82 Maxim 650- given throttle it bogs down and dies

Hey everyone,
Just joined this site today and excited to have some help over here! Been workin on getting my 650 running well for the better part of two months now and think I am close. The carbs have been cleaned thoroughly more than once, all jets are clean and open, new air and fuel filters and spark plugs.
Here is my issue:
The bike will start up fine with or without the choke after the bowls fill up. With the choke on it idles around 4500 to 5000 rpm and without it idles great at around 1800 to 2000. BUT, when i give it throttle, especially coming under load but also just sitting, at around 4500 to 5000 rpms it quits, bogs down, and if I dont let off the throttle it dies.
Like I said, idles fine and sounds better than it has in ages after the carb cleaning and new filter but I dont understand why the throttle kills it. My guess is that it is not getting enough gas, or that there is a vacuum problem along the way somewhere. There is some dryrot on the intake boots but no cracks go all the way through.
Sorry for the novel but I wanted to get as much info out there off the bat as possible!
Any help/thoughts are very much appreciated as this thing is beginning to drive me up the wall!!
Thanks,
John

 

Once you get beyond 2500 rpm's, ... the Engine isn't Idling anymore.
That's MAIN Jets that are letting the revs get on.

Remove the Carbs.
BENCH Sync the Throttle Plates using the thinnest material to start-off with the Throttles CLOSED.

::: Tip :::
Use a Strip of Old 35mm Film Negatives.
Trim off the Sprocket Holes.
Cut the Negative in half, ... lengthwise.
Cut the Strips in half ... lengthwise making four "Feeler Gauges"

Start with #3.
Make 1, 2 & 4 match 3.

Preset the Idle Mixture Screws to:
Exactly 3 Turns Out from Bottom.

Use the opportunity of having the Carbs off to Dress the Manifolds.
Fill Cracks with Sealant
Coat with Black Liquid Electrical Tape.

Seal the Edges of the Manifolds where they contact the Cylinder Head.

Before reinstalling Carbs, ... Set FLOAT Heights to specs.
Clear Tube Method.

 

You have it backwards.

You need to get the valves in spec before you can properly sync the carbs. The floats need to be wet-set to very close tolerances (see the BOOK.)

You need to get your valves in spec, make sure the float levels are absolutely correct and then do a bench sync; followed by a vacuum sync.

THAT WILL FIX YOUR PROBLEM.

OR, you can beat your head against the wall until you finally realize that's what you need to do and do it. Until you do, the bike AIN'T GONNA RUN RIGHT. HONEST. (Been there, seriously. As have most of the folks who've given you the advice you're currently ignoring.)

Get a shop manual and do it right or it won't work. Period.

 

Thanks for the response y'all. I should have been more specific. I did not completely disassemble the carbs to clean them. Trying to avoid that if. I took out all the jets and everything else I could and made sure they were clear and working without messing with the framework of the carbs or anything else.
Im fairly new to doing my own work. What is the clear tube method for setting the floats? And do you need special equipment to do a vacuum sync?
Thanks again.

 

Now you NEED the one thing every XJ Bike Owner should not be without.
A Workshop Manual.

The Genuine YAMAHA Factory Manual is worth treating yourself too.
You get, ... The Bible ... of Maintenance and Repairs.
You also get, ... The Owners Manual for your Bike in the front section.

Buy the Factory Manual.
Keep it in the Bathroom to read while you answer natures call.
Eventually, you'll gain more familiarity with the details presented in Categories and Systems.
From how to change a Flat ... to ... How to adjust your Valves.
Every time you go to the Bathroom you'll know more about fixing and tuning-up your bike because the material is interesting and easy to read and understand.

Before long, you won't have to ask questions in the Forum.
You'll be one of the guys who can provide a correct answer.

People will be thanking you and commenting to others that:
"You're a guy who has his shidt together and really knows his shidt about these bikes!"

 

The answers to both of your questions can easily be found on this site.

The "clear tube method" for setting and verifying float levels has been discussed and illustrated ad infinitum; look in "XJ FAQ Suggestions" for Schmuckaholic's collection of PDF writeups, there's a really good article there. It involves using a piece of clear tubing attached to each carbs' drain in turn, to "read" the level at which the floats are stopping fuel flow. That level is a very precise adjustment, the range is 3mm. The procedure is covered in the manuals, but not illustrated all that well.

You do need a special tool to do your vac sync; but that tool can be as simple as a 6' length of ATF-filled clear vinyl tubing zip-tied in a big loop to a yardstick. At the other end of the spectrum is an actual 4-stick carb sync tool which generally run around $100. In between the tube I mentioned and a CarbTune Pro are two baby bottles w/tubing, a single vacuum gauge, a pair of vacuum gauges, a "gang" of 4 vacuum gauges-- the more elaborate the manometer, the easier it gets. The objective is to compare the vacuum signals of each cylinder and adjust until they match. This can be accomplished in any number of ways.

Rick is right. You need a shop manual. Read it, study it. The carb service you performed sounds like a "basic" service; as long as there aren't other issues (like bad throttle shaft seals) then it's a good start.

Now comes the "fine adjustment" part. You'll need a book + this site to get it right.

Meanwhile, go check your valve clearances. Here's how: http://xjbikes.com/Forums/viewtopic/t=14827.html

 

Had this exact problem on my bike a few years back. I douched the carbs 3 times and this problem wouldn't leave me alone. Turned out there were these tiny little....breather holes?, not sure without looking at it, in the bottom of the float bowls that weren't cleared out. I went through half a can of carb cleaner cleaning out those tiny little things, but that was the issue.

 

Thanks for all the help y'all...still trying everything before having to sync the valves. Ive adjusted the float levels to specs...The guy who had it before me put them in UPSIDE down. That has helped a little but I am still having the same problem: dies when coming under load with throttle. I checked the spark plugs and its running very lean.

Something else to mention. The throttle needles are very far down into the emulsion jets, I had to adjust them to make them at the same level. When i first checked the throttle needles #2 and 3 were "shorter" than the two on the outside so I adjusted them to the outside ones. They now stick out of the slide just far enough to expose a small ridge. I am thinking that maybe they are now too far down into the jets and not allowing enough fuel to get out when the bike is under load and throttle.

Any ideas? I plan to sync the valves or have it done if all else fails. It is still idling better than ever and will rev slightly higher than before but still cuts out when it comes under load and starts to move.

Thanks again for all the help everyone! It was 65 degrees today here and it was killin me not to be out there. and I will definitely check the "breather holes" or whatever they are XJYAMAHA

 

and ive ordered the manual so hopefully that will be in soon!

 

You have it backwards. You don't "sync" the valves; you make sure the clearances are in spec. And you do it BEFORE trying to adjust the carbs. How to is here: http://xjbikes.com/Forums/viewtopic/t=14827.html

You need to get the valves in spec before you can properly sync the carbs. The floats need to be wet-set to very close tolerances (see the BOOK.) Did you wet-set them individually, or dry-set them?

You need to get your valves in spec, and if the float levels are absolutely correct then do a bench sync; followed by a running vacuum sync.

IN ORDER.

THAT WILL FIX YOUR PROBLEM, assuming you did a thorough job on the carbs to begin with.

OR, you can beat your head against the wall until you finally realize that's what you need to do and do it. Until you do, the bike AIN'T GONNA RUN RIGHT. HONEST. (Been there, seriously. As have most of the folks who've given you the advice you're currently ignoring.)

 

Sounds like you really need to listen to BigFitz and do the things mentioned IN ORDER and you won't have your problem anymore.