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Lean or rich?

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Lean or rich? - 3/15/2008 7:55:06 PM

GDM YO

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Joined: 10/14/2007
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I've got an 89 cbr600f, and from what I know, everything is stock. the emissions stuff has been taken off i'm pretty sure, except I put a slip on muffler on it (2" ID)

the bike's been running fine, except under decel, it seems to pop/gurgle, and spit out a blue flame, so I was trying to figure out what was wrong. I put new plugs in, and took it for a spin. I did a couple cruising spark plug cuts (cruising, then shutting the engine off and pulling the plugs to look at them), and there seems to be silvery stuff on the top of the electrode bend. I was afraid that it was running lean,and that could be part of my piston, but it feels very slimy, so i think it's just anti seize that is dripping onto it when i drop the plug down. I think it would be more gritty if it was aluminum from my piston. I'm a little bit worried that it is running lean, although i havn't ridden it more then a mile , since I was afraid it was running lean. It's still gurgaling a little bit when i let off, but the fact that it was throwing a small flame, is why i figured it was running more rich than lean. the old plugs looked ok.

Do you guys think i should just put around on it for like 20 mileso or so, then pull the plugs and see what they look like, or what?

I really don't think the slip on mufler could have released enough backpressure to make it run super lean....

Post #: 1

RE: Lean or rich? - 3/15/2008 8:31:00 PM

Gogar

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It could be a number of things, but the easiest answer is to richen up your mixture a bit and see if it goes away. If it does, YOU'RE DONE.

Where are your mixture screws right now?

If you're nervous about it, it is better to be a little bit rich than a little lean. If it's too rich, the plugs will be sooty and black. Lean, they will be more of a whitish color.

You're right you need to go a little bit farther and get the engine hot before you can tell that way anyway. And try not to remove and install plugs when the engine is warm, cause you're more likely to booger up the threads and then you're screwed.

Good luck!

(in reply to GDM YO)

Post #: 2

RE: Lean or rich? - 3/15/2008 10:22:47 PM

GDM YO

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how do i richin it up? is there a screw on the carbs to do that without re-jetting them or anything?

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Post #: 3

RE: Lean or rich? - 3/16/2008 12:36:19 PM

Gogar

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Go to www.cbrextreme and download the F1 manual. It's easier for you do do some reading than for me to explain it. It's on page 19 of the "section 4-7" pdf. you need a really long, really skinny flathead screwdriver.

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Post #: 4

RE: Lean or rich? - 3/16/2008 4:04:13 PM

GDM YO

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I have the manual downloaded. so please explain what this screw does exactly?

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Post #: 5

RE: Lean or rich? - 3/16/2008 4:07:23 PM

GDM YO

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I see you adjust the pilot screws, but how exactly should i do it to richen it up, etc?

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Post #: 6

RE: Lean or rich? - 3/16/2008 4:28:04 PM

michigan_313

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adjust the jets.

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Post #: 7

RE: Lean or rich? - 3/16/2008 6:05:39 PM

GDM YO

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how do you adjust the jets? please explain, i've never had a carb'd engine before on anything.

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Post #: 8

RE: Lean or rich? - 3/16/2008 6:11:22 PM

Gogar

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IF the "restrictor" caps/tabs are on the pilot screws you won't be able to turn them much at all, like half a turn or something.

I they're on there, CAREFULLY take the restrictor caps off with a needle nose pliers or something. They're held on there with loctite. The actual screw is under there, and it's a brassy color.

Then, you can:

turn each screw all the way in until it stops, count how many turns you did. Should be between 1.5 and 2.5 turns or so.

Back them back out. The more turns OUT is richer. If you were at 2 turns out try 2.5 or something to get a little richer.

This screw only affects your idle and low rpm (up to about 6K rpm) mixture. After that your main jet kicks in.

When you're happy, put a little blue loctite on there and put the restrictor cap back on. If you want to be a rebel, file the little tab off of the side of the restrictor cap while you have it off and you won't have to to the loctite thing any more. But you'll need to check your screws every once in a while to make sure they haven't moved from vibration.

OR, you can just leave the little restrictor cap off and just check your mixture screws every once in a while.

