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Author Topic: Wiseco piston clearance query  (Read 933 times)

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Offline hellfireben

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Wiseco piston clearance query
« on: October 22, 2012, 07:26:40 AM »
I just got the diameter of my newly acquired std bore cylinders measured. I plan to use Wiseco std size pistons with them.
Here are the measurements given to me by the shop guy:
Cylinder 1
Top - 64.035 mm
Middle - 64.045 mm
Bottom - 64.025 mm
Cylinder 2
Top - 64.040
Middle - 64.050
Bottom - 64.035

Not sure the exact positions for the top, middle and bottom measurements.
Since the actual Wiseco piston diameter is supposed to be 63.95 mm, my maximum clearances comes up to 64.045 - 63.95 = 0.095 mm(0.00374") for one cylinder and 64.050 - 63.95 = 0.1 mm(0.003937")
How good or bad are these figures? Is it even the right way to measure clearance? Will i require a rebore and the next oversize pistons to run?
I am not looking for a pure racing setup. My primary usage of the bike would be off-track, and hence will not be going WFO very often.
Also, how much clearance would honing add to the existing figures?

Appreciate your help.

Offline guri131

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Re: Wiseco piston clearance query
« Reply #1 on: October 22, 2012, 09:51:27 AM »
I'd say it's a negative. Will go to 64.25.

The wiseco will be more like 63.93-ish than 95.


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Offline Yamaha179

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Re: Wiseco piston clearance query
« Reply #2 on: October 22, 2012, 07:51:25 PM »
You need to go to the first oversize:  64.25mm.  Piston (brand/type) selection is important.  Do you want to stay with cast pistons (OEM, Vertex, Pro-X) or with forged pistons (Wiseco, Wossner)?
I prefer cast pistons for almost all applications and only use forged for some extreme racing applications.  Cast pistons are set up tighter and you do not have to warm the engine up as long as you do with forged pistons.  Cast tend to be less noisy and the skirts do not shrink.  Forged pistons are very strong and while the skirts do shrink it does not seem to affect performance greatly. 
Lyn Garland
Lyn Garland

Offline SUPERTUNE1

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Re: Wiseco piston clearance query
« Reply #3 on: October 22, 2012, 08:56:14 PM »
I've run them that loose before, but will be noisy for a street bike and not last more than a couple thousand miles.
I setup the Wisecos for street at .0026-.0028 new. New Wiseco pistons will collapse another thousandths (.001) in about 800 miles.
And about 3 thousandths (.003) in 400 miles if racing WFO on a track bike.


Chuck
Team Scream Racing
   
Racegas + Lots of oil = HORSEPOWER
2 time Daytona AHRMA Formula-500 winner '06
'78 RD400E
RD machine work, boring, porting, cranks and engine building.

Offline 78 RD

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Re: Wiseco piston clearance query
« Reply #4 on: October 22, 2012, 11:02:23 PM »
Ok guys here me out..  A friend of mine swears by coating his pistons with a coating that he can specify the exact thicknes he wants on the surface..   I have seen amd measured myself what they put on the pistons.  He coats the skirts and tops of the pistons.. He has also has run his  " Snowmobile " way to lean and I mean like 4-5 sizes lean without damage.  I have watched him and told him is an idiot but he actually never burned down with this coating..    He also sent out used pistons and had them buil them up to take up the used clearance.  This is the set I measured before and after,,, They built it up within .0002 from where it was supposed to be at the temp I measured it.

Have you guys ever heard or used this process on these bikes ????

The reason I ask is because some pistons such as Wisco do wear or collaspe after some ussage. if this is the case why can't we try to build up the size for a street bike ?      Understand a sled runs at 6-7000 RPM all the time and the guys I ride with beat the hell out of our stuff for 15 hours a day every weekend in the winter without problems.  We litlerally wearout the sled before the engine so why would this NOT work ????

Jerry

Offline SUPERTUNE1

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Re: Wiseco piston clearance query
« Reply #5 on: October 23, 2012, 06:24:53 AM »
When it comes to skirt coatings there are hard coatings and soft coatings.
Soft coatings just wear off in a short order in our air cooled engines, the hard coatings do very well as you describe.

Here's the hard ones to use:
http://www.line2linecoatings.com/armorcc.html
http://www.line2linecoatings.com/slickcc.html


Chuck
Team Scream Racing
« Last Edit: October 23, 2012, 06:35:35 AM by SUPERTUNE1 »
Racegas + Lots of oil = HORSEPOWER
2 time Daytona AHRMA Formula-500 winner '06
'78 RD400E
RD machine work, boring, porting, cranks and engine building.

Offline 78 RD

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Re: Wiseco piston clearance query
« Reply #6 on: October 23, 2012, 10:16:49 AM »
I can't remember what the name of it was called but it was a hard surface not soft like Teflon.

Again the reason I bring this up is after 500 miles or whatever rather than new pistons, might it be a better idea to coat them as they wont collapse anymore ??

Offline SUPERTUNE1

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Re: Wiseco piston clearance query
« Reply #7 on: October 23, 2012, 06:00:16 PM »
Big advantage to running the Wiseco Banshee #513 pistons is they're the lightest piston on the market!
     I didn't really care that I needed to change pistons every 3 race weekends and be competitive for the win and did win a lot! Remember stock balance RD400 crank only would redline to about 8500-9000 RPM's, this engine shifts at 10,400 sometimes more depending on the gearing and track, in some turns I would use the over rev to not have to shift, upshifting caused a slower lap time.

Maybe I'll have someone use the Wossner pistons as they use a ribbed skirt, I'll have to weigh them and see if they are heavier, if so, maybe in some area I can put it in the CNC and lighten it up some.
The skirt coating doesn't stop the skirts from collapsing with the Wisecos. I have been reluctant to have them cryo'ed.
But from what I have read maybe should try...

Chuck
Team Scream Racing
 
http://www.enginebuildermag.com/Article/2322/cold_parts_hot_performance_the_mystery_of_cryogenic_engine_treatments.aspx

http://www.iwt.com.au/cryogenics.htm

http://cryopro.com/engine/index.html   

http://www.2strokeworld.com/forum/index.php?topic=10191.0
Racegas + Lots of oil = HORSEPOWER
2 time Daytona AHRMA Formula-500 winner '06
'78 RD400E
RD machine work, boring, porting, cranks and engine building.

Offline 78 RD

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Re: Wiseco piston clearance query
« Reply #8 on: October 24, 2012, 07:35:09 AM »
I don't race just play on the street so I don't need all you have but I like the idea of cryo the pistons and rods.  Not really heard of doing that to pistons but I wonder if it would shrink them and make them brittle as they make themm stronger but I wonder if it makes it not flex ???

Offline edglenn

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« Reply #9 on: January 06, 2014, 09:49:44 AM »
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« Last Edit: January 11, 2014, 01:02:15 AM by edglenn »