Potential Group Purchase - Wiseco GS650 741cc pistons

[Ace07]

Hey Chuck,

Sorry about the late reply, I have been working on a lot of other projects. The way I measured the deck height is by torquing down the 4 corner bolts to 20 ft-lbs, which is what the head is normally torqued too. Then I took several different measurement of the distance between the top of the flat part of the piston, and top of the cylinder sleeve. Most of the measurements I got were .027". With that being said, my total range was from .0265"-.031 thousands. The .031" only showed up in two spots consistently.

To measure the distances I was only using a set of calipers. If we need to be exact, then I will need to buy a feeler gauge and do some really fine measurements. How important is this distance? Is +/-.002" ok, or is +/-.004" ok? I just need to know what kind of tolerances I would need to deal with.

I did my own calculation for my gaskets and here is what I came up with:

With a stock base gasket thickness of (.019" when compressed), .028" for the distance the pistons are above the cylinder without any gaskets, and shooting for a squishband of .04", I would need a base gasket that is 1.24mm (.049") thick when it is compressed. Since I should have plenty of distance before I got to the minimum .035" squishband, I would just go with a 1.2mm head gasket when it is compressed.

Like I said, I am not sure how much a couple thousands distance change will affect how the engine will run, but with the numbers I just gave you for my calculations, I am confident that with a Stock base gasket, and a 1.2mm head gasket, that should keep me within the range of extreme high performance squishband (.035") and stock squishband (.043") as long as the gasket company can maintain their tolerances.

 

[Chuck78]

You will be at an average of .038" quench distance. Your highest piston measurement will be at only .034" quench height assuming it will be the same when block is torqued. I would not have only torqued just the 4 corner studs if I were measuring.

We can get stock oem .5mm, or custom .8mm or 1.0mm base gaskets. We can get head gaskets in 1.3mm (~1.2mm compressed, etc), 1.4mm, 1.5mm, 1.6mm, 1.7mm, etc. I think based on this we should order 1.3mm and 1.4mm head gaskets, maybe 1.5mm for those that may need the block decked more. This all depends on individual deck height, but a resurfacing job is a good thing, & a good machinist can take off a very exact amount off the block to help us dial in the quench distance perfectly for our setup. 1.3mm or 1.4mm seems like be a good bet, & if anyone wants to deck their block more than .07mm (or more than .17mm with 1.5mm head gasket), then they can get a .8mm base gasket made as well.

I'm doing carbs and charging system.upgrade on a K610 Wiseco equipped 77 GS550B-610cc run the next 2 evenings or so, & more soon on that bike for a good friend, but now I am able to get these cylinders mocked up so I can clearance the 550 cases and build my first 740 engine. Should be able to get my own measurements here shortly.


I FINALLY was able to get my more recently acquired rust-seized junkyard 650 cylinders back from the part time / semi-retired hot rod / race engine builder & machinist Bobb Jacobs Friday with the help of a friend. 9-3 shop hours don't work well with my day job! Nice job boring though. He actually chamfered the bottom of the sleeve for me! Most automotive machine shops here don't do that even if I tell them to!

 

[Ace07]

Oh man thanks for checking my math. its been too long of a weekend. So what you are saying is that if we order a 1.3mm head gasket it will compress to 1.2mm?

 

[Ace07]

I will probably take and have my cylinders resurfaced, but I have already had .006" taken off of my head. When does a gasket get to thick?

 

[Chuck78]

Yes, correct.

 

[Ace07]

I will get some better measurements

 

[Ace07]

Hey Guys,

I went ahead and ordered a feeler gauge off of amazon, and received it last Wednesday. Today was the first time I got a chance to take any measurements on the decking. I will go ahead and say that the first measurements I took were not very good, because I took them with a set of calipers. The measurements I took with the Feeler gauge came out alot more consistent. Hey Chuck, please take a look and see if these measurements seem a bit more realistic.


To start off I went ahead and bought bolts to torque the cylinder down completely.


