Suzuki GSX-R Motorcycle Forums Gixxer.com banner

1 - 20 of 24 Posts

·
Registered
Joined
·
1,087 Posts
Discussion Starter #1
I'm installing some 13.5 :1 pistons in my stock bore 1000.

The box says .004" for each 1" of bore, so that makes my stock bore about 0.10", right?

Should all the rings have the same gap?

Any advice here would be greatly appreciated.
Thanks,
Krispy
 

·
GSX-R Enthusiast
Joined
·
2,546 Posts
I'm installing some 13.5 :1 pistons in my stock bore 1000.

The box says .004" for each 1" of bore, so that makes my stock bore about 0.10", right?

Should all the rings have the same gap?

Any advice here would be greatly appreciated.
Thanks,
Krispy
std bore = 73 mm (1 mm = 0.0393701 in) (73 mm x .0393701 in = 2.8740173 in) (2.8740173 in x .004 in = 0.0114960692 in) rounded off to the nearest thousandth = .011" or ten thousandth = .0115"

.011"

I would think you would want the rings to all be the same. But I'm not sure on that.

Isn't there also a plus or minus (+ or -) tolerance range so you can make it on the tight or loose end for the kind of engine you want to build. Such as on the loose end of tolerance for a race motor for less longevity and more power or on the tight end of tolerance for a street motor for more longevity and less power.

Good question for the engine guy's but I believe I got the math right.
 

·
Registered
Joined
·
970 Posts
The manual gives .003" to .008", with a service limit of 0.020", but this is for Suzuki rings.

The required gap depends on the ring material, the bore material, how close the top ring is to the top of the piston, and how the engine is going to be used. I used 0.012" on a Wiseco 75mm kit I did and the leakdowns were 1.0 - 1.5%.

The DIYer method for opening the gap up is a file in a vise. Draw the ring over it from the outside in. If you do it the other way, the coatings on the outer edge of the ring may chip.

The ends of the rings should be beveled on all sides with a little file (a good nail emery board works pretty good), even if you don't open the gap up. The most important seal for the ring is on the bottom of the ring land, and the beveled edges prevent scratching them when installing the rings.

Within reason, there isn't a lot of power available from closing up that dimension. The bore will be destroyed very quickly if the ends contact.

What are you doing for bore prep? The best bet is to send it to Millineum for a hone. This step isn't optional if the new pistons put the top of the top ring higher than the stockers. If it must be done locally, you're looking for someone with a diamond brush hone. Many shops have them these days for reringing dirt bike engines. Ball and rigid hones shouldn't be used. You might get away with no hone, but it really sucks to tear an engine apart again because the rings didn't seat.

I use assembly lube sparingly on the wrist pins and WD40 for the bores. The bores must be surgically clean. If its been honed, you need to start with soap and water before going to brake cleaner. Literally white glove clean, rings and pistons too.

On the clearances for power topic, opening the piston to wall clearance up reduces friction. It also makes it tougher for the rings to seal and shortens ring life. You can easily loose in leakage what you gained in friction reduction.
 

·
Registered
Joined
·
1,087 Posts
Discussion Starter #6
Thanks folks.
MrMW, ( I knew I'd suck you into this)
Can you explain the DIY methods again? Do you mean to make sure the file motion is from the exterior/outside of the ring, to the center/interior of the ring ?

I was going to use a dremil, with a vice, but if you suggest a nail file is better I'll use that instead.


The bore is a stock 73mm bore, that has been repaired, re-plated, re-bored, and prepped. The work was done at Millineum, so it should be good to go, after I wash it (soap and water)and then clean it with Brake Clean. The pistons are Weisco high comp pistons, included in a piston kit with gasket, circlips, and wristpins.

I think I'll stick to the 0.010" piston ring gap guideline for all rings.

I'll be making sure the ring ends butt together nicely and no rough edges or burrs.

Any other motor building advice is greatly appreciated, as this is a critical time for making mistakes.

Krispy
 

·
GSX-R Enthusiast
Joined
·
2,546 Posts
On the clearances for power topic, opening the piston to wall clearance up reduces friction. It also makes it tougher for the rings to seal and shortens ring life. You can easily loose in leakage what you gained in friction reduction.
Makes sense and good advice. Loose tolerances equals less friction that may or may not translate into a safe or consistent increase in power. Not to mention your throwing away engine life if that is a concern. And knowing how far you can or should go is where experience comes into play.
 

·
Registered
Joined
·
970 Posts
The dremel will cut too fast, you'll only need to remove a few thousanths.

