ported head for DRZ

I have never had a bike ported before, but I'm looking for an opinion... would the DRZ benefit much getting the head ported? Oversize valves? Or maybe only when punching it out to a 436?

Someone said the heads on newer bikes are pretty smooth to begin with and its hard to improve.

up simba

Hey I see your getting no bites here so I'll throw something at ya.I know its a different bike but its a response none theless.I had the motor on my 98 DR worked to the hilt.435 big bore,ported head,and cam changed.Porting the head will make the motor flow more air.The more air in and out the more power a motor will make.It cost me 225 dollars and the stock head flowed around 150 cfm's and ported around 190 cfm's.Airbox mods and good flowing FULL exhuast system will only let the ported head work even better.I do not think there are "oversized" valves for the DRZ.

By the way the DRZ head stock would outflow a ported 350 head because of the nature of its design.The 350 uses 30mm intake valves and the DRZ 36mm.No doubt 6mm will let a lot of fuel into a cylinder.I may pull the head on my DRZ over the winter and may get it ported while its off.I will be throwing some tech questions DR.Bills way in the near future.

Port? Not being mean here and I don't know for sure, but don't you port 2-strokes?

Sure you can do head work on a 4-stroke and get a good bit more power out of them, but I think we are talking technicalities here.

I'm not much of a knowledge source on head work on 4-strokes, but my mechanic tells me that is the main way to get power out of a 4-banger....that and displacement changes.

We need an engine person here.............

Hey guys. Porting is mainly just a retouching of the casting that suzuki deemed 'fit enough' for our uses...Granted, the cylinder heads of hi-po bikes like ours and those of modern crotch rockets are head-and-shoulders above that of the common automobile's cylinder head....When considering porting know that normally it will only yield little or moderate gains, probably less than a pipe would. But if you're going to increase the displacement to say 436 or 470 then you are increasing the volume of air moving in and out of the cylinder by 9% and 17.5% respectively....That means that you will want to increase airflow aswell. I would think that the tendency for the 470 kits to not pull up to the rev-limiter like the stock is largely due to piston weight and head flow...But. Less flow is normally also associated with higher velocity all other things constant, and that's what normally translates to low-rpm response...So ask yourself...if you have a stock (398cc) bike then the porting will give you little gains which are mostly going to be seen at midrange and high rpms...on a larger bore which requires more flow for the same rpm, you'll gain the pulling and high rpm power that wasn't gained as much, comparatively, as the low and mid were when increasing the displacement....Summary would be:

stock---revver!

stock w/ porting--- will hit the rev-limiter with even more ease and you'll probably gain about 1-2 hp across the entire power band with higher gains near the high-end.

470 w/stock head---torque beast! but not as willing to hit the 10000rpm limiter(less pull)

470 w/ported head---probably much like the stock powerband but with around 17% more power everywhere!!!! which is about 3-7 hp everywhere!!

That's my 2 cents!!!! I hope it brings some aspects into consideration for you guys. But remember. this is all general rules. In hi-po applications such as a 400cc bike putting out 40hp stock----the gains are often less than would be expected due to constraints of the fact that porting may not improve the flow too much since the casting is already in a high state of tune to start with....You must keep that in mind....

where do I sign up?............

Thumper Racing does porting as I stated above 225 for my DR350 head.Even with the porting the 85cc bump in displacement on my 98 motor made it fade off a bit earlier than stock.Going with a bigger bore seems to pack things up downstairs more sorta like the total opposite of a two stroke.The intake ports get a "satin" finish thus allowing the fuel and air mix better and the exhuast polished smooth to get the burnt fuel out.No doubt a big bore will benifit more from porting than a stock motor.Just the same as my motor with a Vortex airbox,full Yosh exhuast and the bell on the rear of the carb swapped for a larger one would benifit more than a "stock" motor.I noticed on my bike when I threw the Yosh system on that not only did it get more power up top but it got up top faster.I would think porting would do sorta the same thing.One thing is for sure I'm not willing to mess with the valve train of the motor.After I got my motor done on the 98 I was always afraid it was a time bomb from stories of "worked" four strokes.Take the Yosh cams and ignition a real nice bump in power while leaving bore stock.But now there is more stress on all the top end parts with higher lift and duration and add to that an extra 1k rpm's over the stock limiter and there is bound to be reliability issues.

KIBBLEWHITE(BLACKDIAMONDVALVES.COM) MAKES O\S VALVES AND DIFFERENT GUIDES FOR THE DRZ. I WOULDN'T BOTHER GOING O\S UNLESS YOU ARE GOING TO A 440 OR 470 KIT. THE ENGINE RUNS INTO THE REV LIMITER BEFORE YOU RUN OUT OF POWER ANYWAY. I'VE HEARD IF YOU CHANGE THE REV LIMIT, YOU'LL HAVE PROBLEMS WITH VALVE FLOAT AND BREAKAGE. I'M CURRENTLY LOOKING FOR TITAMUIM VALVES AND COMPATIBLE GUIDES. LESS WEIGHT=MORE REVS, WITHOUT GOING TO HEAVIER SPRING. THEN YOU CAN PORT IT, CAM IT, AND GO BIG BORE! IN CASE ANYONE WANTS TO BE A GUINEE PIG, I'VE GOT A FLOW BENCH. I DO HEAD WORK ON EVOLUTION AND TWIN CAM HARLEYS. I'LL BE LOOKING AT MY HEAD WHEN IT COMES OFF FOR THE 470 KIT. TIME TO EAT AN XR650!

I think the more displacement for a given camshaft lift and duration, the lower in the powerband the cam(s) come on, if stock the power is mid to top biased (at 400 cc) than with say 470 cc the cam(s) becomes more torque oriented.

Hence poss the problem with the 470 not revving as easily as stock. With lower cc say 300 now this cam is a top end banshee. Hmmm 470 cc

hi po cam,porting= headache for those orange 520

bikes :)

AMEN BROTHER! NOW JUST SOME SUSPENSION WORK AND CHANGE THE GEARING. ONLY PROBLEM IS, WE'LL HAVE ENDED UP SPENDING AS MUCH AS THE KATOOM RIDER. OH WELL, I QUIT DRINKING AD WOMANIZING, I HAVE ALOT OF EXTRA $.

I spoke with a guy called Larry Beall (915)795-2448. He custom machines valves using 6-4 Titanium alloy, from surplus Nascar valve stock. only $35.00 each. Says he has race experience working for both Yam and Kaw factories, and is now retired. It sounds like he has a state of the art shop. He also does Ti wrist pins, oversize valves, porting, headwork, and other stuff. Like I say, I dont know alot about engine work so I didn't have any intelligent questions for him. :) I'm thinking things over what else I'd like to do to my bike.

Why don't one of you mechanical types call him, and post your findings here, see what all he can do for us. He's in TX. (915)795-2448.

His email: larybeall@aol.com

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