Maybe a pet pieve of mine, but I used to flee when someone had McGyver on because it took only a couple of episodes for his innovations to reveal as more Hollywood idotic than inventive. Valid inventiveness lives within the the hard walls of physics. But I know, it's the thought of inventiveness that counts, so I take that as a complement, thank you!

And within those walls is this sweet zone I love to play with: self-reliant improvement without spending a lot of coin. Though sometimes popping for a quality item like the 330 cyclinder kit, a Moab shock and Watt-Man's Thermo Bob for my KLR650 is money well spent. Don't want to be rediculously cheap, but I also don't want to fall for being market to either. Maybe that's why I no longer own a BMW, and consider an older model KLR650 one of my favorite rides? Or riding a KLX330S as a superior overall solution to the really expensive mounts?

I remember once several fellows approaching after I had seriously impressed them out on gnarly trails riding a lowly 1998 KLR250. You know, "If he rides THAT thing - that good, just think what he could do on a REAL machine like our KTMs!" I never refuse mentally cataloging different machines. I rode them all and said "Thank you." Interesting and nice in a way, but inside I was thinking, "That was an interesting vibrating refrigerator-size bike with brick seat shoved up me ****." I was quite happy to get right back on the KLR. Still love that particular bike and wish my KLX seat was that KLR seat. For me ****, that is.

 

Absolutely a compliment!

We share a common mindset when it comes to "making it yourself" or at least giving it a try, and an aversion to "persuasion by marketing". I remember when I bought my KLX300 and ALL of my buddies were on "big orange machines" or "big white/blue machines". Except for occasional long stretches of deep soft sand or rides in open desert terrain, they could never seem to be rid of me ... much to my delight as I putt-putted merrily along.

But to each his own, it's all about fun, self inflicted bodily abuse, people I've met and friendships made been among the best in my life ... it's all good.

 

Agree on all, especially the friendships. I live pretty remotely in SW Oklahoma, but wish to do some high altitude and desert riding in CO this year. Can't wait to ride some BLM stuff before the socialist-control wackos close it all.

 

Understood. But optimal design over the years has shown that we're working with a smaller pressure delta to drive the flow on the intake side, so it's always a bit larger (witness the size of the intake valves, when compared to the exhaust valves.)

 

Thanks, man.

Me too. I ran the 15 front and liked it, then went to a larger diameter rear tire (MT43 Pirelli, 6.5% larger!) and liked that, now added a steel 39 tooth rear sprocket... and like that too! Commuting daily on it right now so the dirt low-speed tradeoff is a non-issue. To be fair and comparable to the earlier bikes with the wider-ratio 6th gear, ignore the tire change.

Why? The bike is known for a plugged up exhaust system from the factory. Stock is .27 square inches and yours is even smaller at .23. I know there's more to it than that, but I'm thinking your design allows for additional holes, and I'd just think that it would seem reasonable to exceed the stock area. Your baffle-less test run might be an interesting one.

Indicated mph or actual mph? That's flying! The 06-08 speedos are off around 6-7% aren't they? I love my 09's digital dash but that mother is off by 10% on speed - that's just not right. I just want to be sure we're quoting actual numbers.

Keep up the good work, I really like your baffle design.

 

Intake (fuel+air) Mass In = Exhaust Mass Out

... does not change, unless your bike (not you!) gets heavier by the ride!

Intake Volume In vs Exhaust Volume Out ... does change.

Mass flow optimization = volume flow optimization? Sweet situation if you can achieve it!

One reason I believe (just thinkin') that exhaust valve area is less than intake valve area is the density of exhaust less than density of intake charge and thus pressure required to move it past exhaust valves lower = exhaust open area reduced = smaller lighter exhaust valves.

If that's true than the muffler exit open area can be smaller (maybe really smaller) than one might assume vs carb throat diameter, intake valve area etc.

