Power Valve Opens Too Fast?

[mcnut]

Ever since I've taken delivery of the 2012, I've struggled to get some low end torque and throttle response, basically just to make the thing run like a 300. I've tried many different carburetor settings, including 2 different pilot jets, two different main jets, four different jet needles, and various air screw settings. One thing has been constant: no bottom end! I even pulled the 36mm carb from our '11 250 to replace the '12's 38mm. That seemed to help most but is not a viable option; I didn't want to deal with the 38mm on the 250 when it runs perfectly with its original 36.

After going all over the map with carburetion and still not curing the problem, I decided there must be something wrong with the new 300's exhaust power valve. So today I pulled the exhaust pipes from both bikes, removed the right side pv covers, then reinstalled the pipes. When revving the bikes at low rpm and small throttle openings, it's obvious the 250 opens more gradually than the 300. When you blip the throttle on the 300 very much at all, its valve opens completely. When I rev the 250 identically, by ear not tachometer, the valve opens partially. Seems to me I found out what's causing the lack of bottom end, but why?

I do not have a lot of experience with the GG power valve set up. I've never had an issue with one. What would cause the valve to open too quickly and how do I fix it?

 

[moto9]

you could shim the PV governer, which would cause it to open later.
Be nice if it were adjustible like the KTM's

Trusties makes a accessory that bolts onto the left side cylinder and is a adjustible PV by using a spring to preload the pv shaft.

 

[GMP]

First I'm sure you checked that there was no excessive slop in the system and the actuator returns to contact with the stop bolt. That said then yes, like moto9 noted, I'd check the governer to see if it has any preload shims. You can pull the covers off both bikes to compare. Your not the first to notice this, it has come up in the past comparing two older bikes. I don't know off hand the correct number of shims or thickness, or if the springs are different, would be good to check into. Maybe you have some incorrect parts in there. I would think there should be a test in the mfg. process to verify correct operation of the governer, but thats just how we would do it here, not Spain.

 

[mcnut]

If anything the 250 has more slop than the 300. I just walked out to the barn to check.
As I said my experience with the GG power valve is practically nil. I've only done a top end on a GasGas once, and I've slept since then. When you say remove the covers to look at the shims, I assume you mean the water pump and right side engine covers? Looking at the parts diagram, I can't figure out what you mean.

 

[GMP]

The entire primary side cover. The quick access clutch and water pump covers may be left intact, only a couple longer through bolts need to go. Just drain the coolant and oil, pop off the starter and coolant hoses, and have at the bolts. I like the GG PV design, its rugged, simple, and made of steel. The KTM and Husky are way over complicated by comparison, full of orings and soft alloy parts.

If you need a copy of the GG engine shop manual let me know I'll email you a PDF copy.

 

[mcnut]

FORK! That's what I thought you meant. I've got the parts diagram. I don't see the shims you're talking about.
Forgive me but I'm not especially enthused with having to go through all of this on a brand new bike! I've got countless hours in testing, switching carb parts and settings. I bought a couple needles I probably didn't need. Now I'll have to get a right side gasket before I can do anything. Plus, I'm not exactly sure what I'm looking for once I get this thing torn apart. FORK!

 

[Fred1956]

FORK! That's what I thought you meant. I've got the parts diagram. I don't see the shims you're talking about.
Forgive me but I'm not especially enthused with having to go through all of this on a brand new bike! I've got countless hours in testing, switching carb parts and settings. I bought a couple needles I probably didn't need. Now I'll have to get a right side gasket before I can do anything. Plus, I'm not exactly sure what I'm looking for once I get this thing torn apart. FORK!