< Message edited by Gogar -- 3/16/2008 6:21:15 PM >

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Post #: 9

RE: Lean or rich? - 3/16/2008 6:17:07 PM

michigan_313

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my bad, gogar is right, you should be adjusting the pilots first before having to mess with any jetting adjustments.

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Post #: 10

RE: Lean or rich? - 3/16/2008 8:14:02 PM

GDM YO

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so how do i know if i'm "Rich enough" w/ the pilot jets?

here are some pics of one of the spark plugs from about 10-15 miles on it, not really hard on it.

after i wiped off the whitish stuff, it looked clean.

i figure if that whitish stuff was aluminum from my piston, the top wouldnt look so clean, it'd look more burnt...

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Post #: 11

RE: Lean or rich? - 3/16/2008 8:56:08 PM

camoweasel

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Joined: 6/28/2007
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Judging by the pics, I would say that your pilot is running a little lean. I would definitely try and richen up the pilot screws. After you get the pilots set, I would then check the main jets by doing a few full throttle passes through a few gears then immediately shut the bike off after you let off the throttle. Pull a plug and see where your mains are at. You MUST remeber one important fact. Each of the different jet functions inside the carberators are based off of throttle position and not just RPM level. I can rev my engine to 6 or 7 grand while in neutral and only be at 1/8 throttle position. At 6-7 grand, the needle diameter and position have the most influence but since your only at 1/8 throttle, your still running off the pilot jet. By this I'm saying in order to check the plugs you need to take note of where your throttle position is because sometimes even though your revved pretty high doesn't nessesarily mean your throttle position matches the RPM level. I hope you understand what I'm saying.

_____________________________

1990 Honda CBR600F
K&N filter (removed air tubes under lid)
Yoshimura header with Vance & Hines SS2-R muffler
Factory Pro 6 degree Ignition Advancer
jetted

(in reply to GDM YO)

Post #: 12

RE: Lean or rich? - 3/16/2008 9:54:04 PM

GDM YO

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Joined: 10/14/2007
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so should I do a couple passes / throttle cuts at 1/8 throttle all the way up to redline? will that keep my pilots primarily working, and therefore look at the plug. after that I can richen up the pilots?

the reason why i'm worried of riding it, is i dont want to break anything if it IS indeed running super lean......

so after i pull the spark plugs / doing plug cuts for reving up (how high should i go) at 1/8 throttle, depending on how they look, then after adjusting till they look good,then do a couple wide open throttle plug cuts?

after doing a couple 1/8 plug cuts, will the plugs even look different? or no...? since the plugs are brand new.

(in reply to camoweasel)

Post #: 13

RE: Lean or rich? - 3/16/2008 11:25:57 PM

Gogar

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Well, it's definitely not too rich. Take your pilot jets out another half turn or something.

If your bike is sitting there idling and you can smell the unburnt gas coming out of the tail pipe, it's too rich. OR, when it's idling, If you give it a little twist of the throttle and it sputters a bit and then catches and revs up, too rich.

You're not going to hurt the bike really if it's too rich. IF it's too lean and you go out and hammer it, you might hurt it. Probably not, but it's a possibility.

Once you feel good about your mixture screws, go out and hammer it, cycling a few times through the 5-9K rpm range. If you don't feel the bike start to really take off at about 7-8K rpm, then you could probably go up a main jet size.

If it bogs down and stutters a little bit and then takes off, you could maybe go down a main jet size.

What's the altitude where you are? Is your airbox modified or anything? Dynojet or Factory pro or anything like that?

good luck!

Here's a cool "spark plug pictures" page, but it's kind of a drag-racer kind of thing, so take it with a grain of salt.

http://www.4secondsflat.com/plug_chart.html

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Post #: 14

RE: Lean or rich? - 3/17/2008 12:03:24 AM

GDM YO

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Joined: 10/14/2007
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right, i've seen the spark plug page(s)...

anyways, so unscrew (out) the pilot jet screws half a turn, then give it a good rip at wide open throttle, and see if it really takes off, or doesn't?

we're around 1000 feet above sea level, not anything to affect the amount of oxygen / make it run richer, so no worries.

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Post #: 15