RB Swab or RB Mod? 2005 to 2011

[AZRickD]

RB Swap or RB Mod? 2005 to 2011

A special situation.

Having taken possession of adv_rider's 2011 EC250 Race, I am (this morning), doing a squish measurement and such.

My '05 had both a the squish (about 1.05 mm) and the carb mod (old Air Striker 1) completed with excellent and good results respectively.

I am hoping that my old modded head will give me a good squish on the 2011 and then I can send in the stocker into RB to make me a head that is potent at 10,000 feet if I ever visit Colorado. I told RB that my riding in Arizona is usually no lower than 2,000 feet and often at 3,500 for a few races, and even at 6,000 and 9,000 when heading to Flagstaff in the summer. Temps are around 50F in the winter in Phoenix, 95F in the summer (at sun up) at around 85F in Flagstaff at mid-day. The best pump gas we get in Arizona is 91 octane.

So, the head issue is fairly simple. BTW, my modded '05 with about 60 hours on the top-end compression tested out to be about 25 PSI higher than the stock 2011 with 13 hours. More later.

The carby, on the other hand (SmartCarb and Lectron aside) -- I have been told that the Air Striker 2 is a better carb than the AS1. Fine, as it goes. I am wondering whether I should keep the un-modded AS2, swap my modded AS1, or get the AS2 modded by RB.

Thoughts?

Rick

 

[AZRickD]

Measured the stock 2011 head -- Avg = 2.12 mm

Next up is the RB-modded 2005 head on the 2011 jug.

---

Interesting...

The modded '05 head when placed on the 2011 jug measures ~1.33 mm

To check, I re-measured the '05 head on the '05 jug --> .92 mm

On my last top-end on the '05 I used a Vertex piston and a single stack for the base gasket (probably .5mm). I can't recall what was on when I did the original squish a few years ago.

 

[roverhybrids]

I got my AS2 moded And I think I may be unhappy with RB cutting the slide(originally a #7) i bought another stock #7 notched slide and it almost got rid of the 1/8-1/4 throttle lean bog(JD blue needle).
I've tried 3 different needle and before I swapped the slide back to a stock I had a mid throttle bog.
I'm not saying the RB mod can't be made to work, I just haven't figured it out yet

 

[forgiven]

I believe he cuts them to a 6

 

[AZRickD]

The question now is, what base gaskets do I have in there?

I checked with a light and magnifying glass and I can't tell for sure. I may have to do a jug-ectomy.

If it is the common combo of .5mm + .3mm then, as GMP advised me, I could take out the .3mm gasket and I would be at a golden 1.03mm of squishie.

I am not the type to go in and yank the jug (normally), but since the bike is already partially dissembled, what the heck? As long as I can avoid messing up the PV system.

 

[Jakobi]

1.3mm of squish will also run just fine. Port timing will give you a bit more up top, as will the slightly lower compression. Note: on my 250 I'm running a modified head, 0.6mm of base gasket, and 1.35mm squish height. Remember if you take the cylinder off you'll have to replace the base gasket too. And well, torn down that far you might as well re ring it too! hahah..

 

[AZRickD]

Well, there's no reason not to give it a go, I suppose. The motor ran nicely with the stock head, although it was jetted a bit rich (coming from Seattle).

Jakobi has brought out The Lazy in me.

Is there anything I should snag from the RB-Modded Air Striker-1 carb to put in the Air Striker-2 carb? Slide? Needle jet? Needle?

What's a good starting point for jetting the AS2 at Phoenix's 2,000 feet and 95F sunrise temps? I've yet to look at the 2011's carb yet (frickin' hot in my garage).

 

[Jakobi]

Check the carb first and have a look whats in there. It might even be close with current head.

 

[AZRickD]

Yer gonna make me werk for this.

 

[Jakobi]

*nods*

I can't remember what adv rider ended up with maybe 42/45 N3EW#1/N3CW#2 and I think a 180 main. Very much on par with what a YZ250 would be running too. It shouldn't be far off.

 

[AZRickD]

I found the thread, thanks.

http://www.gasgasrider.org/forum/showthread.php?t=14421

 

[AZRickD]

Here is his set up at 50f temps. It will be 110F tomorrow. Elevation = 2000 feet MSL.

I put another 2 hrs on bike yest., And it ran great. Temp was about 50-closer to 40 up top. about 1000ft. - in 6-8" of snow.

I had made a minor change before the ride, and it seems to be just what it needed. I shimmed the needle .018".

So my JETTING IS NOW AT N3cw- #2 w/ shim, 42p, 180m,float height 8.7mm, air screw varies.

 

[Jakobi]

That needle clip position is the same as N3EW#1, which is pretty lean already. I used to run right up around the lean settings on my stock engine as it just wouldn't run clean on anything else until I did the head mod.

For you probably just drop the pilot to a 40, and the main to a 178, as a starting point. Removing the shim on the needle will get you half a clip leaner if you think you need it. You can drop the main down if you need to as well. But.. being that you have now put the modded head on, I'd simply start the bike and run it as is. Then change as required.

 

[AZRickD]

I'm in the carb right now.

That little Number 7 in the slide must mean it's a Number 7 slide.

I'll move the needle clip down to the number 3 position and get rid of the shim. I'll then drop the main to 172. I'll keep the pilot at 42 and see if the air screw gets me where I want to be.

