Powervalve issue?

[Jim Cook]

Bumping in this thread as i am still chasing down a rattle. It comes from the left hand side tough, low rps while the bike is moving.

What i want to find out if there should be play in the PV actuator arm and the PV actuator plate, here is a video i made a while ago
https://www.youtube.com/watch?v=QuJqHtTPUzU

Should i tighten the nut down to remove the play in the arm ?

Regarding a rattle in the pv assembly:

You can tighten the nut a bit, but as was stated, be careful because the stud is "fragile" and will pull loose from the bracket easily. I heat mine retaining nut before removal, and then replace it each time with new 5mm aircraft style locking nut. (mcmaster-kerr is your friend.)

Make sure that you don't need to take the slack out of your pv linkage by adjusting the bell crank governer that it is connected to. This is the cause of most pv rattling. This issue is covered in the forum quite thoroughly.

Also, make sure that you have the spacer behind your pv bracket installed. I saw some bikes come from the factory which were missing the spacer. If you look at this part diagram, you will see it as part #36 in the diagram. http://partsfinder.onlinemicrofiche...=27&c=0&d=2006 DE250 CYLINDER - CYLINDER HEAD

I hope this helps you.

Good Riding and Wrenching!
Jim


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[Jim Cook]

Just learning about the GasGas style PV.

I have a 2000 200ec.
From what I ca tell, the PV is pretty much the same for all of them?

The pivot does sit against the stop, but almost no pressure at all will allow a couple of mm movement.

I get a rattle, but more what I am trying to solve is lack of bottom end and a hard hit.
I know is is a 200 not a 300, but I'm trying for best bottom end power and less top end. As linear as I can get.
If I drop 10hp on top that is just fine, maybe better.

So...from my description does it. Sound like I need to pull the side cover and adjust it?

Any other ideas to get what I want is welcome (already flywheel weight).

Mark

I don't know which exhaust pipe you are using, but if it is not the FMF Gnarly, you can pick up good bottom end power with that pipe.

It made a huge difference in ours, compared to the stock GasGas pipes and the Messico pipes.
That, and proper jetting and good compression.

 

[Zman]

I was in a bind before a ride and wanted/needed a quick fix for a slightly loose PV actuator rod. I used two pairs of pliers to slightly tighten the bend in the actuator rod. it took care of the slop and worked fine.

 

[stian]

Wanting to know if there is any clearence for the right side of the half-moon bushing, and if the silver-bushing is supposed to go round and round?

The silver bushing needs to be pressed with quite abit force, and is stuck there.
The half-moon do not turn around easy, as the double-bearing left side. It is as its some casting-flaws in where the half-moon bushing are supposed to sit. There is also 0,5mm play.

Anyone?

 

[Munch]

Which washers are people removing to make the powerband come in quicker? I haven't seen much discussion on it in this thread.

Do many people do it? Does it make much of a difference?

 

[Jakobi]

The shims/washers preload the spring behind the governor. Rhs of the image.

See em!

 

[Munch]

How many should I take out? I want the powerband to hit a bit harder/sooner. I feel like the power is a bit too boring.

 

[Jim Cook]

How many should I take out? I want the powerband to hit a bit harder/sooner. I feel like the power is a bit too boring.

What year and model Gasser are you riding?

 

[Jakobi]

Mine only has one in it. It's the darker shim hard up against the left hand side of the spring. I didn't remove any and haven't bothered making any adjustments.

One thing to note though is that the shim is simply your preload on the spring. It won't change the rate at which the PV opens, and in many cases if you have the PV open too soon you'll notice a dip in the power curve until the engine can catch up. Opening earlier doesn't mean more power.. think old school PVless bikes that were nothing off song and then everything at once!

 

[barossi73]

All the powervalve does is alter the exhaust length.think of it as 2 exh pipes,1 is tuned for low revs,the other for high revs to take advantage of the 'supercharging' effect.previous to pv the pipe was by necessity a compromise resulting in a narrow powerband.
The powervalve is the switch between the 2 pipes,opened by centrifugal force at ?revs.not saying there arent small losses/gains to be had,(i havent explored)
just trying to clarify the powervalve/powerband thing

 

[Jakobi]

All the powervalve does is alter the exhaust length.think of it as 2 exh pipes,1 is tuned for low revs,the other for high revs to take advantage of the 'supercharging' effect.previous to pv the pipe was by necessity a compromise resulting in a narrow powerband.
The powervalve is the switch between the 2 pipes,opened by centrifugal force at ?revs.not saying there arent small losses/gains to be had,(i havent explored)
just trying to clarify the powervalve/powerband thing

It offers a dynamic exhaust port, by restricting it with the PV flapper. It's not just open/closed at a certain RPM. The spring also determines the rate at which the PV opens.

As you said though, it also offers a dynamic exhaust effect in that the drum valves are open as the flapper is closed, which increases the volume/length of the exhaust. As the flapper opens, the PV chambers are closed off.

So the whole system works to offer the best results at both ends of the powercurve, but also has a large influence on the nature/flavour of the powercurve depending on the timing and duration at which everything happens.

Ideally you'd want access to a dyno with the intent of getting the strongest spread of useful power at all rpms. By having the PV slam open early all you'll really achieve is a delay in the power hitting hard which may feel faster.

 

[Jim Cook]

Excellent analogy barossi73.
It's not just the port height which is changed by the powervalve. The area under the left powervalve cover is part of the exhaust system at low rpms and cut out of the system at high rpms.

