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Giday from Newcastle Australia ! Recently my 07 gen 2 KLR (yes Australia got the gen 2 a year earlier than the US ) started using a heap of oil after 65,000 hard kms - what I found was a broken ring land and a 2 thou tighter oval bore (surprisingly no bore damage.), I happen to have a spare standard low k bore in perfect nick so I would like to utilize it - give it a hone and fit a standard size (lighter) after market piston - it seems that Wossner is the only one offering this option . Anyone gone done this road ? and are they proved to be a good long term fix ? Now... Just as SOME klrs burn oil and many more don't ....it seems that the 2 most popular aftermarket options can do so as well in the long term..so I have no brand loyalty .....And for the record I had a 87 KLR 650 that did 90k and never used oil or had a Thermo bob fitted , it was also mostly a open road bike with no traffic work and and being in Outback Australia never saw cold ambient temps.....
 

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If you have ready access to #93+ octane fuel go ahead & install a Wossner piston & ring set.
They appear to have fairly large oil return oils in the oil ring land.

The forum admin, Tom Schmitz aka Souperdoo is running a Wossner.
 

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I did not go stock bore, but I would not hesitate to do so with the Wössner. I would break it in on whatever passes for premium gas in your area. If the cost of premium is not an issue I would run it. If it is an issue in the long term, then you could experiment with lower grades to see what's what. I run premium with mine but do so equally to prevent pinking and to get ethanol-free fuel.

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I have done both 1mm & 2mm oversize Wossner. They worked great, but, really need good premium high octane gas... couple of times when only regular available, I successfully used octane booster. The high compression piston gives ye olde KLR a bit more snap, pulls with a bit more urgency! The feeling I had tho, was that they were sometimes on the ragged edge of detonation. Re-jetting, running a bit richer would be a good idea to help prevent detonation (i.e. go up a size or two on main jet).
 

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Running a bit rich is a good idea. This is a graph of my mixture from zero to about 60mph. 13.5:1 seems like a decent target.

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Discussion Starter · #8 ·
If you have ready access to #93+ octane fuel go ahead & install a Wossner piston & ring set.
They appear to have fairly large oil return oils in the oil ring land.

The forum admin, Tom Schmitz aka Souperdoo is running a Wossner.
I like what I'm hearing...have been using 95 in the old motor and it loved it, as it was prone to pinging on regular 91... But...the problem in Oz is when you get off the beaten track often the only fuel available is diesel or 91..... hence what is probably the cause of my broken ring land .The piston I'm looking at is the standard size
WOSSNER PISTON KAW KLR650 TENGAI 87-07 99.94MM. Doesn't say anything about higher compression which is not what I need to complicate fuel issues when in the outback.
 

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You'll notice that there's 3 different sizes of "standard" piston. That's because AFTER rehoning, you want .003" or more of piston to cylinder sleeve clearance. Personally myself, I've had better results with .004 or even .005" clearance. If I were you, I'd go max 2mm oversize, get the boring and rehoning done. ALL the pistons listed here are 11:1 compression ratio - they don't make a normal/standard 9.6:1 compression ratio piston for the KLR:

Piston Kit Kawasaki KLR650 Tengai 1987-2007 11.0:1 CR
 

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But...the problem in Oz is when you get off the beaten track often the only fuel available is diesel or 91..... hence what is probably the cause of my broken ring land .
Did your engine ever have a hydro-lock event from a leaking float needle in the carburetor, while using a manual shut-off fuel tap which was left ON?
Our North American KLR float bowls do not have an over-flow stand pipe in the carb, only a drain screw!
 

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As a solution, if raising the compression ratio is a concern/issue due to a piston swap. One can ask/pay the machine shop to perform a 'chamber mod' which increases the volume of the combustion chamber effectively lowering the compression ratio. The formulas are readily available to calculate volume (before & after) to compression ratio.

Best wishes
 

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2008 KLR650/685 tricked out / 2008 XR650L / 1988 XLV750R
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Discussion Starter · #14 ·
Did your engine ever have a hydro-lock event from a leaking float needle in the carburetor, while using a manual shut-off fuel tap which was left ON?
Our North American KLR float bowls do not have an over-flow stand pipe in the carb, only a drain screw!
Never - I still have the standard vacuum taps- A work mate who's very experienced with engines tells me a pinging engine will eventually do exactly what my piston did.. but it took 65,000km !
 

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If you want low compression take the piston for the KLX650
I actually can't imagine that the Valve Relief pockets for a KLX650 piston would be any wheres near the correct position or angle to work inside a KLR650 engine.
The KLR engine has Quite a bit wider included angle of the valves than the newer designed KLX650 engine.

Also, being that the KLX650 engine has a more modern, compact combustion chamber (more resistant to detonation), I'm surprised that Wossner did not bump the compression to 12:1 for that engine.

KLRChris machined down the dome of his CP brand piston a bit, final compression on his KLR650 EFI bike was under 10:1 as I recall. An e-mail to Wossner could confirm if safe to do the same to theirs. They might even tell one how much mm to machine off.
 

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As a solution, if raising the compression ratio is a concern/issue due to a piston swap. One can ask/pay the machine shop to perform a 'chamber mod' which increases the volume of the combustion chamber effectively lowering the compression ratio. The formulas are readily available to calculate volume (before & after) to compression ratio.

Best wishes
Or you can, more inexpensively, mill the piston flat.
 

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Or you can, more inexpensively, mill the piston flat.
Ya but then you don't get the benefits from de-shrouding the valves, such as increased low lift flow. Dual purpose Sir, dual purpose ;)
 

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OK, but headwork is expensive and the KLR is not especially responsive to any performance mods that cost much over $49.95. I've done all of that stuff and it would have been cheaper to get an H2 motor and stuff it in there. Whenever someone takes my bike for a spin they comment on how comfy the seat is, not how fast it is for a KLR.
 

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Discussion Starter · #19 ·
O.K. Gents ,thanks for sharing your thoughts and experience , so what I've come up with is that Wossner doesn't supply a piston at standard compression which is a problem with 91 Octane. So I can mill a new piston to get the right compression- if I'm going to do that why not go the latest "improved" Eagle Mike 661 and take a millimeter out of the bore and keep standard compression ,I don't crave performance but a smoother engine and lighter piston would be good... Might try to richen my fuel mixture to get rid of that pinging all together. ....regards Mick
 

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That "pinging" that you think you may hear may very easily be excessive Balancer chain slack, unless you have inspected or better yet replaced the oem balancer chain slack locking lever & extension spring with better parts.
Line #7 in this list,
 
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