250-500cc Is WR300 racing head a good choice?

[Rodrigo]

I bought a 300 cylinder and now I have to buy the head. What one? The stock or oem high compression?

Thanks.

 

[Johnnymannen]

Depends on how you use your bike. In don't like it for tight woodsriding when i get tired. The bike gets too explosive for me, especially if you use the Keihin PWK carb that also increases the bottom end power. I like the standard head better in the woods combined with a quite lean and smooth jetting on my PWK 38 AS:=). When i was iceracing my 300 then it was another story, but i have another bike for that now:=).

Johnny

 

[marcmo0]

I like the race head. I use mine all over...desert, mtn singletrack, rocky washes that just make you laugh because you cant even believe there is a way over and through the jumbled mess in front of you. I like the extra power in the tight stuff as it helps me get the front wheel up. Note i also have the pwk carb and pro circuit exhaust and now run a mix of pump premium and race gas as the increased compression led to some pinging. Not sure if it will do that without the extras, but just an fyi. If you like a bit more oomph right off the bat then you will like it.

 

[hrc630]

I like the race head. I use mine all over...desert, mtn singletrack, rocky washes that just make you laugh because you cant even believe there is a way over and through the jumbled mess in front of you. I like the extra power in the tight stuff as it helps me get the front wheel up. Note i also have the pwk carb and pro circuit exhaust and now run a mix of pump premium and race gas as the increased compression led to some pinging. Not sure if it will do that without the extras, but just an fyi. If you like a bit more oomph right off the bat then you will like it.

For me, the race head no question. That boost the low end and help to smooth the transition from low to mid. I now make 53.6 whp and 35.6 wtq with my 300 and the motor is very easy to ride but incredibly strong and fast from very low to overrev... I love the 300 motor and even if his a little outdated ... i think its the best enduro bike engine. Habitualy i change my bike every year but i have this 300 since 2010 and i have no plan to change it. I will wait to see the next Husky 2 stroke

 

[marcmo0]

For me, the race head no question. That boost the low end and help to smooth the transition from low to mid. I now make 53.6 whp and 35.6 wtq with my 300 and the motor is very easy to ride but incredibly strong and fast from very low to overrev... I love the 300 motor and even if his a little outdated ... i think its the best enduro bike engine. Habitualy i change my bike every year but i have this 300 since 2010 and i have no plan to change it. I will wait to see the next Husky 2 stroke

What other mods are you running? And i agree...i love this bike! I have had lots and its my favorite for sure

 

[hrc630]

What other mods are you running? And i agree...i love this bike! I have had lots and its my favorite for sure

I have the PWK carb, Powernow, race head, advanced timing and now a ported/ajusted cylinder.
The bike is easy to ride but also stupid fast.

 

[Rodrigo]

My previus bike was a Honda CR250. Very funny, very strong to ride but not effective on the woods. After i rode with wr250 I understand the difference between enduro and mx bike. I dont´t want a mx bike again, this is the point.
Well, I will buy a racing head and if i dont´t like is easy decrease compression.

About this post - http://www.cafehusky.com/threads/wr250-valves-on-wr300.24948/ - somebody can help me?

Thank you for replies !!!

 

[PowerKord]

I have a 250, I had the stock head machined to the same spec as the race head and saved myself about $80. For me no question I like the higher compression. More torque, easier to ride. Even with the race head the compression is still much lower than my KX had standard. I'm not really sure why Husky specs such low comression stock.

 

[hrc630]

I have a 250, I had the stock head machined to the same spec as the race head and saved myself about $80. For me no question I like the higher compression. More torque, easier to ride. Even with the race head the compression is still much lower than my KX had standard. I'm not really sure why Husky specs such low comression stock.

The stock head is really difficult to modifie to bump the compression. You will spend a lot more than just buy the race head. I have done this before on my 300 but its a lot of machining and you need very precise tool... The 250 already have a lot of compression. How do you have modified the head.. very septical...

 

[PowerKord]

The 250 does not have a lot of compression. It only has around 170psi (8.4:1) listed in manual. I sent the head to an engine builder who shaved the head and reworked the combustion chamber as well. It now reads around 190psi.

 

[hrc630]

The 250 does not have a lot of compression. It only has around 170psi (8.4:1) listed in manual. I sent the head to an engine builder who shaved the head and reworked the combustion chamber as well. It now reads around 190psi.

170 psi is perfect for an Enduro bike on pump gas. To much compression on this cylinder design will kill the top end power... The 300 have about 135 psi stock (this is why the high compression head exist) Its not possible to shave the head... its an o ring desing... If an engine builder can machine the Husky head for less than the cost of the OEM race head please give us is name... Still very septical... we have machined the stock head before i receive the oem race head and its a very long and time consuming project that cant be done for cheap...

 

[PowerKord]

Here are the before and after photos. Yes, it is possible to shave the head. The O rings fit grooves in the cylinder, not the head. Any decent shop that builds two strokes can do this. Had the same done to my KX, also O ring head.

