Potential Group Purchase - Wiseco GS650 741cc pistons

[Chuck78]

I'm adding one more gasket to the order in 60mm bore & 1.3mm thickness, as the Wiseco 610cc GS550 is leaking a bit of oil from the head gasket at the cam chain tunnel in front and the left side head stud oil passages.
The owner is very very pleased with the performance of the bike however, & it was an absolute blast for me to tear around on while test riding, with fresh ultra grippy Shinko 230 tires and a bit less weight than my menacing 920cc 480lb '77 GS750 - I twisted my ankle from clipping my toes hard on the pavement leaning over real far in a turn on the GS550-610cc to give you an idea of how much fun I was having on a buddy's/customer's hot rodded GS550... 610cc was quick enough I suppose, gets to 99mph pretty fast, but I'm spoiled with the 920cc... makes most other bikes/riders seem very slow!
I just picked up another D.I.D. 3.50x18 rim laced onto a GS1000 rear wire spoke hub, & I think I'm going to build up my $300 78 GS550E as nearly a clone of my '77 GS750B, but with the sought-after GS450S Sport model knee dent gas tank. I never had any complaints with the handling of my big 750, & very few friends could keep up with me in the twisties with me on my modded out 750-920cc, but the weight of the 550 felt even more inspiring! I think with a quench and compression optimized 740cc Wiseco 650 closed chamber head setup and perhaps some MegaCycle cams, GS500F 37mm forks & 310mm single disc or perhaps Honda VTR1000 Superhawk 41mm cartridge forks & 296mm dual discs, or 43mm RF900R cartridge forks and dual 310mm duscs... Fox Street Shox, wide alloy rims and big tires, MAC 4:1 & Kerker aluminum system K muffler...& GS1100E aluminum swing arm and GS550 rear disc caliper with 1990 1100G Katana floating right front rotor on the rear...frame bracing added behind the egnition coils at minimum... this will be one AWESOME GS550 for the twisties. Maybe my VM29 smoothbore carbs, if not them then the VM28 accelerator pump carbs I have here.

If I do rebuild the wife's 550 as planned, it's getting Fox Street Shox that I bought for it, has Excel 3.50x18 rear rim and 140/70-17 tire already, probably lace a 2.50x18 Excel front rim up as well in place of the steel 19" stocker and add a 100/90-18 or 100/80-18 tire up there to continue in helping her feel comfortable touching the ground flat footed with short legs (& quicken up the steering a bit more), 310mm twin pot front brake mod, perhaps cartridge emulators. Re-upholstered stock seat shaved down to suit a 5'2" rider and look more stylish. And she requested ditch the superbike bars and put her clubman bars back on...
She defected to a fat pig of a slopoke 640lb 58hp 98mph top speed slow accelerating ill-handling no-brake-having 1986 Harley FXR 1337cc grandma&grandpa slopoke cruiser, so I haven't been too thrilled to wrench on her GS550 since that huge disappointment. Hopefully things change on that front when she comes back around from the current state of events here in my household. Tweaking a 1974 Rickman dirt bike for her to ride comes first though.

good things to come out of my garage real soon...

 

[Tooheys]

Chuck,

my post wasnt meant in anger sorry.

from your calculations it looks like a 1.3mm gasket is shooting for the middle ground and we can adjust with machining to allow for manufacturer machining differences yeah?

i don't have my 650 head yet so I can't mock anything up I'm sorry.

 

[Chuck78]

1.3mm is not the middle ground, 1.3mm would require a thicker 0.8mm custom base gasket.1.3mm would definitely not give you adequate quench height

1.5mm head gasket with stock base would be the absolute minimum required from the 2 bikes worth of numbers I was working off of. That would allow no room for block decking. 1.6mm head with OEM base (or 1.3mm head + custom .8mm base) would be what you want if you want to do a tiny amount of block deck machining to mill it down to a fresh clean sealing surface

 

[Chuck78]

I'm torn between stock base and thicker MLS head gasket, vs .8mm custom base and thinner head gasket (more compression, more power, slightly more efficient with less gasket volume.

 

[frankenwabbit]

I'll go with the best recommendation for head gasket and base gasket setup.....this will be my first ever motor build. (so ummm maybe middle of the road spec figure?)

 

[Ace07]

Hey chuck,

i am am glad you got the 610 running!!! That is awesome man. I just bought me a bonneville t120. That is a really fun bike. I am hoping to take a nice trip on it this summer.

In your opinion is there a benefit to have a thicker head gasket and a thinner base gasket? Meaning using the .8 base gasket over the OEM base gasket.

Also I am starting to get back into the swing of working on this bike. I am excited to see what you come up with.

 

[Chuck78]

Thinner head gasket means higher compression and more efficient due to the head gasket bore being slightly larger than the cylinder bore. The quench height area will be the same whether stock base + thicker head gasket OR thicker base and near stock head gasket thickness. With the thicker head gasket the cylinder block will sit lower but the head still in the same location, bit the larger bore of the head gasket area will lower compression and efficiency slightly.


The benefits of a thicker head gasket are that it too will still work out well in this upgrade AND you only need one custom gasket. The thicker base and 1.3mm or so head gasket will be more ideal from a performance engineering standpoint however.

I am finally about ready to build this bike. Actually 2 of them, as I have a 78 550E for myself now.

 

[Ace07]

Yeah I feel like I make one or two steps forward, then I run out of money. For some reason, I keep running out of that precious green stuff. I might be due to one too many projects.

 

[frankenwabbit]

any updates?

