Runs rough at lower rpms but runs fine at wide open
Try this
Carbs need balancing
Pilot jets blocked
Spark plugs worn
SOURCE: I have twin 1995 250 yamahas. One runs fine the
You have an advantage few others have, that is you've got an identical bike with all parts known to be good. Lets isolate the problem for sure. Swap carbs on the two bikes. Does the problem now show up in the other bike? If so, we now know for certain that the carb is the culprit. If so, I would put a carb kit in the offending carb. The main jet 'O' ring could be worn and thus allow the bike to flood out at higher revs. The change in BTC degrees is to be expected when the rpm drops.
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Give it a try then post a comment with any results or questions. Don't forget to rate this answer when all is done. Thanks.
SOURCE: 83 Yamaha XJ550 hesitating and losing power at higher speed
I had a 1981 XJ650 and I can tell you carburetion is a nightmare on these bikes! While every manufacturer on the planet used Kehnin carbs Yamaha decided to contract with a company that NEVER made carbs before - Hitachi...
Because of the year, it could be several different things, let's start with the easiest/common.
#1. Grab a STRONG flashlight, open the tank and look inside...if you see ANY rust, I recommend removing the tank and Kreme it. #2. Remove the carbs, if you can...take a good look at the carbs "boots" the black manifold(s) between the carbs and back of the engine. If done carefully, it's not too difficult and shouldn't take more than 2hrs. Check the boots for cracks or damage that allows air too leak into the engine during operation...if they are damaged, you'll have to Google carb-parts for Yamaha's? #3. The easiest way to clean the carbs is to go to Advance Auto Parts and buy a can of "SeaFoam" and add it to a tank of gas per instructions (more is NOT better).
Good Luck
SOURCE: yamaha fzx manual
try clymers
http://www.amazon.com/FZX700-Clymer-Repair-Manual-M392/dp/B002CLCT40/ref=sr_1_1?ie=UTF8&s=automotive&qid=1252621999&sr=8-1
SOURCE: 1897 Yamaha Fzx 750
Saftey circuit issue! check clutch switch, side stand switch and wiring these are connect to the neutral light switch and the 3 are part of the saftey circuit,
circuit is designed to cut the bike out if the stand is down and you kick it in gear also to stop the bike turning over & jumping forward when you hit the starter and its in gear and the clutch isnt pulled in.
weak stand spring my not be pulling stand onto the stand switch correctly there fore no making the curcuit, switches just make and break the curcuit.
SOURCE: how to find the construction year of my yamaha fzx 750 ?
The bike was only made for two years 1986-87. Most if not all parts are interchangeable. There was also a 700 made for the US over the same years and those parts are mostly compatible as well.
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