Potential Group Purchase - Wiseco GS650 741cc pistons

[Old Colt]

Who is function first motorsports??? Please include your GS username and real name when sending payment! I'm not a mind reader when email address gives no clues to which user sent me a payment!

Chuck,
That is from me, I was not aware my name does not show on my PayPal.
Regards,
Charlie North

[Chuck78]

Also, if you don't have your carbs sorted, there's a guy Ian selling a set of GS650 carbs (more proper needle jet and air jet sizes vs GS550 BS32's) & spare parts and dynojet kit for $250 obo. Too much for me as I have other plans but these will help substantially vs gs550 cv carbs.

I think 1980 GS750 bs32 carbs would be an excellent starting point.

I'm going vm28 mikunis and some boot spacers. If it were my primary bike I'd be going Keihin CR29 smoothbores


Info on 650 carbs and dynojet kit (excellent slide needles!)
From a PM with him:

slink6333 is offline
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Default Re: carbs
Quote Originally Posted by Chuck78
Quote Originally Posted by slink6333
hey, the carbs and all spar parts for them are still available, are you still interested?

I was hoping for about 250 shipped, which would include all of the spare parts as well

-Ian

[Old Colt]

I have the Mikuni 29 smoothbore pumpers on my 550 now. I have run these since the bike was very young. Part of me says keep these on the new motor and part of me says to change to BS32 or 34 carbs. When I was racing I did not like the feel of the BS32s when the bike was heeled to it's limit, but that probably will not matter to me now. I do have a set of BS34 here but they are on a wide rack so they are not suitable as are.

[Chuck78]

Head Gasket orders confirmed:
4 or 5- Chuck78 0.8mm & 0.9mm & maybe 1.0mm (*pd)
2 - Tooheys 1x 0.9mm and 1x 1.0mm. (pd) (ship to Aus)
2 - Ace07 1x 0.9mm 1x 1.0mm (pd)
2 - tkent02 1x 0.8mm, 1x 0.9mm-or-1.0mm?
2 - 5hrine 0.8mm? or 0.9mm (ship to U.K.)
2 - frankenwabbit 0.8mm and 0.9mm (pd)
1 - old colt 0.8mm thickness (pd)
1 - gilldog 0.8mm (ship to U.K.) (pd)

[Chuck78]

Latest news....

I'm going to postpone the gasket thickness specification of the order until we get a little further researched here...

See below:
740cc GS650 piston connected via wrist pin to stock GS550 piston...



I Google searched and found a very well versed builder stating that he has been putting 650 top ends on 550 bottoms for quite some time, & that the compression height of the pistons are different by .025" so he says, & he gets .035" quench by cutting his own 1/32" (.79375mm) custom thickness base gasket .29375mm/.01125" thicker than stock.

The GS550 piston/chamber is a non-quench design, piston is basically all dome no flat edge of crown. It was tough due to that and complicated by it being a cast piston (rougher surface plus carbon buildup), but I came up with 1.98mm taller compression height here on the 650 vs the 550... not the .025" that the builder I read of had stated.

This swap has been done a lot before, & I don't recall any issues, so I am assuming that the piston sits down the hole a fair amount on the 550 stock engine, but that the 650 piston in a 650 black on a 550 engine may possibly be just a hair over a zero deck (i.e. negative deck height) with the stock .019"/.5mm base gasket... further investigation required...


Sooooo......


DOES ANYONE HAVE A 550 UNDECKED ORIGINAL CYLINDER BLOCK TO MEASURE TOTAL HEIGHT GASKET SURFACE TO GASKET SURFACE????

We need to quickly re-evaluate this before placing an order.


I have a good 550 engine that was going to likely be the victim for this swap, sitting on a cart next to 6 other GS engines in my garage.... I was going to mock it up to get a proper deck height measurement, but that means I need to split the cases to clearance the upper case. I don't even have a carbide cutter bit yet.

I think just comparing the overall thickness or height base gasket surface to head gasket surface on the bare aluminum block to compare with the 650 block height is going to get us in the vicinity, which can be adjusted with how much we have milled to clean up the deck.

I was also thinking we could possibly just stack 2 base gaskets up. Air cooled VW's do this with multiple thin copper base gaskets to get their squish band quench height dialed in. The egg shaped oil pressure o-ring seal will have some flexibility in compressed thickness, & also I will compare the gs1000 vs gs1100g egg shaped o-ring part numbers, as the 1100g uses a 1.2mm longer stroke so to make up for the .6mm difference in piston protrusion, the block is very slightly taller (.1mm?) & they use a 1mm base gasket vs a gs1000 using a .5mm base gasket. The oil seal egg shape o-rings may be thicker on the 1100g then, & could potentially be a fit for us.

