Powervalve timing
 

Ok guys, I have read everything here on the powervalve issues folks have been having. What has not been answered, at least clearly for me, is what would the effects of opening the valve sooner or later do?

On the road or in fast trails with my '10 300, I sometimes get a slight sag in the power delivery just as the valve starts to open. I thought it was jetting related, and it does seem to change very slightly for better or worse depending upon what needle and clip position is currently in the carb. The "sag" happens mostly in higher gears, 4-6th, and especially on the pavement.

After reading through all of the posts on here about the way the valve operates, I am starting to believe that my powervalve is opening a touch too soon, causing the sag. When the engine does hit, the hit is smooth. The sag is present on both ignition maps as well.

I bought some side cover gaskets and water pump gaskets to check the free play as GMP and others suggested, but beyond that, I am ready and willing to experiment with different thickness shims but I need to know how it works. Does adding shims and preloading the spring help open the valve sooner or does it keep the valve from opening until later?

I wanted to tune for slightly more power on the bottom end, and a softer hit once the valve opens. I have also read conflicting statements that opening the valve sooner gave the engine more bottom end, vs. some statements that said the bottom end was weaker. Some other statements I've read mentioned that by delaying the opening the bike produced better woods type power but the hit on top was really pronounced.

Anyone experiment with this?

The governer ball and ramp assembly pushes inwards when the engine rpm increases.
Adding more shims preloads the spring, which delays the opening of the power valve.

Thanks for pointing me in the right direction. I will adjust the free play out first then maybe add a small shim to delay the opening.

The sag is slightly annoying. Just when you can hear it coming onto the pipe, it backs off a bit and sags. In the higher gears it seems that I have to nurse it past this zone, then the power rolls in. In lower gears the sag is still there but it goes through the zone quicker to get to the good stuff.

As a side note, what brought this about is interesting. My buddy is keeping a YZ250 at my house for short term storage. He asked me to ride it every once in a while. I almost killed myself on it, the power came in so hard! I feel that the YZ made more power than the 300, but not the kind of user friendly GG style power. His bike had no "sag" before the hit.

I have an 05 300. When I shimmed the powervalve it put more of a flat spot before hitting hard. Sag as you refer. I ended up turning the outside of the spring down some which mad the valve open sooner to get rid of the Sag. I still thought the power was to agressive after the power valve opened. I then limited the valve from opening fullly. For a reference I also have a 250 YZ with a FWW. GasGas hooks up better until the power valve opens at which time it is similar to the YZ.

OK, so you think the powervalve is opening too late, and that is the cause of the sag?

I bought a few side cover gaskets so I am good to experiment a few times. I will make sure all of the play is out first, then preload it a little using the .005" feeler gauge method I've been reading about.

It wouldn't bother me if it hit sooner, or even later, but the "sag" does tend to get a little annoying when you are expecting things to happen and it doesn't. I just wanted a consistent point at which it comes on to the pipe.

It is harder to ride his YZ, but damn that thing does go! If I got used to that style of power delivery I would be fine. Heck, everyone and their brother runs a YZ in the woods... I will check and maybe remove the shims then if I find any. Some folks mentioned that they found more shims in the later models than in the earlier 300's.

Remove the shims, then adjust the timing to taste, + or -.
Get head mods. If you don't have .055" squish you're not combusting right. You'll not sag with .055".

Reducing O.D. on govenor spring. Brilliant, I did that back in the day to my '89 KDX. Sweet.

This 'saging' thing.

Bailey,

Have you expermented with the different PV valve shims? I've been helping a friend solve an off idle deadness and he just checked his free play tonight on his 2010 300...The actuator is touching the stop but he says there is no real spring resistance for a few millimeters of movement possibly letting the PV open early. I have gone the route of the head mod on my 300 and, frankly, it seems to make the bike a bit "chuggy" like the KTM. He does not want that. Does anyone know if that lack of resistance would make the bottom soft just off of idle? Thanks for your help!

Eric

I don't have the gaskets yet. Go Fasters is taking a long time to get them in... I paid but don't have them yet..... Steve??

I'll report back with any findings .

You are not the only one waiting for gaskets.
<edit>.:mad:

My first car was a 1975 Peugeot 504GL. Great cars. The quality of the dealers determined their fate in this country. :(

Too bad my dealer is an oil tycoon now. :D
That man delivered some serious service.

I just bought two sets from hall's cycles, for case and powervalve covers.
Call Jeff Kaylor; (217) 789-0107

Rob