Engine starting and idle speed - Yamaha Forum : Your Yamaha Motor Products Community & Resource
 
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post #1 of 8 (permalink) Old 06-18-2008, 06:23 AM Thread Starter
 
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Engine starting and idle speed

The 600R engine uses 4 carburetors and has a choke. I normally leave the choke fully closed (like you would during normal riding) when the bike is just sitting. When I try to start the engine in the morning with the choke fully open I always have to give the throttle a little twist to rev the engine and get it to start - is this normal or should the engine just start up without having to give the throttle a little twist? The bike does have an aftermarket slip on exhaust if that makes a difference.

After the engine is started with the choke fully open the engine idles around 3000 RPM. I usually immediately close the choke about halfway which drops the idle speed to around 1500 RPM. I wait about 10 seconds then start driving the bike and close the choke fully. Is that start up procedure ok? What is a normal engine idle speed for an engine such as an inline 4 cylinder with 4 carburetors?

After the engine is warmed up and the choke is fully closed it seems to idle fine around 1000 RPM, but idles a little rough when adjusted to about 900 RPM. If it adjusted any lower than that it gets very rough and occasionally stalls out.

There was one morning where I started up the engine and it just didn't sound right. It sounded as if there were twice as many exhaust pulses compared to what it sounds like when it runs normally. I played with the choke setting but it only changed the idle speed. I started riding and about a minute or two into the ride the engine seemed to have sorted itself out. Anyone have any idea what could have caused that? Did I not let the engine warm up long enough?
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post #2 of 8 (permalink) Old 06-22-2008, 12:37 PM Thread Starter
 
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Well, while adjusting the rear brake light switch I found a sticker on the inside of one of the rear cowlings that says the normal engine idle speed when warm is 1300 RPM. So in case anyone else was wondering, there you go.
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post #3 of 8 (permalink) Old 06-22-2008, 02:34 PM
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When you're saying "fully open" are you referring to the choke being pulled out entirely? I think you have the terminology reversed. A choke that pulled out is closed (closes the choke plate in the venturi to limit the amount of air).

1300RPM sounds about right on those. I typically idled my inline-4 bikes warm at about 1300-1500.
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post #4 of 8 (permalink) Old 06-22-2008, 03:58 PM Thread Starter
 
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Hi fjorn. Yes, you are correct. When I said open or closed I was referring to the choke valve and have the terminology reversed in my first post. As you could probably tell I'm not too familiar with carburetors!

What I meant to say was:

"I normally leave the choke fully open (like you would during normal riding) when the bike is just sitting. When I try to start the engine in the morning with the choke fully closed I always have to give the throttle a little twist to rev the engine and get it to start."

Last edited by BWRX; 06-22-2008 at 04:00 PM.
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post #5 of 8 (permalink) Old 06-24-2008, 08:42 PM
 
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Points to rememer about this bike. it is not an injected bike so yes a little rev at start up is what should happen that gets the gas flowing. the next thing is to wait till the bike warms up a bit before riding give the oil a chance to heat up some and thin out a little i live in TX so its not so much a big deal for me an my bike warms up quick with out the choke, now durring the winter it's a different story. good find by the way on the idle setting. just remember this bike doesn't like to start when its cold most carb bikes don't like to start when it's cold out side.
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post #6 of 8 (permalink) Old 06-25-2008, 09:45 AM
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I also have a 600R and the process you explained in your first post is almost identical to the way my bike starts and runs.
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post #7 of 8 (permalink) Old 08-11-2008, 07:50 AM
 
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Quote:
Originally Posted by BWRX View Post
Well, while adjusting the rear brake light switch I found a sticker on the inside of one of the rear cowlings that says the normal engine idle speed when warm is 1300 RPM. So in case anyone else was wondering, there you go.
I'm a newbie and I got my YZF600R last week and this was a big help. The previous owner had the idle speed set at 3000 RPM and I was getting use to riding with it that high, but when I would downshift and put it in first, it would rev real high. I thought it was too high, and now I know and it sounds much better. But now that I have it set at around 1500 RPM, I'm finding it difficult with upshifting from first to second. It seems like I getting a higher speed in first and when I shift into second, it seems to slow down and I feel the transmission pulling (probably wrong terms). Is this really happening or is it just me? Does having the idle speed set lower than what it was when I first got the bike have an affect on shifting?
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post #8 of 8 (permalink) Old 08-11-2008, 07:55 AM
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Should have zero affect on shifting. It's most likely due to your being used to running at a higher RPM. Give it some time and you'll get acquainted to the lower RPM's. But, you may not be shifting at a high enough RPM anymore.
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