Altitude and Idle

[feederbb]

I apologize if this was covered in another post but will ask anyway, does altitude effect the carb adjustment/jetting/idle mixture, etc, and how do I go about correcting issues caused by it?  I don't mean to sound ignorant because I know it does I'm sure to some extent but want to direct my attention where it's needed.  To make a long story even longer, I moved from St George Utah to Mooresville NC.  I originally bought My 90 from a guy that lived in Flagstaff AZ which I think is around 5-6K ft, in Utah I was around 3, and now here around 800.  The bike was running fine when I loaded it up and after the trip here, it seems to not want to idle but runs "good" once in motion.  Sometimes it even idles "fair" although very low rpm but if it's a long red light it will eventually feel like it loads up and sputters out.  I've never had the carbs off or adjusted in the 3 yrs I've owned the bike and it seems to have run good with the exception of some post winter clean out a couple of times.  I'm also not sure if the carbs were re-jetted for the high altitude where the bike originally came from.  While were at the carb questions would it make a difference in adjustment and such with the 93 octane non ethanol fuel that's available here?  Thanks for the info anyone would like to share.  Kevin

[FJmonkey]

At higher altitudes your carbs are getting less O2. If re-jetted for higher levels, at lower levels the carbs will be rich. However, not having any experience with setting carbs for higher altitudes I will let others chime in. I run from 2000 feet at home down to sea level as well as up to 8000 feet to the ski resorts up in the hills with no issues. So I am not sure how much altitude will cause problems. Maybe its time to borrow a carb sync tool and make sure they are balanced. If that does not help then a good cleaning might be in order.

[Dads_FJ]

I apologize if this was covered in another post but will ask anyway, does altitude effect the carb adjustment/jetting/idle mixture, etc, and how do I go about correcting issues caused by it?  I don't mean to sound ignorant because I know it does I'm sure to some extent but want to direct my attention where it's needed.  To make a long story even longer, I moved from St George Utah to Mooresville NC.  I originally bought My 90 from a guy that lived in Flagstaff AZ which I think is around 5-6K ft, in Utah I was around 3, and now here around 800.  The bike was running fine when I loaded it up and after the trip here, it seems to not want to idle but runs "good" once in motion.  Sometimes it even idles "fair" although very low rpm but if it's a long red light it will eventually feel like it loads up and sputters out.  I've never had the carbs off or adjusted in the 3 yrs I've owned the bike and it seems to have run good with the exception of some post winter clean out a couple of times.  I'm also not sure if the carbs were re-jetted for the high altitude where the bike originally came from.  While were at the carb questions would it make a difference in adjustment and such with the 93 octane non ethanol fuel that's available here?  Thanks for the info anyone would like to share.  Kevin

Ethanol additive was created to 'Oxygenate' the fuel, which has an effect of leaning.  So if your bike was running good at higher altitudes then that isn't helping anything when riding in lower altitudes.  Sounds like a minor rejet (if there is such a thing!) is in order.  Have you noticed a drop in fuel mileage?  I would suspect so...  If it were my bike I would remove the carbs and see what size pilot and main jets are installed and get back with us.  my .02

[Alf]

Hi!

I copy from my web, CBX mods section

Last step in my search of the perfect carburetion set up: I observed that when the altitude was high, the performance in my bike was less, more between 6-8.000 rpm. When reaching 1.500 m. above the sea (only a question of 20 kms riding on Tenerife mountainous island) the hole was so pronounced that it was even difficult to pass above 8.000 rpm. again during hard acceleration

My bike was clearly running in its fringe area, so, at difference from my FJ 1200, very tolerant with different carb combos, I had to work to fine-tuning the carburetion set up

Typically the Japanese motorcycles can function with minor modifications without any noticeable flaws at air/fuel ratios ranging from 14:1 to 11:1. Adjustments in carburettor jetting that fall at either end of this range is referred to as FRINGE JETTING

Fringe jetting is responsible for the common myth that performance jetting must constantly be altered for normal temperature and/or differences in altitude.

If a machine is operating in the rich fringe jetting range, (let say an air/fuel ratio about 11:1 at the sea level at 20ºC), it is likely that a difference of 800 m. elevation and + 20ºC could change the air/fuel ratio to perhaps 10.5:1 thus causing slight carburetion problems during hard acceleration. The same thing can happen on the other end of the scale, although is not as common

So I adjusted the needle to the next 1/2 step learner position, simply by moving the needle e-clip to the next learner groove position and then placing the Dynojet adjusting washer beneath e-clip.