I would much prefer to shim up the base gasket or cut my own or order some from gasketstogo.com vs running a really thick head gasket. Less volume in the larger step between the head and block where the gasket hole is bigger than the bore ever so slightly), THE BETTER. Yes, it will run seemingly quite good either way, but I am splitting hairs because I want to build this with attention to every detail bit possible.

[Chuck78]

If I don't hear from anyone else with proper measuring tools and a 550 cylinder to measure, I will tear apart one of my engines tomorrow. I already have a GS1000 engine apart on the dining room table, and the wife will be back in 8 days! So I wasn't looking to tear down any other engines until I have my shop built & that 1000 engine it it's proper place, which is what I was working on prior to losing sleeping time over this last minute dimension checking exercise which proved very fruitful...

I have a 650 block here that is a good stock bore, was hoping to find a trashed one to bore out and save this one for 650 pistons. Anyhow, I can measure that, and I don't believe I needed to have it decked at all, had 40,000mi and very good bores, I doubt it was ever torn down before.

Best thing yet would be - if anyone has their bottom end back together and already clearanced for the 650 cylinders, can you do a test run of the pistons with the base gasket installed, no rings necessary to make it easier, and do a mock-up of torquing the head down, which I can help walk you through? You would also need proper measuring tools. Then measure the critical dimension here that no one has been able to do yet, piston down in hole with base gasket and block torqued to spec without head...crown top edge at piston pin axis, measured on left and right side of each piston, all 4 pistons at top dead center.


Sorry for the slight oversight, I will have to do some more reading of previous builds to make sure I didn't just forget this a long time ago. It was on Cafe Racer.net, a "GS550 performance" thread, that I found the mention of using a custom hand cut 1/32 inch base gasket to make the taller 650 piston height work on a 550

[Chuck78]

From CafeRacer.net:

OK. The shoulder height on the 650 piston is about .025" (.635mm) higher than 550/750/850 (and I'm guessing 1000). This is why a thicker base gasket is needed if using the gs550 bottom end with 650 jugs and pistons

[frankenwabbit]

I remember reading about the custom cut base gasket off caferacer (as I was digging/researching bout the 550/650 swap).

[Chuck78]

Alright so I could not bear to order these gaskets without doing some more in-depth measuring, which was very worthwhile. As noted last night, the compression height on the 550 piston as much shorter by nearly 2 mm. Today I pulled apart a good 550 engine and used some CPVC water line pipe speacers to torque down the block. Unfortunately the 550 pistons are a full hemispherical design, and have zero flat quench area, so my deck height measurements were fairly crude but I believe in the ballpark. Nothing too terribly precise though. I was having to measure off of the intake valve pocket edge which was the closest thing to the crown edge that was measurable.
I came up with a ballpark figure of the edge of the crown sitting down in the hole 1.34 mm. This was similar to what I expected.

Tonight's exercise would have been substantially easier & more accurate if I would have had the cases clearanced and could have the 650 or 740 Pistons on the 550 crank with the 650 cylinders.


The 550 piston is definitely down in the hole however. Quite a bit. I approximated 1.34 mm down in the hole with some rough measurements off of the intake valve pocket edge, the closest thing I could get to a proper quench measurement. Then I had to add the distance from that point down to the edge of the crown. Not precise but I am in the approximate range.


Going off of the numbers from the caferacer.net GS550 performance thread, that guy who said he has built many of these 550/650 hybrids, basically ended up with the equivalent of a 1.6mm compressed head gasket if his was the same as this aftermarket head gasket that I have here, KP Gasket Company Made in Japan. 1.3mm compressed head gasket + .29mm (the additional thickness he got from using the 3/32" gasket material over stock .5mm base gasket).


So that equates to the equivalent of 1.6mm compressed to achieve .9mm (.88mm/.035") quench height.


My approximations on my 550 block torqued down using cpvc pipe spacers and crudely measuring the pistons lowest measurable point and doing some more math, well it equated to nearly the same thing. 1.7mm (1.6mm MLS compressed) w/stock base gasket, or 1.2mm with 1mm base gasket.


I think I'm leaning toward this. .040"/1.0mm base gasket, 1.2mm-1.4mm head gasket, the taller specs so I can deck more off the block for cleanup if needed. I can always have more shaved off if needed.




I don't know if I'm going to have time to clearance cases and throw on the 650 cylinders. Especially since that means splitting the cases. I suppose I could clean them with acetone on a rag and tape off the crank case and go grinding at it without dismantling, but that is not ideal in my book, but I am tearing the whole thing apart when I build this for real, as both spare 550 engines have transmission issues. One gets stuck in neutral and one gets stuck in first. Just intermittently. Worn shift forks I believe. From riding the shifter pedal too much...


