Potential Group Purchase - Wiseco GS650 741cc pistons

[Chuck78]

Crunching numbers all evening here and re-revisiting all of this information.
I am torn between the stock base gasket and thicker head gasket, vs thicker base and thinner head gasket for less compression ratio lost.

With the custom base in thicker size, Suzuki_Don said he simply left the material the same as the 650G gasket - the 650G is a plain bearing engine and does not use cylinder base egg shaped oil pressure o-rings - it just has a smaller cutout for the oil to transfer, & uses some sort of brass restrictor jet in the crankcase oil feed hole, since it is a plain bearing engine which operates on different oil pressure psi than our roller bearing engines.
The 650E & 550 base gaskets have a cutout for the egg shaped o-rings, so that the o-ring seals metal to metal.
In Suzuki_Don's build, he had substantially thicker base gasket by .3mm or 60% thicker, and I believe he used the 650G gasket as a template and allowed the o-ring to sit down in the 550 crankcase recess intended for it on the bottom side, but the top side of the o-ring would mate to the custom thicker base gasket, and not touching the aluminum cylinder block.
In doing this, the O-ring would have to be compressed .020" thicker than it would otherwise, or thereabouts, perhaps the base gasket would compress a little bit more in that area.

I checked into using thicker cylinder base oil feed o-rings, but the GS400/425 & 77-79 750 o-rings were slightly larger diameter, and look to be a real squeeze to get them to fit in the 550 crankcase and base gasket holes/recesses intended for the smaller 550/650E egg shaped oil feed o-rings.
Parts fiches list the GS400/GS750 8V/GS1100G o-ring as 3.05mm thickness. I measured more like 2.7mm on a 5 year old used version.
I measured the OEM new in package 550 oil feed cylinder base o-rings at 2.2mm thickness. I measured Athena brand new 550 versions of the same o-ring at 2.45mm thickness.

I like the OEM method of o-ring sealing metal to metal using stock thickness base gasket. This seems far better, although Suzuki Din and minder have reported no problems with their thicker base gasket stacked version of this sealing method. With the area in question needing to compress an extra .020" or .5mm, with it torqued down that hard, I'm sure it must create a very firm seal against the oil pressure.

I also got the head gasket bore reduced slightly, as we were going 1mm over the 65mm piston size for the head gasket cylinder bore diameter. Well as I've recalled recently, the 65mm piston, after cylinder to wall clearance added to it, dictates a bore of 64.75mm or so. So we can go with a head gasket cylinder bore size of about 65.7mm or so instead of the previously discussed 66mm. This saved us any further compression loss.

So based on Andy's mockup measurements showing piston out of hole .016" after base gasket (tallest of figures I have collected so far), I am thinking 1.7mm (uncompressed) head gasket is so far the best safe bet.
This would give Andy .046" quench height, so he could safely deck .006"-.008" off the block.

Suzuki_Don's findings 7 years ago would indicate that he may perhaps have needed to mill .014-.016" off the deck to arrive at the optimum .040" or so quench. But even on an unmilled block, quench area starts to have an effect at .060" height, with the biggest positive effect being at almost zero piston to head clearance at speed. So .040" + .014" = .054" quench height. Acceptable still, although not considered the ultimate in performance figures. But allows this gasket to be run on stock block deck surface, or block milled as much as .014-.016".

I'll have to continue this in the AM, brain is getting foggy late at night. Up all night last night after getting home from animal hospital, caring for my dog with a head injury. will pick up these thoughts in AM.

[Chuck78]

Head gaskets - 1.6mm to 1.8mm recommended

Okay so I've done a lot of math and milling over my extensive notes and measurements, stressing about engine variances... best to err on the slightly thicker side to be safe, a light milling can get each engine to tighter quench specs if the builder desires.

Basically, I'm coming up with 0.1mm variances in figures between different engines. This is pretty much exactly as I had stated a while back before I did such an extensive measurements, I always like to triple check my triple checking just to make sure I'm not making any big mistakes on a $1,000 order.








THE GOOD STUFF:

on the tighter side of engine deck heights, undecked block, we're looking at needing:
1.6mm (as ordered, uncompressed) MLS head gasket to achieve .040" quench (1.016mm)

on the taller deck height end of engine tolerances, we're looking at needing: 1.5mm (as ordered, uncompressed) MLS head gasket to achieve .039" quench (0.99mm)

If wanting to deck the block slightly (.006" to .008"???) for a clean true gasket surface, probably want to go with 0.2mm extra head gasket thickness.

The absolute minimum quench anyone with a tight bottom end in my opinion should even consider approaching is .035", or 0.89mm. So if you ordered a 1.5mm but your engine should have had a 1.6mm to get 1mm quench, it would likely still safely run, and very efficiently at that, but that's on the dangerous edge... crank bearing wear and cylinder bore wear / piston rock could change that in time.


