Potential Group Purchase - Wiseco GS650 741cc pistons

The 650 and 550 piston domes are quite a bit different. When I bought the head and cylinders form the guy who tried this build before said that he had to lower the deck hieght a lot when using his 650 head and 750 Pistons, to keep everything from hitting. He also told me that the 550 and 750 pistons are similar but the 650 have different piston domes and combustion chambers.

[Chuck78]

GS650 k740 wiseco pistons = 740cc in GS650 closed chambered head
GS550 bottom/650 cylinders/gs750 pistons = 740cc and 9.6:1 (???the big mystery here???) with milled(?) GS550 8v hemi head
Obviously the 650 head and Wiseco pistons will be the most powerful and efficient, but I want to measure the 750 vs 550 combustion chambers once I get a 550 apart. If they are similar as I suspect (550 piston = huge dome hemi, 750 = lesser dome due to higher compression via bigger bore)
Then I will calculate any differences and then slap that together bored into 650 cylinders and mill the head accordingly until I get above 9.5:1 or up to 10:1.

The gs750 8v makes more torque, but 748cc GS750 8v = 72hp, 673cc GS650 = 73hp & better fuel mileage due to more advanced head design

Next time I'm at the yard, I may snag the lower mileage of the 2 80+ GS550 crankcases & head, & the GS650 top end... swap all the guts into the ran out of oil/shifting issues GS550 kickstart crankcase bored out for 650 cylinders... Franken-zuki for sure. I just want to try this unknown combo. If chamber size and domes don't work out, it gets the 650 treatment.

[tkent02]

GS650 cylinders bored for GS750 pistons (740cc hemi) & 80-82 550 head with gs400 boot spacers & vm28 carbs...

Hmmm, with the 650 pistons we sere stuck with 650 heads, how do these 740 pistons fit the 550 head's combustion chamber?

[Chuck78]

As far as gaskets, that gets us at least 11. Quantity of 1 to 4 gaskets are $120 each if I recall, 5+ are $80-something each. I don't believe there is a further price break but I can inquire if interest puts us up there in numbers more.

Anyone need 650 top ends still? There's another 650 at the local yard now. 1 or 2 others but I think they're staying complete/projects. Several 550's too.

I'm torn between taking the blown up 77 gs550 kicker engine (all new used bottom end from junkyard since wife ran 'er outta oil many times cross country - & then bought a Harley in Minneapolis that left her stranded in Cali!!!) and doing my experiment:
GS650 cylinders bored for GS750 pistons (740cc hemi) & 80-82 550 head with gs400 boot spacers & vm28 carbs...
OR
Just slap another 650 top end on it, have it as a spare... I have new 650 rings still, pistons, nice honed good std bore cylinder.
Heck the gs750 pistons at 740cc and substantially milled cylinder head (more compression) sounds more adventurous...

I've got 2 extra sets of Wiseco k740's but one I bought with a friend in mind who didn't have the cash, he hopes to buy them off me this next season. The other as a spare or if I build a 650E or another 550/650 maybe for myself

[Chuck78]

Ya know what when I had my 650 head done, I recall the factory manual showing that due to the improved port design, it basically got only a 2 angle valve job. Raised intake port runners for more direct air/fuel flow into chamber. If I recall correctly. I remember seeing seat angle specs in a factory manual or clymers.

[Chuck78]

Dan Schumann does excellent work (ebay guy),
Locally at the real good head shop it runs about $240 for a Serdi machine valve job plus $80 for resurfacing the head gasket surface. Valve guides & replacement not included in the $240. Another shop does it a good bit cheaper but not with a Serdi machine, just standard 3 angle valve job seat cutting tools. The Serdi is a smoother transition than a 3 angle job and computer controlled to cut them all to the depth of the deepest seat for uniformity in chamber volume and cranking compression.

Hey chuck do you know what the next price break is? I am in for 2 gaskets for now.

hey does anyone know how much it should cost to get my head redone? I found this service on eBay, and I am not sure if it is a good deal or not.

http://m.ebay.com/itm/231865125106

[tkent02]

I've got a bit of house rehab to do Nov-Dec but the rest of the winter is dedicated to motorcycle projects all the way, & this 740cc GS550 is top of the list... Especially because I have to get the wife on something (THIS 740cc GS550) that's about 200x better than that piece of $#!÷ '86 Hardley-Goeserson FXR 1337cc 58hp (when new/tuned properly) / 600lb / almost rigid rear end / super saggy front end / no brake having / 99mph top speed (when new/tuned) / old retired guy turd cruiser that she bought... Aaaarrrggghhhh....

Tell us how you really feel.

[Chuck78]

I believe he quoted me in the $80 range plus shipping for MLS head gaskets if we buy 5 or more.

It's been a minute since I have visited this build of mine, but I believe I was planning to order head gaskets around .043 inch thickness at least for myself.

Colt, have you nipped your cylinder down to the case yet to measure your piston-in-hole TDC deck height? What is your preference on thickness?



I've got a bit of house rehab to do Nov-Dec but the rest of the winter is dedicated to motorcycle projects all the way, & this 740cc GS550 is top of the list... Especially because I have to get the wife on something (THIS 740cc GS550) that's about 200x better than that piece of $#!÷ '86 Hardley-Goeserson FXR 1337cc 58hp (when new/tuned properly) / 600lb / almost rigid rear end / super saggy front end / no brake having / 99mph top speed (when new/tuned) / old retired guy turd cruiser that she bought... Aaaarrrggghhhh....

[frankenwabbit]

I'm in for two.

[tkent02]

Is anyone else wanting to get an MLS gasket? It looks like I will only be ordering the minimum order of 5 to get the price break. I was figuring everyone would want a spare or one gasket per set of pistons they ordered minus the five or so NOS Wiseco gaskets that were sourced on ebay

I want at least two, maybe a few spares. How much are they?

[Chuck78]

Is anyone else wanting to get an MLS gasket? It looks like I will only be ordering the minimum order of 5 to get the price break. I was figuring everyone would want a spare or one gasket per set of pistons they ordered minus the five or so NOS Wiseco gaskets that were sourced on ebay

[Chuck78]

It was $40 per hole 2 or 3 years ago the last time I had one done. I think another place quoted me $130 or 140 for all 4 even. Years ago (3-6yrs?)
Bore tech in Cincinnati OH is a great place nationally known but a bit more $ than M&M Cylinder Head Service that I had do mine

No. I paid 80 when I got my girlfriends xt350 bored. It's just a 1 cylinder.

[tkent02]

Cylinder boring, isn't $75 per hole a little steep? I thought it was less....