Here is the deck height measurement for piston 1. It looks to be about .035" for a deck height


Here is the deck height measurement for piston 2. It looks to be about .036".


Here is the deck height measurement for piston 3. It appears to be about .034".


Here is the deck height measurement for piston 4. It appears to be between .034" and .035".

The thing that the feeler gauge is sitting on is the handle of a metal pick. I laid it across the cylinder sleeve to start off, and then raised the piston out of the cylinder. As the piston raised out of the sleeve, the pick handle would lay flat on the piston surface. This allowed me to measure off a surface that is constantly parallel to the piston surface (assuming the sleeve surface and piston surfaces are parallel). this in turn allowed me to measure the vertical distance between the cylinder and the top of the piston when it is at top dead center.

P.S.: to start off I measure the circularity of the pick handle by laying it flat on the cylinder surface and measuring every surface in the same place. It was .001" or less all the way around. Just to be sure I always measured from the same spot on the same surface on every piston.

How does that sound? Does it make sense?

Thanks,

Andy

 

[Chuck78]

So about .036" max with NO BASE GASKET??? This is more what I was expecting based on Suzuki_Don & Sci85 550-650 builds. They needed .3mm more deck height to use stock 650 head gasket
Did you compare this method using a caliper at the wrist pin axis of the pistons? Evenly torqued is much better to ease my mind vs your 1st attempt! I like the one stud method plus 1/2" copper pipe as spacers as a torquing method though, bolts won't be 100% full thread engagement unless you get them long and measure and cut them down very precisely.
Aluminum or brass washers on deck surface would be very nice on the 4 corner studs if not planning to have block milled.

I'm trying to get this gs550-610cc out if my shop this week to make the owner happy and get on to my dirt bike/gs550 projects FINALLY.
Ready to order head gaskets after some calculations and emails to all of you (no one has been replying here...)
I'll crunch some numbers tomorrow. Bedtime here.

 

[Ace07]

Yeah sorry about the first attempt. It was sloppy. I was not in the right mind set last weekend.

I did not use any calipers this time.

Yes all my measurements were taken without a base gasket, and as far as I know nothing has been done to the cylinders.

In terms of the bolt, I know I was about 3/4" engaged threads. I went to the local hardware store and bought new bolts for measuring the deck height. I also tried to find some aluminum washers, but they didn't have any.

So for me. If I was to get the stock base gasket thickness which compresses to .019", and I was shooting for .04" for a squish band. Then, I would originally needed a head gasket that would compress to .057", but I had .006" taken off the head to smooth it. In the end, I would need:

A head gasket that compresses to .063" and a stock base gasket that compresses to .019".

Does that sound right?

 

[Chuck78]

So for me. If I was to get the stock base gasket thickness which compresses to .019", and I was shooting for .04" for a squish band.
Then, I would originally needed a head gasket that would compress to .057", but I had .006" taken off the head to smooth it. In the end, I would need:

A head gasket that compresses to .063" and a stock base gasket that compresses to .019".

Does that sound right?

.006" off of the head does not affect the squish band at all. it only affects cam timing and piston to valve clearance.

So, Andy has:
Deck height = +.036" max (piston out of hole, no base gasket, bock torqued)
wants approximately .040" squish band quench height with gaskets compressed
stock base gasket compressed = .019"

.036" - .019" = .017"
.017" + .040" = .057"
.057" x 25.4 = 1.4478mm compressed (1.45mm)

1.45mm compressed head gasket = order a 1.55mm head gasket.

they come in in 0.1mm increments. So you're either going to have a 1.4mm/.055" compressed (1.5mm ordered) head gasket,, or a 1.5mm/.059" compressor (1.6mm ordered) head gasket.

.055" - .017" = .038" squish band
.059" - .017" = .042" squish band

how tight are your crank bearings (mileage on engine? Well cared for? I often measure cam chain stretch to determine how cared for an engine is. Measure the crank bearing tolerances (rod big end / crank pin being the most critical - fastest wearing on these long life roller cranks)
Either would work in a tight engine. 1.5mm compressed (1.6mm ordered) giving you .042" squish band is still a great number, but not the ultimate ultimate race bike maximum performance seeking quench, but rather a nice but minimal safety margin.

