kordasn Posted June 21, 2007 Posted June 21, 2007 Hi everyone, As you can tell I'm new to this forum, and relativly speaking new to motorcycling. I've been riding for only 2 years, I'm 22, but enough of my life story. I'm trying to throw the line out here for some help; I've found a few forums that I'm going to be posting on for some advice. [edit to include information at the top] I have a 1984 Yamaha Maxim XJ750 with ~32000 km on it. The issue: The bike runs normally, everything is fine at any other range of speed, heat, weather, etc., except for 4500 - 5500 rpm, with the worst being at 5000 rpm. And, for lack of better description at exactly 5000 rpm it sounds like the engine's going to fall out. At any other speed (at least up until say 7000, I never pushed it further) it sounds fine, quiet and normal. It has ~32000 km on it, starts fine in hot or cold. I am running synthetic 10W30. In terms of engine-area replacement, I've replaced the stator and rotor, as well as the spark plugs, though I suspect those have nothing to do with it. As far as I know this sound could have been around for a while (I've only owned it for about 1000km), but I never really noticed it as I don't often push the bike above 4500 rpm when you can hear that engine noise over the wind. At highway speeds ~110 it runs at 5500 and I notice no problems, at say 90km/h it's almost exactly on 5000 rpm, and there is not too much of an issue. But if you're accelerating in say... 1st-4th you can hear it in the engine at that speed, and I can even feel the vibration. I suppose I might as well line up the questions... 1. I have been told that the 80s Maxims have had many valve problems, or that it is the first thing to go, I assume this is the case? 2. If it is indeed a valve problem, I believe it's a $1000 job? 3. The bike is 23+ years old, it cost me about $2300, 32000 km. I really like the bike and it's pretty much perfect (except for when some jackass knocked it over in the parking lot...), what would you suggest? Thanks very much for anyone's time who reads this and advice upon reading it, Matt
kordasn Posted June 22, 2007 Author Posted June 22, 2007 Just to provide an update, I adjusted the auto-cam tensioner and although it made it quieter, I found that (I believe) something is loose in the 4-2 collector underneath the bike. Does anyone have any experience of removing the exhaust on a Maxim?
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