1982 XJ650R Project 95% Complete. Need Help With Carb Issue

It is 95% done!

I ended prepping and clear coating the silver tank on my own. My brother finished it off with an automotive clearshield that gave it a nice gloss and a lot of paint protection. It drives great after fixer an issue that I had with the shifter. However, it runs somewhat poor.

We have the jetting right with the pods (spark plug readings look fine), but I believe the carburetor throttle springs seem to not return the throttle valves to a complete close. The engine is idling very high. It returns to a normal idle when I press down on the throttle valve adjustment screws. This is what leads me to believe that it is a return spring issue.

We were also able to sync carb #1, 2, and 4, but #3 is reading very high, almost like it has a vacuum leak. We tested for it but could not find anything. I am kind of lost on this one, so any help is appreciated!

The only other issue is that the pads seem to be wearing unevenly, and the rear brake needs some adjustments. Otherwise, it is complete! What a fun project it has been!

Here is a list of customizations and aftermarket parts!:

• Completely overhauled electrical system with mo.unit control and RFID ignition
• Custom seat with solenoid latch. Opens with a push button when ignition is on.
• Speedometer/choke, signal, and license plate brackets were made. They are kind of rough, but I had a lot of fun learning how to make them.
• Acewell 2853 digital tach/speedo.
• 13" big mouth slip-on mufflers. I went as short as I could because I didn't want to make a bracket to secure a longer muffler, but I think a longer muffler would look better. These are surprisingly quiet though.
• Cheap off-road tires. I like the look that they give the bike. They ride much better than I thought they would, but I will swap them out for a more practical road tire later on.
• Custom stainless/braided front brake lines from HEL Performance.
• Renthal ultra-lo handle bars with domino throttle, grips, and clutch. Grimeca brake master cylinder. Motone push button switches (4 buttons total that control l/r indicators, horn, headlight hi/lo/on/off, and start/stop. Mo.unit is programmable to work with a 4 button setup, instead of 5).
• There was a dent in the tank and a failed repair that left screw holes. They were filled with a tig welder, but it left pin holes, so a tank sealer had to be added. I think the unfinished look being clear coated makes it kind of cool!

Let me know what you think!

 

I've seen this a few times on the forum, usually ends up being that the carb bodies were not assembled correctly when they were put back together. What happens then is one butterfly is out of adjustment and it will hold the others open resulting in a high idle (as evident by lower idle when applying pressure the adjusting screw down) and also having one cylinder out of range when balancing.

I can't find the thread(s) explaining the procedure to remedy this but I'm thinking one of the carb guys will jump in on this. I've never had the issue but I've seen this three or four times on here. Pull the carbs and look at the balance adjustments across the whole rack, I suspect you'll see something out of whack.

Bike is looking good considering what you started with! Always good to finish someone else hackjob and get it back on the road

 

Here is what I would do myself. Split the rack, keeping springs assembled to the shafts. Loosen the screws on a butterfly a little so the plate can move. Snap it open and closed a few times so that the plate will seat nicely in the cavity. Tighten the screws. Do all four and then reassemble the rack. Check and adjust the bench sync of each carb.

 

Thanks for the input! I will give that a try. Hoping one of the carb guys can jump on here too, as I am lost! It has been a fun project though and it is nice to see it almost complete.

 

I will give this a try! Thank you for the input.

 

He can do that without breaing the rack apart.

@XJ650SECATAY , Did you bench synch the carbs?
Are you synching #1 to #2, and then #4 to #3, and then the two pairs to each other?
#3 is the master, and is only controlled by the idle speed adjustment knob.

 

It is far easier to do if the shafts are not linked together. Linked shafts can prevent the full closure of a butterfly in one or more carbs, negating the effect needed to seat each plate before tightening. Each throttle shaft needs to move freely and independent of the others. My opinion from experience doing it both ways.
Of course it can also be done without breaking the rack but it means adjusting all the throttle adjustment screws so that only the single carb you are working on will have the needed contact of butterfly plate to body. Tighten butterfly screws and repeat.

 

We did sync the carbs. However, we started with #1 to #2, but could only sync #4 to #1 and #2 because we were not able to sync #3. #3 was reading off the charts with our sync tool and we couldn't bring it down no matter what we tried. I have to buy liquid refills for our sync tool because #3 was pulling the liquid into the cylinder. The idle speed knob was not even engaged in this case, but #3 was still too high to read. That's what lead us to believe that there was a vacuum leak somewhere, but we couldn't find one.

Thanks for this info too. I still have not had time to pull them, but this info will help a bunch!

 

This is all good info. I'm having a similar issue where when I try and do a running synch on the bike it will idle high around 3-4K rpm and just hang up there and I'll have to kill the engine. I wasn't sure where to start and this thread has given me some focus areas to start with so I'm not just pulling the carbs fully apart over and over. I went through the Church of Clean religiously last winter and I could have eaten off of the carbs. So I suspect its mechanical and not a cleanliness issue.

 

Let me know if any of this advice works for you. It's funny, because I have been driving it around town pretty regularly now, but I have not performed any of these fixes yet. It runs and drives awesome until it, intermittently, has this high idle issue. I will put it into gear and slowly let out the clutch and it will bring the RPM's back to a normal level. I thought, for sure, that it was a carb issue as well, but engaging the clutch to bring back to normal RPM's makes me think it could be something else.

Anyone have any ideas?

 

I have cured the same issue by tweaking the mixture screws richer and another sync.

 

I'll let you know how it goes. I haven't had a chance to ride it yet. I've got an oil leak that I need to fix that I suspect is coming from the oil pan. Need to fix that first so I can stop smoking up the garage while I'm trying to sync my carbs. I've got the mixture screws at 2.5 turns out from the bottom and the engine runs decent when starting. Just got to sort out the idle and sync issues.