250-500cc GasGas piston in WR 300

[MOTORHEAD]

there's nothing wrong with vertex pistons, they're one of the top brands for pistons (they worked very hard in the last couple of years to get where they are now).

r

Never said there was. But, I know WISECO will run small lots of custom pistons, I've had some run off before. I was just suggesting that he get a hold of them to have a domed 300 piston made.

 

[PC.]

I spoke to a gentleman today from Zip Ty racing named Steve. Very nice and helpful guy! He wasn't 100% sure, but he was pretty certain that Mitch Payton either modified the cylinder intake port or modified the GG piston to remedy the narrow intake skirt contacting the port. He also said they did use a Vertex Gas Gas piston and they're becoming very hard to find.... said he got his from Glenn Kearny's shop on the East Coast.

He also said Mitch Payton is truly the only person with all the answers as he single handedly did all the cylinder, head and piston mods. At the end of the conversation he said the best bang for the buck would be to omit the GG piston (as it requires cylinder and head mods that aren't cheap and cannot be reverted back to stock) and to do the PC pipe and the digital ignition off an 04' CR250. He said the ignition will hold the most promise for stronger power, but will lose all lighting capability.

I'm going to watch ebay for the ignitoin, black box and wiring but I wont buy it unless I find a smoking deal. I also got a call into my dealer to order me an OEM piston kit.
It was fun trying, but this project is going to require far more internal mods and money than I'm willing to throw at it. I already ate about $200 on the GG piston, gaskets and o-rings, so its time to cut the losses and get the ol' girl back to her former glory.

I would much prefer to put a Husky-spec forged piston into the motor, but cant find one. Does anyone have any knowledge if one exists?

 

[NWRider]

The CR ignition would probably make it run much different. If you find a pdf of the service manual there are graphs of both the WR and CR ignition maps. The CR has a lot more advance early on.

 

[Motosportz]

What is the end goal here? All out fire breather? Seems a well jetted WR300 is more than enough. Maybe you just want to tinker?

 

[Johnnymannen]

I spoke to a gentleman today from Zip Ty racing named Steve. Very nice and helpful guy! He wasn't 100% sure, but he was pretty certain that Mitch Payton either modified the cylinder intake port or modified the GG piston to remedy the narrow intake skirt contacting the port. He also said they did use a Vertex Gas Gas piston and they're becoming very hard to find.... said he got his from Glenn Kearny's shop on the East Coast.

He also said Mitch Payton is truly the only person with all the answers as he single handedly did all the cylinder, head and piston mods. At the end of the conversation he said the best bang for the buck would be to omit the GG piston (as it requires cylinder and head mods that aren't cheap and cannot be reverted back to stock) and to do the PC pipe and the digital ignition off an 04' CR250. He said the ignition will hold the most promise for stronger power, but will lose all lighting capability.

I'm going to watch ebay for the ignitoin, black box and wiring but I wont buy it unless I find a smoking deal. I also got a call into my dealer to order me an OEM piston kit.
It was fun trying, but this project is going to require far more internal mods and money than I'm willing to throw at it. I already ate about $200 on the GG piston, gaskets and o-rings, so its time to cut the losses and get the ol' girl back to her former glory.

I would much prefer to put a Husky-spec forged piston into the motor, but cant find one. Does anyone have any knowledge if one exists?

Hi Brandon. So what you are saying is that it´s not a good idea to just put the gasGas piston in and ride? Should this be a problem?

 

[PC.]

Kelly,
I just like to tinker. Bike has plenty of power, but it's not close to its potential. I just like to see how much cheap and easy power can be had. And I'm the typical hot-rodder American


Johnny,
I cant say for sure, but the GG piston was designed for an entirely different type of induction system so it's a safe bet to say the cylinder is going to need to be modded. I put about 1.5hrs on the GG Wiseco piston in my stock 300 cylinder and there was undeniable piston slap. I cant say for sure if it was the intake port getting knocked by the skirt, but it certainly could have been. And once the piston starts to wear and gets loose in the cylinder the problem will worsen IMO.

I'll tear the top end down tonight or tomorrow and have a look. If it was the intake port getting knocked then I would not install it. And, in all honesty, I'm not so sure I like how it ran with the domed piston. The bottom end felt stronger and made the power curve more linear, but I dont think it pulled on top like the stocker or the extra bottom end made the top end less inpressive... cant say for sure. I'm sure with porting and head mods it would be a brute, but just putting the GG piston in the stock motor wasn't worth the chance of damaging the cylinder IMO. I'll take some pics of the cylinder and post them later.

 

[PC.]

The CR ignition would probably make it run much different. If you find a pdf of the service manual there are graphs of both the WR and CR ignition maps. The CR has a lot more advance early on.

Sounds about right. If I happen to run across one I'll pick it up, but I'm not about to break the bank buying it from the factory.

I wonder how much I can advance the WR ignition for a bottom end boost... does anyone know if the WR ignitions adjustable at the flywheel? With 6.9:1 compression I bet I could advance it a decent amount before pinging becomes an issue.

 

[MOTORHEAD]

Good info PC, thanks for sharing. I'm also watching for a CR ignition for my 250.