Anyhow, at this point I am strongly encouraging at least one or more other people who are close to being ready to assemble their bottom end and cylinders to do a mock-up with the 650 pistons, even if just the OEM, provided they are the same compression height as the Wiseco pistons. Mine are, it is just the 550 OEM pistons that are a shorter compression height. 5hrine said he found that his 650 piston was the same compression height as the 550 piston, which are both substantially shorter than the Wiseco 650 piston. This puzzled me a very extreme degree.


Hopefully my midnight logic for the second night in a row is making sense. I am falling asleep just trying to type this. Pardon any nonsense

[Chuck78]

UPDATES...

Okay so after some piston comparisons and rough measurements, we need an absolute minimum of a 1.53mm compressed head gasket thickness if using the OEM base gasket. They compress about .1mm when installed, so a 1.6mm is really pushing the limits of the piston smacking the head. 1.7mm may be the best thickness based on my rough calculations.

My rough calculations showed the 650 piston sitting a hair over .025" out of the hole above the deck surface. This is darn near exactly what this guy said here, who has built several 650-650 hybrids...

http://www.caferacer.net/forum/project-builds/16794-gs550-performance-5.html

Post 48. I think that was a typo because he says compression height, but then says a 3/32" base gasket cures this, which is .074" thicker than a stock .019" .5mm base gasket.

I am holding off on ordering until we figure this out more precisely, & figure out if we should run a thinner head gasket as planned and add a thicker base gasket to the order, or if we should just do it all in the head.

Base gasket oil o ring thickness is a slight concern there but perhaps we can fit a GS1100G o ring in thete, as they use .040" base gaskets and the o ring part number lists 2 thicknesses, 3.05 and 3.50. The 3.50 being for the 1100g with thicker 1mm base gasket.

John can cut us base gaskets fairly cheaply, they are just paper gaskets. I'm sure he has much more selection of material thicknesses vs what we commonly can access.


I want to at least mock up the deck height this weekend with stock 650 pistons and at this point with these recent fact checjs, I do not want to order $1000+ of head gaskets for us without at least one of us doing a deck height check. My cases are not yet clearance and my shoo is still cluttered and mostly in boxes, so this will be a long weekend... hopefully in can ignore the phone and other obligations entirely, & work diligently on this. Sorry for the last minute hangup, I was jumping the gun saying we were ready to order, because at least 1 member is ready to assemble their engine and very eager to get a head on it... I assumed the 650 top was a direct bolt on after case clearancing, as all other gsr members who have done this swap seemed to imply. I think they all have very very close head to piston clearances and possibly some high rpm piston to head contact....and that is with OEM head gasket thickness of .050" or so.

[Chuck78]

I'm going to go pull another 650 top end at the vintage salvage yard here shortly, as my only 650 cylinders were freshly honed stock bores and check out nearly as good as new despite 44,000mi & ending up the the junkyard. I'd hate to bore such a nice set that could be used with fresh rings and OEM stock bore pistons. And I already paid to have then Sunnen honed...

I picked up a $30 carbide bur grinder bit at the local tool supply warehouse. Hopefully I can move on it good today and get my shop stuff unpacked from a move and get things set up enough to get the good spare 550 engine on the bench and cut the cases to fit the 650 barrels. Then I can get the measurement we are all waiting for. My above approximations are not exact as I was not comfortable committing to the deck height specs I arrived at from crudely measuring the 550 cast hemi pistons with no flat quench area to measure off of. If I can't get this done Sunday, the boss lady gets back in town for 2 weeks, so my honey-do list will start all over again and I'll be pretty occupied there, I may need some mock-up support elsewhere for one or more of you to install 650 cylinders on your clearanced 550 block to measure the puston-in-hole (or above deck) deck height. I think with stock base gasket we will be looking at .025" above the un-milled stock deck, that's over a half a millimeter.
I will also yank a 650 oil passage o-ring at the salvage yard and compare to the thicker 1100g o-ring to see if a 1mm base gasket can be fit and if that will help us get the head gasket thickness down some. The taller the head gasket, the lower the compression will be as the head gasket bore is larger than the cylinder slightly. Over 1mm base gasket and sourcing thicker viton o-ring oil seals will be necessary, which would likely mean going round as the factory egg shaped rings are likely proprietary. The hokes above and below in the case and block are round, so this may be a non-issue, but I wonder why Suzuki made them egg shaped to begin with, creating a chamber to fill with oil vs just a straight oil feed passage.


Here is a link to the cheapest (must be Chinese?) set of "carbide" (? @ that price, really carbide?) bur grinder cutting bits I have seen. The part number they list can be Google searched to find others but this link was cheapest. The bit I bought locally at the same price as this entire kit looks like the one on the right:

https://alteregokc.com/epages/6f7f10a1-c17c-4694-bc57-05347712caec.mobile/en_US/?ObjectPath=/Shops/6f7f10a1-c17c-4694-bc57-05347712caec/Products/11-1171

I'd also like to pitch a side comment - no wonder all the 550/650 hybrid engines reportedly run so strong, their quench /squish band height must be beyond optimized if they are using OEM head and base gaskets, as they must be running about .0005" piston to head clearance at high rpm at the piston pin axis point! I wouldn't be surprised if the piston rocking in the bore cause the front or rear to gently smack the head at top dead center. Any future GSR members want to do just a stock 673 top end swap, they could also order a gasket from gasketstogo.com in the stock bore to correct this is very very tight or non-existent quench distance.

