Have to build a new engine for my local bike. It gets run locally and drag raced a few weekends a year. What is the largest inch Evo I can build with a stock aftermarket case. I Have axtell cast iron jugs at 3.875 and was wondering if I can run a 5 inch stroke with it.
The bore of your cylinders is irrelevant for the subject at hand.
What is important is the length of the cylinders, length of the rods and compression deck height of the pistons.
Curious to know what you meant when you said your 'Local Bike'?
Quote from: turboprop on March 23, 2025, 12:24:00 PMCurious to know what you meant when you said your 'Local Bike'?
I'm assuming he meant his bar hopper.
Ran a 3 13/16 sputh cylinder and S&S 4 5/8 years ago 105" did heaps off miles and the odd drags . 5" stroke piston speed is the problem, track only bike IMO .
As Hossamania says its a bar hopper and I run eighth mile with it several times a year for fun. I am slowly finding out I am limited to either a 4 5/8" or 4 3/4 stroke with a 3.875 bore to keep the height of the engine roughly the same to fit in the bike. Just might have to settle for 112 cubic inches. Basically I am looking for torque numbers
Quote from: rsbjt1 on March 24, 2025, 01:39:37 AMAs Hossamania says its a bar hopper and I run eighth mile with it several times a year for fun. I am slowly finding out I am limited to either a 4 5/8" or 4 3/4 stroke with a 3.875 bore to keep the height of the engine roughly the same to fit in the bike. Just might have to settle for 112 cubic inches. Basically I am looking for torque numbers
Again, the amount of stroke that cane run is determined by the length of the cylinders, length of the connecting rods and compression deck height of the pistons. You have provided nothing.
Stock STD crankcase deck height is 5.375, Axtell cylinders are 5.550 (5.556) in length, rod length is stock at 7.440. Compression height on pistons is 1.200. Can only raise the engine in height by .100 before having clearancing issues in frame. The only possibility I am seeing is a 4.75 crank with those pistons with a thicker base gasket and/or stroker plate to set deck height. Heads are already milled 0.050
Crank Centerline to Case Height + Cylinder Length + Base Gasket = Engine Block Height.
(5.375" + 5.550" + 0.020" = 10.945")
Stroke/2 + Rod Length + Piston Compression Deck Height = Piston Deck Height.
(2.375" + 7.440" + 1.200" = 11.015")
Delta = .070"
Fix = An additional.020" gasket + .050" plate.
You have a man here. Try John . I might be breaking rules by saying. Or Randy .