1987 fz-700 problems please help - Yamaha Forum : Your Yamaha Motor Products Community & Resource
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post #1 of 6 (permalink) Old 06-30-2010, 06:45 PM Thread Starter
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1987 fz-700 problems please help

Hello everyone! I am new to motorcycles, and just bought my first bike about a week ago. Unfortunitly i have some issues with my bike. My first issue is that the red wire coming off my altinator is extreamly hot when the bike is running for about 3 mins, maybe not even that long. I cheaked the battery and found that it was no good. So i replaced my battery and the wire is still hot. I havn't gotten around to cheaking the altinator output yet, but i do notice that all the lights are flickering wile the bike is running. So am i correct in saying I need a new alternator? Now my next issue is I cant seem to get the bike to stay running at idle...I have replaced the spark plugs and fuel filter cleaned out the carburators a little bit and ran some seafoam threw the motor. Holy cow what a difference but, it still wants too die after i push the choke in all the way. it will run for 10 seconds and slowly die out everytime. If i hold it in a higher rpm it seems to pur like a kitten with a slight missfire/backfire sound occasonaly. Sometimes when i give it gas for a second the rpms shoot too 4000 and stay thier untill i hit the gas a few times then it will drop back down and die. Anywone have anythoughts? Just so you all know, when i bought this bike thier were really no issues other then it seeming to bog down when you gave it gas. but now that my friends screwed around with the main adjustment on the bike(it bring the idle up and down and connects to all 4 carbs)along with some other screws that i have no clue what they are,when i wasnt around, the bike wont stay runnning and i cant seem to get it back to normal now so any help would be great i am also a mechanic for a honda dealership so i am not afraid to take apart the bike. thank again guys
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post #2 of 6 (permalink) Old 06-30-2010, 07:29 PM Thread Starter
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Ok a little update. I started to look around for some anwsers , should have done that first. But my question is now this. How do i adjust my carbs correctly? like whats are the spects for each thing and what screws should i turn and what do i half to take apart. Im more of a fuel ingected guy, i know very little about carbs.
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post #3 of 6 (permalink) Old 07-02-2010, 02:46 PM
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I can try to address some of the issues you're having with the carbs........
It sounds like your friends started twirling the set screws that are used to synchronize your carbs. To get these adjusted correctly right you need a set of carb sticks (they are 4 long glass tubes with hoses on the end and a reservior at the bottom filled with mercury), or a set of 4 vaccum gauges.

In terms of "adjusting" your carbs the air mixture screws are the only adjustments you can make with a tool - aside from the 3 syncronizing set screws. To change the jetting you will have to remove the carbs & the float bowls & also take the carb tops off. Doing this gives you access to the needles, pilot jets & main jets. There are really useful online sources for info about jetting & what jets control a particular rpm range.

Hopefully this gets you pointed in the right direction.

Good luck
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post #4 of 6 (permalink) Old 07-04-2010, 09:32 PM
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Yeah thats what I get too. Your friend was trying to sync the carbs. Need a guage to do that.
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post #5 of 6 (permalink) Old 07-04-2010, 09:38 PM
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For the hot wire. Need to check the v at the start and end of the wire. There is to much resisitence for it or too much v. Corroded connectors are most problematic. Maybe the reg is out.
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post #6 of 6 (permalink) Old 11-29-2018, 05:25 AM
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you can also visually bench sync the carbs which will get you in the neighborhood and probably have you running/idling well enough to sync with proper equipment....
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