Munch,
I asked which model you have because, depending on year, there are things other than the powervalve which can change the power delivery characteristics to a harder hitting delivery. (these items will also have compromises in other areas of operation)

Some examples of what I'm referring to are:
On older models with the Boyesen Rad Valve the Power Reeds can be replaced with Pro Series reeds, carbon fiber reeds. Our first experiment, back in 1997 was to install the Pro Series reeds for a '99 Honda CR250. It gave the bike an instant hit.

Installing a MC silencer or a FMF motocross silencer (no spark arrester and very short).

Replacing the right side flywheel weight with the aluminum crank shaft spacer that comes on the MC250. This would remove 7 oz of flywheel weight.

The RB designs head mod made a huge difference in the delivery of my 2006 DE300.

Different year and model cdi boxes will have different ignition curves.

What year and model are you running?

 

[Jim Cook]

It offers a dynamic exhaust port, by restricting it with the PV flapper. It's not just open/closed at a certain RPM. The spring also determines the rate at which the PV opens.

As you said though, it also offers a dynamic exhaust effect in that the drum valves are open as the flapper is closed, which increases the volume/length of the exhaust. As the flapper opens, the PV chambers are closed off.

So the whole system works to offer the best results at both ends of the powercurve, but also has a large influence on the nature/flavour of the powercurve depending on the timing and duration at which everything happens.

Ideally you'd want access to a dyno with the intent of getting the strongest spread of useful power at all rpms. By having the PV slam open early all you'll really achieve is a delay in the power hitting hard which may feel faster.

Excellent advice as always Jakobi.
I figure that Munch is looking at the adjustable powervalve featured in newer models and on KTMs and such and trying to bring that over to his bike.
I wish I could offer him more help, but am not knowledgeable enough to give him any help in the manner he has requested.

 

[Munch]

The bike is a 2007 250ec but I've only put about 2 hours on it myself and half of that was breaking in the bike, it's spent more time with the engine in pieces than together since I've owned it.

I'm not looking to change anything right now but will do in the next week or 2 I think. From what I've read and from the time I have spent on the bike the powerband doesn't seem as aggressive as I want. I do mostly trail riding but since I am coming from a kx 125 with that engine I was almost always in the powerband and I am think I am going to find the GG a bit too boring, it's definitely quick enough but just not the sort of power I want if that makes sense.

It was previously owned by a woman in her 40's so I think it was super tamed down. I have checked the flywheel and it looks stock, the only thing I can see having been done is the reed block has a huge spacer in it.

In regards to the RB mods I was looking into the carb & head but I am from the UK and I imagine it would cost so much to send it over and then a really long delay to get it back and stuff.

 

[GGRider01]

My bike started as an XC 300 and came with the Kokusan 2K2 ignition.. It's a smaller diameter and quite a bit lighter flywheel. This allowed the engine to spool up very quickly, but mitigated the tractor like quality these bikes are known for. Just something to consider for faster acceleration, especially if you don't need a lot of electricity.

You could remove the reed spacer, which I believe will hinder low end, giving a (unnoticeable in my opinion) slightly stronger hit when the PV opens. You'll need to pick up shorter socket head bolts for this. It does make messing with the carb a bit easier, and took a bind off my air boot and let it relax around the shock a bit nicer as well.

Other than that, there are ways to adjust the PV but not something I have any inclination to mess with so I never have read into it much.

 

[Jim Cook]

My bike started as an XC 300 and came with the Kokusan 2K2 ignition.. It's a smaller diameter and quite a bit lighter flywheel. This allowed the engine to spool up very quickly, but mitigated the tractor like quality these bikes are known for. Just something to consider for faster acceleration, especially if you don't need a lot of electricity.

You could remove the reed spacer, which I believe will hinder low end, giving a (unnoticeable in my opinion) slightly stronger hit when the PV opens. You'll need to pick up shorter socket head bolts for this. It does make messing with the carb a bit easier, and took a bind off my air boot and let it relax around the shock a bit nicer as well.

Other than that, there are ways to adjust the PV but not something I have any inclination to mess with so I never have read into it much.

Yeah, what he said.
Plus, you should have the cdi with the two different ignition mappings. I believe that they all did from late 2005 and on up. A switch run to the two wires coming from the cdi that plug into each other (but don't go anywhere else) are where you connect the switch.
One map is definitely more aggressive than the other. (MX vs Enduro, or sunny vs rainy)

I've found that the EB designs head mods are definitely worth the money, as you tighten your squish band at the same time, raising compression.

As I stated before, you can replace the 8 oz crank balancing weight on the right side of the crank with an aluminum spacer from the MC250 (which will result in more vibration), and you can also use a FMF Shorty MX silencer (or even better, a Messico MC silencer.

A FMF Gnarly pipe will give you a bigger hit down low, but will cost you some top end performance. A Messico pipe. a CRD, or a DEP pipe will be softer on bottom, but will enhance top end performance.

Good luck and Good Riding!

 

[Jim Cook]

One more thing. If you keep the GG250 in the meat of the powerband, (5,500 rpm and up), or like you kept the KX while riding it, you will not find it boring.

 

[barossi73]

Also check what jets/needle you have in there.the style of delivery can be quite different just from a needle swap

 

[barossi73]

Also check what jets/needle you have in there.the style of delivery can be quite different just from a needle swap.
There is also a 'trusty' powervalve cover which allows pv adjustment,replaces the lh pv cover.

 

[Munch]

I think if I post more about it I'll end up taking over the thread, I'll get some hours on the bike and decide how I like the power and if I want it changed I'll create my own thread with videos of bike and jetting info ect.