The result is an spectacular flat horsepower delivery through all the rpm range, without dead steps, flat stops or any other form of hesitation. There is immediate acceleration directly from your right hand to the rear wheel, at any kind of throttle aperture or any rpm.
My FJ1200 is more tolerant with jetting/needle combos, but until I got the perfect CBX carb set up has been one year of fighting. After many different times of dismantling my carbs, and a lot of "on the road" tests, it was a case of two steps forward, one step back ! Now, I've got the perfect Dynojet set-up, so other CBX owners (and of course myself) can extract a lot of power and driveability safely, out of their own bikes.

I've tested 4 different sets of main jets, 4 different positions for needles and 2 different needles. Good job! ;-)

I hope this helps

[movenon]

At higher altitudes your carbs are getting less O2. If re-jetted for higher levels, at lower levels the carbs will be rich.

Good morning    I think higher altitude = less O2, so if jetted for high altitude the jetting would be less (leaner). At lower levels I think you need to go richer. Rule of thumb use to be 1 jet size for about every 2000 feet. That's why mark gets about 10% more power than I do at 4000 feet at least on paper (more hot air and gas ).

I would not go pulling carbs yet. First I would probably inspect the air filter, set the idle to 1150, do a blip test and adj. the idle air fuel mixture screws, check the carb sync.. And run it for a while. If it's still a problem then you might have to pull the carbs and take a look.

Just a thought about the non ethanol fuel. I use to run it most of the time locally here,  as much as a dislike it I have since decided to just run the ethanol fuel.

My theory is standard gas is good but can leave deposits, ethanol fuel contains 10% alcohol which is a solvent that can "clean" deposits in the fuel system. Mixing it back and forth might not be the best for the carbs ? Not that I have had a problem, just a thought.

Down side of ethanol laced fuel is that the alcohol is a water magnet (especially if stored in a vented tank), the solvent property's of ethanol are not kind to old rubber. Ethanol fuel is not recommended for storage beyond 3 months by some accounts. That's in an air tight environment. Just can't win.......  
I now run "Star Tron" fuel additive most of the time. I keep a bottle of it in my tank bag. http://mystarbrite.com/startron//content/view/12/34/lang,en/ It is sold at most Wally worlds sometimes in the boat section. I have been using it for 3 years now with no problems. I store my bike and mower etc. for at least 4 to 5 months a year. During the winter if I am here I try to start and run the bike in the garage until it warms up a few times. Keep the fuel tank as full as I can.

George

[Dads_FJ]

please ignore anything wrote!  I should know better than to post so early in the morning!

[Pat Conlon]

Yep, George's advice is (once again) good.

The type of carb the FJ uses is called 'Constant Velocity' (CV). This type of carb design utilizes a slide which, based on throttle plate opening (and thus the velocity of airflow thru the carb) raises and lowers the jet needle (that is attached to the bottom of the slide) Twist your right wrist and the throttle plate opens, air velocity increases, the slide reacts and raises the jet needle which lets in more fuel, keeping your air/fuel mixture correct.

The beauty of this type of carb design and why it's so popular for street bikes, is that it automatically compensates for air density as density affects velocity and velocity affects (via the slide) the jet needle position.
This is for the time the bike runs on the needle, prolly 70-80% of the time on a street bike.
The other 20% of the time your bike is running it's either 1) at idle to 2500 rpm on the pilot jets and idle air mixture jets...or 2) WFO on the main jets
There may be where you need adjustment, either the 1) pilot jets, idle air mixture jets and/or 2) main jets....you should be fine on the needles, which again is 70-80% of the time.

So George's advice is spot on, before you worry about jets, clean and balance your carbs and adjust your air idle jets via blip test. While your cleaning your carbs, note the size of your pilot jets and main jets while you have them out.
That will give you a starting point for jet changes if you need to go down that road....

Or....if you just want to be done with it..do it all at once, order new pilot jets and main jets and replace them while you have your carbs apart. For 800' elevation I suggest #40 pilot jets and 117.5 main jets. They are very inexpensive from RPM.

Or...just send your carbs to Randy and he will clean them (ultrasonic) and jet them, and balance them for you.

