Carb tuning questions...

[Jon]

Finally got my vision running, but not well... ?these carbs need some serious tuning. ?It runs ok at idle (half choked) and above 6000 rpm, but inbetween is trouble. ?I really have to coax it up to speed or it will just bog and stall when I open it up. ?I figure the main jets are doing their job (over 6000rpm it runs well), but perhaps the pilot jet is responsible for that lower rpm lagging??
I am in Colorado at 5000 ft. and was hoping someone might know the correct settings for this altitude. ?Jet sizes...etc. ?Ballpark even?
Haven't bought manual yet so I'm at a loss. ?
Of the two screw adjustments on the carbs (one screw near the bottom and another halfway up)... can anyone tell me what is what? ?These carbs don't exactly lend themselves to a backyard mechanic. ?
Thanks!

[Rick G]

H2o  lawyer may be able to give you jet sugestions, he's in mile high country too, you really need a manual . Lucky sell a CD version for little money.

[h2olawyer]

Hi Jon -

Where abouts are you located?  Be nice to get a High Country Vision ride going!  If you're not too far from the Fort Collins area, I'd be happy to get together and help you sort it out.

As for the jets - I'll need to take a look at mine to be sure.  I didn't write them down on my last carb rebuild  ::) so it'll take some doing to get at them.

Mine's running great now.  I know my dealer in Steamboat Springs did the airbox mod and he said they really spent time on the carbs before they sold it to me.  Didn't help much - still suffered from major stumble even the day I bought it.  Just learned to be gentle with the throttle.

[Glyn Pickering]

What carb balancing equipment is recommended for the Visions and how often should it be done?

I've got a set of dial gauges but they don't work well.

Regards

Glyn

[h2olawyer]

Hi Glyn -

You can make a carb balancer (manometer) with some clear plastic tubing, a yardstick, some tape, wire ties and ATF.  Plans for one can be found on Lucky's site in the artwork section.  ( //www.xz550.com/art.html )  Look in the third row from the top, far right side.

I spent about $5.00 US for mine and it works great.

H2o

[Jon]

H20
Thanks for the offer.  I'm in Boulder, so your tuning specs would be spot on!  If you get a chance to check them out I would be very grateful.  Can't wait to get her going well!
If you could tell me your main jet size and perhaps where you've got the other screws positioned, I would love it.
Free tip: The Yamaha dealer in Boulder is a bunch of monkeys.
Thanks
Jon

[h2olawyer]

Jon -

You're just down the road a ways.  Sounds like your Yamaha dealer is like mine.  When I went in for a side cover gasket this spring, the parts guy started looking for XZ550 under Suzuki!  He seemed quite surprised when I told him it is a Yamaha.  The guys that worked there last summer knew what I was talking about by vague description when I'd forget to look up the part # before I went in.  Good help is hard to find.

I can't get to my carbs until Monday but I'll see what jet sizes I can locate then.  I do know that setting both mixture screws at about 4.5 turns open from lightly seated got mine real close.  They're within 1/2 turn of that now.  I've got an extra set of carbs - Thanks Kiawrench! - and will also check them to see if the jetting is the same as mine.

H2o

[h2olawyer]

Jon -

My carbs have 135's for both pilot air jets (the ones on the carb tops). ?Factory manual says 130's for the pilot air jets. ?My front main jet is 122.5 and the rear main is 127.5. ?(behind the 10mm brass plugs) ?If these don't help, I could remove the carbs to get to the pilot jets at the bottom of the carb bodies but that would require a resynch when I reinstall them. ?The factory manual says #60 for the pilots though. ?I'd be happy to do it if you really need the specs but don't want to go to the trouble if you don't need those particular #s..

I'll post what all the jet sizes are on my second set of carbs later today. ?Those came from the southeastern part of the US so they might be different.

Hope this helps.

H2o

Just got out the second set of carbs. ?Somebody really messed with them! ?Found a 120 and 130 in the pilot air jets and a 130 in one main. ?Couldn't remove the other main - the amount of gunk in them is amazing! ?Couldn't get light to the jet to even see it. ?Rust & fuel evap varnish abound. ?Going to let them soak in rubber friendly solvent for a while. ?At least I know I now have a set for some parts. ?Haven't taken them apart to check the floats yet but I am anticipating a major dredging operation in the bowls.

Just one quick thought - do you have the vacuum flapper mod in the airbox?  Early '82s did not have the vacuum operated flapper and it was a dealer retrofit.

[Lucky]

H2O,
there is no reason to re-synq the carbs if your only pulling ot the pilots underneath the carbs.  only if you loosen the braces that hold the 2 carbs together.
--Lucky

[Riche]

Jon

From your first post it sounds like your idle circuits are not clear. Have you cleaned your carbs? if not do so or send them to Lucky or one of the other guys providing the cleaning service. Make sure the off idle holes, above the throttle plate, are clear.

[h2olawyer]

Thanks Lucky -

I was under the impression that when the carbs were removed, they could lose their synch. somewhat.  I decided to check the synch again anyway this evening (went for a ride this afternoon - power seems a little down from last year and exhaust tone is different) so I'll get to those pilot jets then to see if they're different than the No. 60s that were factory installed.  Just need to let things cool down a bit before I pull the carbs.  I believe I remember my dealer saying that the only jets they changed for high altitude were the pilot air jets so I'm assuming that I've still got the 60s for the pilots.

