So, I'm going to go in and Dyno tune my F2 this coming weekend. I won't to make sure everything is golden.

I've got a micron slip on, K+N filter (recently cleaned) and I've got a Dynojet stage 1 kit installed. Not feeling the results I got though, as it's a bit lean still. Went with the recommended second needle position, thinking I'm going to go to 3.5 for my baseline.

Anways, the tuning is next Sunday, and here's the game plan:

-Pull carbs all off, clean like a mother trucker. Adjust to the 3.5 clip position. Carb Sync. Take a test ride to see how it works out.
-Install new clutch kit. Clutch is slipping. Got EBC kevlar "street racer kit" coming. New fibers, plates, and springs.
-Go to Dyno, get baseline, hopefully not be very far off. If I am off, I'll fix, take another dyno run and hopefully be spot on.



So, look for a dyno results sheet soon in this thread along with pictures and full information. This will be a pretty good indicator of how the dynojet kit actually delivers along with these modifications.

 

Oh yeah, and the symptoms that lead me to beleive I need to step the needle up:

Lots of popping and sputtering from 6.5k down to 3 on deceleration. On acceleration you can hear the light gurgling/sputtering feeling of being lean. Not a rich feeling, which is a bit sluggier. My Dr350 dirtbike (one of two I own, not my best) is way fat right now so I can tell a rich mixture from a lean. It's not a rich mixture. Pilot jet is a possibility, but stepping the needle up will affect 1/4 to 3/4 throttle.

Carbs definitely need synching in combination with mixture being corrected. Lots of vibration through the foot peg probably caused by imperfect detonation.



On my way into the carbs I'll take a picture of a spark plug so we can try and glean any information from that as well.


Hopefully this tuning, with demonstrative horse power and A/F mixture graphs will help others. I haven't seen anything of the like on here yet. I'll happily be the first.

 

This has the making of an excellent thread. I love picture stories .

 

subscribe...

 

in - my bike sounds exactly like you describe on deceleration. Thought I'm running lean as well.

I also think I'm fat on the pilot circuit, but dunno about the lows and mains. Pilot circuit is really only at Idle, correct?

I have the bike adjusted to idle at ~1400 but once good and warm will sit there idling and then jump up 200-300rpm for a second and go right back. It repeats this every 5-8 seconds. Not sure exactly what that is indicating.

 

Your jetting is slightly off.

-A/F Mixture screw only affects up to 1.5k or so. It can be used to determine if your pilot jet is off to a certain extent.
-Pilot jet affects 1.5-7k
-Main Jet affects 6k to 13.5k
-Needle taper affects 4k-13.5k but different parts... so... it's interesting.
-Needle position affects 4k-11.5~k.. It has no affect at the highest rpms as the needle will be all the way out of the jet allowing the full fuel to come through. It has more of an affect on the high end than the low end.


I need to scan the graphs from my Yamaha WR400F manual. Best visual representation of how Jetting works I've ever seen thus far.


This graph is somewhat representative, but not nearly as good as the Yamaha Manual stuff:

 

According to that graph, my problem appears to largely be with clip position, as I'm rolling off the throttle and when dropping down from 7k I get lots of popping, and on acceleration at that range it feels gurgly. It's almost a shade like as if you're starting to run out of gas, but the very very early part of that.

 

This graph is a bit better, and not quite meant for two stroke dirtbikes!

 

Got the carbs all the way removed...



Carbs removed. Cleaned the jets since I was in there, and then adjusted the needle position. I was on the second clip, so I went out to the fourth clip just to be sure.


YouTube - May 2, 2011 10:09 PM


Analog carb synchronization setup... what the heck is going on with this thing... The higher the RPM the more stabil the needles get... so I may jsut have to raise my rpm really high and tune it that way. It'll **** my neighbors off, but meh, whatever

 

I didn't put these inline... I'm thinking I need to do so...


EDIT:

Yep, those are the inline restrictors. These carb tuners lack of directions definitely didn't help! I also need to sync the carbs to each other so as I know They're all accurate and I'm getting a proper reading. On my lunch I'll be hitting an auto parts store, picking up three T intersections and some extra hosing. I will then connect all of the carb syncs together (one T per carb sync, one t to connect them, three t's) and using my mitey vac sync them. Once that's done, I'll add the inline restrictors and get the carbs perfectly synced up. WOOHOO!