Porting 4 strokes, bigger (Ti) valves: benefits?

[ballistic]

I did a search on PORTING, theres very little info on the topic.
So heres the Q's:

My bike: 2001 DRZ, with many mods already. I found a fellow named Larry Beall in TX who can do the following type of work fairly reasonably.
--titanium alloy (6-4)valves... stock size or oversized, $35. each
--Ti alloy wrist pins
--porting

In general terms, what likely benefits is there from those items?

Lighter weight Ti wristpin: Will it allow faster revving, or what?

Ti valves: again.. what would it do? allow faster revs? more power?

oversized Ti valves: any downside to going a little bigger? Is the jury out? Is the DRZ head just fine the way it is?:think

porting: same questions.

Any feedback appreciated guys. Cost/benefit aside, what are the pure benefits? Is this stuff definite upgrade material? Would YOU do it? I find it curious that a search turned up almost nothing.

 

[Rich Rohrich]

Originally posted by ballistic
I did a search on PORTING, theres very little info on the topic.
So heres the Q's:

My bike: 2001 DRZ, with many mods already. I found a fellow named Larry Beall in TX who can do the following type of work fairly reasonably.
--titanium alloy (6-4)valves... stock size or oversized, $35. each
--Ti alloy wrist pins
--porting

In general terms, what likely benefits is there from those items?

Lighter weight Ti wristpin: Will it allow faster revving, or what?

Possibly but it would depend on the weight difference. The gain would be small at best.

Originally posted by ballistic

Ti valves: again.. what would it do? allow faster revs? more power?

If the shape of the valve head is the same as the stockers then there is really nothing to be gained without a cam change. A cam with a more aggressive opening rate could take advantage of the lighter weight of the Ti valves. If the shape of the valve head is different then the stocker then there MAY be some power to be gained, but the stock valves could likely be ground to the same profile for considerably less.

Originally posted by ballistic

oversized Ti valves: any downside to going a little bigger? Is the jury out? Is the DRZ head just fine the way it is?

Oversized valves will tend to raise the torque peak to a higher rpm. Whether or not you'll see a power increase depends entirely on how the machining is done. I've seen as many engines lose power as gain from these types of mods. Clearance issues near TDC are something to consider especially if the cam is changed.

Originally posted by ballistic

porting: same questions.

Porting done correctly can usually get you a moderate gain in performance, but don't expect some massive change. Japanese four-valve cylinder heads are awfully good out of the box these days. The throat area near the valve seat tends to have machining flaws and ridges from initial manufacturing so there is usually something to be gained here. A proper valve job with appropriate angles can gain some power as well. Whether or not the cost to benefit ratio is good depends entirely on who you deal with and how skilled they are. A good valve job will cost in the $125-$175 range, porting is all over the map cost wise and in most cases it's over priced for the gains made. It's easy to make a pretty looking port and valve seat that works much worse than the stock setup.

These engines seem to have some issues when the rpm ceiling is raised, so mods that move the power up may prove to be a liability in the long run.

Engines are systems, and good engines like these don't respond well to old school throw a bunch of cool parts at it type mods. Subtle changes that tend to be closer to blueprinting are the more logical place to start.

 

[cujet]

I would suggest that for the same money as an expensive port job you could install a big bore kit and gain more HP.

Chris