About to give up on 83 XJ750

Hey all, I have an 83 XJ750 that I bought about 2 years ago now. It sort of ran OK for the past 2 summers. What I mean by that is that it ran, took a little to start it up and once it did run it was always very spuddery. I cleaned the crap out of the carbs 4 times. Then late last summer I found parts to finally rebuild the carbs. I did everything right, replaced needles, seats, gaskets, floats, washers etc...

After I did that it would barely run if at all. I took the carbs back out, looked them over making sure all parts moved freely etc, and that there were no leaks.

I really like the bike and got so upset with it that I actually threw it in my shed for the winter and had the "I don't give a crap" attitude. I feel bad now about that. I am wondering if ANYBODY who knows even a little bit more about carbs than I do (I don't really know anything) that lives near St. Paul Park, MN that would be willing to hook up with me and check out the bike sometime here in the spring after all the arctic MN ice melts?

I have no friends that know anything and all repair shops want to rob me blind. I am not afraid to invest some money in it but at this point, I am about ready to just throw it away ya know.

 

Well, i have a 1983 XJ750 Maxim. I bought it from a guy i worked with, and his uncle had the bike before him. the story is the carbs were rebuilt twice with new stuff. When he sold it to me, he told me he wanted to take it to a small shop down by us and have the carbs synchronized. it was going to cost $65. (This is Ormond Beach Florida, a few miles north of Daytona Beach).

I happen to have a carb synchronizer or "carb stick" as they call them. It uses mercury and you adjust the carbs till they all pull the same level of mercury. One carb was so far out that the bike was literally running on 3 cylinders and it would pop and sputter. There is a "pilot jet adjustment" and some folks say 1.5 turns some say 2 turns, well mine are at 2.5 turns and maybe this summer i'll tweek some more and put them at 3 turns. These pilot jets seem to make the bike idle. Getting all four carbs in sync makes the bike run smooth. There is a tool you need to slide into the engine which blocks a vacuum passage that interconnects all four intake ports.

I would think this is what your bike needs, each carb is running ok, but you just need to get the pilots right and all carbs in sync.

I'm sure there is a discussion on this website about this topic, search for "carb synchronization"

 

pull the carbs and do a bench sync. there are some very good articles on here about that. Also, check those pilot jets. I'd start at 2.5 turns and go from there. After the bench sync, maybe get a color tune plug to get that final touch on there. If those carbs are too far out of sync, the bike won't run. I had that same issue on my 85 x. Also, play with the idle adjustment. After the carbs are off, take a peek at it. One more thing that MIGHT be part of the issue would be float level, but I'd leave them alone until you positively rule out all else. Start taking notes too, keeping a log if you will. I don't know that winter is the best time to do this accurately, but I could be mistaken

 

Digie, give Rick-O-Matic a shout. With his postings, you can put those carbs at parade rest and rebuild them. Or, if you find you've not the knack, you can hook up with him and ship your rack to him. I expect you should first try to do it yourself as shipping charges are getting silly. Good luck and don't throw in the towel on that XJ, they are a rip-snortin good time (and no chain to futz with either!).

 

The post is in - - - "XJ FAQ Suggestions"
Titled- - - - - - - - "Clean your own carbs" old school method by: Rick

Tons of info and details, but I'd like you to try something;
Since your carbs are "clean" and "rebuilt", get a regular, cheap $2 welder's wire brush, saw it in half and remove some bristles. Straighten the "U" out and make sure it is strong and won't break. (your tool)
Your going to carefully run it thru 12 holes delicately to verify that crud is not there. This is not a hack job. Chase with carb cleaner.
4 jets in the float bowls an inch down !!! Tricky
4 emulsion tubes AND the little side vent (16 holes!)
4 pilot jets next to the HUGE main jets
then blast all passages clean and re-assemble.

Then bench sync. All butterflies need to be equal. look it up.

3 turns out on the "pilot" to start, or 4, it'll run rich--cold motor

I built a "manometer" 4 tube and it works great to get the final sync dead on level. I can idle at 900 RPM, and pull thru grass at 500 without a miss!

To find your "problem child" right now? run your bike the best you can and spray water on the header pipes--the cold one is the bad one !!!!!!

I still need a color-tune ! Hope this helps you

 

Only cleaned them 4 times? You still have a few more times to go. I must have cleaned mine about 16 times before I got it to idle pretty well.

 

Don't give up!

It will take time and patience, but you can fix this bike. There is great advice and clear step-by-step instructions that have been posted on these pages that can help you through just about anything you need to do. Plus, the folks here are very good about giving quick clear answers if you run into troubles.

I have never been mechanically inclined, but the help I have found here encouraged me to turn a non-running '82 Seca 750 into a great ride. Plus I have the satisfaction of knowing I did it myself.

Start by doing a forum search on carb cleaning and bench syncing. Then pull those carbs and get intimate with them. Take your time and be ready to do things more than once (at least I had to do them more than once). It won't cost much more than some carb cleaner and your time. And it will be time well spent.

 

I'll tell ya what, I wish more people were as cool as you guys around here. Everybody I know rides rockets and I am just not into those. I mean they are fun and all but I don't like how uncomfortable they are. I have ridden a few Harley's and those rock but I swear the seat on my XJ is the most comfortable there is, not to mention I love how my gears change like butter. I will give it a go again once the weather warms up. Thanks for the back...

 

8O

Most of us really love our XJs. I think you're all alone on that one though.

 

figure this is a good enough thread to make my first post

I'm in MN (bloomington) and could give you a hand once the weather warms up a little bit.

I have an 83 that i just picked up for $100, so i'm gonna go through it, get re-aquainted with my synch tool (been spoiled by EFI, making changes with my laptop), and then we can whip your bike back into shape for riding season.