I have pretty much finished picking the low hanging fruit.  The mods I have done so far have been relatively inexpensive and fairly easy to accomplish.  My total cash outlay has been about $264.  Here are the mods I have done so far:

-Airbox modifications with K&N filter.  Cost $56.  See post "Airbox Performance Tests" 4/9/18.

-Carb mods including drill out mix screw plug, drill out pilot jet, drill hole in slide, raise jet needle, replace main jet.  Cost $4.50 for main jet.  See post "Stock Carb Slide Mod" 4/12/18.

-Transient enrichment valve mods.  Cost $0.00.  See post "Transient Enrichment Valve (TEV)" 4/15/18.

-DR 650 cam install.  Cost $165.  See post "DR650 Cam Evaluation" 5/2/18.

-Stock muffler modifications.  Cost $38.  See post "Stock Mufflar Eval & Upgrade"  5/15/18.

-Flywheel removal.  Cost $0.00.  See post "What's the Flywheel for?" 6/18/18.


It was time for a dyno run so I went to see my good pal Ted Davis at RevTek Speed Tuning in Waipio Gentry, Hawaii.  He's got the goods when it comes to dyno testing.  

The modifications listed above have resulted in a 11.3% increase in horsepower and a 20.6% increase in torque.  I must admit I expeceted more but the seat-o-da-pants evaluations just don't cut it.  Too many variables closing in on my pea brain to digest all at once.  Noise, wind, vibration, adjacent vehicles, etc. all combine to make an accurate evaluation almost impossible.  The dyno is the only way to go.  

Here is a pic of the dyno run:

The first dead ringer is that torque.  It increased by 6.6 ft-lbs.  More importantly, it exceeded the maximum stock torque (31.8 ft-lbs) all the way from 2300 rpm to 6000 rpm.  Now that's a power band.  No dips.  No hic-ups.  Just a nice smooth arc.  I think that explains my impression of "smooth acceleration".


Where the stock engine made 30 HP from about 5200 rpm to 5700 rpm, the modified engine exceeded 30 HP from 4500 to 6500 rpm.  So it's not the total gain in horsepower but the gain combined with the extended power band that make this little beast feel so much better.

Regarding intake & exhaust restrictions.  If you look at the power curve you will note that this thing doesn't just sign-off.  I had Ted chop the throttle when he reached 7000 rpm.  I'll never take it that high so why hurt it.  But it was still pulling nicely at 7000 rpm.  That tells me that the engine isn't being chocked off by the induction system and isn't constipated.  The intake and exhaust mods look like they've still got some more to be had.  The mods support what I have now and will probably support even more.  To me, that's a very good sign.  I should be able to get more out of it and still maintain the current noise levels.

Regrading the fuel curve.  I'm still a bit lean.  I really want it down about 13:1, but it's much closer than it was on the stock run.  I will eventually raise the needle .030" to .060" and bump it up from a 152.5 MJ to a 155 MJ.  Those adjustments should get the mix from 3000 to 4200 and from 5000 to 6500 pretty close to 13:1.  But for now, I will leave it as-is until I get some sort of device to measure my acceleration.  That way I can correlate the existing setup with known dyno data to G-force.  Then I can start testing the mods individually.  I will keep you posted.


My initial dyno numbers were a bit discouraging until I took a better look.  It's the total package that counts.  The bike feels great and the dyno test explains why.  It's not the total gain in HP that tells the story, it's the extended powerband.

Hope you all find this post useful.

Good info.

Great info. Thanks.

BTW, those smooth blue curves are very pleasing!!

Regarding Armen's post "What's next?".  I was hoping I would get some clues from yooz guys.  Right now, I am planning on installing an AutoMeter device that measures G-Force.  I want to be able to test and evaluate every single change.  If the instrument is sensitive enough, I am hoping to be able to share the good & the bad & the ugly associated with each mod with the rest of you.  So what ya got folks?  

Actually, I have been toying with an idea about installing an insert in the exhaust port that smooths out the abrupt transition from head port to exhaust header.  Right now, it has an abrupt small-big-small transition that most certainly kills flow velocity.  Any thoughts?


Regarding Batman's comment on real world conditions:  I agree, the dyno is simply a tool that measures HP under almost ideal conditions.  It can't replicate all the variables encountered on a real road.  But given the fact that each dyno pull is accomplished under those same idyllic conditions, it most certainly will give you better insight than seat-o-da-pants.  The limitations of the dyno (mostly financial) are what have led me to the conclusion that I need some sort of instrument that allows testing after EVERY change and under almost exact conditions.   So I have ordered such an instrument.  I intend to share the fruits of that device with all of you so that we can focus on mods that actually pay off.  My last dyno run tested about five or six mods.  I can't afford to test every mod individually.  If the AutoMeter instrument proves to be reliable, I will be able to test each one and evaluate on it's own merit, test in combinations, etc.  It's gonna be a gas.


Regarding Island Road's comment: I agree, smooth curves are nice but I wanna make those curves steeper.  Thanks for the kudos.


Regarding HotRod's question about removing the engine:  No need to remove the engine.  It's a bit tight up there but you can get her opened and closed without too much trouble.  I suggest doing several dry runs to figure out all the angles and dangles you will need to do in order to get the head cover back in place without messing up the sealant.  Take a look at my post on "Sealant Applicator"  for a cheap & simple tool that will ensure a very, very light coat of sealant.  Also look at Dave's comments regarding use of a syringe.  The sealant application is the trickiest part of the job.  Keep this in mind, I'd rather deal with a small leak than a burned up top end.  Keep that sealant away from the chamfers in the cam bearings and any oil passages in the head or head cover.  Also, be aware that I am still uneasy about the DR650 cam's lack of oiling holes.  I did a good visual inspection after several hundred miles and everything looked OK.  I will be doing another visual shortly and I will post the results.  See my post on DR650 cam for more info.  

I agree with Verslagen.  It is possible to carve away some of the ring in the exhaust port with the engine still in the frame and the head still on the bike.

Make sure the exhaust valves are closed, then sStuff a small amount of greasy rags in the exhaust port.....then work some magic with a Dremel or similar tool.

DBM,
That is a really nice improvement in the torque curve. Must be easy to feel the extra torque. And it is so smooth, all across the power band!