[Rick G]

I've synqed them with  a vacuum guage manifold , a mercury manometer and a home mand manometer that uses ATF. all work ok, but you need to make repeated adjustment  and tap the guages after each adjustmant on the vacuum guages to get a close synq, on the mercury and atf type , don't run it above 2500 rpm or you will suck the mercury or atf right out of the guage!

[Jon]

Thanks H20. ?That really helps me out. ?As soon as I get a chance I'll have her tuned up and let you know how it works out. ?Thanks again. ?We should go for a ride when my bike is ready.
And yes, I do have the vacuum flapper mod.

[h2olawyer]

My pilot jets are 60s. ?I have all sizes for high altitude setup written down and now posted.

front main - 122.5
rear main - 127.5
pilot jets - No. 60 (both)
pilot air jets - 135 (both)

All are as stock except the pilot air jets - the factory setup for lower altitudes is 130. ?Now, if I could get her running as well as she was before I did the carb R&R. ?Oh well, I've got some time to get things right - its not far off.

When I synched mine the first time last summer, I got the homemade ATF manometer hooked up, and proceeded to fog the whole neighborhood with burning ATF ?::) when it all got sucked into one carb - they were really out of synch! ?I didn't have the problem @higher RPMS after they were set close. ?Even ran it @ 5,000 to check them and one side did rise a bit but not even close to getting to the carbs.

Jon - I was thinking the same thing - maybe a trip to Estes Park and over Trail Ridge to Grand Lake for lunch.  One of my favorite rides.  The Peak to Peak Hwy between Boulder & Estes is tons of fun.

H2o

[Jon]

Sounds like a blast, H20.  I'm afraid it'll be a while before my bike is road worthy, but hopefully not too long!

[Henri]

Guys,  I'm riding in Bozeman, MT and have been doing a lot of tinkering w/ carbs to get them tuned for altitude.  We're at around 5000ft.  I'm actually running a bit leaner than H2O.  I've tried his setup -135s in each pilot air jet and 122.5 front main,127.5 rear main.  It seems to still run a bit rich.  I was experiencing a subtle hesitation throughout all revs.  I leaned things down by keeping 135 pilots and going with 120 front main and 122.5 rear main.  It seems to be about as good as it's going to get.  No stumble or hesistation at all.  I think for my bike at this elevation it is the ideal setup.  You might give it a try.  I agree that the problems you described are more related to blockages in the pilon circuit - probably in the group of tiny ports that enter the main ventury right at the butterfly flapper.  Mine were clogged at one time and required the choke to keep her running.  The choke basically bypasses these tiny passages and dumps fuel right into the intake below the flapper.  Anyhow let me know how it turns out for you.

[nvdranger]

I had the exact same problem as Henri with having to keep the choke on to keep it running.  I cleand those very passages (plus the one jet I missed) and she runs great.  Pay close attention to those passages and I recommend using the carb tool you can get from yamaha (i used a welder tip cleaner from any parts store which is basically the same thing).

Ken

[h2olawyer]

Thanks for the input, Henri.

Might go get myself a 120 jet and do some jet swappin' and experimenting in the next few days.

H2o

[h2olawyer]

Today, I tried the 120 front - 122.5 rear jetting Henri is using in Bozeman, Montana.  The elevation there is almost the same as here, (60 miles north of Denver, CO) at about 5,000 ft.  

After I made the jet swap, I found I had a very flat spot in acceleration from 4,500 to 5,000 RPM.  ??? Not the stumble I've had and eliminated in the past but just a very noticeable drop off in performance right at 4,500, and coming back @ 5,000.  I was not experiencing it at all before the jet swap.  Maybe something dislodged and clogged elsewhere in the carb but unlikely as I had the carbs out, did a minor clean & blew out all the passages w/ compressed air & checked synch on Thursday.  Ran good Thursday, Friday and today before the swap.

Played around with the f & r mixture screws and got them as close to correct as possible.  The flat spot remained and is very consistent. It does not matter whether I'm using lots of throttle, lightly rolling it on or anything in between.  No stumble off idle and great power to 4,500 and from 5,000 to redline.  Maybe a little stronger in the 6,000 - 9,000 meat of the powerband than with the larger jets but difficult to tell for sure.

I happened to have the 120 sitting around so that was a no cost test.  I need to go get myself a 125 to try in the rear.  If the flat spot doesn't go away, I'll probably go back to the factory 122.5 / 127.5 setup.

This is not really a question, but more of an observation and possible point for discussion.  It was running very well before I decided to try the jet changes.  I know it runs well on the factory jetting (with 135s for the pilot air jets) but was just curious if I could pull a little more power out of it up here.  I had it running a little better last summer & fall (lifted front tire 1st to 2nd and got very light in front 2nd to 3rd)  8) and with a little more futzing with it, will be running quite smoothly once again.

The bike shops will be closed here Sunday and Monday as usual so I won't be able to get the 125 to try until Tuesday.  The 2 size drop in the rear may be just a bit too much for mine.  Will keep y'all updated.

[Kevin]

I think this is a question on the basic side but here goes.  When doing a carb setup where are the adjustments that I should be concerned with.  I have found the mixture screw at the bottom of the carb right before it goes into the manifold and I know of the synching rod that can also be adjusted.  Are there others that I am not aware that need to also be adjusted?

Kevin
Still workin at it.