 

[Chuck78]

If you want to build more compression by not losing it with head gasket bore volume (thicker head gasket, gasket bore is larger than our 65mm cylinder bore), then it **might** be a better idea to run a 1.3mm head gasket and add .3mm to the base gasket thickness.
That would give you the same quench height as stock OEM base + 1.6mm ordered / 1.5mm compressed head gasket.

I am really needing to get this Wiseco 610cc GS550 rebuilt and out of my shop space so I can tear into the 77 550 donor engine and measure my deck height!!! Almost there... I want to get the block skimmed more than .003" just in case, which is about all I'd skim yours Andy if you order the 1.6mm head gasket.

.1mm head gasket thickness additional means .1mm or about .004" to skim off the block if mine is the same as Andy's block height and installed deck height.
So If those were my measurements, I'd go 1.7mm (stock base gasket or equivalent head gasket using .8mm base) so that I could have .040" quench distance and be able to mill .007" off the top of the block deck if necessary.

Thoughts????

 

[Ace07]

How doesn't surfacing the head affect squish band? If you take material off the surface of the head it will move the pistons closer to the head chamber. How is it different than surfacing the cylinders?

 

[Chuck78]

How doesn't surfacing the head affect squish band? If you take material off the surface of the head it will move the pistons closer to the head chamber. How is it different than surfacing the cylinders?

Because the squish band is the distance between the flat surface of the head just outside of the combustion chamber to the flat surface on the edge of the piston's top, next to the dome. if you were to look at the 650 head after you removed it, you would see carbon or some other markings that show you that the head gasket bore is much larger than the combustion chamber (especially on a closed chamber heads such as the 650), and if you measure the combustion chamber, it is substantially smaller than the bore of the piston. The squish band is the distance between the two flat surfaces at top dead center.

some older bikes and models like the gs550 do not have a quench area to measure the squish band from, the 550 piston is 100% dome, no flat area on the top, & the combustion chamber mirrors that. a lot of older Hondas are like this from what I gather. The quench design is more efficient than the full hemi bore / full sized chamber.

the only thing that surfacing the head affects like I said is piston to valve clearance, & cam timing (the chain is shorter distance between the crank and cams). And compression ratio of course.

on major head resurfacing, if you had high domed high-compression pistons, you would need to be concerned about the piston dome contacting the chamber.

 

[Ace07]

How close are we to ordering these gaskets?

 

[Chuck78]

so far we've only got two deck height measurements, I should be finished with this bike I'm working on tomorrow and can pull out the 550 engine and measure my own deck height after dismantling & clearancing the case
I've been meaning to compare your deck height measurements to Suzuki Don's:
Posts 132 through 150ish+
http://www.thegsresources.com/_forum/showthread.php?164443-Camshaft-Top-End-Rattle/page4

Wife is mostly around the Midwest next 8 weeks so I'll be getting more pressure from her to get her "superbike" (the 1st of 2 550 builds here) done... I will definitely be needing these gaskets soon!

Doesn't appear that anyone else has as much priority placed on it as you and I Andy, but sheesh I'm sitting in a garage now filled with 9 bikes & 6 spare GS engines, 2 Rickman bikes in basement, 2 more GS engines and 2 do are Suzuki 250 Enduro engines... lots to keep me busy here!!! 1 more bike coming in for service from a friend, too! May as well put up a mailbox at the garage door!

 

[Old Colt]

So what is the status of the gasket order? I paid for a gasket on March 28 and it appears this order is not going to be done.

 

[Tooheys]

How close are we?

I paid for 2 on The 19th of March.

 

[Chuck78]

I'm back on it as of now, sorry have not been getting email alerts on my phone for some reason. The biggest hangup is we have only managed to have 1 person mock up deck height so far and provide hard measurements to properly order from, a second or 3rd comparison would be very helpful due to machining tolerances and variances.

