DRZ - Forum

Hi.

So i rode it again yesterday. Long ride.
I'm baffled.
Maybe the head needed running-in or it's just me having to get used to it, but it runs great.
WOW!
(i also changed the carb jetting a little, still needs some work i think)

For illustration
At 2500 rpm (almost stationary), 2nd gear, crack the throttle open: BRAAH powerwheelie.
At any rpm it makes more power, but as the rpms rise the gain is more and more up to 10.000. Nice sound.
Same in 3rd gear from 45 km/h and up. Just sit and throttle, front wheel lifts. Also at 85 km/h WraaaAAAAP!!!
Stock SM gearing.

Love it.
Greetings from Holland.
Jazz.

Sorry i cannot make it to the meeting.

(just for the record: this is not ABP porting like the title says, but Eddie Sisneros porting, ask sumobob about ABP's good results)

Wichtig ist, das der Kopf immer auf Betriebstemperatur gebracht wird bevor er den vollen Druck bekommt. Durch die Bearbeitung ist er nicht mehr so stabil wie im Originalzustand.

Danke.

Uberigens heb ich andere carb-einstellungen probiert.
Lauft noch etwas besser.

Dyno results are in

51HP peak at 8200 rpm (rearwheel, sae corrected with dbkiller and a/f reader in the pipe)
Uncorrected was 54 hp at 1023 mbar and 10 deg. C

Jetting is confirmed to be correct at 12.8 mostly.
Bit rich at low throttle openings.

The HP has gone up 5 hp from 5500 to 8000 rpm, but the gain lowers to 2 hp at 9500.
The midrange is crazy strong: 40HP at 6000 already and 47.5 at 7000.
The old hp was 48 at 9000, so the peak has moved back in the rpm range.

There are 2 reasons for that:
1) the cams are at 108/108 so not set for max peak hp, but more midrange power. The old cams were 104/108 and milder.
2) the fcr 39 is just too small for the head. i am 100% sure it is the bottleneck for peak power.
The fcr 39 flows a little less then an unported head already, and WAY less then the ported/big valve one.

I made a chart that puts the old and new graph togetger.
You see where the fcr39 starts to flatten the curve.

I guess a fcr 41 may take it to 53,5 HP at 9500.
I don't think i will try.

So i can confirm sumobob: the head porting works great. 5 HP through a large part of the range.
So bigbore and ported head are quite similar in performance gain.

Made lots of km on it.
Big smiles.

by the way: changed the gearing from stock 15/41 to 16/39.
The 1st gear was useless light.
2nd gear runs up to 95km/h GPS now. (stock is 105 in 3rd)
5th must be somewhere near 190 km/h GPS.

I put up the results in a comparison chart.

Lowest/brown is stock SM 34HP
Green is E model 40HP
Purple is E model BigBore Yoshimura Ti 48HP, exactly like my previous situation and dyno.
Blue is the same but with the Old style Hotcams with 108/108 and higher lift and duration. That is hard on stock springs/valves.
Orange is my current setup. So with +1 oversize one-piece valves, ssw springs and ssw porting (but with shortended guides this time)

So the change is purple to orange.

The dyno operator went of the gas too early at 9500 rpm by the way.