McNut, Do a search on powervalve and you'll come up with a lot of threads. There is one in particular that gives you all you need to know. It is not that big a deal to do and sounds way harder than it is.
This may be it- http://www.gasgasrider.org/forum/showthread.php?t=9517&highlight=powervalve on page 4 of that thread there is a post by mlbco that has very good pictures to help you, it has a lot of info in it. Also worth a try to take the side cover off, a lot of times the gaskets will stay intact, I've done it several times myself. If you have trouble getting a gasket let me know I keep several here

 

[Loosenut]

My 2005 EC300 lacked the low-end power that my 2000 XC300 has. The big difference was compression. I ended up swapping the stock head for a RB modified head and I got my monster back. With a CCL needle, it's a rheostat.

 

[forgiven]

I had the misadjusted powervalve...fixed and it is everything you could want in a 300. LOTS of people have had this.

 

[mcnut]

Thanks everybody. This issue has been very frustrating, costly, and extremely time consuming.
I always try to search the forums for answers but can't seem to find the right posts. The one Fred gave me was very infomative.

 

[GMP]

Not a big deal. A few years back, there was a tendency for the shift shaft fork and sliding "scorpion" (part that engages the shift drum) to have burrs from the stamping process. Many of us would pull the cover, clutch, and shift shaft on a new bike to check and dress these parts if necessary to avoid a stuck shifter. If the PV looks sloppy on my '12 it will be apart before its first real ride. Get a gasket and get to the bottom of it.

 

[mcnut]

Perhaps my standards are too high. I have a hard time understanding why a company would ship known issues out the door. If this was my first experience with the company, it might have been my last.
I was never able to forgive Kawasaki for that piece of crap 1975 F-7 I bought.

 

[Jakobi]

Perhaps my standards are too high. I have a hard time understanding why a company would ship known issues out the door. If this was my first experience with the company, it might have been my last.
I was never able to forgive Kawasaki for that piece of crap 1975 F-7 I bought.

Why would they ship an engine with a 3mm squish band? Why do they ship them all with the same substandard thirsty jetting specs?

It would depend on the assembly order. My guess is that the RHS cover and everything is put on before the cylinder which is why there are some variances in the preload between bikes. Ideally the cylinder should go on first and then have the preload set.

I expect some variance from the production line. How much is acceptable? I know if I was a dealer I'd be doing all of this as part of my predelivery.

 

[GMP]

As an engineer comming off Hondas and KTMs, I was shocked at the lack of detail in fit and finnish of my first GG, a '00 XC250. It got worse as I took the bike down for prep. All was forgotten after the first couple rides and first enduro. The newer bikes are MUCH better, but are still GGs. Just like Ducatis.

 

[nato]

I also have a 12 300 in on an n3cj needle and it has loads of torque! Wonder why yours is different?

 

[Jakobi]

I also have a 12 300 in on an n3cj needle and it has loads of torque! Wonder why yours is different?

Wence seems to have just had a good run using 38 N3EH#2 180. He knows hes a bit rich on the main but likes the safety buffer for the sand they hit. He's stoked with the power delivery of his too.

I believe this is more likely a mechanical issue with the powervalve preload being off though. Basically if the preload isn't correct the power valve will start to open almost immediately instead of holding shut a bit longer.

 

[GMP]

According to parts manuals, springs have been the same since '03 at least, except on the 125 which gets its own spring. Shims varied from one .2mm to x2 .2mm + .5mm. '11 and '12 should both have two .2mm shims. No difference in 250/300.

 

[mcnut]

Big THANK YOU to Cam Norris at Indy Moto! Cam spent a good portion of his day yesterday trying to get this 300 to run like a 300 should. First he added two shims. That was too much. PV wouldn't open completely. So he disassembled, then reassembled with one shim. PV now opens more slowly yet completely at high throttle openings. Bottom end seams better but I'm fairly certain I need to re-jet a little for the PV changes. I'll have my racer assist with testing when he gets home from school today.

 

[Fred1956]

Good news ! I think mot people were removing all the shims, but what ever it takes. Did it start with no shims?

 

[savage sausage]

Brand new bike ????

Take it back to the dealers mate, you paid a lot of money for it, I dunno how much those new bikes cost but if you bought a new television with a crap picture would you contact the store??