Start with a clean flat file with fine teeth and put it edgewise in a vise. Turn the vise so the file points away from you. Hold the ring so the gap is towards you, and the rest of the ring is away from you. Hold the ends of the ring square with the file and each other while drawing the ring towards you across the stationary file. The motion should always be inward towards the piston side of the ring, not outwards towards the bore side of the ring. Be careful not to scratch the top or bottom of the ring. After a few passes, switch the ring top to bottom and give it the same number of passes.

Measure the ring gap, give it about 3 passes on each side, and measure it again. Now you know about how long it takes to remove 0.001". Don't try to do it in one shot, 2 or 3 file and measure cycles will let you dial it in. Clean the ring before you measure it.

After you have the gaps set, go back with the nail file and bevel or round the ends of of the ring in the gap.

These days tolerances are so good it doesn't matter nearly as much as it used to, but the holes should be bored/honed for each piston, and the rings be fit to individual holes. A change of 0.001" on the bore gives 0.003" on the ring gap.

The Voegelin book "Engine Blueprinting" ISBN 1-884089-26-7 gives a pretty good overview of a lot of common operations. Unlike most car based books, it has a section on degreeing asymmetrical cams, which is the method that should be used for bikes. Voegelin writes some pretty good stuff, but is a writer rather than an actual builder so everything has to be used with some caution. This is in addition to the usual car to bike translations you need to do.
 

·
Registered
Joined
·
485 Posts
Krispy-
Make sure you get full clearance when you gap. I set my 2 over rings "right there" and had some slight touching of the ring ends (that according to a tech at JE).
Let us know what you get from the new pistons. Enjoy.
 

·
Registered
Joined
·
485 Posts
A trip to the notes shows
top ring/ .012"
middle ring / .009"
specs to set from same tech at JE
JE 75mm pistons and rings
rings measured down in bore placed with piston
All were fit right on spec.
No big damage to cylinder.
Oval track use, not as severe as road race (no long straights OR downshifts) but heavier duty than street.
 

·
Registered
Joined
·
1,553 Posts
Wiseco quotes the XA top piston ring as .031" alloy steel, ferrox coated, chrome faced.
Is the sealing face chromed?
What thickness head gasket do you use with these pistons?

Even with the higher compression there still isn't much to gain from a minimum setting?
Yet the car guys seem to be obsessed with end gaps.
HowTo

JE Pistons have this little table:



The standard or spec Suzuki end gap of the top ring is 0.003"-0.008" and a thickness of 0.0382"-0.039",
thicker than the Wiseco ring.
If we use the JE table guidelines for oval track use the multiplier is 0.0055", so for Flip's 75mm bore the end gap should be around 0.0162" for the JE ring. Reducing the gap to 0.012" caused them to touch.
Any power difference Flip when you put the engine back together with a greater end gap?


The K5 supposedly has a new top ring. I say "supposedly" because that technical document is full of crap.

 

·
Registered
Joined
·
970 Posts
Wiseco quotes the XA top piston ring as .031" alloy steel, ferrox coated, chrome faced. Is the sealing face chromed?
Yes, for that ring. Chrome can be really hard to get to seat. A first class hone job and an agressive break in are good ideas. Moly is also used, and easier to seat. The current state of the art are IVD coatings. The problem with coatings is they're really thin. Once they're gone, the ring wears out very quickly. A strong argument against aftermarket air filters.

What thickness head gasket do you use with these pistons?
Depends on what else you did to the block, including both piston to wall clearance and deck height. When I send a block to millenium, I pretty much automatically have it decked 0.008". This puts the squish within reason with a standard Commetic 0.030" gasket. I take more off of my personal stuff when it's not for high milage street use.

It also depends on how you're going to use the engine and for how long.

Numbers like these are good reasons to buy the piston kits from guys like Kevin.

And to not be the first one.

Even with the higher compression there still isn't much to gain from a minimum setting?
If we start with a steel ring for a 73 mm (2.874") bore, it has a length of 9.0244". Steel has a coefficient of thermal expansion somewhere between 6 and 9 E-6 in/in-F. If we heat that ring from the 60 F in our shop to 200 F in the running motor, it grows somewhere between .008" and .012".

If the bore didn't also grow, a 0.012" bench gap would be gone. If the ring heated any more than that, and it likely does, it would put incredible pressure on the bore.

If the bore is aluminum, with an expansion coefficient of 12 e-6 in/in-F, and it heats up to the coolant temperature of 180 F, the circumference grows 0.013" and the gap would actually open up.

