Slide Theory, Carb Models, and Jetting

[swazi_matt]

@Jake your jetting advice has been spot on for me, the v-force is strong with the young jakobi air-striker

There was however a lot of swearing as I pushed my bike up a hill with a suspected fouled plug, followed by embarrassment when I realized it was because I forgot to turn the fuel tap on again after adjusting the needle clip ;-/

 

[GMP]

Jake,

What is the ethanol (or other oxygenate) content of fuel in your area of Austrailia?

 

[Jakobi]

We have E85, E10 (performance ethanol and povo brew). We also have Normal is 90-92RON. Premium is 95RON and then the special blends are 98RON. I always run mine on 98 - BP Ultimate.

Our RON ratings are also a bit different to the ones you have in the states which are a RON/MON average.

For what its worth though, the bikes that have sparked this discussion are all running in Australia in similarish conditions. I haven't heard of anyone running their bikes on Ethanol based fuels, but I guess it could be happening.

 

[GMP]

OK, so what you are saying is that you run your bike on 100% gasoline, not E10, correct? The RON/MON is a wash, just a number, premium fuel is premium fuel.

 

[rod]

Holy shite, you've thrown me with "oxygenate".

Ethanol based fuels are optional at the bowsers here in Australia.

It's a fair assumption that no one uses it, mostly we'll choose 95 or 98 ron unleaded. Our std pump fuel is 91 ron unleaded.


PS: Jake, you posted whilst i was typing. I think their envious of our fuel choices!

 

[GMP]

Not ethanol "based" fuel, but fuel with ethanol or another oxygenate like MTBE (we used to use this here in the USA) added. Basically any oxygenate means a leaner burning fuel. That is my point. I guess I should have asked exactly what you guys run in your bikes, not what you have available.

 

[rod]

OK, so what you are saying is that you run your bike on 100% gasoline, not E10, correct? The RON/MON is a wash, just a number, premium fuel is premium fuel.

Glenn, we are not forced to use ethanol based fuels in Oz yet!
In most servos(gas stations) there is only one or two pumps out of 8 or 10 that actually dispense the stuff.

95 or 98 ron petrol(gasoline) is still affordable and readily available and thats what we run in our dirt bikes and i run in the family car until we're forced to do otherwise.

 

[GMP]

Thats part of the reason why your jetting is leaner. 10% of our fuel is crap that must be compensated for.

 

[rod]

Not ethanol "based" fuel, but fuel with ethanol or another oxygenate like MTBE (we used to use this here in the USA) added. Basically any oxygenate means a leaner burning fuel. That is my point. I guess I should have asked exactly what you guys run in your bikes, not what you have available.

You've thrown a curved ball at me there, i don't know enough about our fuels to answer with authority, i'll leave that for others.

This is a great forum, lots to be learnt.

 

[GMP]

Its OK you already answered the question. You run real 100% gasoline.

 

[jpelaston]

Can anyone tell me if the slide from an AS1 will work in my AS2?

 

[GMP]

Yes, they are the same slide design.

 

[n_green]

Jakobi I am about to send off my carb and head for a bit of work, between that and my current schedule I won't be able to ride for the next month or so.

And when I get my carb back it'll be oval bored 36/39mm so I'll have to start from scratch with my jetting before I can run back to back testing with non-notched #7 slide.

So, in light of education would you be up for testing my notched #6.5 slide and posting up results. I'm happy to post it up to you and leave it with you for a week or two. If you're keen let me know.

 

[GMP]

I just tried the notched #7 again, this time with a richer #48 pilot. Same JD Blue #3 and 180 main. MUCH better! Does not exhibit the lean pilot symptoms and low end is stronger. This is absolutely contradictory to what I have been told about notched slides(that they make the pilot ckt more sensitive and require a LEANER pilot).

 

[Jakobi]

Thanks for the offer re the carb. I don't think I'll really have the time other than to drop it in for a quick squirt down the street though. Gimme a few days to recover from the weekends ride and I'll get back to you. I'm all biked out! Should be some good pics and vids coming shortly!

 

[john r b]

I hope some one can tell me if I may use a jd jett kit for a 36mm.
On my new 12' 250 xc which has a 38mm I believe. A shop has sold me a kit for a 11' gg. I won't name the shop. Thanks

Presently I'm running in the bike
170 main
38 pilot
Blue needle 4th position
#7 slide no notch
air screw 2 turns out

 

[Jakobi]

I hope some one can tell me if I may use a jd jett kit for a 36mm.
On my new 12' 250 xc which has a 38mm I believe. A shop has sold me a kit for a 11' gg. I won't name the shop. Thanks

Presently I'm running in the bike
170 main
38 pilot
Blue needle 4th position
#7 slide no notch
air screw 2 turns out

The needles are the same between the kits and for 2011 some bikes came with 36mm and 38mms so JD offered one kit with instructions for both carbs. Your shop wasn't wrong What does sound wrong is running the rich needle in a rich clip position with a main that small. The settings you have settled on actually sound alot like what those with 36mm carbs are enjoying.

If it is a 38mm your settings willl depend if its an AS1 or AS2. Either way one would generally expect a much larger main to be used. You haven't specified any details re fuels, temps, altitude etc. so hard to provide any more specific info.

 

[n_green]

Hmm just pulled the slide out of my mates KTM300 and he has a notched #7 slide so I don't think there will be any point in comparing the two now.

Bugger.