DRZ - Forum

still waiting for the head..

???

ported head with 1mm oversize intake valves is on its way from the usa.

i'll report back

Es ist da!
Sieht sehr gut aus.

ein 'cam journal' war leider nicht ganz gut.
konnte gefixt wurden.
fast fertig.
dauert so lange..

Endlich!

Ich hab es geschafft.
Nun auf english, ist besser fuer mich..

This really took a long time...

So i got a SSW/Eddie Sisneros ported head.
With 1 mm oversized intake valves, RHC springs (progressive/titanium) and (one piece) valves.
The plan was to use it with Hotcams old style stage2. (More duration and lift, needs the better springs) on my 94mm (435cc) bigbore.

The flow is +25 CFM at max lift (9.5mm), and +5 at small openings already.
The velocity is not really different.
(The head is best for 470cc bigbore/strokers, may be my next step)

Problem with the head:
-IN cam journal was a little bad (fixed by 0.04mm line hone)
-Valve cover thread damaged in the cam cap (fixed with helicoil)

So..
My engine mods before
-94mm bigbore
-fcr93
-hotcams stage1
-Yoshimura Titanium pipe
resulted on the dyno in 48HP on the wheel

After
-Added ported/bigvalve head
-Cams to hotcams stage2

Sorry, no dyno, the shop where i had that done caught fire (!) dyno destroyed.
But my first ride impression is that it is not the same as the change to the bigbore.
It got more powerfull and more agressive but maybe 3 HP, especially midrange.
Also very smooth, revs nice, great response to the gashand.
Maybe it needs jetting changes, i dont know.

Some things i understand what you writing here.
But the question is: If all the work and money pays off for you?

Also ob der ganze Aufwand und das Geld die Sache Wert war?
3 PS und ein besseres Ansprechverhalten...

Gruß
M@tt

The 3 hp's , not worth it really.

I hoped for a little more, like sumobob's results did suggest.
It is big fun to ride however, don't get me wrong.
Power wheelies in 3rd gear at most rpm
Just sit and turn the handle.
Stock SM gearing.

and this was only a step.

Next up is 470cc's with 47HP (+5 stroker crank)
But that cannot be done properly with the stock head, springs, valves, cams.
I got the head cheap and it came with the (expensive) RHC cams needed for the 470.

Maybe i'll never do the 470, but the one piece valves and ti springs are
nice insurance that i can rev the hell out of the current wild cams without damaging it.

Still, why sink the time and money into a dr-z?
-for fun, i like wrenching, modding, learning as i go. moto-nerd.
-i really think the dr-z is a very fun bike to ride
-the dr-z stays reliable/mainainable with this power if done correctly
-i have Sumo and Enduro wheels so 2 riding styles in one.
-i will keep it for many years, maybe make a nice streettracker out of it one day

The 48HP + estimated 3 gain i have now I think this build is same or better then for example ABP's stufe 3.
The specs are about the same but my build has a some (proven on the dyno) better parts.
(ABP say 55HP but they measure more optimistic then i do)

Interessant wäre der Kurvenverlauf in einem Leistungsdiagramm. Die maximal Leistung ist ja nur ein Kriterium von mehreren. Im Vergleich zum Original wird mit den größeren Ventilen im mittleren Drehzahlbereich bestimmt einiges mehr an Leistung anliegen.

Hi Minimax,

Servus

I read german good, not write so here it goes.

First off i just do not know how may HP the ported/bigvalve head makes extra.
3 is a guess, but in my experience guessing hp-gains with the seat-of-the-pants is hard/impossible.
I hope to find a dynojet dyno somwhere in my neighbourhood and will post it up then.

I agree completely the mid-rpm is where the extra flow would benefit most.
And my Hotcams old type stage 2's (high lift, little bit extra dur) would even add to that: the way they are degreed favors mid rpm too.

For high rpm (over 8000) the FCR39 is the limiting factor (dyno proven). That is even so with a stock head.
Putting a fcr41 on a 435cc with stock head gives 1 or 2 HP gain around 9000, but the low/mid rpm goes down because carb is too big for 435cc.
Yes, the stock head flows a little better then fcr39. (flowbench)
(Did you know the dr-z head was designed by the same guy who designed the famous hayabusa head? It even uses the same partnumber guides)

So with this head (made for fcr41) i could probably gain quite some max HP i i use a FCR41.
But the mid and esp low rpm's will suffer from that.

If i can find a good/affordable fcr41 i may try it out.
I know a norwegian guy who had that exact setup some years ago (now 470cc/57HP)
He said the fcr41 ran great on the 435 with ported/bigvalve head.

Yesterday i made the 2nd testride.

I found out that the bike has way more power with the ported head, but i did not really notice on the 1st testride.
In 1st and 2nd gear the bike you cannot go all out, because it just wheelies like before.
The 1st testride was short and only in the city.
To go full power and high rpm in 3rd gear takes you above 50km/h. I did not test that.

2nd ride i did. Above 6000rpm (60km/h 3rd gear) it opens crazy power!
Wow. 60-100 km/h in 3rd is a snap. It wants to lift the wheel all the way. A little scary. (not a great rider)
braaAAAAAP!
Below 6000 is only a little change.

So normal street riding is not much different.
You only taste the extra power when revving it at hi speed.

So much for the midrange theory