Cheers Pat

[feederbb]

Thank you once again gentlemen, thanks.  I know which way I must head in my quest for a smooth running (and Idling) FJ.  Hopefully I will have the time between my home purchase and living out of boxes to find my tools and fix the 90 before it gets too cold to ride.  I'm sure there will be at least one of you who will chime in that there is no such thing as too cold but I guess I'm not what I used to be when I HAD NO CHOICE and rode no matter what the weather.  Unfortunately with some minor automobile problems during and after the move I found it more time consuming to find proper tools than to actually do the repair itself, hopefully this will not be the case with the bike.  Happy trails and send me a message if your ever out this way.  I know it's a slow ride but the Blue Ridge Parkway is spectacular this time of year!

[andyb]

It's also colder than it was, which can alter how you're running.  And did the bike sit for any real length of time because you were, y`know, busy with moving?

Start with clean carbs always, before changing things too much.  Yes, it's more work, but you're more likely to get things exactly right.   If the act of moving and sitting didn't get things plugged a bit (which would make you leaner, not richer.. a plug check will tell you if you want absolute confirmation), then a couple twists on the mix screws should get you a nicer idle.

Will also point out that humidity has some effect, in addition to the elevation and temperature.  And then there's the part people forget about, the fuel quality itself.  I know when I get fuel in certain places, like when I'm on a long road trip, the machine acts noticably different.  And usually better, frankly.  Seems fuel around St Louis is much better than the fuel in northern IL.  Not that I'm bitter.  @!#$@#$

[feederbb]

Wanted to add a little side note on the whole carb issue.  Driving around the area I found a "performance motorcycle shop".  Found them online and figured I'd be lazy (and not UNPACK my tools) and if they could get her going for a hundred or so (figuring $75+ an hr labor) I'd let someone else do it.  This guy who owns the shop is a "record holder" in some motorcycle classes (1/4 mile and top speed stuff), and I stressed in the email as well as on the phone, that it was probably beneath their skill level but wondered if they would be interested?  Well long story short they would work on it but estimated around $600 plus to clean and sync. the carbs.  Well, good thing my escrow is supposed to close on the house in a couple of weeks because I can definitely wait that long to find my tools and do it myself.  I enjoy working on it and learning new skills and this was that little voice, once again, telling me, DON'T BE FU...N LAZY!  Of course I had to hear his dissertation on how the manifolds were probably old and rotten, etc, etc, etc.  I wonder if they were going to draw straws in the shop for that fix?  Maybe I'm so far out of the loop and used to doing stuff myself that it's a "reasonable" price?     Thanks again guys.  Kevin

[racerrad8]

I can sell you a brand new set of carbs and intake manifolds for less than that...

That is much too expensive. I rebuild carbs for $135.00 plus parts and they are bench synced when you get them back. When I get them apart if the cost of labor & parts comes close to or exceeds new then new is the way to go.

Randy - RPM

[movenon]

Randy is a true gentleman and a lot more polite than me. They are screwing you....... I would estimate by the time they get done with you you will be into it for a lot more than 600.00... Just my opinion.

Have Randy do them or buy a new set of carbs from him. Or live with it until you can pull the carbs and do it yourself.

If you buy a new set from Randy you could probably sell your old set to defray some expenses....
Manifolds cracking.... possably but I bet not. If you do the carbs yourself or get new ones I would recommend you replace the O rings that go between the manifolds and the head while things are disassembled and you can inspect the manifolds then. Cheap and easy to do.

Call or PM Randy for the cost of new carbs, you might be surprised. Are there any members in the area of your new diggs that might give you a hand ?
George

[Pat Conlon]

Run away. Run away fast. Delete their e-mail address. They are not your friends.

Get settled. Unpack your tools. Pull off your carbs, box 'em up, and send them to Randy.

Plug and play.

[rktmanfj]

If you're not going to DIY, send 'em to Randy.

Here's what he did with a set I sent him:

http://www.fjowners.com/index.php?topic=10053.0

[feederbb]

Rest assured, I would NOT pay someone $600 to work on my carbs. I just thought I'd offer my experience to give others the incentive to do "on their own".  There's always someone out there ready to stick it to you if your feeling a bit intimidated or lazy.  I know most others on this site enjoy their FJ and treat it much like a family member and you know that guy who's ready to ream you won't treat it with loving care like you would!  This guy works on high dollar drag bikes and customs for people with money to burn and to him, my "old FJ" is just some beater from the old days, certainly nothing special.  It's getting cold here now and riding isn't as desirable, at least to me, so I'll bide my time, wait and unpack and if I get overwhelmed by the carbs, I'll send them off to those more knowledgable and know my money went to someone in the family not just some guy wanting to make a buck at my expence.  I appreciate everyone on here who I am able to gain info and moral support from!  You guys are the best.  Kevin