Potential Group Purchase - Wiseco GS650 741cc pistons

[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.