Idle adjustment question

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MaParkerColo
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Idle adjustment question

Post by MaParkerColo »

Hey guys,

I tried searching several different ways but didn't find what I was looking for, so here's hoping someone has seen it before. So I just tried starting the bike after having the carbs off to rebuild them and having to replace a burned out fuel pump caused by a bad VR (blew every bulb on the bike too it looks like) When I got it to fire it was running at really high RPMs I turned the idle adjuster all the way out and it still runs really fast? Looking at the throttle where the idle adjuster screw hits it isn't dropping all the way down. Even if I push on it, it still doesn't go all the way? I've rebuilt these carbs more than once and never had a problem before. Anyone recall having seen this before? Did I screw something up in re-assembly? Just wanted to ask before I pulled the rack of carbs off again!

I just want to ride! It was almost 70F here today!!!!

Thanks as always,
Mark
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1981 Suzuki GS450
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apsolus
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Re: Idle adjustment question

Post by apsolus »

yeah dont let that weather get away from you, ill be riding tomorow spose to be 60. i think your sync is off or you have a vacuum leak, likely to be sync cause you had the carbs apart. spray the intake system with carb cleaner or equivelent and if rpm changes you have isolated your problem. sync is also important i had an xj750 that would idle like 5k and would drive me crazy turnd out i had a throttle plate sticking and a sync fixed my problems. oh and if you set your idle screw to the lowest setting the throttle braket wont be able to make contact with it. its the throttle plates hitting the bores.
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Sooty
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Re: Idle adjustment question

Post by Sooty »

Have you checked your throttle cable free play? May be that when you put the carbs back on you have not left enough free play on the open and close cables to allow it to close to the throttle stop. Free play if I remember right is about 3mm.
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MaParkerColo
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Re: Idle adjustment question

Post by MaParkerColo »

Thanks for the replies. Bound throttle cable was my first thought too, but I checked that. With these bikes how much difference do you see in starting it with the air filter out, air box off, completely buttoned up? Just curious how much of a difference air flow made on idle/starting?
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Re: Idle adjustment question

Post by yamaha_george »

MaParkerColo wrote:Thanks for the replies. Bound throttle cable was my first thought too, but I checked that. With these bikes how much difference do you see in starting it with the air filter out, air box off, completely buttoned up? Just curious how much of a difference air flow made on idle/starting?


Theoretically quite a lot but I have had mine running with just carbs to the open air no tank cover
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MaParkerColo
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Re: Idle adjustment question

Post by MaParkerColo »

Theoretically quite a lot but I have had mine running with just carbs to the open air no tank cover[/quote]

Thanks for the reply George, I thought that I had done some tuning on them with the airbox off previously. How else could you sync? I tried to start it again this AM and it fired up pretty quickly even though the temp is back in the 30s, so much for my riding weather! It still idled pretty darn high once it started to warm up, but I'm wondering if I don't have the carbs seated all the way down on the intakes. A leak there would give me fits too I bet. It was running great before my VR fried taking the fuel pump with it. I went ahead and pulled the carbs are rebuilt them since it had sat for a couple months with gas in them. I still need to sort through everything that the VR may have fried. It looks like in addition to cooking the fuel pump it also blew all my turnsignals, taillight and my low beam :yikes: I hope that it didn't do anything else!

Best,
Mark
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rotortech
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Re: Idle adjustment question

Post by rotortech »

MaParkerColo wrote:Thanks for the replies. Bound throttle cable was my first thought too, but I checked that. With these bikes how much difference do you see in starting it with the air filter out, air box off, completely buttoned up? Just curious how much of a difference air flow made on idle/starting?


You can run at idle with air box off but not much more than that. It may be hard to start. Check for air leaks between the airbox and the carb bodies. That is most likely if you have been working on them.
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Re: Idle adjustment question

Post by fzrbrandon »

rotortech wrote:
MaParkerColo wrote:Thanks for the replies. Bound throttle cable was my first thought too, but I checked that. With these bikes how much difference do you see in starting it with the air filter out, air box off, completely buttoned up? Just curious how much of a difference air flow made on idle/starting?


You can run at idle with air box off but not much more than that. It may be hard to start. Check for air leaks between the airbox and the carb bodies. That is most likely if you have been working on them.

+1 It will idle but as soon as you start turning the throttle it'll start drowning in air. By the time you get to around 3k'ish or so, she'll probably want to shut down. Also, the bike should start without the airbox / filter. I've been successful with it. YMMV... :cheers:
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Re: Idle adjustment question

Post by sweekster »

Sounds like you're out of synch. Try turning the center screw (in between carbs 2&3) counter clockwise while it's running. It'll start to "calm down". Id suggest getting some fuel, building or buying a synch tool, and the adult beverage of your choice and diving into a good synch session. Should run tip top after that.
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MaParkerColo
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Re: Idle adjustment question

Post by MaParkerColo »

sweekster wrote:Sounds like you're out of synch. Try turning the center screw (in between carbs 2&3) counter clockwise while it's running. It'll start to "calm down". Id suggest getting some fuel, building or buying a synch tool, and the adult beverage of your choice and diving into a good synch session. Should run tip top after that.


Hey just wanted to update this as I hate reading through threads with the same problem I'm having and never finding out what the final solution was!

Sweekster had it right. I pulled the carb bank off and #1 was so far out of synch with the rest that when it was fully closed the other carbs remained held open leading to a high high idle. I did a bench sync (I use the shaft of tiny drill bit, I don't like bending my feeler gauges up) and everything is much better now. I need to borrow a carb tune to do a really good sync, but this will get me close and riding!

Just have to find all the burnt bulbs and get them replaced and I'm back in business minus a chain issue I started another thread on.

Thanks for all the advice.
Mark Parker
1993 Yamaha FZR 600
1981 Suzuki GS450
Colorado
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Re: Idle adjustment question

Post by yamaha_george »

MPC,
why not build the simple two bottle synch tool from the WIKI rather than wait
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