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WD Serious Thumper 2005 No Login Offline Professional "scooter trash". Posts: 5207 Rosemark TN Gender:	Re: OUCH Reply #15 - 03/31/15 at 23:02:34 Because performance style pistons tend to need the extra rigidity. The engine is going to run a touch hotter (usually), making the piston "grow" a bit more in operation than a stone stock version. You ought to see the skirts on a low compression forced induction piston... normally look like a 1930s or 40s flathead truck engine component.
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Re: OUCH
Reply #16 - 04/01/15 at 03:03:12

If you search Wossner Piston Image on google...you will get 100's of photos - but none have the bench in them nearly as wide as the piston for the DR650/LS650. Obviously the 2 stroke pistons are fully round, the 4 stroke pistons either have a full skirt...or some version of the thinner slipper skirt piston. A few have a reinforcement around the piston pin that looks similar to the bench on the LS650 piston - but none are as pronounced. Wonder if they would entertain a "Technical Question" about it? I sent them an email asking them about this unusual design.

And to make this more confusing.....this is the piston that fits the early DR650 and our LS650, and it weighs 371 grams.

Wossner for the DR650/LS650

And this is the piston that fits the later DR650SE with the 100mm bore, and they don't list a weight.

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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10663 Oklahoma Gender:	Re: OUCH Reply #17 - 04/01/15 at 06:48:20 The newer DR has a much shorter stroke; seems like that would affect the yankin' & bankin' of the piston in the bore.
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Re: OUCH
Reply #18 - 04/01/15 at 07:13:01

LANCER wrote on 04/01/15 at 06:48:20:

The newer DR has a much shorter stroke; seems like that would affect the yankin' & bankin' of the piston in the bore.

It could be something to do with the long stroke and resulting rod angles. If you look at your piston/cylinder....the most severe scuffing occurred at the bottom of the stroke where the rod angle would be the greatest - and causing the piston to have the most pressure on the piston skirt.

Is this the big piston you were talking about WD?

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Re: OUCH
Reply #19 - 04/01/15 at 09:51:08

Well.....that Wossner design might not be the latest "hot ticket" design. This is what Wossner responded with:

Thank you for your email and questions. Wössner doesn't participate or post on bulletin boards or forums however please feel free to post my answers to your question(s) on your Suzuki Savage forum.

Our part numbers indicates what pistons were made first as a stocking part, the 8501 series would have been the first 4-stroke stocking piston then 8502 etc. The round skirt 97mm piston has not been updated to a newer style "slipper" style forging and without steady/increased sales they never got updated. On the 100mm bore pistons Wössner had a slipper style forging that the piston "laid out" pretty well on so that is why it was used. On many later 4-stroke pistons the Wössner family heavily invested in more and more dedicated lightweight forgings as the business and demand grew.

So....we have an old style engine..and the early DR650 and LS650 owners just aren't creating a big demand for the newest performance piston styles.....and the market doesn't support the design or tooling necessary to make it. That isn't to say the 97mm Wossner doesn't work well - it just may not be the ultimate piston that they could have made if the demand justified it.

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Re: OUCH
Reply #20 - 05/08/15 at 03:36:28

Lancer:

I have developed a recent concern about anyone dumping the oil and changing the oil filter on any bike that has been in storage for a while. My thought is that most of the oil has drained away from the piston and cylinder during storage - and then when you dump the oil and change the filter the oil system has to be refilled by the oil pump before any oil is actually pumped through the moving engine parts. The critical "dry start" time that everyone claims is when the most engine wear occurs......has now been extended a considerable length of time by the empty oil filter.

I believe we should warn folks "not" to change the oil and filter before they start up any bike that has not been run for a while. It would be better to start the bike and get it warm before doing an oil and filter change.

Do you remember if you changed the oil and filter before starting up REX following the dormant period?

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Gary_in_NJ Serious Thumper Offline LS650 Cafe Racer Posts: 2633 Amongst the Twisty Roads	Re: OUCH Reply #21 - 05/08/15 at 05:05:04 Dave, Another way to prime the system would be to crank the starter for 10-15 seconds with the sparkplug cap removed (preferably with the sparkplug removed). While this will not pressurize the system, it will prime it.
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jcstokes Serious Thumper Offline SuzukiSavage.com is very useful Posts: 2119 Mauku New Zealand Gender:	Re: OUCH Reply #22 - 05/08/15 at 12:53:14 Agree with Gary In NJ, take the plug out and put a couple of drops of engine oil down the plug hole, replace the plug loose and crank a few times, or if you are scared of it starting, put in gear, very loose plug, ignition off and roll the bike around in gear, should get the bore oiled.
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Re: OUCH
Reply #23 - 05/08/15 at 13:05:02

jcstokes wrote on 05/08/15 at 12:53:14:

Agree with Gary In NJ, take the plug out and put a couple of drops of engine oil down the plug hole, replace the plug loose and crank a few times, or if you are scared of it starting, put in gear, very loose plug, ignition off and roll the bike around in gear, should get the bore oiled.

The point I am trying to make......is don't make the situation worse by draining the oil and installing a new oil filter - which results in a dry system at start up. It would be better to start the bike with the old oil already in the bike.....then once it is warmed up and running again you can change the oil if you want to.

Adding some oil to the cylinder is a good idea if the bike has been dormant for a while, and running the engine starter a bit to prime the oil pump can help - and even changing the oil might be OK as long as you don't take the oil filter off the bike.

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Jeff71 Senior Member Offline I'm a bike noob!!!!! Posts: 378 South of Chicago, the suburbs Gender:	Re: OUCH Reply #24 - 05/08/15 at 16:00:14 Could you just leave the decompression switch open a bit instead of pulling the plug? (You'd pull the coil wiring so it wouldn't start.) Jeff
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: OUCH Reply #25 - 05/08/15 at 16:57:14 Yeah, easier, quick er ,safer.
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