 

[Rob578]

RB Designs can do the head but I opted for the race head. Think I paid around $120 for it.

My stock compression was around 135psi and went to 170psi with the race head. I just put a new piston and rings in it and it feels like a very notable increase in compression so I plan on checking it again this weekend.

Excellent mod for the money

 

[hrc630]

Here are the before and after photos. Yes, it is possible to shave the head. The O rings fit grooves in the cylinder, not the head. Any decent shop that builds two strokes can do this. Had the same done to my KX, also O ring head.

The 300 head is not like this... They have a lip to support the o ring. So shaved is easy on the 250, but not on the 300. For the 300 the best way is definatly de OEM race head.

 

[windsurf]

Depends on how you use your bike. In don't like it for tight woodsriding when i get tired. The bike gets too explosive for me, especially if you use the Keihin PWK carb that also increases the bottom end power. I like the standard head better in the woods combined with a quite lean and smooth jetting on my PWK 38 AS:=). When i was iceracing my 300 then it was another story, but i have another bike for that now:=).

Johnny

Totally disagree Johnny - race head is the best value for money mod you can make to a 300, especially in the tight woods gnarly sections. It becomes impossible to stall and has bags more low end/mid range torque especially with the PWK. Top end doesn't feel compromised but certainly doesn't feel much different to standard. It would be nice to see a comparative std versus race head torque graph if anyone has one.

I paid less for the head than that bloody overpriced 'powernow' thing!

 

[shawbagga]

Totally disagree Johnny - race head is the best value for money mod you can make to a 300, especially in the tight woods gnarly sections. It becomes impossible to stall and has bags more low end/mid range torque especially with the PWK. Top end doesn't feel compromised but certainly doesn't feel much different to standard. It would be nice to see a comparative std versus race head torque graph if anyone has one.

I paid less for the head than that bloody overpriced 'powernow' thing!

interesting thread gents. excuse my ignorance windsurf but what are these powernow things? ive heard the name or seen it somewhere before but what are they and what do they do? hi comp head sounds like a goer! any reduction in reliability with the higher comp? do you just bolt em (straight swap for stock)on and ride or have to measure squish etc?

 

[Johnnymannen]

Most guys like the racehead in the woods, but i think i'm faster with the slightly less explosive powerband. I already get tired and get a lot of armpump as it is. My body is not "designed" for durability:=). I would probably be even faster with a 250. I bought my 300 to also use it for iceracing, which i did. But now i have a prepared Honda CR 500 for that, so therefore i want my 300 as smooth as possible in the woods. If i want to jump over some trees there is power enough for that as it is:=). Nice to see that you still here, Francis;=)! My CR 500 gives 63 BHP at the wheel at 5800 rpm and 64,2 ft/lb at 5250, so there is torque. I ported it myself and did the engine spec myself.

A little offtopic, but here's the dynorun of my 500.

View: http://www.youtube.com/watch?v=t3NtKKAARBU


Johnny

 

[Brian Scott]

Pardon my ignorance; where can one obtain this high compression oem race head and what is the approximate cost?

 

[windsurf]

Pardon my ignorance; where can one obtain this high compression oem race head and what is the approximate cost?

I bought mine form Husky Sport in the UK, only because it was half the price of here in Oz. I think it was only about $140.

interesting thread gents. excuse my ignorance windsurf but what are these powernow things? ive heard the name or seen it somewhere before but what are they and what do they do? hi comp head sounds like a goer! any reduction in reliability with the higher comp? do you just bolt em (straight swap for stock)on and ride or have to measure squish etc?

The power now thing is a piece of thing tube with a divider plate accross the middle. The device slides into the back end of your carb behind the slide. the plate is horizontal behind the slide. The idea is that at anything upto half throttle air can only be drawn below the plate smoothing airflow through the carb. More than half throttle air is drawn either side of the plate. (I think there is also a version that fits infront of the slide).

So far as the hi comp head goes it's a 15 min job - remove your exisisting head, probably worth buying two new water inlet fittings as they are difficult to remove from your old head and easy to damage. Fit new head - go and have fun! I dont see any reduction in reliability so far and have done 1500 miles on it.

 

[shawbagga]

I bought mine form Husky Sport in the UK, only because it was half the price of here in Oz. I think it was only about $140.



The power now thing is a piece of thing tube with a divider plate accross the middle. The device slides into the back end of your carb behind the slide. the plate is horizontal behind the slide. The idea is that at anything upto half throttle air can only be drawn below the plate smoothing airflow through the carb. More than half throttle air is drawn either side of the plate. (I think there is also a version that fits infront of the slide).

So far as the hi comp head goes it's a 15 min job - remove your exisisting head, probably worth buying two new water inlet fittings as they are difficult to remove from your old head and easy to damage. Fit new head - go and have fun! I dont see any reduction in reliability so far and have done 1500 miles on it.

worth checking squish ya reckon?