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Discussion Starter · #1 ·
As an engine builder and someone who spends time around late model circle track and 1k+ Hp drag cars, Im not shy to engines and how to build power.

I've had a 685 kit before to stop oil burn, as expected very minimal gains, less vibes was the most noticable thing other then no oil usage... However my buddy highly recommends the 705...I've never rode a 705 yet

I see wossnerr makes an 11.1 piston, never used anything from them however.

I don't expect a race bike obviously, but a little boost in power never hurts..I've never really needed extra power, maybe 2 or 3 times I just needed a little extra to go through/up something...I try to avoid that on a KLR...

Just curious why we never hear much about the high comp..

Hopefully some other knowledgeable engine guys can chime in.
 

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As an engine builder and someone who spends time around late model circle track and 1k+ Hp drag cars, Im not shy to engines and how to build power.

I've had a 685 kit before to stop oil burn, as expected very minimal gains, less vibes was the most noticable thing other then no oil usage... However my buddy highly recommends the 705...I've never rode a 705 yet

I see wossnerr makes an 11.1 piston, never used anything from them however.

I don't expect a race bike obviously, but a little boost in power never hurts..I've never really needed extra power, maybe 2 or 3 times I just needed a little extra to go through/up something...I try to avoid that on a KLR...

Just curious why we never hear much about the high comp..

Hopefully some other knowledgeable engine guys can chime in.
Similar vein, was just talking to a buddy about porting/polishing to get a few more horses. I know the klr is a plow horse, but just curious if that’s been done as well?
 

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Since you have some experience building engines, then you know that higher compression, other factors being equal, does not build much power. Rule of thumb is that a 10% increase in CR results in about a 3% increase in power. To take advantage of the increase in CR to make more power than that, you have to do other complementary things, such as changing combustion chamber shape, recalibrating the timing, cams, etc.

A guy named KLR Chris did a lot of this development work and got up to about 60 HP, IIRC. One of the things he discovered was that the intake ports need to be reshaped to raise the floor of the port and narrow it, NOT make it bigger. So some one doing a “port and polish job” is more likely to make the flow worse.

If you’re building a racing or high performance engine, you will do all those things. But for the KLR engine, do you really want to? It would need a lot of head work too because the intake does not flow well at high RPM. It would be cheaper to sell it and buy a KTM or other brand. Of course, if you can get a Wossner piston for about the same price as a J&E from Eagle Mike, and you don’t mind feeding it 92 octane fuel, then go for it. 3% is more than nothing.
 

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Discussion Starter · #5 ·
Since you have some experience building engines, then you know that higher compression, other factors being equal, does not build much power. Rule of thumb is that a 10% increase in CR results in about a 3% increase in power. To take advantage of the increase in CR to make more power than that, you have to do other complementary things, such as changing combustion chamber shape, recalibrating the timing, cams, etc.

If you’re building a racing or high performance engine, you will do all those things. But for the KLR engine, do you really want to? It would need a lot of head work too because the intake does not flow well at high RPM. It would be cheaper to sell it and buy a KTM or other brand. Of course, if you can get a Wossner piston for about the same price as a J&E from Eagle Mike, and you don’t mind feeding it 92 octane fuel, then go for it.
Right, I'm not wanting to change a whole lot, I figured bigger valves is and some type of piston at most, after that I'll buy something else...fuel grade don't bother me, my RTW plans are unfortunately gone, but I plan on touring around the US one more time.

If I'm gonna do a piston in this bike, I figured do a little why I'm there..not searching for big gains...just a "hey that better pulling hills at highway speeds" gain...I'm a big dude..

But winter is coming...I really miss my GS 800..and I've been looking hard at a few...but still a bit to high priced.

All reality I'm bored with the KLR...but it's just a good do all bike, not pretty, not great...but just loyal...kinda why I've kept it around
 

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I like the Wössner. Coupled with 1mm larger valves and some modified valve timing with adjustable cam sprockets, it does quite nicely. The head is ported, but that probably didn't help. It will pull a 16/38 final gearing to about 100mph pretty easily. I've never tried to go faster than that, though it would. Its best trick is the acceleration at freeway speeds in the range of 60 to 80mph.
 
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All reality I'm bored with the KLR...but it's just a good do all bike, not pretty, not great...but just loyal...kinda why I've kept it around
Agree 100%. Did a 300mi trip today in high elevation & god awful winds. Couldn’t squeeze more than 65mph going up a steep 3mi grade today. Wished I had another 20hp, but it is what it is.
It’s an overweight, ugly, underpowered “great at nothing” bike that always seems to find its way back in my garage :ROFLMAO:
KLR’s are here to stay in my stable.
 