Have you looked into the Husky spacial parts head for the 300?

 

[PC.]

Good infHave you looked into the Husky spacial parts head for the 300?

What!?
Got a link?

Is there more material in the head? My tuner cant do much with the stocker as there really isn't much material to safely remove. If this one is cast different then it might be a worthwhile upgrade.

 

[MOTORHEAD]

Part #8000H0944 Cylinder head high compression race.

I just noticed it does not show up in the 2010 catalog, but it was listed in 2009. Might give your dealer a call and see if it's still available.

 

[Johnnymannen]

Kelly,
I just like to tinker. Bike has plenty of power, but it's not close to its potential. I just like to see how much cheap and easy power can be had. And I'm the typical hot-rodder American


Johnny,
I cant say for sure, but the GG piston was designed for an entirely different type of induction system so it's a safe bet to say the cylinder is going to need to be modded. I put about 1.5hrs on the GG Wiseco piston in my stock 300 cylinder and there was undeniable piston slap. I cant say for sure if it was the intake port getting knocked by the skirt, but it certainly could have been. And once the piston starts to wear and gets loose in the cylinder the problem will worsen IMO.

I'll tear the top end down tonight or tomorrow and have a look. If it was the intake port getting knocked then I would not install it. And, in all honesty, I'm not so sure I like how it ran with the domed piston. The bottom end felt stronger and made the power curve more linear, but I dont think it pulled on top like the stocker or the extra bottom end made the top end less inpressive... cant say for sure. I'm sure with porting and head mods it would be a brute, but just putting the GG piston in the stock motor wasn't worth the chance of damaging the cylinder IMO. I'll take some pics of the cylinder and post them later.

Ok, great info there Brandon! Maybe it´s better to change to a standard piston instead and see what that racehead is! looking forward to get info after you have taken it apart again!

Johnny

 

[rasputin]

there's a reason why this race head is not available any more...

r

 

[Johnnymannen]

there's a reason why this race head is not available any more...

r

And what is that!

 

[MotoXotica]

that race head part # 8000-h0944 is in stock in the US.they have 2 of them.the retail is $119.dan

 

[PC.]

that race head part # 8000-h0944 is in stock in the US.they have 2 of them.the retail is $119.dan

Is it a new cast or just a worked stock head? Do you happen to know?

 

[MotoXotica]

i dont really know anything about that head.i was not even aware it was a part for sale untill today.dan

 

[PC.]

Thanks Dan!

Johnny,
here's the pics. Cylinder had 69.0 hrs when I installed the GG piston and 70.4 when I removed it. 1.4hrs of use.

As you can see the bottom of the intake side piston skirt was getting polished, but I would not call it abnormal wear. The intake port still looks good (Thank God!). There was no sign of any hard metal to metal contact at all but I'm still not comfortable running this piston without having some kids of relief work done on the piston and/or cylinder. If the Wossner piston clears the ports then I'd be comfortable running it. Although I think the head will need some work before it truly runs proper.
Keep us posted.

On a side note...I love that I can remove the cylinder without having to remove the head or reed cage. Very nice

 

[zilly]

Okay,

While I don't want any more power from my bike than I currently have
I would love to know that I can re-piston/ring as needed, and I am getting concerned about compatiblity and cost..!

I am sure all of you have seen this right?
http://motocrossactionmag.com/Main/News/WE-BUILD-A-FULLRACE-HUSQVARNA-WR300-MOTOCROSS-BIKE-6887.aspx

Isn't this what many of you are trying, or are doing?

I ride trails, and roads when I have to. I don't race, but sometimes like going fast (for me) and I am hoping to keep this bike going for some time...so is there a piston ring kit out there for just your average fat old guy who likes to keep his bike running well and at a reasonable cost?

Not trying to hijack just keeping the idea of a 300 rebuild rolling along.

 

[PC.]

Yeah.... that it what I was attempting to do. Minus the port work.

From what I can tell there's only 1 piston specifically made for the wr300 and it's made by Vertex (this is the OEM piston that comes stock in our bikes). They do not import them into the US themselves, but let Husky handle it, so you can only get them through a dealer. I tried getting one directly from Vertex and from a Vertex dealer, but no dice.

Shop around as prices varied wildly between dealers.....from mid $200's to over $400 for the entire top end kit.

 

[Motosportz]

Okay,

While I don't want any more power from my bike than I currently have
I would love to know that I can re-piston/ring as needed, and I am getting concerned about compatiblity and cost..!

I am sure all of you have seen this right?
http://motocrossactionmag.com/Main/News/WE-BUILD-A-FULLRACE-HUSQVARNA-WR300-MOTOCROSS-BIKE-6887.aspx

Isn't this what many of you are trying, or are doing?

I ride trails, and roads when I have to. I don't race, but sometimes like going fast (for me) and I am hoping to keep this bike going for some time...so is there a piston ring kit out there for just your average fat old guy who likes to keep his bike running well and at a reasonable cost?

Not trying to hijack just keeping the idea of a 300 rebuild rolling along.

We (Motosportz) have the replacements in stock, no problem with supply as far as I know.