I need jetting help....

[Jakobi]

I'm running my squish at 1.35mm currently. I don't think its massive. Col also had Dave set his up with 1.6mm and has been happy with how it runs.

[n_green]

Originally Posted by Jakobi

I'm running my squish at 1.35mm currently. I don't think its massive. Col also had Dave set his up with 1.6mm and has been happy with how it runs.

Good point. Based on my piston dome it looks like the burn is spread nice and evenly so ill probably just leave it alone. Plus if I do send it back down that's a week or so I have to go without riding.

[Jakobi]

Also, not sure if you ran the verniers over the base gaskets. I'd say its most likely the old ones were just a touch thinner (or new thicker). You could always drop one of the 0.5mm's for a 0.3mm.. pick up some more torque, some more comp, and some decreased squish..

[(F5)]

Don't think you can ascertain much from the piston crown of a dirtbike. A roadrace bike will be run through peak power with every gear change & then if shut down in correct plugchop manner can be assessed. That will check mainjet jetting if done right.


Heck when I ride my dirtbike (usually fair to gnarly terrain) I spend quite a bit of time away from peak power, esp on the 300,

. . . too often on the seat with legs flailing every which way

loads of time with non optimal combustion.

[n_green]

Persistence has paid off, finally.

Using Jakes 38mm ASII carb and with a fresh top end I did a 2 day ride totalling 200k's with the following jetting specs:

42p AS 7/8to
NEDJ #2
175m

Weather was perfect all weekend between 15 - 20 degrees and 60-75% humidity. Elevation from 300 - 700m asl.

This ride has everything in it, tar road transport sections, fire trails, twin trails, single trail and a little bit of goat track thrown in for good measure.

Day 1 consisted of 110klms of all of the above, probably 50k's of 2nd and 3rd gear single and the remaining 50k's being 4th/5th/6th WOT fire/twin trail. Jetting was brilliant pretty much everywhere. Would lug right down without stalling and crawl up most hills in 2nd. Nice and punchy through the middle, perhaps a bit rich up top as the power definitely fell away once past 3/4 throttle.

Day 2 was 90k's of 90% fire trail and twin trail.

Fuel use on both days was brilliant - approx 10l on day 1 for 110k's and approx 6.5l on day 2 for 90k's.

I like this 38mm carb now, reckon Jake will notice if I send my 36mm oval bore back to him instead of his 38mm? haha

[Jakobi]

Hahaha! I reccon you'd notice.. once I start posting how my old specs don't work anymore.. Hahah! You should drop the same config into your 36/39mm now you've freshened up the top end and main seals. I think you might find it pretty close. Maybe drop to a 40 pilot and call it done..

I've taken a note out of your book now and moving over into the suspension side of things. Watch out for some space kidet threads ahead..

[n_green]

Originally Posted by Jakobi

Hahaha! I reccon you'd notice.. once I start posting how my old specs don't work anymore.. Hahah! You should drop the same config into your 36/39mm now you've freshened up the top end and main seals. I think you might find it pretty close. Maybe drop to a 40 pilot and call it done..

I've taken a note out of your book now and moving over into the suspension side of things. Watch out for some space kidet threads ahead..

I tell you what the suspension side is very satisfying when you start making progress. I've finally got my forks to where I'm 95% happy with them, its a bloody good feeling considering I've done most of the work myself, with a bit of help and advice from a few people.

Quick question, I note in another thread elsewhere you said a rich bottom end will start and run easily when cold. My motor was doing this this morning, would of been 18 degrees and once it started i turned the choke straight off and it kept running fine. It also didn't take too long to come up to operating temp. Funny though it didn't seem too burbly or load up throughout the day and it's definitely not using excess fuel, I'm also only 7/8's of a turn out on the air screw which would indicate the 42 is the right size if not a tad lean wouldnt it.

So how can this be?

[Jakobi]

That sounds good to me Nath.. It started easily with the choke (enricher on).. and ran well when you took it off shortly after it started. Didn't burble up during the day. Sounds like a cleanly jetted bike running how it should.

Rich, will be like it doesn't really want to start well on the choke. Wants the choke off, or the throttle cracked slightly on a cold engine, and it will run best right away and get fluffier as the engine comes up to temp. If its super rich it won't make a difference. It'll run like crud breaking up and burbling all the time, smoking heavily until the plug fouls.

[n_green]

Sweet sweet sound of 2 stroke:

http://youtu.be/cvCdpLeynlw

[Simmo737]

Originally Posted by n_green

sweet sweet sound of 2 stroke:

http://youtu.be/cvcdpleynlw

awesomely awesome