jdburke Posted September 1, 2008 Share Posted September 1, 2008 I'm in the process of bringing a 1981 xj550h Maxim back from the almost dead. I hope someone out there has some YICS experince they'd be willing to share. This one has a huge vaccum/air leak by #4 carb. (it's really screwing with my freshly cleaned BS34 carbs) To properly repair this leak, I'd have to change the head gasket. Has anyone had any luck with any improper (High temp RTV) repairs on this type of leak? Is this a common failure on YICS motors? Lastly, does the YICS have a very great effect on the overall perforance of the bike? If this is a common failure and if I have to pull the head, I'm thinking of fixing this so this failure never occurs again. Or is there a better way to handle this I just don't know about? Thanks in advance for your expertise and experience. John 1981 Yamaha 550 maxim 1978 Kawasaki KZ 1000A2 Link to comment Share on other sites More sharing options...
JimR Posted September 2, 2008 Share Posted September 2, 2008 I'm in the process of bringing a 1981 xj550h Maxim back from the almost dead. I hope someone out there has some YICS experince they'd be willing to share. This one has a huge vaccum/air leak by #4 carb. (it's really screwing with my freshly cleaned BS34 carbs) To properly repair this leak, I'd have to change the head gasket. Has anyone had any luck with any improper (High temp RTV) repairs on this type of leak? Is this a common failure on YICS motors? Lastly, does the YICS have a very great effect on the overall perforance of the bike? If this is a common failure and if I have to pull the head, I'm thinking of fixing this so this failure never occurs again. Or is there a better way to handle this I just don't know about? Thanks in advance for your expertise and experience. John 1981 Yamaha 550 maxim 1978 Kawasaki KZ 1000A2 I worked on XJ550 in this country where they were current machines and never had problems with the head gaskit blowing from that area ... the UK model had o rings sat in the head gasket at the swill chamber entry points (yics tube), my adive would be to have the head off & fit the gaskit and o rings. While the head is off you could check the valves for leakage and seating and if the budget allows replace the valve guide oil seals and genrally service the head. Dependat on mileage it may be an idea to put a cam chain in and check the tensioner for gauling (people do tend to over tighten the tensioner bolt). Yics itself improved the fuel consumption by storing mixture in it's chamber rather than behind the valve which in turn produced better cyclinder filling. On rebuild don't forget you will need a YICS shut off tool (fits in where that odd 12mm headed bolt is on the back of the cylinder head) or you will be wasting your time trying to balance the carbs. Regards Jim Link to comment Share on other sites More sharing options...
jdburke Posted September 2, 2008 Author Share Posted September 2, 2008 Thanks for the information. I should have added to my initial post but wanted to keep it as brief as possible. This bike had been sitting for at least the last 8 to 10 years, and probably a lot longer. The previous owner had bought it with visions of fixing it up and then gave up on it. When I got the bike it had 3 sparkplugs broken off in the cylinder head and just to add insult to injury, one of those had an easy out extractor broken off in it. The odometer only shows 11,000 miles, so I'm hoping that the internals and cam and valve train, with the usual exception of gaskets and seals, will be in good shape. The parts diagrams I've seen show only the head gasket sealing the YICS ports, no o-rings are shown or listed in the parts info. I've looked a little bit and so far haven't found a head gasket. One dealer did volunteer that they were out of stock and that Yamaha showed them on backorder. Do you know if the tool to seal off the YICS port to sync the carbs is the same for most all of the YICS motors? I'm asking because as soon as I get done with this one I have another YICS motor (1982 750 Maxim) to start on. Thanks again, John Link to comment Share on other sites More sharing options...
JimR Posted September 2, 2008 Share Posted September 2, 2008 Thanks for the information. I should have added to my initial post but wanted to keep it as brief as possible. This bike had been sitting for at least the last 8 to 10 years, and probably a lot longer. The previous owner had bought it with visions of fixing it up and then gave up on it. When I got the bike it had 3 sparkplugs broken off in the cylinder head and just to add insult to injury, one of those had an easy out extractor broken off in it. The odometer only shows 11,000 miles, so I'm hoping that the internals and cam and valve train, with the usual exception of gaskets and seals, will be in good shape. The parts diagrams I've seen show only the head gasket sealing the YICS ports, no o-rings are shown or listed in the parts info. I've looked a little bit and so far haven't found a head gasket. One dealer did volunteer that they were out of stock and that Yamaha showed them on backorder. Do you know if the tool to seal off the YICS port to sync the carbs is the same for most all of the YICS motors? I'm asking because as soon as I get done with this one I have another YICS motor (1982 750 Maxim) to start on. Thanks again, John Hi John, The Tool was the same across the 4 cylinder engines XJ550/750, thinking back it may have been the 750 with the o rings .. it was a long time ago, but I'm sure a head gaskit will be your only fix. Regards Jim Link to comment Share on other sites More sharing options...
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