I'm going over this stuff again. I have all afternoon and this week evenings to do this, GS750 cylinder head swap, Kawasaki KDX Wiseco piston kit / carb rebuild / tubliss system and tires...

Going to be crunching some number comparisons right now vs Suzuki Don and Sci85's figures from years ago. Hope to do my own real world mockup in next few days.
Sorry for delays but waiting for you or any of the others involved to pool more deck height data together as has been stated this entire time. The more accurate, the better.

Thanks,

Chuck

 

[Chuck78]

I now see that I have 2 angry posts before this, not just 1.
Once I discovered info that led me to check compression heights of 650 vs 550 pistons, & then realized we can't go with OEM head gasket thicknesses or thereabouts, I put a screeching halt on ordering and asked for more mockup data from all those involved.
Andy ordered these pistons through a very long process and lots of time on his own at zero charge to you all. I am trying to get an accurate head gasket thickness order together as well at zero cost to you. When I realized we need to do some more research almost on a case by case basis due to different engine machining and tolerances, I reached out to all of you for you to each get your cylinders bored and deck height mockup measured. I have gotten Suzuki_Don's from his build threads many years ago, & 1 other good set of numbers.
If you are all okay with me ordering based on those two sets of data alone, I can place the order any day now. The funds have all been sitting in my PayPal account since day one waiting, & gasketstogo is on standby to commence production for us.

Sorry I haven't been driving this harder but my life has been a hectic mess and most of the others involved have been non-respondent when I have asked for more data or ANY feedback.

Re-visiting the deck height numbers again right now.

 

[Chuck78]

Okay... based on Andy's 2nd set of (fully torqued) deck height figured based on my previous posts, to achieve a hair over 1mm quench /squish band (.040"), he would need 1.55mm uncompressed head gasket thickness with stock base gasket OR 1.25mm head gasket and custom .8mm base gasket.

We can only order in 0.1mm increments, so 1.5mm or 1.6mm head gasket if he is using stock base gaskets.]So going off of a minimum .038" quench height spec, a 1.6mm uncompressed head gasket on Andy's particular machining tolerance spec engine would allow .05mm-.07mm of cylinder block decking to machine it perfectly smooth and still be within minimum street bike quench specs.

Re-visiting Suzuki_Don's findings now...





Don's detailed findings 7 years ago with detailed measurements:
Uncompressed OEM .048" head gasket and .020" base gasket came up a minimum of .010" short on deck height if shooting for minimum .038" quench (he only got .028" with OEM gaskets after gasket install and compression).

Veteran race engine builders said .035" is the bare minimum and closer to .040" quench is better for street bikes.

Sooooo....
Don's findings say:
.058" (1.47mm) head gasket + OEM .020" base
-OR-
.030" (.076mm) custom base gasket + .048" (1.22mm) head gasket will give .038" quench height.

we seem to gave a .1mm discrepancy here between 2 different 550-650-740cc engine mockups.... likely just die to factory machining tolerances or possibly Andy Ace's block was decked once or crankcase machining tolerances were a bit different.
my crude 550 deck height measurements and comparison of 550 vs 650 cylinders and pistons seemed to support needing .3mm more than OEM gasket thicknesses.

easier to err on the thicker side and mill the block .1mm and arrive at perfect deck height AND a perfectly clean smooth gasket sealing surfsce...

Thoughts? Those were Don's .048" measurements on both a brand new Suzuki OEM head gasket and a used previously installed OEM head gasket that was installed/compressed/run for some time/removed
Perhaps composite gaskets don't compress as much as MLS spring steel shim gaskets?
Again, better to err on the thicker side as we can always have the blocks decked more.



Old Colt, I do remember/realize you wanted ultra thin .8mm or 1.0mm (?) head gaskets due to the fact that you wanted to machine down the quench area of the pistons to adjust quench height so that you could get the absolute maximum compression ratio.


Can anyone else add to this discussion in terms of decision making?