Here’s a largely misunderstood part. The Vacuum Operated Electric Switch (V.O.E.S.) was standard equipment on all Evolution® engines and works in conjunction with most all late model electronic ignitions, both factory and aftermarket. It senses high and low manifold vacuum and signals the ignition to change its advance slope. Under high load, the switch signals the ignition module to electronically retard ignition timing to reduce the possibility of detonation. In low-load conditions such as cruising at light throttle, the ignition stays in the advanced mode for increased fuel economy and lower operating temperature. All controlled by the magical V.O.E.S. switch! Available with the switch activation pre-set to operate at 4, 5 or 6” of Mercury for your calibration requirements. If your pre-Twin Cam® engine doesn’t have one, it should.
Turn your 107" M8 engine into a 117" by simply boring your stock cylinders! No case modifications necessary, the factory 107" can be safely bored from 3.937" to 4.125". These forged pistons are manufactured for us by CP-Carrillo in 3 different compression ratios (flat top compression ratio is 11.2:1 with an unmodified 87.5cc head) and feature 1.5mm compression rings with 3mm oil rings for superior oil control. Piston kits include pistons, rings, wrist pins and circlips. USA made!
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.
Customize your HighFlow or MaxFlow air cleaner with one of these lids. Fits Zipper's HighFlow and Zipper's MaxFlow Air Cleaners.
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.
Zipper's MaxFlow Air Cleaner Kits for ThunderMax® throttle bodies includes a beautifully CNC-machined, radius inlet billet backplate, 2-3/4” deep MaxFlow filter, breather plumbing and heavy-duty support brackets.
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.
Please choose your application below then select the radio button next to the item to purchase, then add to cart
Zipper’s Popular Muscle 107” Kit for Twin Cam® 96/103” engines boost torque and horsepower north of 120! The Muscle 107 is a top end and cam kit that gets its displacement boost by increasing the cylinder bore size to 3.937”, while retaining the factory 4-3/8” stroke. Your cylinder tops are decked for trueness and new 10.6:1 forged pistons are precision-fit using the latest Sunnen equipment, while your heads receive Zipper's high-breathing Stage III treatment with CNC porting, new guides, oversize valves and performance springs. Our Red Shift 577 cams are perfectly matched with the heads and piston to provide big torque & HP across the entire RPM range. Red Shift Dual-Piston cam tensioners are included with Pro-Taper pushrods for a stable valve train and EZ-Adjust covers, with all gaskets needed for assembly. Highly recommended option: our 417-498 blueprinted cam chest/oil system upgrade for improved oil delivery, increasing reliability and durability.
This kit is for the aggressive rider that likes to regularly twist the wick and run up front!This kit uses your factory head and cylinder cores sent in for modification. An exchange may be possible once your cores are cleaned, inspected and qualified for exchange.*To ensure you enjoy a premium experience, Please fill out a Build Sheet/Job Order Sheet prior to completing an order on the website.
Click here for Zipper's Build Sheet/Job Order Sheet
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.
Zipper's is here to help, if you have a question(s) please scroll down and fill out the form and hit send. We will review your question(s) and we will be in contact.
Zipper’s Muscle 117” Kit for Twin Cam® 96/103” engines increases displacement with new 4-1/8” bore cylinders while retaining the factory 4-3/8” stroke. New cylinders are stress-relived before being fitted with 10.6:1 forged pistons using the latest Sunnen equipment, while your heads receive Zipper's high-breathing Stage III treatment with CNC porting, new guides, oversize valves and performance springs. Our Red Shift 577 cams are perfectly matched with the heads and piston to provide big torque & HP across the entire RPM range. Red Shift Dual-Piston cam tensioners are included with Pro-Taper pushrods for a stable valve train and EZ-Adjust covers, with all the gaskets needed for assembly. Case boring required for 4-1/8” cylinders, Timken® bearing conversion and cam chest/oil system upgrade recommended. Amazing increase in Power and Torque!This Kit uses your factory head cores sent in for modification. An exchange may be possible once your cores are cleaned, inspected and qualified for exchange.*To ensure you enjoy a premium experience, Please fill out a Build Sheet/Job Order Sheet prior to completing an order on the website.
Click here for Zipper's Build Sheet/Job Order Sheet
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.
Zipper's is here to help, if you have a question(s) please scroll down and fill out the form and hit send. We will review your question(s) and we will be in contact.
883 SPORTSTER® TORKSTER 883-1200 KITZipper’s Torkster 883-1200 kit Increases Your 883’s Horsepower output by 63% and its Torque by 72%! The key to this huge increase is Zipper’s High Velocity Stage II CNC headwork and carefully matched forged piston design. Your cylinders are decked on both ends, bored from 3” to 3.5” then honed on a state-of-the-art Sunnen SV-30. Heads receive Zipper's CNC porting to Stage II specs and are fitted with new Step Lock valve guides, stainless steel valves and upgraded valve springs. This combination promotes a great power curve, with torque topping 80 ft/lbs and HP over 75 - with factory camshafts! Supplied with a quality top end gasket set. Easy to install, fantastic results!Note regarding late 2009-up 883 cylinders: Since the 883 was introduced in 1986, H-D® used a thick iron insert in the casting that allowed the 3” bore 883 cylinder to be safely bored to 3.5” for 1200cc displacement. Mid-year 2009, this changed. Less cast iron was used, and the cylinders can no longer be bored to 1200 (see cutaway photo). If you can see aluminum on the outside of the cylinder spigot (arrow), your cylinders can not be bored to 1200 due to the step circled in red. We try to keep used, earlier versions in stock that we can use for these applications, but this is subject to availability and finish. Contact our sales department for availability. An exact color may not be available and you may need to paint to match your engine. H-D® sells color-matching spray paint you can use for this. We do not recommend powder coating as the heat required to cure the PC will alter the precision-bored finish of the cylinders.
*#517-912 Includes reconditioned ’04-‘E09 cylinders (see above note)This kit uses your factory head & cylinder* cores sent in for modification
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.
Zipper's is here to help, if you have a question(s) please scroll down and fill out the form and hit send. We will review your question(s) and we will be in contact.
Zipper’s Air Filter kits are designed to maximize available airflow and minimize intake turbulence at the entry point. We start with a fully machined, radius inlet billet backplate, and add special mounting and crankcase venting hardware that allows the installer to route breather venting internally or externally (purchase vent filter separately if external).
*1 Accepts stock '07-up oval Sportster® outer air cleaner cover (not included)
*2 Accepts EV BT round cover or accessory 8" covers (not included)
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.
Please choose your application below then select the radio button next to the item to purchase, then add to cart
Designed to be used on a stock, unmodified Keihin CV carb for improved throttle response and overall performance. Previously modified carburetors may require installation of stock needle jet, jet holder and needle for proper operation with this kit.
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.
A lot of money is spent to obtain gains in airflow for increased performance. One often overlooked area is the air filter; since it’s the first thing the air sees, it must keep up with the carburetor and cylinder heads’ demands. We’ve designed this MaxFlow air filter kit to meet the requirements of our high performance engines.
Not legal for sale or use in California on any pollution controlled motor vehicle.
Not legal for sale or use on any EPA pollution controlled motor vehicle.