 

[Chuck78]

I hope to have good updates real soon as I am in engine building mode now...
I've been building up my paypal balance beyond the group gasket purchase amount so that I can order several extra gaskets, as I also plan to try and fit GS750 Pistons into gs650 cylinders with big port BS32 carb gs550 heads and VM28 carbs... onto GS550 bottom ends. Not quite as much hp potential as the 650 closed chamber head, but a budget version.

Has anyone else gotten any mockups for deck height measuring?

 

[Chuck78]

Due to my hectic summer and time constraints (I still have not mocked up any deck heights with the 650/740 pistons on 550 bottom), I was just about ready to pull the trigger on going, off of the only measurements that any of us have gotten, combined with Suzuki_Don's measurements from many years ago. I can still do that if anyone wants to say the word. Basically the variables here would be thinner head gasket plus custom thicker base gasket, vs thicker head gasket and stock 650 base gasket. The other variable would be whether or not you wanted a thicker head gasket to accommodate for decking the block substantially.

Comments?

Sorry for the delays perpetually, I would like to get this off of my plate and have some of these screamers ripping around the globe.

 

[tkent02]

Getting closer on the gaskets? My 675cc 550 needs to be bigger.

 

[Old Colt]

I placed an order for a headgasket back in March. I specified a thickness based on an assembled engine utilizing an off the shelf base gasket, the new pistons from the group buy and a new off the shelf 650 head. Why has there been no gaskets ordered?

Is this because people are trying to come up with gasket thickness using factory 650 pistons? They are not the same as the group buy pistons.
Please either supply the gaskets that were promised or return our money.

 

[Chuck78]

It has been placed at the top of my immediate to do list (as of yesterday, actually!) since no one else is able to get the installed deck height.
Compression height is same between Wiseco and OEM 650, but very different on 550. I paired each combination of pistons together both half installed on the same single wrist pin simultaneously, to arrive at that information as verified.

Colt, your very thin request, as you told me, may require an extra extra thick base gasket, or else machining down piston quench area as you and I discussed.
We need a minimum of 5 ordered, preferably all of them at once, so I was unable to order just 2 or so gaskets

I was really wanting to order after we got a couple of different engines,mocked up, but all summer has gone by now and no one else has been able to get any mockups done other than 1 of us and a thread from 5 years ago.

I will be trying to get my cases dismantled, clearanced for 650 sleeves, and mocked up to verify height/thickness again for better accuracy.

Worst case I will place the order with everyone's guesstimate on thickness or round up slightly to be on the safe side, can always mill the block down, good idea anyway for a fresh surface.

This was a GROUP effort, I was contacting the manufacturer, but needing more data from the GROUP aside from your ultra-thin custom request, because I didn't want to be responsible for ordering too thin of gaskets for everyone.

I am sorry it has taken almost all of us this long and still no additional mockups since June.
I will take a vacation day to do so if I have to!!! I will be building up at least one this winter, maybe 2 or 3.

You can text me or email me for extra motivational push if you feel the need.

-Chuck

 

[Chuck78]

Old Colt - I will give you your money back and a free head gasket as partial trade for that ported head of yours if you want to part with it. I want to do an experiment on 1 of these five 550 engines I have here, using 550 head 750 pistons 650 block

 

[Old Colt]

At this time just return my money, I will run the copper gasket I have here.

 

[Chuck78]

I have re-established contact with John at gasketstogo.com yesterday/today, he will send me a paypal invoice as soon as I confirm exact sizes and quantity.
Charlie, I will contact you after I get off work

I will see if I can afford to eat the shipping costs since I decided to spearhead this order and have not done so in any sort of expedient manner since discovering the deck height/compression height discrepancies between the 550 and 650. Until then, I was ready to send payment and get them here months ago, but since then, I was very fearful of ordering them the wrong thickness. And I am a very very particular sono***un, so if I'm not happy with the fine technical details or uncertain they are 100% correct, I can't be happy until that is resolved. I was hoping anyone else would be able to jump in and do some case clearancing, mickups, and measuring, but only 1 person was able to do that thus far and I was hoping to take an average of a few mockups to get more accurate data for thickness specs.
I'm back on this after work.

-Chuck

 

[frankenwabbit]

chuck...with the new hg measurements that you have taken, are we going to have to order different (different from stock gs650 sized) sized base gaskets as well now?

 

[Chuck78]

Can do either as I talked about in past posts here.

Life always happens and I get busier than I planned (the last 2 nights), so I used some of my remaining vacation days and took tomorrow off, 74 degrees blue skies no humidity, perfect!) to spend in the garage and go riding perhaps. Should get some case clearancing and mockups done with the Wiseco pistons. Cylinder is bored. Head is refurbished. Need to re-stock some of my spare 550 engine seals and build one of these suckers!

The good parts are coming soon.

 

[Chuck78]

Okay so I got quotes back from gasketstogo.com for base gaskets, $37 each, which was a good bit higher that I was expecting.

I, personally, am still interested in using the thicker base gaskets, as it will decrease the extra volume added by the head gasket and slightly increase compression, but I don't expect everyone to want to go this route certainly. I requested a second quote for quantities less than 5, and John said that would not change the price, same price for 1 paper base gasket as it is 19.

If anyone gets this sooner, please email me from the link in my profile, not gspm, that inbox is perpetually almost full. My email address can also be accessed from my profile information. Send me an email with your gsu's or name so that I can send out one mass email and get back individual replies. I will be finalizing the thicknesses of gaskets in an email I will be typing up this evening. Choices of thinner for more compression or not resurfacing your block deck surface, thicker if you want to resurface your block deck slightly. And then also option B1\B2, substantially thinner than those if using a thicker base gasket.