81 xj650 lean mixture

Hi all my first post on here but been lurking for a couple months. A couple months ago I picked up an 81 xj as a project for $100. It's been sitting for I'd guess 10+yrs (last registered in 98). Iv brought it back after a lot of time and money to a running driving bike and boy have a learned a lot along the way. I'm no stranger to mechanical work as I have a heavily modified street car, snowmobiles, and boats.
So some background as to what Iv done to the bike,
Rebuilt carbs, new jets, orings, springs, needles, shaft seals etc.
New carb to engine flanges
Valve clearance checked and in spec
Removed rust from gas tank with inline filter
New plugs
New used tci
New fuse box
New Mac 4-1 full exhaust
New air filter in stock air box non hi flow
The rest is basically tires, brakes, switches and so on.
So my problem is it seems to be on the lean side from reading the plugs. Iv wet set the float level, and vacuum synced them. 3 turns on the air/fuel jets. I read the thread about recommended jetting for different modifications so I went to 112 main and 41 pilots for the 4-1 exhaust. Plugs are light colored grayish looking. My question is which jet should I change to richen up the entire mixture? What about shimming the needles?
Bike runs pretty good, 37mpg so far around town. It cold starts hard though, full choke it will fire but die right away. I have to use a tad bit of throttle to keep it running then after a minute it will run on it's own but idle very low to the point of almost dying. Iv gone through the plungers and sprayed out all the passages and no improvement since.

On a side note I wasn't expecting to enjoy this bike as much as I am. I have a new outlook on 80s bikes now.

 

http://www.dragstuff.com/techarticles/how-to-read-plugs.html
read this and think about the plugs again. 3.5 turns out on the mixture screw isn't unheard of.
did you poke out the enrichment jet in the bottom of the float bowl?

 

Thanks for the link. It says that the info is only used for Full load acceleration situation though. I'm more concerned with part throttle mixture right now unless the same info can be used in this situation?
Yes I did go through each bowl and clear the enrichment passages and sprayed carb cleaner into the brass pickups on the carbs. They are clear.

 

Picked up an Xj, but WHAT XJ? For most of them, you should be getting around 48-50. If you're getting only around 38, I sure don't think you're running lean. What plugs do you have in it?

 

Title says 81 xj650....
New bp7es at .027"
The bike seems sluggish under 4K like I'll roll into the throttle and I can hear the intake noise and the bike will slowly start to pull and accelerate. I started at 2 turn on the jets and going to 3 helped the low end throttle response so that is also why I'm thinking it's a little lean.

 

seems everything is covered except a running sync, that will make a difference starting and smooth the idle. get it good and warm first.
set the idle after the sync when it's warm

 

find a nice long hill to roll down, throttle closed,listen for popping in the exhaust. sure sign of lean idle mixture

 

Running sync? I assume you mean a running vacuum sync correct? If so I just did it again for the 3rd time with a carbtune pro. They are very close. Once warm it idles great at 1k but cold starting is tricky to keep it running

 

Good idea never thought of that. I'll have to give it a try tomorrow. Although around town I engine brake quite a bit and haven't noticed any cracks or pops

 

I doubt you're running lean if you're only getting 37mpg. Sounds to me like your waaaay rich, and the reason it runs good with the throttle cracked is because now the butterfly valves are open a tiny bit so more AIR can get sucked in.

Methinks your are inadvertently reading the symptoms and signs backward. It is easy to get caught like that.........don't feel bad.

 

Ok so for curiously sake if I wanted richen the entire mixture what would I do?
Also any ideas why cold starting is so difficult?

 

Have you checked the float heights? Have you tried bumping up the idle just a little (recommended is 1050)?

 

I checked all floats via the clear tube method and all were within the 3mm +-1mm spec. I currently have the idle around 1100-1150

 

Alright, you want to keep going with the 'get richer' idea.......I'm going to stay with the 'already too rich' idea.

If you want to richen up the idle mix, turn the screws out more.
If you want to richen up the main jet mixture, you install bigger jets, and/or swap out the needles for a thinner/different contour which will let more fuel flow thr0ugh the main needle jet/emulsion tube.

