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Discussion Starter #1
Hi everyone. My bike has great throttle response, mid range and all, but my fuel range is shot to hell. I can barely squeeze out more than 250 Kilometers out of a full tank, with warning light....So I suspect that my bird has been re-jetted, because my exhaust tips are black, and If I run my finger in them, it comes out withblack sooth(if you can call it that) that is not oily, my engine does not drink oil.
:crap:
I was thinking of changing the main jets on all four carbs (I have a 97), is this the right path to follow???The bike runs smooth, and the temperature gauge very rarely reaches the half way point, indicating a rich carburation..of what I deducted.
:huh:
So, if anyone has a suggestion, what jets to buy to put it back to original specs. I have a stock airfilter, and stock exhaust system.

Thanks, your help is appreciated...:thumb:
 

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Well, with a stock exhaust and stock air filter, I doubt someone would have thrown in a jet kit, or simply some jets..
You'd have to check this before you can think of your next move.
If you take the tank off, and possibly the airbox, you can then remove the top cap of one of the carbs and have a look at the needle it runs.
If its got grooves and a clip then its aftermarket. If not its probably oem.

For the bad fuel economy I would suggest you take the carbs off, for a check, a clean and a balance/tune up.
While you are at it, check the plugs too.
Finally when have you had the valves last looked at and at what mileage?

Cheers,
Chris
 

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Discussion Starter #3
Well, with a stock exhaust and stock air filter, I doubt someone would have thrown in a jet kit, or simply some jets..
You'd have to check this before you can think of your next move.
If you take the tank off, and possibly the airbox, you can then remove the top cap of one of the carbs and have a look at the needle it runs.
If its got grooves and a clip then its aftermarket. If not its probably oem.

For the bad fuel economy I would suggest you take the carbs off, for a check, a clean and a balance/tune up.
While you are at it, check the plugs too.
Finally when have you had the valves last looked at and at what mileage?

Cheers,
Chris
Hi Chris. I will check the needles, they might have been shimmed, if so, then I'll lower then out. It idles fine I had the bike at 32K. I changed the plugs in 2010, dumped iridiums in there. Maybe the guy before had slip ons, had it rejetted or needles shimmed, and before he sold it, slapped on the oem cans without re-opening the carbs, I don't know. For sure, I will eyeball the needles.

Thanks for the info Chris, take care over there in sunny Greece!!
 

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No worries man. :)
I dont use iridium pugs on the carbie. There is no need for them and no advantage to use them really.
I actually believe, whithout being able to support my 'feeling', that it runs better on the plain old plugs! :p
Depending on where you live the stock jetting on the bird is 142 on the outter and 145 on the inner cylinders (2 each). But this deviates according to region/country etc.
If you do take the carbs out, then I'd suggest you inspect the fuel float levels and the jets themselves very carefully. Worn (enlarged/oval etc) jets will contribute to bad fuel economy and the fuel levels on the floats commands a lot on how the carbs respond as a group of 4 working in synch.
A carb balance wont hurt much either!
Good luck with it man!
 

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My 98 was getting 275km's before the fuel light was on hard,..and that's mixed riding around town and a bit of highway stuff. Note the gearing on it was also 16-45 at the time,..so the odmeter may have been off a bit. Still..the pipes never got black and performance was fine. If you think it's running rich be sure to give the engine oil a sniff to ensure your not diluting the oil with fuel to some degree. If there is a float issue (stuck open...sunk float) this may also cause a rich condition in one or more cylinders. If you could accurately measure the exhaust gas temp of each cylinder you might be able to see if it's one cylinder or more. As Elvetost states..the jetting is staggered for the inner cylinders versus the outter two. Here is a somewhat related post that deals with jetting for a aftermarket exhaust system. You will find some info in the Factory Pro attachements that list the stock jets sizes I think. They (Factory Pro) bump the #1 and #4 cylinder jets to 142' from 140's...and leave the #2 and #3 cylinders with the stock 142 main jets,..of course this jetting will depend on intended state of tune and exhaust and air filter set up. Maybe this info will help..maybe not. I think the service manual also gives the jet sizes that come stock. Anyway..here's the link:

http://www.cbrxx.com/engine-airbox-exhaust-fuel-delivery/4293-recommended-carb-settings.html

Tony

btw..what's the condition of the air filter?...is it aftermarket?...is it oil'd?...could it be over oil'd?
 

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Discussion Starter #6
No worries man. :)
I dont use iridium pugs on the carbie. There is no need for them and no advantage to use them really.
I actually believe, whithout being able to support my 'feeling', that it runs better on the plain old plugs! :p
Depending on where you live the stock jetting on the bird is 142 on the outter and 145 on the inner cylinders (2 each). But this deviates according to region/country etc.
If you do take the carbs out, then I'd suggest you inspect the fuel float levels and the jets themselves very carefully. Worn (enlarged/oval etc) jets will contribute to bad fuel economy and the fuel levels on the floats commands a lot on how the carbs respond as a group of 4 working in synch.
A carb balance wont hurt much either!
Good luck with it man!
All good stuff, but before I dare bring the whole carb assy to a shop and get throat slashed, I'll take a good look at the needles. If I understand the logic behind this, depending where the e-clip is slotted, it will either rise or lower the needle, thus allowing a bigger amount of fuel to go in because the needle penetrates less in the hole. So If I open the carb tops, and I see for instance that the needles are clipped at the 3rd groove, I simply reduce and put them at the second groove, that should lean out the fuel delivery, am I right???

Is there a factory setting for these needles? I checked the service manual, and they don't seem to be adjustable...I might have to bring the whole slab to the shop and get a good clean up and float adjustment.
 

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Well you got the logic behind raising and lowering the needles right. The needles are tapered, hence lowering them, will make a thicker part of the needle, penetrate the jet hole, hence reducing fuel...
The oem needles are indeed fixed. The only option with them is to use shims (like little spacers) to lift the needles further up. Note that there is one shim on the needle from the factory there.
The dynojet and factory pro ones, both have clips and positions.
Hence if you open one carb up and its fixed, chances are you are running on original carb set up.
Badly synced carbs, worn jets and clocked carbs will also cause high consumption.
As Tony has suggested, check the oil for smell of fuel too..

My bird drinks about 10-20% more than other standard well running birds. But then again its pushing +10-20% more power depending on what revs you are looking at, so I can live with that... ;)
 

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I had a problem with low fuel mileage on my 98 Bird. I found that the float valves was leaking and causing the engine to run rich. I also found that the slides were drilled and when I went back to stock slides my fuel mileage jumped about 6-7 MPG. Even with the alcohol laden fuel I'm getting over 41 MPG with a K&N, Dyno jet kit and Yosh full exhaust. What condition is your air filter in? I know when I went to a stocker my mileage dropped.
 

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Discussion Starter #9
So here we are, opened all 4 carbs from the top, and they all have aftermarket needles. They are adjustable, so I lowered them 1 notch and will test run it for a while, see the outcome, but I don't want to lean it out too much although.....
 
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