Jetting for high altitude

[artbone]

I finally got the Vision out on the open road yesterday and I believe I have a jetting problem. The bike ran perfect in Atlanta and in the mountains of N. Carolina and all the way down to sea level. Now I'm at 7000 ft and it seems to be really rich.

When I accelerate to 5000 RPM it starts surging unless I back out of the throttle to about 2/3 then it will continue to accelerate up to about 8500 or 9000. If I hold it wide open a few seconds then close the throttle it picks up speed before starting to slow.

The bike is an '83 all stock with everything hooked up and new plugs.

Do the carbs have to be taken apart to change the jets and does anyone have some specific sizes I might need or a range of sizes?

Also, is there any way to adjust the idle mixture. According to the handbook it's set at the factory but isn't there a plug I can take out and get to the mixture screw on each carb?

Art

[h2olawyer]

I'm currently (slowly) working on a set of '83 carbs for my '82.  I live at 5,000 ft. and consistently ride at 6,000 - 9,000 ft with several yearly trips over 12,000 (Trail Ridge Road).  My 82 uses the stock jetting and works great up to about 10,000 ft.  I've even had it over 14,000 ft. on Mt. Evans (the highest paved road in North America).  So, for my $0.02, the 82 works well from 1,000 ft. to 14,000 ft. using the stock jetting.  I'm anxious to find out how the 83s operate at higher elevations.

The 83 mixture screws are behind a plug and yes, they are adjustable.  I'll see if I can find a diagram.  I know the diagram in the Haynes manual is for 83 carbs.  If someone gets it posted before me, great. 

edit: I just emailed the Yamaha diagram.  Hope it helps along with my convoluted description.

H₂O

[Brian Moffet]

Isn't it the brass plugs shown in this photo of 83 carbs (the ones with holes in them)?

Brian

[h2olawyer]

Them's the ones - thanks for getting a better image, Brian!  the originals wouldn't have the holes unless they've been adjusted at some prior time.

H₂O

[akvision]

Art,

We had similar problems with the "AkV", where  it would bog then surge when the thottle was rolled off.

Check the postings by RHPAW on "Vision Stumble"  and find pages to read and profit from our errors.

Hope this provides insite.

[artbone]

Art,

We had similar problems with the "AkV", where  it would bog then surge when the thottle was rolled off.

Check the postings by RHPAW on "Vision Stumble"  and find pages to read and profit from our errors.

Hope this provides insite.

After reading all that it seems to me that the problem was that he had the flapper door hooked to intake vacuum and it was opening when it should have been closing. And he changed the plugs. Other than that, everything was just like it was when he first encountered the problem. It that correct?

I don't think the door is my problem but I'm going to look to be sure. It might be plugs even though I installed new ones, I've been screwing around with the engine and letting it idle a lot and they could have gotten gas fouled. I haven't balanced the carbs yet so that's the next step.

Should I yank out the little brass plugs that cover the idle screws or do they serve some purpose other than making it a pita to adjust the mixture. Mine have holes just like the ones in the picture and I have a small screwdriver set that I can use to turn them but the screwdriver handles are so small it's hard to get them to turn. I didn't take the screws out when I dipped the carbs because I didn't realize there was anything behind the plugs and there very well could be all kinds of crap in there.

Also, what are the little screws in the back of each carb that have the little rubber boot on each one? Are they some kind of adjustment?

You guys are great. It's so much easier to learn from someone else than to make all the mistakes yourself.

Thanks

Art

[akvision]

Yeah, He had a couple of hoses assbakwardrs.  He says it all works fine now.

The small screws with the spring, washer, 3X1 o-ring is the idle jet screw.

Loads of posting on those too.

[rhpaw]

Yeah, He had a couple of hoses assbakwardrs.  He says it all works fine now.

The small screws with the spring, washer, 3X1 o-ring is the idle jet screw.

Loads of posting on those too.

yeah, I wouldn't want to confuse the issue by bringing our AK bike into the conversation... Basically I wound up going over everything in the air/fuel part of the bike about a dozen times chasing a drivabillity issue above 5k. Eventually it was found to be a misrouted vac line.
Now the bike is damn near perfect. Stock jetting, living at 6000 feet.
It has 82 carbs though.. different monkey, different football.

[h2olawyer]

Actually, the screws with the spring, washer & tiny "O" ring are the idle jet screws on the 82 carbs.  On the 83s, those are the ones behind the plugs.  The only screw I can think of on 83s with the little rubber boot are the carb drains.  I haven't looked at my 83 carbs in months, though.