[Chuck78]

Wife is back in town until next monday, & I didnt get cases clearanced. Is anyone else able to measure their deck height on a 550 block with the 650 block and 740 pistons? 5hrine and I are both separately trying to get ours mocked up so we can be certain of the gasket thicknesses for the order. I am delaying the order until we get a more concrete number down.

Good read:

http://www.thegsresources.com/_forum/showthread.php?212952-Measuring-squish-band-and-deck-height

Seems as if Suzuki_Don and Sci85 both ended up needing a .031" or .040" base gasket to mate their 550 bottom with a 650 top to get .038"-.043" clearance.
Elsewhere I have read of needing 3/32" base gasket.

States oem head gasket used was .044" compressed. That's about 1.11mm I believe.
Other accounts I have read stated 3/32" base gasket was needed, but had some conflicting information if you do the math. I think there was a typo in there somewhere.
I am thinking as long as we can source various thicknesses of gasket material, we may be best off going with around 1.2mm thick head gaskets & cutting our own base gaskets, or maybe order 1.7mm head gaskets (1.6mm compressed) to make up the extra .020" needed here. 1.8mm head gasket would allow more block decking to mill a clean mating surface.

I myself am more in favor of a thicker base gasket, as the head gasket bore is larger diameter than the cylinder, & will contribute to extra tiny crevasse areas of air fuel mixture to be hiding in, therefore I'm more in favor of running the base gasket thickness up to promote more combustion efficiency.

Thoughts?????

[Chuck78]

I should be able to start in on clearancing a set of 550 crankcases for 650 cylinders this Sunday as my wife is leaving then for her traveling job. Hopefully I can have her drop off my newest set of junkyard GS650 cylinders (& head) off to the machine shop to be bored out this week for the Wiseco k740 pistons. If not, I can at least mock up the stock 650 pistons in a stock bore cylinder. This is what we ate still all waiting on. Alex in the UK us also racing to make time to do the same.

I just got an email from John at gasketstogo.com about what our status was. I told him to go ahead and invoice me for the cost of gaskets so that they can go ahead and put us in line for production, & start in on the CAD file work and tooling setup, although we do not yet have thickness specifications for him yet.

we could go .8mm or .9mm base gaskets and factory thickness head gaskets (1.2mm or 1.3mm uncompressed) or we could also do stock 650 oem base gasket and 1.5mm or 1.6mm thick head gasket. The taller of each option would be for those who may need to mill their cylinder blocks 0.1mm or possibly need 0.2mm thicker head or base gasket if you resurface both the head and block and don't want to bother checking cam degreeing and are okay just running it approximately where it was from the factory.

by the way, I have read some interesting things in this researching about actual deck height on the 650 top end swap. The 650 cams are timed oddly at 106 intake lobe centerline and 103 exhaust. This is reversed from the typical lobe centerline positions for boosting street torque, the intake would be 103 or 104 and the exhaust would be 106 or more. Rapid Ray pointed this out. He said his top street recommendation would be 650 cams degreed to 104/106 or thereabouts, not 106/103 as factory. 550 cams will be best for high rpm horsepower but 650 with slotted sprox and degreed as stated will be best for a fun and powerful street bike.

I may experiment with 650 intake and 550 exhaust cam but ideally want a Megacycle Cams .354" lift regrind profile, or Web Cams .365" lift regrind profile.

Also swapping the 550 sprockets to the 650 cams may not retain the exact factory timing of either cam. Also, the 550 cam do rickets apparently have some rubber dampeners on them, and one account noted that the builder used roller bearing chain drive gs650e sprockets instead of the larger 6t0g sprockets or the correct sized 550 sprockets same size as 650e's but without the rubber dampener cushions.

[5hrine]

Hi, sorry for possibly Hi-jacking the thread. i managed to get hold of a set of the Wiseco 65mm 740cc pistons off a forum member who kindly sold them to me. But, unfortunately I will not be going ahead with the 740cc upgrade and therefore have a set of brand new Wiseco 65mm Pistons which i dont really need anymore. if anyone is interested please PM me and we can sort something out. I thought one of you may want an extra set. Cheers

[Ace07]

Hey chuck,

sorry i I haven't been around. I have been really busy with work. I finally got my new cylinders sent off to the machine shop, but they won't be done until next week. Then I could get it measured.