Newby and trying not to pull my hair out. Help!!!

I picked up a 82 xj650 maxim a couple weeks ago. Someone had already attempted a bobber project and failed. Most of the parts were in boxes. over the past couple weeks I have been going through it working out the bugs. I got it to run but shitty. I pulled the carbs apart and cleaned and inspected them. everything looks intack and they didnt seem to be too dirty. However I did not soak them. Put them back on with a nice clean tank and fired it up. Fired right up with the choke and idled fine after about 30 seconds. let it warm up and went to take it for a spin. if I peg the throttle it will shut off. if i ease into it it acts like its only running on two cylinders and slowly starts to get better. then while still holding the throttle it will go fine. If i keep it in the upper rpm i can go through all the gears and it runs great. if i let the rpm drop it will start studdering again. I dont know if it makes a difference but i am currently running with the back half(including crossover) of the exhaust off. I have tried it with the four cone filters and with no filters. Any help or ideas would be great.

At this point I am considering pulling the carbs off and soaking each one seperately. I spent several days going through wiring and tightening everything. it was like they put the whole bike together and didnt tighten any bolts. tried to upload a pic but cant get it to work yet.
Thanks

 

You have the typical "pod" problems. You are running lean. The CV carbs on Yamaha XJs don't like the increased airflow pod filters give. Pod filters present challanges , search the site and you will find many opinions both good and bad on the subjuct.

You have several options;
1) re-jet the carbs to account for the increare in airflow. Not a exact science, its a trial and error process.Main and pilot jets will need to be changed.
2) find a stock air box and boots and instal it. Your bike will be easier to tune.

 

Welcome to the forum.

In addition to the direction mlew is pointing you, you'll need to check your valve clearances and clean/rebuild your carbs.

NOT "soak them," as doing so will melt any rubber inside, necessitating a rebuild. The ONLY way to clean the carbs is to fully tear down each one, and a full rebuild will include breaking down the rack. Force spray carb cleaner through each passage is the only way to ensure they are clean, as a soak can only eat away what it can reach. Expect to spend anywhere from 10-20 hours on your first one, and at parts costs can range from $100 on (but it's impossible to know until you're in there).

Once you have the carbs/valves done, you'll still need to tune the carbs by adjusting the pilot mixture screws and syncing the carbs, before it'll run well.

Consider returning the entire intake/exhaust to a stock condition, learning how to tune the bike properly, before modifying it. Otherwise, you won't know if you are tuning for a mod, or troubleshooting due to lack of maintenance.

Finally, how are the brakes? Tires? Is the bike SAFE to drive? For your own safety, please don't go testing a bike that's just been started for the first time by "pegging the throttle." It takes a lot to get a 30 y/o bike roadworthy, and getting it running is only half the battle.

 

No disrespect but I cleaned all 3 sets of carbs on my bikes and did not break down the rack on any of them. If you have bad o-rings in the connecting pipes then you need to break them apart but otherwise it is not necessary. You can get just as deep into them as a group as individually.

Also you can soak them in pine-sol for about 24 hours and it will do a good job of cleaning the crud out. Just blow compressed air through all the passages afterwards to make sure they are clear. It will not hurt the rubber seals and actually rejuvenates the rubber and softens them up. I soak the air duct boots along with the carbs but remove the slides with their diaphragms as i do not want to take any chances on those delicate items. It stands to reason you first remove all jets and floats before soaking them. That is just a given.

 

None taken. Also, you need to break the rack to replace throttle shaft seals, where are a common source of air leaks.

When someone says soak, I always assume a can of carb-dip, which will ruin the seals. I don't have any experience with pine-sol.

I did just see that the OP mentioned soaking each individually. So he's willing to break down the rack. Removing all of the little bits and soaking won't hurt anything. I just wanted to discourage the OP from trying an "easy" way (soak without removing jets, mixture screws, etc) which won't clean the passages adequately. Also, with a 30 y/o bike that has been sitting neglected for who knows how long, I generally err on the side of replacing just about any rubber that I can, so I won't pull out my hair later. Sure it costs a bit more, but is it worth it to save a couple of dollars to have to go back and repeat the process several times?

 

Thanks for all the info. I am no stranger to cleaning carbs. I been building and running muscle cars, drag cars, motocross, etc since I was a kid. However none of them had four carbs. I have no problem tearing them down again and giving them a good soak. I too have never heard the pine-sol thing. Might have to try it. I just know that every set up has its tricks. Im new to dealing with these types of bikes so this is a learing experience also. The bike was on he road about two years ago and that owner rode it about 5k miles in a year. Its in really good shape because it was stored indoors all its life. Just a few little bugs that I need to work out along with some old connectors that like to wiggle loose. Not that i dont believe it but i never would have thought that these carbs were set so particular that giving it a little more air flow (pod filters) would make it run as shitty as it does off idle. I guess anything is possible and I just gotta start checking things off the list. Thanks again. And why cant i post pics.

 

Even after a THOROUGH cleaning, new seals, ,etc... and re-assembly, you will STILL need to do a shim clearance check, then:

1. a bench sync....this will get you to an 'at least it runs' state so that you

2. can do a carb balancing procedure to start dialing it in.

Don't worry--it sounds like a LOT of stuff, but if you just jump in a go slowly and methodically, it is NOT difficult.

Dave F

 

Valve check, carb clean, carb sync, colortune.

And these guys are right.
Return to stock. Intake, exhaust, and all the jets in the carbs. Check for needle shimming.
Then start modding if you so desire

 

thanks again for all the info and thoughts. soaked two of them last night and put them back together this morning. other two are soaking now and hope to get them back together tonight. Atleast I will know they are clean and go from there.

 

Did you break the rack (I'm getting this mental image of carb rack sitting in a can of carb dip, with two sticking out :lol: )?

Did you remove all of the components before soaking, including pilot air screw, emulsion tubes, throttle shaft seals etc?

You didn't mention it, but you might already know, blow out all of the passages with compressed air after any soaking. Carb cleaner is a solvent, which means that it'll break the bond between the contaminant and the surface, but if you let the solvent evaporate, you'll be left with the same contaminant. You need to mechanically remove the solvent+contaminant mix from the passages.

 

WICKIDSIX the picture posting issue is a quirk of the website. You can use a Photobucket account (free) and upload your pics there. Once uploaded to Photobucket just click the 'direct link' option for each photo, then while composing your post here clink on the 'html photo' button and paste in that direct link. I usually resize photos to no bigger than 1200 in either direction so they fit better.

It seems like no one has mentioned this but your exhaust is too wide open. It will effect the mixture and if your valves are out of spec it can be an even bigger factor in messing things up. It doesn't have to be stock but you need something similar to stock, or much bigger jets. Those 4 CV carbs create a very small tolerance to changes in flow. So changes in intake/exhaust will require changes in jetting and it's tricky-just in their nature.

 

Everyone (except ManBot) appears to be talking RIGHT AROUND this very important detail.

You CANNOT get "as deep into" the carbs while they're on the rack as you can dealing with them individually. The throttle shaft seals are trapped; and soaking carbs with them still in there can destroy them.

You should not submerge partially assembled carbs; and if they're still "racked" they aren't far enough apart to be safely soaked.

 

Ahem.....uh-- me too. Here's a copy of the beginning of my first sentence.


>>Even after a THOROUGH cleaning, new seals, ,etc...

See that right there after 'cleaning,"? It says "NEW SEALS".

Dave F

 

It's full blown political season...truth is overrated. Sorry Hog your innocent and 'moi aussi' since I never even broached the subject of proper cleaning, but I didn't dance around his viral headers bleeding and causing fubar.