H₂O

[artbone]

Actually, the screws with the spring, washer & tiny "O" ring are the idle jet screws on the 82 carbs.  On the 83s, those are the ones behind the plugs.  The only screw I can think of on 83s with the little rubber boot are the carb drains.  I haven't looked at my 83 carbs in months, though.

H₂O

I think the screw I'm talking about is #38 on the carb view and the cap is #45. When I tightened mine I looked inside the throat of the carb and it was deforming the venturi so I just backed off it until the venturi wasn't pushed out. The screw is tapered on the end and doesn't have a head, just a slot cut into the outer end. The little rubber cover looks like something you would use to seal off vacuum lines but I guess they put it on there to discourage tinkering. They obviously didn't know the Riders of Vision would be working on these pigs.

Art

[supervision]

   The ones behind the drilled brass plugs, are the low speed ajusters. They are a very strange arrangement of making a 90 degree turn out of the ajustment.  The screw head in the hole, has a large dia fine thread, with a tapered end, that when turnned, allows the spring loaded needle in the carb to adjust. The things are stupid.  I have one, that after removing the plug and large screw, the needle is still frozen in the carb!   The actual needlle, has no threads, it's only spring loaded upward, and is suppose to be free to move, making adjustment possible. Mine were not drilled, I had to drill and pull the plugs. I would seal those plugs, cause the water can get on that fancy screw thread, causeing siezure, of thread.

[Rick G]

I'd toss the stinking '83 carbs and put a set of '82's on it. But thats just my opinion.

[akvision]

I may have a set of 82  rebuilts available after September.

[artbone]

   The ones behind the drilled brass plugs, are the low speed ajusters. They are a very strange arrangement of making a 90 degree turn out of the ajustment.  The screw head in the hole, has a large dia fine thread, with a tapered end, that when turnned, allows the spring loaded needle in the carb to adjust. The things are stupid.  I have one, that after removing the plug and large screw, the needle is still frozen in the carb!   The actual needlle, has no threads, it's only spring loaded upward, and is suppose to be free to move, making adjustment possible. Mine were not drilled, I had to drill and pull the plugs. I would seal those plugs, cause the water can get on that fancy screw thread, causeing siezure, of thread.

SUCCESS!!!

I removed the brass plugs and made sure everything was moving in that recess, Simonized my carbs, set the low speed adjusters, poured in some fuel additive, and took her for a spin. Man, what a difference! It pulls like a freight train now all the way to red line. I think the plugs might still be a problem but it runs so much better I'm just going to ride it a few hundred miles and see how it goes.

For what it's worth, the vacuum on the front carb was much higher meaning it was running on the rear cylinder. As soon as it got close to the same vacuum it sounded like a new motorcycle. It now idles at 1K, starts fast, and returns to idle like it should.

I want to thank everyone who offered suggestions and advice. I probably could have done it without you but it would have been a lot harder and more expensive and taken longer.

Thanks guys,

Art

[Tiger]

...Simonized my carbs

Congratulations, well done...and you waxed your carbs too... :o ;D :D :D :D :D :D OR should that read "SYNCRONIZED"  ;)

             8).......TIGER....... 8)

[h2olawyer]

Great!  We're always glad to keep anyone from reinventing the wheel here.   ;D

I figured giving the carbs a Simonize Shine just meant cleaning them.  Waxing them probably makes them flow more air faster . . ..  ;)

H₂O

[artbone]

...Simonized my carbs

Congratulations, well done...and you waxed your carbs too... :o ;D :D :D :D :D :D OR should that read "SYNCRONIZED"  ;)

             8).......TIGER....... 8)

Just trying for a little style in my writing. That was while I was happy before I discovered an electrical fault. I'll start another thread for that but it looks like I have the dreaded dead stator. I only have 12.5 volts at the batt. at 3K RPM. It just keeps getting better and better.

ARt

[Kevin]

Owning a vision will make a mechanic out of you. And a electrician.

[h2olawyer]

ARt -

If you need any moral support with the stator, let me know.  It's really not a difficult repair, just one that has about the highest price tag for parts.   ::)  Run through the Electrosport fault finding chart to make sure it is the stator.  However, with 12.5V at the battery, that's the most likely suspect.

Have you checked the condition of the main ground?  It is on the inside of the frame up near the steering neck.  Also, make sure the negative cable from the battery has good contact with no corrosion where it is bolted to the engine.  Never hurts to make sure things are well grounded.  There are some R/R faults that may cause a low voltage, but I've yet to hear of any of those as an issue with the Vision.

H₂O

[Rick G]

Just be carefull with the fuel additive , it  will eat the wax right off your carbs! ;D ;D ;D