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Discussion Starter · #9 ·
Agree 100%. Did a 300mi trip today in high elevation & god awful winds. Couldn’t squeeze more than 65mph going up a steep 3mi grade today. Wished I had another 20hp, but it is what it is.
It’s an overweight, ugly, underpowered “great at nothing” bike that always seems to find its way back in my garage :ROFLMAO:
KLR’s are here to stay in my stable.
Reminds me going up pikes peak...just miserable haha, I've traveled the country on 2 of my KLRs... definitely been some choice words going down the road on KLRs...

The DR650 wasn't far off either honestly 👀...but the KLR is still with me
 

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I did the Exhaust cam mod with my valve adjustment and it raised the static compression from 90 psi to 131 psi. Im guessing the change could be in part to tight valves and different timing on the decompression function of the cam. At the same time I modified the airbox and did the jetting/needle spacing. These changes made a Huge Difference in the performance of my KLR. Its nice to hear you riding buddy on his Africa twin say "that thing has a lot of power, did you rebuild tor engine".
 

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I did the Exhaust cam mod with my valve adjustment and it raised the static compression from 90 psi to 131 psi.
Most of your static compression increase would have been created by the advancement of the closing angle of the KACR as compare to crankshaft angle.

The running or de-activated KACR compression would not have changed much unless any of your valve tappets were a fair bit Under Specs.
 

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Most of your static compression increase would have been created by the advancement of the closing angle of the KACR as compare to crankshaft angle.

The running or de-activated KACR compression would not have changed much unless any of your valve tappets were a fair bit Under Specs.
My smallest feeler gauge was .002 and it wouldn't fit before the valve adjustment. The guy I bought the bike from never adjusted the valves and it had 36k on it.Your explanation makes since. I was going to do a 685 kit before I did the mods, but honestly I think I will leave it alone for now because it runs so good now and barley uses oil. I am considering the fmf power bomb and port matching it to the head. Any thoughts?
 

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My smallest feeler gauge was .002 and it wouldn't fit before the valve adjustment. The guy I bought the bike from never adjusted the valves and it had 36k on it.Your explanation makes since. I was going to do a 685 kit before I did the mods, but honestly I think I will leave it alone for now because it runs so good now and barley uses oil. I am considering the fmf power bomb and port matching it to the head. Any thoughts?
Though it hasn't been tested (AFAIK) with porting at the same time, some member here dynoed his bike before and after swapping on the FMF powerbomb and he confirmed my long held suspicion; there is no functional difference; his dyno result showed a 0.4hp increase in the midrange and a corresponding drop in the top end - nothing you would/could ever notice. If you did the airbox and jetting mods properly, you should have picked up 2-3hp.......a good silencer may give you another hp or two which is better than the header swap. If you have a Gen1, there is probably a bigger difference between the Gen1 and Gen2 header than there is between a Gen2 and FMF - I run Gen2 headers on both my Gen1's. If you still want/need more power after all that, a 685 is the next step....another 3hp-ish

Dave
 

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Though it hasn't been tested (AFAIK) with porting at the same time, some member here dynoed his bike before and after swapping on the FMF powerbomb and he confirmed my long held suspicion; there is no functional difference; his dyno result showed a 0.4hp increase in the midrange and a corresponding drop in the top end - nothing you would/could ever notice. If you did the airbox and jetting mods properly, you should have picked up 2-3hp.......a good silencer may give you another hp or two which is better than the header swap. If you have a Gen1, there is probably a bigger difference between the Gen1 and Gen2 header than there is between a Gen2 and FMF - I run Gen2 headers on both my Gen1's. If you still want/need more power after all that, a 685 is the next step....another 3hp-ish

Dave
I agree there would be minimal power increase with the header on s stock engine. My big concern is a big header on a lightly modified engine can sometimes hurt you somewhere in the power band. I had hoped with the cam, air box and jetting mods I may be closer to 1 plus hp with no loss. This being said when I go to ride in the mountains of AZ in the Summer its 75-80mph mostly uphill for 1-1.5 hrs. I would like to get rid of the exhaust heat as quickly as possible.
 

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If heat is part of your consideration, consider keeping the stock muff. I’ve had both an FMF and SuperTrapp, and they were much lighter in weight, but also radiated more heat from the exhaust pipe and muffler than the stock muffler. Smaller mufflers with less and thinner metal will do that. I’ve gone back to stock on both my KLRs to reduce noise as well as heat.

Maybe if I get really motivated to lose 5 lbs high and back, I might try a Leo Vince.
 
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