BUT---if you're ALREADY running rich (seems evident because your mpg is so terrible.....you're dumping fuel through), making it richer is going to start drownings your engine. I think you're borderline flooding things.

Now, if you were really running lean.....you'd be getting mileage pushing toward 60-65mpg.

 

I get that you think I'm too rich, I was purely asking from a knowledge stand point so I know for the future. I'm going to put some more miles on it and see what the plugs look like.

 

Hi 2many!
We are neighbors. If I ever get my carbs back on my bike we should do a bit of riding (but already thinking about winter - the radio said a chance for frost tonight in our neck of the woods).

Anyhow - your bike...
I don't think I saw it mentioned.
Do you still have the factory airbox on it?

Some folks set the idle adjustment (when engine is warmed up) closer to 1200. 50 RPM's isn't diddle when you have the obnoxious parrallex issue of adjusting the knob on one knee and craning your neck to see where the needle is, but make sure you set your idle speed when the engine is at operating temperature.

 

Yeah we're not too far away! I too am thinking about starting to work on my sleds since the temps will be starting to get close to freezing.
Anyway yes I do have the stock air box in place with a new non hi flow filter. This morning it was a bear to start again. Takes a lot to fiddling with the choke and throttle to finally get it to stay running. Maybe my pilots are too big and it's getting too much fuel. Idk I'm new to bikes specially of this era. After all it is older than I am lol

 

Is that a paper style or foam style filter?

I am newish to bikes also - this is my first bike and have had it about 8 years now.
Here's some of what I know:
Reliability and safety should always be first.
These bikes are a dream when dialed in; sometimes the dialing part can make you crazy - they are not forgiving for "close enough". And they aren't keen on their air induction being tampered with (hence the paper vs. foam air filter question).
There are a bunch of helpful intelligent people on this website. Strongly consider all of the responses given and see if you can apply them. Generally when you see "likes" attached to a response it is a nod of agreement from the people who know.
When possible it is best to do 1 change at a time to judge the impact it has on reliability and safety.
Troubles cold starting could be more than a mixture thing - bike and components are 36 years old... clean/ grease/ tighten all electrical connections; check battery voltage drop when cranking; check charging system (battery doesn't charge at idle and if she is weak at cranking then stays weak during startup yada, yada, yada).

How did you clean your carbs and where did you source your rebuild parts?
The accepted norm is going to Church and getting parts from the local website vender (XJ4Ever) - many (me included) have been burned by e-bay/ Amazon/ even on-line Yamaha dealers with delayed deliveries/ wrong parts and poor customer service. Check this out:
http://www.xjbikes.com/forums/threads/in-the-church-of-clean.14692/

Here is another interesting thread:
http://www.xjbikes.com/forums/threads/mac-4-1-exhaust-rejetting-needed.115426/

Finally, being new to the Northwoods, I have learned that some of the deer will actually turn and move off/ away from the road when they hear you coming; others... not so much.

 

At 41 your pilots should be fine, or possibly too lean with the 4-1 exhaust. I have 41 pilots on my otherwise stock configuration.

As hogfiddles says though, it sounds more like you are too rich.

 

It is a paper filter. I'm definitely not ignoring any input from anyone, I'm here to learn as much as I can and appreciate the help.
Iv gone through 90% of the electrical and ignition as I ended up having to track down a no spark issue. Went through connections coils, new plug boots, checked pickup coil, new agm battery and it does charge over 13v when I rev it up. But I do agree it's an old bike and things are likely not as strong as they once were.
I bought a carb rebuild kit from eBay which I later found out is a salvage place not far away. Scrambler cycle I believe it is. Lots of parts were bought from xj4ever like shaft seals and plug caps. I disassembled and used carb and choke cleaner throughout and left them in my parts washer over night. Then sprayed all passages with carb and choke again.

 

whaT is in your parts washer? it may have ruined your throttle shaft seals and fuel rail seals

 

I replaced all seals and orings after I soaked them

 

Ok guys Iv put about 200mi on now. Last 3 fill ups were 42, 50, and 44mpg. Been doing more 60mph hwys and 40-50mph back road cruises.
Here is what my plugs look like. In order from 1-4