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Discussion Starter #1
The weight of a KLR 650 piston suited for standard bore is 478.3g. Note that this weight does not include the wrist pin, keepers or rings.

Does anyone have the piston weight for an Eagle Mike 692 kit?

Jason
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Not just the piston but from EM's site: The stock ring, piston, wrist pin and circlips weigh 640 grams. This exclusive piston kit weighs 490 grams.

I didn't weigh mine but I have no reason to doubt him.


Dave
 

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Discussion Starter #3
Not just the piston but from EM's site: The stock ring, piston, wrist pin and circlips weigh 640 grams. This exclusive piston kit weighs 490 grams.

I didn't weigh mine but I have no reason to doubt him.


Dave
Mike's website shows the 685 and 692 piston kit weighing the same 490g, which doesn't seem right to me. My guess is that the 685 kit weighs in at 490g and the 692 kit is a bit heavier?

Jason
 

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You're probably right; there is likely a few grams difference.....I doubt it's much. When you get your piston, weigh it and let us know.

Dave
 

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100mm is stock bore; 685 is 2.5mm over stock, 692 is 3mm over stock........I hafta think that the .5mm ( 0.020") difference is darn near negligible.

Dave
 

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Discussion Starter #6 (Edited)
I just weighed my complete stock piston assembly (guts, beak, feathers and all) and came up with 638g, which is quite close to Mike's figure of 640g.

I roughly estimate the difference in weight between a 685cc and a 692cc piston to be about one gram or 0.035oz; so indeed, the delta is "darn near negligible".

Jason
 

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Legend has it: The dynamic weight balance calculus of KLR engines began with the KLR 600's piston weight; when the heavier KLR 650 piston entered the mix, no compensating changes were made reflecting the difference in reciprocating weight. Thus, with KLR 650s (stock), there's a whole lot of [needless] shakin' goin' on (apologies to Jerry Lee Lewis). Further legend, the 685 piston weighs less than the stock KLR 650 piston; thus approaching the KLR 600 piston's weight, providing smoother running, less vibration, approaching the dynamic balance model of the long now-departed KLR 600, for which the initial balance calculations (yet unchanged) were made.

True? False? Undetermined?

I don't know! :D
 

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Discussion Starter #8
Legend has it: The dynamic weight balance calculus of KLR engines began with the KLR 600's piston weight; when the heavier KLR 650 piston entered the mix, no compensating changes were made reflecting the difference in reciprocating weight. Thus, with KLR 650s (stock), there's a whole lot of [needless] shakin' goin' on (apologies to Jerry Lee Lewis). Further legend, the 685 piston weighs less than the stock KLR 650 piston; thus approaching the KLR 600 piston's weight, providing smoother running, less vibration, approaching the dynamic balance model of the long now-departed KLR 600, for which the initial balance calculations (yet unchanged) were made.

True? False? Undetermined?

I don't know! :D
Yes, that's the same story/legend/lore I've heard over the years.

Jason
 

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Yep; same here. What would be interesting is to know the weight of a KLR600 piston........I bet it's heavier than a 685/692

Dave
 

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Discussion Starter #10
You're probably right; there is likely a few grams difference.....I doubt it's much. When you get your piston, weigh it and let us know.

Dave
Ok, I just received my 692cc piston and it weighs 497.5 grams, which is a mere 7.5 grams heavier than the claimed weight of the 685cc piston.

Following are a couple of pics of the new piston on the left and the stock 651cc piston on the right. Notice the significant difference in the length of the wrist pin. The new 692cc wrist pin is much shorter than stock, but has the same OD. Notably the new wrist pin has a slightly smaller ID ~0.010" for some reason.

Jason
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IMG_0988.JPG IMG_0988.JPG IMG_0989.JPG IMG_0988.JPG IMG_0989.JPG IMG_0990.JPG
 

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Maverick, How about a better view of the oil return holes in the oil ring groove of both pistons side by side.
Maybe elevate them on a wood block so the camera can be level with ring grooves.
And a right side up pic with the oem wrist pin connecting the 2 of them to compare deck heights & ring groove spacing?
 

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Discussion Starter #13
Did you happen to weight the stock piston alone?

Dave
Yes, see below:
[
I just weighed my complete stock piston assembly (guts, beak, feathers and all) and came up with 638g, which is quite close to Mike's figure of 640g.

I roughly estimate the difference in weight between a 685cc and a 692cc piston to be about one gram or 0.035oz; so indeed, the delta is "darn near negligible".

Jason
 

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Thanks, I thought the cylinder cross-hatch pattern that Eagle Mike did was perfect. Here's a close-up that was supposed to be included in my earlier post.

Jason
View attachment 27813
Doesn't EM actually just walk across the street to visit Matt at Import Automotive & Machine with the cylinder & heads?
 
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Looks just like my 692 kit, which I’m halfway through installing. ALrhough Mike measures the parts after he gets them from the machine shop, I still double check everything. The side clearance of the new JE piston to the bore is .004” the top ring end gap is .014”. The second ring gap is .015”. I took his advice to install the base gasket dry. We’ll see how that works out. Since it has no water passages, I’m not worried about leakage from the oil to the coolant or vice versa.
 

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Discussion Starter #19
The side clearance of the new JE piston to the bore is .004”
+

Wow, are you sure about that? It's my understanding that the KLR cylinders are bored using compression plates to simulate the compressoion of the cylinder head after its been installed and torqued. Did you use compression plates when you took your measurements? If so, I think your bore is too sloppy, even for a forged piston.

Jason
 
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