Which is line with what I've read/heard from folks who engineer/tune truly high performance machines (8000hp dragster, Formula 1 etc.) - bigger performance gains to be had on INTAKE side i.e. remove airbox lid and air filter, re-jet and you'll get a bigger HP boost than running a straight open header (no muffler) + rejetting. Doesn't mean you ignore the exhaust end, but compared to intake side (flow, mixture, combustion process) exhaust is simpler to deal with.

But then again I could be totally on Pluto here.

 

LongmontKLXr,

We agree. (I know you know the following but I'll say it for general understanding of others reading)... Overall, there's only so much room in a cylinder for valves. Making one set larger means the others must get smaller, and we see the final result in the sizing used.

On the intake side, at best we have 14.7 psi of air pressure to push the intake charge in. Exhaust pressures when the exhaust valves start to open is typically in the 70-100 psi range, so we have a higher pressure available to drive the flow, which I think is borne out in the final valve sizes chosen in the head.

Agreed about the intake vs. exhaust gains - a one psi loss in the intake tract cuts your power to 13.7/14.7, or 93% of what it would have been... but a one psi loss in the exhaust tract will be a much smaller percentage loss.

I didn't really want to turn this into a 'physics thread' as someone else mentioned, but was just pointing out that Einfahrt might have a more restrictive exhaust system than he did when it was stock, that's all.

 

Yes, my exhaust area may be constricted, but I know it's not worse than stock. My top speed is indicated, and the speedo is typically optimistic, so when I said I was goin 90 MPH, it's probably more like 84. As I said earlier, opening it up more is just a matter of adding holes, one at a time.

My airbox lid is more open. I use the stock air filter and real foam filter oil. I have no use for expensive and, in my opinion, less effective ways of trapping dirt particles and shedding water than foam filter with real foam filter oil. I like a more open air box for the simple pleasure of hearing the intake for precise feedback for throttle control. I like a quiet exhaust for the pleasure of hearing the intake (and to not screw the sport I love). When I ride any distance at all, I always use ear plugs stuffed near to my brain. I find I hear through the wind roar better that way.

Interesting upping of gearing your `09, Watt-Man, you are among a small group who understand gearing more comprehensively and actually 'go there' to find out.

During my 1,320 mile trip from Michigan to Oklahoma, I had on street tires. The rear was a huge for this bike, a 130. That and one tooth up on the front made the long trip at speed much more reasonable. Now with a smaller 4.50 Kenda dual sport tire, I find the one tooth up on front trick barely adequate for stretches of highway. But then 1st gear is almost too high for tight work.

I find it pitiful that dual sports don't have true wide ratio gear boxes. Fanning the shifter then running out of 'leverage' at speed may be exciting, but it's not practical. It's like a ladder where the rungs are compressed to half the ladder height. Not practial.

The latest model KLX even went further the wrong way (in my most humble opinion) by lowering the 6th gear! That's one reason I opted for the previous model.

This narrow stuff would be fine if we also had a high and low range like those Suzuki 90s of the 1970s. How about a 7 or even 8 speed? We could have our cake and eat it too.

I think there may be a liability or 'stupid friendly' aspect to this too. Speedometers and gear ratios may be off for no other reason than to protect people from themselves, by making it seem they are going faster through higher indicated speeds and greater intensity at speed. After all, our energy is proportional to the square of the velocity, the implications of which are lost on most.

I've gotten lost in diatribe and forgotten the rest of the points to address.

 

AMEN. I was surprised the magazines made such a big deal of the 15% gear spread between 5th and 6th on the '06, '07 and '08, so KHI made it 10% on the 09's and newer. I've definitely considered finding someone with an earlier bike who prefers the close-ratio setup on the '09, and swapping the parts.

 

EinFahrt ... "When I ride any distance at all, I always use ear plugs stuffed near to my brain. I find I hear through the wind roar better that way."

Smart.

I can't tell how many riders I know (both off and on road) with lot of miles under their belts who found out too late they've suffered hearing damage.

Because it's a cumulative effect "Noise level x Exposure Time" it can creep up on you, then it's too late.