250-500cc wr 300 head mods

Has anyone got a modified head on they're 300, have you machined the stock head or have you installed the husky hi comp head?

Any wisdom on this?

There were some threads on this here or TT ... some guy was getting ~50HP out of the engine... with the results on a dyno sheet ...

This thread is all over but it has some info:

http://www.cafehusky.com/forums/showthread.php?t=10628&highlight=dyno&page=2

Hi, my engine is almost stock, except for the shaved head (the oem design is absolutly horrible, the squish are very bad). To correct the head, its very hard and you need good skill and tools. I think the very best is to buy the race head (i have one, but not tested since my oem modified head work incredibly well !)

My timing is also advanced 4 degree.
My carb is a Keihin 38mm AS with 180 main and EEL needle in 3nd clip. I also have a Powernow +. This little piece of metal give me a very strong buttom and eliminate the hit from the low to middle.

With these little mod, my bike is VERY responsive and have a ton of power from very low RPM to overrev.

Sorry for my bad english!


*** Also, with 5 month on riding this bike (about 135 hours now) i can say this bike is bulletproofs. Nothing have broke, my compression is at 165 psi (tested last week-end) and the cylinder/piston have absolutly no sign of wear. Its my first Husky and am very impressed by the quality of this machine. Just changed the oil every 10-15 hours with Mothul Transoil, cleaned air filter each 1 or 2 ride and put some tire (i have pass 5 tires this summer !!!) and mix it at 40/1 with Mothul 800. Never fouled a plug !

I REALLY LIKE THIS BEAST

That's weird. My piston was toast at 70hrs and had bad grooving from the intake window of the cylinder. And this bike only sees woods riding with very little high RPM use.

70hrs out of a cast piston is a lot. 135hrs is playing with fire IMO.

Love my bike too and it's been very reliable.

Those numbers can't be real... What happened to the days of riding a bike till it started loosing power or the engine started making a ringing sound?

I rode an 02 CR250 over 6 yrs on one piston ...Had to be several hundred hrs at least .. Nothing broke on the bike but maintenance items .. U guys adding much oil to the gas?

It's like we are bean counters now

Mine is like new and the bike have seen very high rpm for long period (fire road).
What oil do you use and what mix ratio??? Do you clean your air filter often ???

I know 135 hours is a lot, but all seem perfect. I will change the piston this winter by prevention but for now my engine feel very tight.

On my old CR500, i have made 200h + on one top end.

Also, my freind have about the same hours on is KTM 300 XC-W and is also on is first top end.

70H seem bad for a 300cc...

I run Klotz R50 32:1 and always clean filters.

I'd run a forged piston on a woods bike until 100hrs (with a ring change at 50hrs), but never a cast piston.

Here was my OEM piston at 70hrs

Would any of you install that 70hr piston back into your motor?


Back to the topic....
I'm going to get my head done one of these days. I couldn't get a measurement using .125" solder, so it is way outa whack.

My engine guy says there's not much material to work with, but he can improve upon it. Also says the head was designed for a domed piston, but came with a flat top piston.

I personnaly dont like Klotz oil, bad burning and a lot of gumming in power valve
Can you post a pic of the top of the Piston ?

Before modding your head (very hard job), i think you should try the race head (good design imo).

Hi Comp head just came in, will post results as soon as I can bolt it on

I agree about the klotz not being the easiest to burn oil.
I really like it in my dune and mx bikes, but they are seeing much higher combustion temps than the Husky. I have no issues with it on any of my bikes though. My 4 stroke lawn mower doesn't like it too much though as it builds up and clogs up the exhaust

I like sharing gas between the bikes though and not having to worry about mixing different oils for different bikes, so I'll live with it.

Please do.
Is the race head from a different mold or is it the same as the stocker with different chamber specs?

forgive my ignorance, what is a power now?

http://scaryfastracing.net

$50 !!
Every one of you need one at that price, i have pay $100 +++ and very happy with it.

The 300 still uses the TMX with the flat side slide doesn't it? If so I am almost certain this is the same carb as the 01 and up Honda CR250. Also the Husky 125 had the same carb from 08 back.

The Powernow was their first product and it sits before the carb (airfilter side). The plus came later on and sits behind the carb (engine side).
I believe they feel carbs are phasing out, and need to take advantage while there are still some new bikes with carbs. I had it on a few bikes in the past (never on a 2t) and didn't feel like it did anything, but for sure some bikes gain more than others.
hrc630 has the Keihin, so not sure if what he uses would fit the TMX. hrc, which one did u use for the PWK?

The Powernow Plus is also positioned after the carb, on the air box side...

Here is the part #
From a previous tread,

Yes, the Item code on my invoive is PNP38PWK A/S.
The description is: 00-09 YZ250, 00-08 KX 250, 01-08 RM250
03 KTM 300MXC, 00-04 GasGas EX 125/250/300
TM Enduro 250. 08 Husky CR125

This is for the Powernow Plus.


Dont forget my bike run with a Keihin, not a Mikuni.
On my bike, the Powernow + have really help the low rpm power to come sooner and the low is more responsive.

Dont forget that the Husky 300 really need a propper jetting to perform at is full level. With all the small modification (Keihin, jetting, powernow, mod head, timing) this bike can really make serious power from way low to very high. (incredible improvement from stock). Also, with the Keihin i dont have change the jetting after i have find the good combinaison. Praticly no change with the temps variation.

My friend with is KTM 300 XC-W cant believe the difference in power and crispness. Not even close on pavement. (except for the better top speed of the KTM).

Hi. As HRC says the difference in low end power is big! I laborated a lot with the Mikuni on my WR 300 and found a needle and jetting combo that was good for that carb, but even if it was running clean and idled nice and everything, it´s not even close in low end performance compared to the Keihin! I have tried a lot of different needles with good help from HRC, and we found a very good setup. The dynoruns that HRC did shows this. The Keihin is a GOOD investment!

Johnny:sweden:

Votre mauvais anglais est bien mieux que mon mauvais Français!

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