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It should all be in the Yamaha Shop Manual....
 

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Discussion Starter #4
Well i dont have a shop manual and I can see there is spark bit in higher rpms it is not igniting enough or it is getting too much fuel, one of the two. It cuts out at higher rpms and loads the cylinders up so it idles high for a few seconds.

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When was the last time you synched the carbs? What jets are you running? Stock intake and exhaust? What is the PMS set at?
 

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Discussion Starter #6
I just eyes it to sync the carbs. Everything is stock I think. I know the ais is removed.

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It may also be too lean at high RPM....like a plugged jet. Not enough fuel to ignite so raw vapors get pumped out. The carb would be the first thing I'd check. Coils on 1100's rarely have an issue.

If it was me, I'd pull them off, clean the jets and everything else, make sure the needles are seated, reinstall and synch.
 

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Discussion Starter #8
I went through and cleaned the carbs. I did not remove tamper caps and low and high speed needles though.

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Discussion Starter #9
If it were lean why would it continue to idle high when throttle is let off rather than go back to normal idle?

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I'm not saying it is...but it's a possibility I've seen many times. Either a vacuum leak or PMS not adjusted correctly will cause that as will a sticky throttle cable.

There is only one needle in these carbs. Did you check the side holes in the pilot jets when you had it apart? It would be a damn good idea to note jet sizes as well.... you never know who'sbeen in there unless you've had the bike since new.

I'd definitely drill out the caps on the PMS too....just to check them.

Also, doing a vacuum synch is extremely important.

If I were you...i'd invest in a shop manual and test everything..
 

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Discussion Starter #11
Vacuum leak I would think the idle would stay high rather than high only for a few seconds? I have checked throttle cable and it moves like it's new. There is not a high and low needle? What does pms stand for? Jet sizes should not matter too much as this bike ran fine prior to sitting too long. Side holes I made sure we're clear in the pilot jets. Could out of sync carbs create that much trouble?

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Yes....outg of synch carbs are one of the most common causes of "slow to return to idle" that I've seen, especially if they are way off. One butterfly is open just enough to allow the idle to linger. Missing at higher RPM too....if you are positive everything inside the carb is correct. Synching is a 5 minute process and needs to be done anytime you mess with anything on or in the carbs.

The only way it could suddenly get richer is if the main jets magically got bigger or the PMS (pilot mixture screws) have opened too far.

Go HERE and read...you'll find some very interesting stuff. After that...go HERE to read on how to adjust the PMS correctly....then HERE on how to synch the right way.

Again..I can't see it, hear it or touch it.....it could be a coil...but it's unlikely. The first link I gave you should give you enough material to test that as well.
 

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Discussion Starter #14
Ok the link for syncing only shows a YouTube video for baseline bench syncing. Don't you use a vacuum gauge to sync them on the bike? Also I have noticed on this bike the oil light comes on when it's on the kickstand running but as long as you are riding or sitting upright it stays off. Is that normal?

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A high idle, assuming your idle set screws are not turned up, is usually an indication of a vacuum leak and too much fuel. More air and more fuel = higher RPMs. I totally agree with Mick and get a manual for it. I am willing to bet you can find an online one so you do not have to wait for shipping to get it to you. Just hard to turn the pages on your computer with greasy hands.. trust me I know this first hand.
 

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you cant test the trigger side of the coil without a noid light, the pulse is to quick, the only thing you test is the internal resistance, these bikes don't use coils at all, they use pulse transformers or a step up transformer , very different form a conventional coil of the old points system.
 

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Yes....outg of synch carbs are one of the most common causes of "slow to return to idle" that I've seen, especially if they are way off. One butterfly is open just enough to allow the idle to linger. Missing at higher RPM too....if you are positive everything inside the carb is correct. Synching is a 5 minute process and needs to be done anytime you mess with anything on or in the carbs.

The only way it could suddenly get richer is if the main jets magically got bigger or the PMS (pilot mixture screws) have opened too far.

Go HERE and read...you'll find some very interesting stuff. After that...go HERE to read on how to adjust the PMS correctly....then HERE on how to synch the right way.

Again..I can't see it, hear it or touch it.....it could be a coil...but it's unlikely. The first link I gave you should give you enough material to test that as well.
syncing only matches the secondary butterfly to the primary one, i can't see how changing jets or moving needles could knock the butterflies out of sync, before there were fancy vacuum synchronizers, a very small drill bit under the throttle plates worked just fine, syncing only keeps the vacuum even, the only way i can see a carb getting out of sync is by the mechanical parts wearing in unevenly, if you see it differently tell me you theory on how butterflies can get out of wack from each other, vibration wearing the tip of the sync screw maybe? but that would be mechanical wearing in, i think?
 

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No theories on my end, just what I've seen in the real world. Anytime I've worked on carbs, I always double check the synch. It's just a part of the job. It's not always off, but in my experience more often than not, (especially if the carbs have been off the bike) they are going to be noticeably off.

If you just look at the carb linkage and the twisting and manipulating you do when you remove and re-install them.....I'm sure that could be all it takes to cause things to change....but who knows. I've never had a lab with proper instruments measure the linkage positions, and I don't plan to. It's just not worth the time and effort to me.... so that is just a plain flat guess.

Besides, if you go through all the work to diagnose and attempt to fix an issue, why wouldn't you want to double check anything that could possibly be the cause or partial cause of that issue? I hate leaving anything to chance and don't mind taking an extra couple of minutes to make sure it's done right. In many cases it simply means I'm not doing to the job 2-3 times and I'm turning out a tested quality product. 5 minutes well spent IMO.
 

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i do check the sync every winter because i remove the carbs for valve adjustment's and such, but i'v never had to turn the sync screw yet and i'm at 60,000 miles, maybe i'm just lucky or the 650 doesn't get out of wack easily, but your right checking the sync often is a good idea and it's easy to do, what i was trying to say is even if the sync is off slightly it won't make the engine run really badly, it may may cause a rough idle and a little more vibration but it would have to be way off to make the engine run really poorly, and most times if it's off that far it's because someone messed with the sync screw. it just can't get that far off with normal wear and tear or removing and installing the carbs. if you separate the carbs from each other it can cause sync problems, that why manuals always say do not separate the carbs unless absolutely necessary.
 
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