To err on the thicker side, figuring the most negative deck height measured (piston protruding above deck surface the most of all examples - .022" w/base gasket), even running as thick as a 1.8mm head gasket would still yield .049" quench, not quite as efficient or as high of compression ratio, but still ineffective quench band. .010" more and it would not really do very much to improve efficiency as a tighter quench band would.


For reference, 0.1mm = 0.004" (.0039 actually)


For now I would say 1.7mm is a very good efficient but safe thickness to run on a GS550/650-740cc hybrid engine. those wanting to deck the block more substantially, perhaps go with 1.8mm? Those not wanting to deck (surface mill) the block at all if possible, go with 1.6mm IF you want to run on the tighter quench side for max performance.


IF you have a complete GS650 engine, the factory 650 gasket I believe was around 1.2mm to 1.3mm thickness, which would require a bit of decking for maximizing quench if the piston is down in the hole the typical .020" or .5mm.

I am pretty sure this is the assumption Charlie / Old Colt was making when he asked me for a 1.0mm or so head gasket. I'm estimating you'd need a 1mm or .9mm gasket on an undecked 650 top and bottom to get decent quench. Err on the safer side though!!! 1.2mm, deck block to suit?





this is all figuring in using stock style (enlarged GS550 gasket for 650 sleeves, or just 650E) base gasket to have the top end oil pressure o-ring sealing between metal & metal instead of compressing against a 650G style (not 650E style) non-o-ring base gasket. I like this idea better, o-ring to block/cyl not o-ring sealing against gasket, making gasket seal oil pressure. The 650G just uses the gasket to seal the oil pressure as well, however... but that is a plain bearing engine which has different oil pressure requirements than the 550 and 650E with roller bearing bottoms

Also I had better check, but I thought I recall perhaps someone, maybe just one of us, was inquiring about ordering these pistons for a gs650 ( almost all of us are doing the 550 bottom the 650 top end, which is why we had these issues come up with deck height and gasket thickness). In that case, they would just need to default to a stock base gasket thickness. I will order at least one like this because I want to mock up one engine with 650 cylinders bored for 750 pistons, same diameter as ours, but using a big Port 550 head instead.

if anyone wanted to do the thicker base gasket route, that is still possible as well.

Also, doing the thicker head gasket / stock base gasket route, you can use a GS650G base gasket, but just need to trim out the holes on the rear outside corner studs to allow use of the 550/650E egg shaped oil pressure o-rings (trace the 550 base gasket if you have one)

[Chuck78]

Long story short, I am estimating from mockup data, on a GS550 bottom with 650 top end, we will get the following:

1.6mm uncompressed MLS head gasket + undecked block:
.041" - .045" quench

1.7mm uncompressed MLS head gasket + undecked block:
.045" - .049" quench
(.041"-.045" if decking .004")

1.8mm uncompressed MLS head gasket + undecked block:
.049" - .053" quench
(.041"-.045" if decking .008")

*for planning to deck (surface mill) head gasket surface of block to clean up, add 0.1mm head gasket thickness for every .004" you want to deck off block.
**best mock up pistons in block and torque down (without base gasket?) to truly measure exactly how much you can have milled off of the block deck, but I feel this a safe rough suggested guideline
***I've got a 0.12mm variance between the two 650 cylinders I've got here, and between Suzuki_Don's very well measured/documented setup, and Andy Ace07's deck height mockup (.036" above deck, no gaskets), I've also arrived at a .10mm variance between engines - hence the .1mm/.004" differing range in quench figures)






For GS650 bottom, probably best to go with 1.2mm or so and mock up bored cylinder to measure how much you should mill off to get to at least under .050" quench (zero deck)
If I were to take a wild guess, I'd venture to say a .2mm (.008") light skimming off the 650 engine block deck (on a 650 bottom) would give .040" quench with a 0.9mm head gasket.
I HAVE NOT RESEARCHED THIS!
Getting a 1.2mm head gasket and just about zero decking the block, whatever that may take (.45mm milling I'm taking a wild guess at) would also give you a good number around .043" quench.



GS750 pistons in 650 block on 550 w/550 big port head:
I still have not verified the valve pockets or chambers will match up enough to work without modifying the pistons, but I think this can be done. The 750 piston compression height is exactly 1mm shorter than the 650 pistons, however.

[frankenwabbit]

Any updates? Is the headgasket order ready to go?

[Chuck78]

Any updates? Is the headgasket order ready to go?

Gasket order has been placed, but since GS550/650 gaskets are a new one for them, they have no existing tooling to use, and have to make up the tooling do produce these, so it will take a bit longer due to that.

