The main reason for compression releases is to reduce the amount of compression during the start up of your bike. Primarily if you have altered the compression ratio and have cranking compression numbers that are higher than 180psi. If you are using S&S electronic compression releases and you are not sure if they are working properly here are some methods of checking them out. 1. Note that when you are cranking the engine that both releases are opening; this can be done by looking to see of they both drop down or by putting your finger on top and feeling the drop down motion. 2. Compression releases not sealing; to check for proper seal of the release you can do a leak down test. If the leak down percentage is high and you can here air in the exhaust it is possible that a release may not be properly sealing. If this is the situation you will need to remove both releases and verify condition. (When ever you are installing or removing compression releases it is best to remove the rocker boxes it makes the job much easier.) To verify condition, after the releases are removed look for signs of the plunger not properly sealing. Some times a poorly tuned engine will cause access carbon to build up on the release causing it to stick. The releases can be cleaned and reinstalled. If the release seems to be damaged call your S&S tech line for assistance (1-608-627-TECH (8324)).3. Check the wiring; If you do not have the releases properly wired they may not work properly and you could run the risk of damaging the releases or some thing else on your bike. If you are unsure you can see the instruction sheets for installation online here. 4. When removing or installing our releases it is much easier to remove the rocker boxes and also the use of the S&S two piece socket will help PN 53-0045. If you choose not to use the compression releases you can install the plug into each head PN 90-4916.
In many respects, S&S SSW+ engines are similar to Evolution style engines, but when it comes to the way they handle crankcase venting, they are a whole 'nother animal! Most S&S Evolution style and SSW+ engines have two engine breathing systems that can be used separately, or together, commonly referred to as case breathing, and head breathing. For case breathing, SSW+ engines still uses the venerable breather gear to regulate the engine's internal airflow, just like the Evolution style engines before it. However, the head breathing arrangement is markedly different. SSW+ engines don't use hollow breather bolts to vent excess crankcase pressure to the outside. Instead, the head breathing arrangement of a SSW+ engine consists of two hoses—a small hose on the front head, and a larger hose, equipped with a one-way check valve on the rear head. (More on the check valve in a minute). The front hose is routed from the front head to the intake manifold. It applies manifold vacuum to the crankcase anytime the engine is running. The rear hose is routed from the rear head to the carburetor backing plate (or other suitable location). Its purpose is to relieve excess crankcase pressure at all RPMs. Unlike the hose on the front head, the hose on the rear head doesn't do anything until pressure builds in the crankcase. Just remember, the front hose sucks, the rear hose blows. The rear head breather hose on an SSW+ engine performs the same function as the breather bolts on an Evo engine; that is, venting excess crankcase pressure to the outside, without allowing outside air back in. Both engines use a check valve to perform this function. Evo engines use a pair of umbrella valves located inside the rocker boxes, while SSW+ engines use a one-way check valve, S&S Part #50-8122. It is located outside the engine, placed in the aforementioned rear head breather hose. The one way check valve must be used with the rear head breather hose, no exceptions. (By the way, SSW+ rocker boxes will have provision for Evo style venting, but it is not functional). The front breather hose supplies vacuum to the crankcase as added insurance against engine blow by. In most applications it is beneficial. However, there have been a few cases of this hose pulling oil into the intake, causing the engine to smoke. Using the front hose is optional. If the front hose is causing a problem, it can be removed and the fittings capped. If the front hose is removed, a check valve is still required in the rear head hose. The one-way check valve is critical to the engine's operation. It must be installed in the hose so that air can flow out of the motor, but not back in. The valve is light colored on one end, and black on the other. You can blow through it to determine which end faces the motor, or, if you'd rather not wrap your lips around the thing, just remember—"black out"— the black end always faces out, or away from the engine.
Stock, S&S Engine or S&S Kit: To order a replacement manifold, refer to the manifold size chart for your particular engine type. Manifolds are listed for various sized carburetors and throttle bodies in the correct lengths for engines and kits offered by S&S.Custom Engine: If the effective cylinder length is different from the standard offerings, a special manifold can be machined to your specifications. Order manifolds using the special order part numbers listed in the charts. Allow two weeks for delivery.