How does my jetting sound?

[n_green]

After some feedback on my jetting. I'm pretty happy with it, feels really good everywhere but was hoping people with more experience can tell me if I'm in the right ball park. Pretty rough based on sound I know, I'm just after confirmation that I am interpreting things like burble, loading up etc correctly.

Running at 1000-1200m altitude. Temp was around 12-15 deg.
38 pilot, air screw 2 turns out.
JD Blue needle clip #2
168 main.

Any feedback appreciated

http://youtu.be/Q5MszZ-nLdU?hd=1

[Jakobi]

Nice vid Nathan. Good to watch and listen to.

Really hard to judge jetting from video though. My GoPro makes everything sound way higher pitched than it really is. I think the mic in its broken. How does the bike feel in the mid range? How'd it compare to JD Blue in clip 3? What difference did you feel? Also just for others, this is a 2011 EC300 with the ASII 36mm.

If you were chasing perfection I think you could drop a step or two on the needle diameter, up a size or two on pilot, and possibly pick up a half a clip richer in the mid range. But thats purely speculation just from listening, and pretty unachievable with the JD Kit. The main thing is that the bike runs in a way that you are happy and isn't showing any signs or symptoms of being lean (falling flat, racing idle, pinging, overheating, etc).

[n_green]

I do have the 36mm carb. Also fitted with a #6.5 notched slide.

I started the weekend running 40 pilot, JD Blue #3, 170 main. Was too rich and very burbly and doughy through mid and top. Hit reserve at 69k's 50/50 single track/fire trail pushing reasonably hard.

Went down to a 38 pilot and 168 main and it improved the off idle burble and mid range response a lot. Also woke up the top end a fair bit. Still felt a bit doughy though and only improved fuel consumption by an extra 5 k's.

I wanted to drop a size on the main but was wary of going too lean so opted to raise the clip instead. With the needle on clip 2 it noticeably made everything a lot crisper. I feel I may have lost the smallest amount of torque off the bottom however it could still easily torque it's way up hills in 2nd without clutch or stalling. Loved the crispness through the mid was awesome coming out of a corner in 3rd and rolling the throttle on to loft the front wheel. Instant smooth response. Still seemed to lack balls up top though I found if I was up high in the revs it lacked the power to wheelie even with aggressive clutching. So maybe I am still a fraction rich up top? Hit reserve at 75k's with this jetting. All up used 9.2l for 87k's.

In any case this jetting if slightly rich should be good for sea level? May drop the clip back to #3 or since it's getting warmer will leaving it in clip #2 be ok?

I'd like to try a leaner needle, would this improve fuel economy or because I'd then have to use larger jets would the benefit be offset?

[Jakobi]

It does sound very clean off the bottom for a small carb with the blue needle and richer slide. My bike burbles so much if I run a G diameter needle. I was just watching some old footage from when I did and even with the needle in top clip it would still be too rich and then fall lean in the mid range.

Your fuel economy is about right for a stock engine while riding it pretty hard too. If you want to try some other needles let me know and I can probably mail you a N3EW/N3CH to test out and a suzi needle too if you wanted.

I'm also not sure about the top end if its falling flat from being lean or slow revving from being rich or if its just the nature of the 36mm carb which will favour bottom end response.

[n_green]

So a JD Blue needle is same diameter as 'G' series needle? Didnt know that cheers.

I have NEDW, NECW, NEDJ, NECJ needles and access to KTM needles. Just haven't really played with them yet as the JD blue was Simmos favored jetting. And I really like it too. I keep telling myself one day I'll devote a day in the bush doing jetting loops, pick a loop with tight single, steep up and down hill and open fire trail and then play with the jetting to get a good feel for what is what. But that hasn't happened yet.

I'm pretty confident it's not lean up top. I started with a 172 in it and stepped down one main size at a time and each time it got better. Also had lame straight line drags with a mate on his KTM and he is now only pulling one length on me from standstill to flat out instead of 20 metres (the top end was that rich when i first got the bike). I'm happy with it at the moment and if I did step down again it would be purely curiosity based.

The power actually feels very similar to my old '04 KTM 300 which had super impressive torque and meaty mid with an unimpressive top end. '09 and '11 KTM in comparison has noticeably less torque off the bottom with a snappier mid and then a rocketship top end. Different bikes I know, wondering if it has anything to do with the flywheel though? Older KTM and my Gas Gas look to be running very similar flywheel, though GasGas has e start gear bolted to the outside. Newer e start KTMs run a different lighter from memory flywheel? Could there be any weight to my thinking?

I'll be getting the head modified ASAP to hopefully improve fuel economy. Does the head mod assist top end at all? If I'm still chasing silly top end power I could always oval bore the carb?

[n_green]

I take it Jakobi you don't have any issues with top end signing off early? So wondering if it is just a difference in carb size?

Anyone else with the 36mm carb have similar sign off? (I should add its still pretty damn good, just feels like the power curve becomes flat for the last few thousand RPM instead of continuing the linear uphill trajectory from low down through mid. All tested using my ass as a dyno mind. )

[gasmonkey]

Hi there Greens,I feel your are in the same position I was with my 11 300r untill I did the head mod.Piss easy to do if you are/know a lathe jockey.After that every thing fell into place.Sweet running,ultra responsive,just a blast to pilot.

[Jakobi]

If you're sending your head to Dave I'd probably send the carb too Depends how much you want to spend.

The JD blue is closer to a F diameter needle if I remember correctly.

I watched your mates video (Stu) and his bike sounds like its jetted more like I have jetted mine. Very crisp and clean with a strong top end.

Considerations for top end power are:
1) The 36mm carb
2) The base gasket stack/port timing
3) The compression ratio

Have a look and see how many base gaskets are in it. I think for 2011 they dropped to a single 0.5mm gasket which will probably have your port timing set to favour lower to mid. If you want to shift some grunt up thats something to address when you get the head done. If you get dmcca to do the work he will run sims and give you a graph to work off showing different configurations and plans and how the effect the power curve. Here is the one he did for me. (if you want to read up on the subject see here: http://www.gasgasrider.org/forum/showthread.php?t=11970)


Stock my 300 ran the port timing favoured for the top end and with the 38mm carb it had more than enough of it for me. Any comparisons since then are bleh as my engine is now a 250 running a slightly modified cylinder, s3 head with custom insert.

The gassers do use a 2k3 ignition which has quite a bit of mass. Shouldn't stop the power coming on though. Just make it less aggressive.

Its really your call on how you want your bike to run. If you're happy with it now then maybe just keep being happy with it! I've tried just about everything under the sun now, and every time I try another setup I keep coming back to the same settings which suit me best.

[n_green]

The carb will definately get sent into Dave as well at some point however the curious part of me wants to do things one at a time to gauge exactly what it affected and how.

And you're right I am happy with it now and could quite happily live with it. One of the things I love about this bike, or any modern two stroke really is the multitude of different options and methods to setting them up there is. And thats just the basic engine stuff you can do yourself. I'm naturally curious, so that part of me wants to try every available option be it jetting, head mod, reed block spacer, oval bored carb etc and evaluate for myself if I like the effect.

Can you PM me Dave's contact details if you have them, I've only PM'd him on DBW at the moment and he hasn't replied. No doubt unlike me he has better things to do then browse bike forums all day

[Jakobi]

I've only dealt with him through PM. He'll get back to you. He's just in the process of expanding his business at the moment. Pretty sure he gets a steady flow of pms coming in too.