 

[AZRickD]

I took the Gasser for a spin this evening (87F at 11:30pm).

Seemless powerband with a bit of an exponential curvey rise in power with RPM (definitely not a "hit"), which is what I like. It ran well. Perhaps just a tad rich off bottom, but I tend to like it that way. It's difficult to sort out performance in the neighborhood over speed humps.

The trail awaits.

 

[AZRickD]

I took the bike out at 6am Saturday and Sunday to test boingers, carb, and just to get acquainted. I decided to install my LTR PV-extender thang as well.

The jetting is in the ballpark and I don't see a lot of need to tweak it. The pilot _might_ be one step rich, but it's behaving the way I want it to.

This 2011 bike's motor rips. The bike really gets up (even with the heavy fly wheel and 48T sprocket -- compared to my 52T in the 2005). The 2011 bike is faster.

The map switch makes a difference. In Sun-mode it rushes to power. Screams. My KTM buddy was all, "Holy Fawk !!" In Rain-mode, the bike is somewhat slower to climb to power and I had to make a concerted effort to twist the throttle to get on the pipe. My other friend's 2008 GG300 barely tickles the pipe when on Sun-mode. On my bike, if I'm tired or just in over my head, I'll go to Rain. It's just enough margin while still allowing full power (eventually).

The one thing my 2005 did well was kick-start in a nano-second. I am the hole-shot King on that bike. My technique and jetting on the RB-Modded 2005 wasn't nearly as clean on the 2011. I would crack the throttle a bit on the 2005 to light it. If I do that on the 2011 it will go rumble-rumble then die. I practiced several imaginary flag-drop starts today and my new functional technique suggests that it doesn't like any more fuel in the intake than a normal slide-closed shutdown and slide-closed start will allow.

 

[Jim Cook]

I took the bike out at 6am Saturday and Sunday to test boingers, carb, and just to get acquainted. I decided to install my LTR PV-extender thang as well.

The jetting is in the ballpark and I don't see a lot of need to tweak it. The pilot _might_ be one step rich, but it's behaving the way I want it to.

This 2011 bike's motor rips. The bike really gets up (even with the heavy fly wheel and 48T sprocket -- compared to my 52T in the 2005). The 2011 bike is faster.

The map switch makes a difference. In Sun-mode it rushes to power. Screams. My KTM buddy was all, "Holy Fawk !!" In Rain-mode, the bike is somewhat slower to climb to power and I had to make a concerted effort to twist the throttle to get on the pipe. My other friend's 2008 GG300 barely tickles the pipe when on Sun-mode. On my bike, if I'm tired or just in over my head, I'll go to Rain. It's just enough margin while still allowing full power (eventually).

The one thing my 2005 did well was kick-start in a nano-second. I am the hole-shot King on that bike. My technique and jetting on the RB-Modded 2005 wasn't nearly as clean on the 2011. I would crack the throttle a bit on the 2005 to light it. If I do that on the 2011 it will go rumble-rumble then die. I practiced several imaginary flag-drop starts today and my new functional technique suggests that it doesn't like any more fuel in the intake than a normal slide-closed shutdown and slide-closed start will allow.

What elevation is that Rick? 172 seems pretty lean for an extended wfo runs (gravel road or sand wash sort of run).
Have you tested to see if it leans out after you open it up for 5 or 6 seconds straight? (Does it drop immediately and smoothly back to idle when the throttle is shut and the clutch pulled in, or does it surge as it drops back to idle? That's the technique I used to keep from burning up ITs, back in the old days. If it doesn't surge, I'm not going to melt a hole in the piston. )

I'm really interested, as I'm waiting on my '11 GG 250 head to get to and back from RB Designs, and I'm thinking of the jetting I'm going to try. Before the mod, I have been using the N1EG - clip in #2, 42 pilot, and 175 main. Compared to the stock jetting, this really picked up the power off idle, and still pulled pretty snappy out in the open; but it's still spooging badly and dripping on that pretty new swingarm (single track situation, mostly).

 

[Jakobi]

Jim,

Double check your carb model. The PWK AS2 jets much leaner than the AS1. A 172 main is still on the lean side for a 250 though. I heated mine enough to burn oil under half the piston dome with a 175, 300M, 30C.

 

[Jim Cook]

Jim,

Double check your carb model. The PWK AS2 jets much leaner than the AS1. A 172 main is still on the lean side for a 250 though. I heated mine enough to burn oil under half the piston dome with a 175, 300M, 30C.

I've got the newer carb on my 2011. From reading all the various threads, I can see the differences in "new" and "older" PWK38 jetting specs. I sure appreciate all the info you folks have shared.

In the "old days" ( ) I could easily jet the Mikuni carbs that came on Yamahas and Huskys. When we started with GasGas in '97, I quickly found that the Keinin PWK carbs were a different breed, and didn't respond to changes the same way as what I was used to.

I'll probably try the CCK first, after I reinstall my head and get things back together.

Good Riding!
Jim


.

 

[AZRickD]

My riding area NW of Phoenix is at 2,000 feet. It's also hovering above 90F at 6am and climbing to 100F when I finished at 8am. Afternoon highs at 117F this week.

The Seattle sea-level jetting that adv_rider had was just too rich on top and it cluttered up the bottom a little as well.

The idle didn't hang after my 200-yard WFO sprints. It did have the ol' bah bah buh bum bum bum kind of idle for several seconds afterward, tho.