If the bore is cast iron (edit), with an expansion coefficient of 6 e-6 in/in-F, and it heats up to the coolant temperature of 180 F, the circumference grows 0.006", leaving a final end gap of .006" - 0.010"

Those car tables are generally for cast iron bores. Another huge difference between cars and bikes is bike pistons are oil cooled, greatly reducing the ring temperature. On the other hand, the specific output of bike motors is much higher than cars.

Most of the heat that goes into the ring is from friction, not the combustion gasses. Nickasil bores significantly reduce ring and piston friction.

There are 3 things to remember about ring gaps;

1) The leak isn't across the whole ring, the area is the gap times the piston to wall clearance of 0.0025", or whatever the piston to wall clearance is at temperature (figure its tighter)
2) The bench gap generally tightens up significantly
3) If you hose your guess by more than a thou or two, anywhere in the engines operating envelope, at any time in its life, the ring will break or the bore will be damaged.

It should also be obvious that hot pistons in a cold engine are a bad thing. The coolant needs to be up to temperature before you hammer it.

Yet the car guys seem to be obsessed with end gaps.
Good link, I buy a couple copies of Circle Track a year for articles like this one, but seem to have missed that one.

This isn't obsessive, its just covering the basics. Decide what the gaps are going to be, and it should change with application, control it to 0.001" or so, keep the ends square, detail the ends.

The oil ring thing really shouldn't be applied to bikes, especially street bikes. A better method is with a fish scale pulling the piston with just the oil ring mounted through the bore lubed with WD40. Old, low performance bikes might need 10 lb to pull it through. I hear numbers like 30 from the Harley guys. The low tension oil rings that come with aftermarket pistons are usually ~3 lb. Go much below this and the motor will use a lot of oil. The motorcycle expanders also don't always lend themselves to tweaking their ends like the article shows.

I have a low performance standard bike in the garage. I rebuilt it with first oversize (+0.010") pistons to clean up the bore and reused the oil ring expanders from the stock bore to reduce the oil ring drag from 10 to 4 lb. The back of the napkin indicates that was good for ~2 ft-lb, ~4 hp. How bad do you need that power and how many times are you willing to take the motor apart?


The standard or spec Suzuki end gap of the top ring is 0.003"-0.008" and a thickness of 0.0382"-0.039", thicker than the Wiseco ring.
GSXR750s use similar numbers since '96, a ZX10 spec is .006" - 0.012". All Nickasil bores.

My old FZR1000 manual recommends 0.012" - 0.020". Cast iron bore.


The K5 supposedly has a new top ring. I say "supposedly" because that technical document is full of crap..
I took an early TL1000 apart once and it had the L shaped, "Dykes", or pressure backed ring (PBR), so I don't doubt its in there. It's an expensive version of gas porting. The idea is to reduce ring friction on everything but the power stroke, and to increase sealing.

I found that document informative (Thank you JeffW and Northface), what did you find wrong with it?
 

·
Registered
Joined
·
1,553 Posts
[...]I found that document informative (Thank you JeffW and Northface), what did you find wrong with it?
Okay, maybe not crap but some inaccuracies seem to have crept in, and yes thank Jeff and Northface.

A) The document mentions the same tappet (or bucket) diameter as the K4 yet there is a drawing but the dimensions are missing...why is there a drawing if the dimensions are the same, or are they different...

B) It says there are 'Dual valve springs with increased pressure on the intake. Dual? As in the
coil within a coil car type?

C) "Increased intake and decreased exhaust spring free length" yet they list the same 39mm free spring length for both?

D) The small end has apparently been increased from 15mm to 16mm, yet my manual tells me
my service limit is 16.040mm. Big service limit 1.040mm, just kidding.
 

·
Registered
Joined
·
970 Posts
Okay, maybe not crap but some inaccuracies seem to have crept in, and yes thank Jeff and Northface.

That flier was never intended for the public.

If you blindly follow even the service manuals, eventually you'll screw something up because of the Janglish, a bad metric conversion, or the fact that the manuals and the bikes are developed at the same time. There is no substitute for understanding the context, actually measuring, and some experience.

The performance we're buying for what we pay is absolutely astounding, as is the rate it progresses.

It's like the rest of the internet, be grateful for the useful information and never expect it.
 

·
Registered
Joined
·
1,553 Posts
Point taken about what to expect.
A few torque settings are wrong in the K3 manual, luckily I had this math teacher who used to say you have to
do the work yourself to get a feel for what the answer will be as if you use the calculator you will never know if the answer is correct or not but you always get and answer from.
I need to do my own work to get a 'feel'.
 
1 - 20 of 24 Posts
Top