| Author | Message | ||
     Higbyal |
I am currently having some cylinders bored using Thunderstorm 10:1 pistons(part 22676-98Y). Does anybody know what the piston to cylinder clearance is suppose to be with these pistons? | ||
| Rocketman |
Try here S1 manual Rocket | ||
| Higbyal |
Thanks but the manual does not have spec for piston to cylinder wall clearance either. | ||
| Tim |
It does spec the bore diameter for new components and service wear limits for standard bore and .005 thru .030 oversize (Message edited by tim on January 17, 2007) | ||
| Tim |
There is also a paragraph about fitting the cylinder to the piston. (in my 99 M2 service manual.) | ||
| Rocketman |
The manual has ALL the information you require. The measurement you are seeking is something you must (and can to a degree) work out for yourself given the information the manual presents. The reason there is no measurement listed of what you require is because there is really no true measurement. This is because a piston is not a perfectly round shape. It is elliptical, therefore the measurements are not equal around the pistons diameter. If such a measurement did exist, the only way it could be considered accurate to industry standards would be to make the measurements (yes there'd be a min and max) in a controlled temp test facility. I believe the temp is 20 deg, but don't quote me. So I'm afraid the best you can do is measure the bore you have and determine the measurement you seek by knowing the size of a new, or not worn piston, and calculating the difference between the two. Be warned though, the measurement will read different back to front, side to side. The S1 manual I linked you to does have ALL the info you require to do that, except the piston measurement. The piston measurement should be known by whoever manufactured it, as the allowable tolerance between one piston and another is so tiny at manufacture they are all damn near identical. Whether the measurements are general information from the manufacturer I couldn't say though. All the above said, if all you are seeking to do is bore the cylinders you have to match the pistons you have, then follow the bore sizes in the manual for whatever piston size you have - STD or whatever oversize. Rocket (Message edited by rocketman on January 17, 2007) | ||
| Higbyal |
I am willing to be wrong but almost any after market piston you buy, they give you a cylinder to piston wall clearance, but not Buell/Harley? When giving your cylinders to any machinist to be bored, the first thing they need is a piston to cylinder wall clearance. This way they can as closely fit each piston to the individual bore. The Buell/Harley manuals seem to give it to you the same way they do it in a production environment, bore a couple holes and that's close enough. I really appreciate all the information. I guess that's all I can do Thanks Alan | ||
| Xldevil |
but almost any after market piston you buy, they give you a cylinder to piston wall clearance. Referring to B.Buzzelli, HD recommendation is .002".,set for worst-case situation. Buzz himself says .0005" of clearance is best Ralph | ||
| Rocketman |
Alan, in recent years I have purchased two pairs of Wiseco forged pistons for Buell. A set of Thunder Storm pistons too. Nowhere does it say in any literature I read with these pistons about a piston to cylinder clearance. I have in the past bought a pair of used race pistons for a Bonneville, and had the Bonneville cylinders bored to suit. The clearance was done to the Triumph Factory Manual spec's. That is the correct thing to do I believe. When a piston is manufactured for a particular application, the specification is set by the engine designer. After market pistons are manufactured again, to suit the manufacturers tolerances if they are direct replacements for stock pistons. There exists a formula used by the old guys that you could possibly apply. I won't attempt to quote it but it was something like 1 thou wall clearance for every 3 inches of piston circumference - as an example only. I don't have any of my Denish's tuning guides here at home, though I don't recall Denish mentioning anything like a formula for what you seek. Hope this helps. I'm not an expert  Rocket | ||
| Pammy |
Harley gives a bore size as well(as opposed to a cyl to piston clearance). Stock bore is 3.4978in/88.8441mm 0.005 over is 3.502in/88.951mm 0.010 over is 3.507in/89.078mm 0.020 over is 3.517in/89.332mm 0.030 over is 3.527in/89.586mm all bore sizes +0.0002in/0.0051mm They also recommend that you do not fit the piston any tighter than 0.0007in/0.0178mm | ||
| Alex |
Harley claims that the piston can not be measured accurately with normal equipment (read micrometer) according to the piston´s shape for Evo Sportster and Evo Big Twin engines. Here is what the manual says: Because of their complex shape, the pistons cannot be accurately measured with standard measuring equipment. The pistons have the typical elliptical shape when viewed from the top. However, they are also barrel-shaped when viewed from the side. This barrel shape is not symmetrical..... Therefore there is no sense in giving a piston-to-cylinder fit number. Instead they tell You the bore sizes. | ||
| Higbyal |
Thanks everybody for all your valuable informative and educational input. The cylinders are currently being bored "by the book" The Harley /Buell Book that is. | ||
| Rocketman |
That would be the wise thing to do in my book given you are boring for TS pistons Alan. Rocket | ||
| Jimidan |
I have this from a very good source: "For stock pistons, stock cylinders, I run 0.0025". For stock pistons in an aluminum bore, I run 0.0030 For the Wiseco's in a stock cylinder, I run 0.0030-0.0035. For Wiseco's in an aluminum cylinder I run 0.0035 For 3 13/16ths Wiseco in Millennium cylinders, I run really loose, up to 0.0050 You measure the clearance about 3/4" up the piston skirt to get the piston diameter, and about 1" down in the bore using a bore gauge, along the axis of the bike centerline." jimidan |
