250-500cc Race head on WR300

[windsurf]

I have just ridden my 300 for the first time today with the race head. I have to say it isn't quite what I expected. The bike has a PWK which is jetted pretty well and was running fine with the standard head.
I did a quick compression test before and after, 152 psi before and just over 180 psi with the race head. The main improvements are in the mid range with what feels like a lot more torque, what I also expected was also more bottom end. I don't know if it is because of the greater mid range but the transition from bottom to mid seems to spin up the back wheel and is no where near as smooth.
Todays ride didn't matter too much as it was forestry tracks and open areas. Normally I ride tighter technical stuff where smoothness is important. Anyone any advice or relevant info on using these heads, or should I just change back to standard?

 

[racer726]

The higher compression in turn gave the bike more of a hit to the power. My 300 before the head was like a tame 300, now she rips. I would go back to the stock head if you don't like it. The high comp head works wonders for MX.

 

[MOTORHEAD]

I've seen the same thing with KTM 300 riders. They love the power until they have the head done, then it's too much. Like racer726 said, go back to stock if you don't like it, or try to fatten up the jetting a bit.

 

[Rob578]

I love mine, really woke the bike up....... I may send the stock head to RB and have him make me a Race Fuel only head and see what it does.

 

[windsurf]

Rob, you are right it really does liven the bike up especially in the mid range. I might try a divideder plate to see if to see if it will bring up the bottom end to match.

 

[Twatty]

I've just ordered mine!
Has anyone tried a thicker, or extra base gasket with the race head to bring the compression back and raise the ports? In theory this would turn it into a top end monster!

 

[MOTORHEAD]

The way to make that work best for you would be to add base thickness then deck the cylinder off the same amount you took it up and keep the race head compression the same. The race head compression isn't high enough to hurt top end, it will actually help it at that level.

But, the better option would be to simply set the exhuast valve stop a little higher.

 

[MOTORHEAD]

Got my head yesterday.

Stock head: more of a bowl or tube design with a lot more squish angle.

Race head: Very hemi with a flatter squish.

Squish width and depth are pretty much the same.

BTW- A tube head works better with crappy gas. Even if the compression was the same.

 

[hrc630]

Try the Powernow from Scary Fast. This help a lot on smoothing the transition from low to mid. In fact it help to have a stronger bottom.

 

[MOTORHEAD]

WOW!

It runs a lot better with this head. Starts, idles, responds and jets in so much better. I really like the roll-on, too. Very good investment.

 

[marcmo0]

Motorhead. Where are you at? and what jetting do you run? I'm at high elevation here in UT, but like to compare. I am ordering my head tomorrow! Thanks for your input********************************************************************************!!! You said Hall's correct? Fricking psyched!!

 

[MOTORHEAD]

I'm in the south west part of Indiana, 500' ASL. And yes, I got my head from Hall's.

I'm running a Keihin 38mm PWM with a #6, N3VF-3, 48 / 165.

Also have an FMF Gnarly / power core combo.

 

[Xcuvator]

Got my head yesterday.

Stock head: more of a bowl or tube design with a lot more squish angle.

Race head: Very hemi with a flatter squish.

Squish width and depth are pretty much the same.

BTW- A tube head works better with crappy gas. Even if the compression was the same.

I'm not very heads up on 2 stroke tuning so...
I had RB Designs work on my 250 head. The finished product was shaped similar to your race head, but the squish was set up closer. Hard to tell from your picture, but I think my squish area is about half of yours and the compression is just a little more than stock.
At the same time I had him put one of his divider plates in the PWK. I'm getting close on the jetting and the bike runs much better. I was surprised to find I had to go leaner on the needle and pilot, because of (I guess) increased signal created by his divider plate? The bike always chugged along really well in the tight stuff and now does it even better.
It won't ever pull and rip on top like a 300, but it works pretty good.

 

[marcmo0]

Just ordered mine today BUT I have to wait 3-4 weeks . I'm curious. What did you have to do to the jetting, if anything after the head mod. Did you need to richen it up any?

 

[MOTORHEAD]

Yes, I'm a size larger on the pilot and main, and may try one more size larger on the main just to make sure it's not still lean.

 

[marcmo0]

Thanks man!! you have been really helpful. I figured that was going to be the case. I was also told to replace the hose nipples on the head too, so I ordered those as well. Did you have a hard time removing them from the stock head? Guy at Halls said they strip real easy. Better them than the head, I guess.

 

[windsurf]

Yep they do strip easily, they are tight in the head and only have a very shallow hexagon to get a socket on. One of mine came out easily the other was more of a fight although warming the head helped. Probably easier to get two new ones to go with the head. You'll notice a big difference in the torque, the bike feels unstoppable now especially second gear. Just wind the throttle open and feel your arms getting pulled from their sockets - on any hill!

 

[MOTORHEAD]

I ordered new hose fittins with the head.

 

[MR54L]

If you you were to to buy a new bike with such an power, I'm sure over time you would learn to resect what you riding and be happy after a few practice rides. Smile and be happy, It's like a new model bike with a bit more go :-)