?t=14873

[Earwinder]

Thanks for the feedback

I am at 1330m above sealevel
My bike has a A/S 1 (screw cap) 38mm
Float level sorted
Airscrew 1,5 out
Not sure about idle screw

I like smooth power delivery
The N3EH was recommended by my GG dealer. Is this needle too "aggressive"?

I rode a proper enduro loop of 90km today. I noted the rattling on deceleration and acceleration
It is higher pitched than the engine itself. very noticeable from 1/8 to 3/4 of throttle on acceleration and deceleration. engine performance not really affected (I'm no pro)

Thanks again for the help!!!

[Jakobi]

Thats a really really small main. I ride similar elevations on an AS2 which prefers leaner jetting, and have over heated pistons using a 172 main. Thats in a hot and humid climate.

Can you elaborate more on the roughness/rattle. Is it like a vibration you can see or feel? Is it through the bars or just a sound. Does it sound like its the engine or could it be the pipe o-rings? bash plate etc?

[Earwinder]

the rattle does move through the bars, but only slightly. The front fender has a slight quiver up and down the revs.
BUT it seems more audible.
higher pitch metallic
The noise comes from the engine area, not the exhaust area.

I listened to the " GasGas EC300 Powervalve Rattle FIX PART 1 of 2 and 2" on youtube. Only the part 2 of 2 opens. I reckon the noise is closer to this problem, but mine is on both acceleration and deceleration.

It wasn't really noticeable prior to the jetting change.

The bike is brand new; only 6 hours on the clock. still smoking plenty with the new (lean) jetting :confused

How difficult is it loading a audio/visual clip on youtube for Jacobi,GMP,etc for assessment?

[The Angry Chook]

The main jet comes on at over 1/2 throttle. I'd try needle then idle jet before making such a huge jump in main jet.

Have you owned a two stroke before? They do rattle a lot compared to 4 strokes. Mine has a rattle but it's exhaust based and it's had it since I bought it.
If it's only 6 hours old it is unlikely (but not impossible) to be something internal.

[Jakobi]

My exhaust o-rings would have been lucky to last 6 hours I reccon, and sounds like a vibration from the engine itself. You also have the whirring sound of the clutch when blipping the bike in idle, clutch lever out. You also have any other end noise reverberating off the skid plate if you fitted an aluminium one.

When it doing it use your left foot (boot) and push forwards on the pipe. If it stops/changes the noise thats your culpret.. Otherwise as suggested, try the air screw, pilot jet, or clip position (clip position is easiest and most profound and would be my choice). Make a change to one circuit and evaluate what/if any effect it has had.

[Jakobi]

Heres some video.

This one was with blown pipe o-rings. Very noticable blipping the throttle at idle. http://www.youtube.com/watch?v=JSm46ermdPE