New Pistons
New Pistons
I looking at big bore kits, and seen two different pistons. Most I've seen are flat top and some are domed top. Does anyone know what the difference is and what is the best to use?
Thanks
Mark
Thanks
Mark
Seasoned HDF Member
Joined: Dec 2010
Posts: 7,736
Likes: 1,524
From: Coromandel Peninsula New Zealand
No such thing as a big bore kit for an Evo, stroker kits are the only way to properly increase cubes....you can bore the cases and get fancy with bigger cubes that way but it ain't no kit, its a totally different scenario.
Some of the "Big Bore kits" for Evos are merely the largest rebore size available and the increase in cubes is insignificant......unless you ride a Sportster, in which case the answer to your question will be much longer.
Some of the "Big Bore kits" for Evos are merely the largest rebore size available and the increase in cubes is insignificant......unless you ride a Sportster, in which case the answer to your question will be much longer.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,070
Likes: 2,115
From: Ohio
Strokin it is the only way to go, if you convince yourself of a larger cylinder setup you usually have to have the crank balanced anyway and remember one thing, say no to Revolution Performance Nika-sil
If you are dead set on a big bore then Axtell is your answer. 97" with a stock crank and 106" with a 4 5/8 arm. The 97" stock cased Harley engine has been around for a while but stressing the cases with the spigot overbore
Revolution Performance a large overbore aluminum jug with nickel material coated cylinder walls
Axtell is a cast iron jug with steel cylinder wall that is tougher than puttin a wet noodle in a wildcats a$$ but heavy in weight
Sputhe has something
S&S is setup for a 96" with a 4 5/8 arm
If you are dead set on a big bore then Axtell is your answer. 97" with a stock crank and 106" with a 4 5/8 arm. The 97" stock cased Harley engine has been around for a while but stressing the cases with the spigot overbore
Revolution Performance a large overbore aluminum jug with nickel material coated cylinder walls
Axtell is a cast iron jug with steel cylinder wall that is tougher than puttin a wet noodle in a wildcats a$$ but heavy in weight
Sputhe has something
S&S is setup for a 96" with a 4 5/8 arm
Last edited by 1997bagger; Oct 18, 2012 at 07:49 PM.
Club Member
Joined: Jun 2007
Posts: 45,429
Likes: 2,897
From: Bedford UK
I looked into converting my stroker to yet bigger, by boring the cases. I soon realised that was not wise so costed for new cases. I seem to recall Axtell and Sputhe made suitable new strong cases, but the total cost was getting silly. A new S&S motor was even more, but built like a Sherman tank! I just wish I had gone even bigger than my cute little 107"....
Further to what Spanners said, our 80" Evos are actually around 82" stock, and every rebore size adds approximately 1", so an 85" kit is simply max oversize, with high comp pistons. If you want to really gee up your ride contact HDF sponsors Hillside Cycle. There must also be a decent tuning shop or two near you?
Further to what Spanners said, our 80" Evos are actually around 82" stock, and every rebore size adds approximately 1", so an 85" kit is simply max oversize, with high comp pistons. If you want to really gee up your ride contact HDF sponsors Hillside Cycle. There must also be a decent tuning shop or two near you?
Road Captain
Joined: Nov 2007
Posts: 517
Likes: 6
From: Ottawa, ON
Was strongly suggested against strokin an evo by a local dealership guru (whom I do trust).
Had a big bore kit before, where you have to bore the cases - total crap, sleeves get warped coz they are too thin, starts sucking oil, no possibility for reboring (again coz the sleeves are too thin).
The only sound way to sup-up an evo, imho, would be head porting and higher compression pistons. May also look at Edelbrok or S&S heads...
My 2 cents
Had a big bore kit before, where you have to bore the cases - total crap, sleeves get warped coz they are too thin, starts sucking oil, no possibility for reboring (again coz the sleeves are too thin).
The only sound way to sup-up an evo, imho, would be head porting and higher compression pistons. May also look at Edelbrok or S&S heads...
My 2 cents
Trending Topics
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
Likes: 12
From: Bluffton, South Carolina
OK then there are "big bore" kits for that. Stick wit the flat top pistons as the larger bore will increase the C/R by itself. Higher compression will give you more power, but with fuel not getting any better it may not be the way to go with an every day rider. Additionally to get scientific for a minute "Flat top pistons allow for the propagation of the flame front, thereby getting more efficency out of the engine".
John
John
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,070
Likes: 2,115
From: Ohio
OK then there are "big bore" kits for that. Stick wit the flat top pistons as the larger bore will increase the C/R by itself. Higher compression will give you more power, but with fuel not getting any better it may not be the way to go with an every day rider. Additionally to get scientific for a minute "Flat top pistons allow for the propagation of the flame front, thereby getting more efficency out of the engine".
John
John
Would like to hear more on why someone would advise against putting a 4 5/8 stroker kit in a Evo case, straight install - no clearancing, no spigot problems, one disadvantage is more piston speed is created for a possible cylinder wear factor but not that big of deal. I know that more stroke creates more torque and in a big bike is the answer, big bores can't create torque from a mechanical advantage like a longer armed crank and he with the most cubes wins in a natural aspirated environment.
Seasoned HDF Member
Joined: Dec 2010
Posts: 7,736
Likes: 1,524
From: Coromandel Peninsula New Zealand
Stroker kits tend to use oil and have some interesting piston speeds...but boy oh boy are they fun to ride!!!! I look after an FXR with an S&S Stroker kit....I look forward to seeing it and nearly try to buy it off the guy every time I ride it :-)