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CLARIFICATION: Page 48, SRIS. The Type 1 arrangement is used on machines up to engine #31343. The Type 2 arrangement is a better working system and was installed on all engines from #31344 until the end of production. There is a kit, part # 13100-31830, that contains all the parts necessary to convert an engine with the Type 1 system over to the Type 2 system. As well, all the “J” models used SRIS check valves that are pressed into the crankcase. If any of these valves fail in the “open” position, there is an external style check valve available to take over the function of the failed valve. This external valve is available under part #16710-31990 and is inserted into the SRIS hose downstream of the failed valve. The problem of the pressed-in style valve failing in the “closed” position is not addressed in either the service manual or any service bulletins. Such a failure can happen if the bike has been standing for a long period and the valve becomes clogged with degraded injector oil and/or fuel. You may be able to somehow pry the failed valve out of the crankcase casting but I have never personally attempted this procedure. All the “K” and later models used a screw-in style check valve so that removal and cleaning of a valve failed in the “closed” position on those models is not a problem. Additionally, the check valves were not supplied with any kind of a filter or strainer on the crankcase side and problems arose in service with small foreign particles causing the valve to fail in the “open” position and thus causing improper operation of the system for that particular cylinder. The factory installed a plastic mesh strainer on the end of the check valve facing the inside of the crankcase beginning with the first “K” model engines with screw-in style check valves. Unfortunately, the plastic mesh would not stand up to the heat of the engine and metal strainers were supplied from engine #39084 and later. Thus, early “K” model engines from ~#31400 to #39083 should have the plastic mesh strainers replaced by the metal mesh style. Metal mesh strainers are available as single pieces under part #16521-31010. The plastic mesh strainer was discontinued entirely when the revised strainer began to be installed on production line engines during November, 1972.