Also, their website states that quotes are only good for 30 days...
He re-quoted me $120 & $130 based on thicknesses, each gasket, quantity of 15 total - so even with the price break.
I managed to compromise and get the price down some, but not to the original $85 per gasket. When it comes time to ship them, anyone who feels generous enough to throw in another $15 or so each, please do so, as I have paid the difference out of pocket.
To get it to that price, beyond haggling, we had to opt to have all external rivet tabs to secure the multiple layers together, vs having the studs and bolt holes "bushed" - one outer later of the gasket would have the hole cut smaller so that the extra material would basically be riveted through the other layers by pressing and folding it through. Cometic does all external tabs only on theirs anyway, and I think after the fact thus was the better choice to begin with in terms of uniform thickness and clamping forces.

They will still be embossed in critical areas, and hopefully if their engineering department sees it within the price quote, they will emboss the outside perimeter as well.

See attached.




Not sure why the resolution and size of that got downgraded (.png file?), I'll upload a full size from my computer when I'm home from work

EDIT - Resolution should be fixed after exporting PNG to JPEG format and resizing

[Chuck78]

Hi Chuck,


I just found an image of an MLS we made for a similar motorcycle, not sure which model though.


Will you be happy with embossing like this?


Regards,


John

See quoted email above. I replied that this looks fantastic aside from as we discussed the outside 4 corner studs need embossing around them as they also double as an oil pressure feed passage. I also said that I prefer the cam tunnel have an embossing mirroring its shape, but that this style should not pose any problems.

[Chuck78]

I fixed the file attachment of the invoice receipt for the gaskets. see above screenshot

[frankenwabbit]

thanks for the update chuck

[Chuck78]

Gaskets are ready to ship!!!!

They will be shipping all of the U.S.A.-bound orders to me first, then I will mail out individually, but to save from havimg to pay international shipping twice on the remaininf 3 gaskets, I am having the two non-USA orders for Tooheys and Gilldog shipped direct to Australia (1.7 & 1.8mm) & the U.K. (1.8mm)

LOOKS GREAT!!!

[boris.h]

ok, nice work
So may it be possible to make us a short résumé with all the links and prices to be able to see, quickly, the prince for a set of 4 wiseco pistons with wiseco ref, and also for the head gasket? This topic is going bigger and bigger and if someone who did not follow the whole topic is coming here and want to buy something, I find it hard to find prices, ref, etc... Or you can add it to the first message of the topic... thanks a lot!

[frankenwabbit]

any updates? have the gaskets arrived to be shipped out to us? I finally got off my duff and separated the barrels from the donor motor. Now to send to a machine shop.

[boris.h]

any chance to order sets of pistons again??

[Chuck78]

Hey all, sorry for my delays getting back on here. Gaskets got hung up in customs (which I got slapped with a big customs fee on the entire purchase price), I got real sick after being worked to death, and am just getting free time again for about 36 consecutive hours (FINALLY!).

Gaskets have arrived here & are in my hands, although unfortunately I may send some back due to quality control issues with the left and right alignment dowell holes in the MLS gaskets being slightly off (bores not centered due to this, & they won't drop over the dowels without some trimming or dremel sanding drum if DIY).
Until I noticed that, I was astonished at the overall product sitting here on my bench which we have for our builds.
I assume that everything would be dead on from the OEM gasket as templates, but apparently there is a bit of margin of error that needed to be spoken of with the dowels to the bores, while we were in the spec/design phase. I didn't want to ship the whole lot back until I had examined every one while sitting on a 650 cylinder block to verify alignment.

Originally John had said he will send me a test gasket after the first one is done to make sure everything looks good, but did not do this and sent the entire batch at once.

Stay tuned as I sort this out, and if this is substantially holding you up substantially and you need one immediately, I will send them out accordingly prioritized if you EMAIL me at my yahoo address (GS inbox = perpetually full of useful saved information)
I don't see an issue with very carefully trimming them with a Dremel sanding drum and fitting each one to the block, as the alignment dowels were too close together, therefore should be a non-issue to trim them out and have them located perfectly, but that is a lot of work on my end!

Don't worry about shipping or any other fees from customs, that's all on me in a remorseful attempt too make up for me not being able to adequately handle this purchase in my very cluttered and demanding life (one of these days I will learn to say NO but it's hard when it's family and close friends and career always needing everything I've got to give).




Boris:

If 2 other pepole come along and want 1 set of pistons each, Wiseco would be happy to make a batch of 12 pistons total (3 sets) or more. The more, the better the price per set.

[boris.h]

ok thanks!
because I'm located in France, I'll ask on some local suzuki gs forums, to see if some people are interested...

1 question: If I want a set now, is it possible? If yes, what is the price without waiting? with waiting?
thanks

[Old Colt]

ok thanks!
because I'm located in France, I'll ask on some local suzuki gs forums, to see if some people are interested...

1 question: If I want a set now, is it possible? If yes, what is the price without waiting? with waiting?
thanks

You would need to ask Wiseco those questions. We are the customers, not the seller. Ace worked with them for one large purchase that went very well, and you or someone would need to arrange future purchases.