Carb / Timing Question????????????

[The Lorax]

I have a question for those that know more than me....I have a 79 F model, recently rebuilt engine...runs strong. the vacuum advance line is run to the wrong place, it goeth to the #2 Boot and not the carb....the problem is, the bike runs better with the line in the wrong place. now for the question, how far retarded is my timing for it to run this way? I figure that the boot puts more vacuum on the line than the carb does because it idles higher and smoother with the vacuum line attached to the boot. If I can get a baseline as to how far I need to move it, I can tweek it from there. thanks much in advance gentlemen, I know some wise fellow will be able to get me in the ballpark.

[GNEPIG]

.. do you have any vacuum at the tube on the carb at all? it could be pluged. i'm not completely sure but i dont think that there is more vacuum at the intake tube. the difference between the two is the carb vac tube is metered for a smoother draw on your vac canister[so it doesnt jump around from the intake pulses].

[mro]

Hi Mr Lorax,

First make sure vac advance is moving freely.
Put vac hose where it belongs on No. 2 carb body.
Set idle at manageable level.
Sync carbs.
------------------------
then set fuel/air screw (in tech tips)
re-sync carbs agin


mro

[The Lorax]

Thank you sirs, I will check those things, to be honest, I have'nt fooled around with the advance at all...I've not noticed it broken, so I saw no real need to fix it...just a minor little nagging thing I know isn't right and I would like to make right. Thank you again gentlemen for your promt and expeditious response to my querey.

[randy]

Lorax,

When you moved the vacuum line to the #2 carb nipple, did you also plug the intake boot nipple? If not, you'll never get it right. There's not much play in the timing plate, so it can't be too far out, but you will need a timing light to verify dynamic timing.

As an interim check, without a timing light, you can check static timing by rotating the plate, line up the "F" mark with the pointer then look through the small hole in the plate (there are three holes) and you will be able to see the reluctor line up with the pickup mark. If you don't see it, rotate 180 and check again.

[Pat Kelly]

If you hold #1 plugwire with the bike running (even better in the rain) and blink every time you get shocked, you should be able to look at the timeing and adjust as needed

[The Lorax]

Answers to Questions...Yes, I plugged the line port on the boot. as to holding on to the wire while running...instead of waiting for rain and subsequently being chilly cold...Brrr... couldn't I just lick my fingers before I grab the wire? I did ride it to work today, It was approximately 52 degrees F when I left the house...Ran REAL Good...Makes me suspect that my mixture is a little fat. I have some stuff coming from "motorcyclecars.com" when it gets here, I will get the mix set, set the timing, and sync the carbs....no, I don't have a set of gauges as of yet, but I expect to get a set soon. I am actually suprised that the bike runs as well as it does, I bought the carbs out of a bone yard...they're off an '80 model...I put them on the bike, put gas in it and fired it up....well, after alot of other non-carb related work. you know, the basic stuff, clutch, tires, battery, clutch cable, throttle cable, plugging several holes in the tank, 300 miles later...complete engine / trans teardown, rebuild....you know, minor stuff. oops, looks as if I've gone and got all wordy and such again so, now I'm done..........................................for now.

[DiverRay]

The '80 carbs are set to run a little leaner than the '79. They also have a different needle and seat, and the jetting is different. Make sure you look at the specs for an '80 when you do the carbs.
Ray

[GNEPIG]

.. there are two different sets of carbs for 1980 also. one set is just like the 81 and 82 carbs, the other is a bastard set used only part of 1980, it's kind of a mix of old and new.

[The Lorax]

How nice, a bastard set of carbs. is there an easy way to tell them apart? I bought mine from a boneyard close to my home, if I can figure out which ones I've got, it will make them easier to tune.........I think

[TopCatGr58]

Hey Lorax,

The trick 80 carbs are ones that still have the fuel tunnel between the main and pilot jet towers. They will require the larger main jets(~137.5), and the pilot jet tower PLUGS in place!

The regular 80-81 carbs don't have that little tunnel between the main/pilot jet towers, and use the smaller 110-120 mains, and the pilot tower is NOT to be plugged!
Good Luck.
T.C.

[The Lorax]

Thank you very much, I will check that out. I am presently waiting on a carb rebuild kit from motorcyclecarbs.com...Need the mix screw in the kit. when it comes, I will yank the carbs and verify what is in there. Once again, thanks for the info...

[GNEPIG]

.. the only way i can tell a difference between the two from the outside, is the bastard set has the old drain plugs, and the newer set has a drain screw. in the picture, bastard carbs on the left, newer carbs on the right. if you remove the float bowl from the carb on the left, you should find a rubber plug over the idle tube. newer carbs no plugs. both of these sets of carbs has the chromed steel top/caps

if you bought a set from the junk yard, then it's posible you dont have either one of these sets of carbs; you could have the old set with the three holes in the ventury cast aluminum top/caps and the drain plug float bowls.
show us a picture and someone will tell you.

[The Lorax]

My carbs are looking very much like the ones on the left, with just a drain plug.....I don't know, 11mm wrench maybe. It has been a little while since I had them off the bike. however, I recieved my rebuild kit in the mail today, so I will be tearing them off very soon now. I need to get the Idle mixture screw out...(buggered up the slot). and my headers need re-Painted, has anyone else had issue with the paint on the Jardine 4-1 header? My paint seems to have burnt off...I got a lead on some flat black header paint from a friend, I will be re-Painting them soon....I'm off on a tangent...reset...it would make better sense if I had the older set of carbs as mine didn't have jets in them when I bought them, and I bought a set of 136's, and found two 110's and two 112.5's. When I originally put it together, I used the smaller jets as I thought it closer to what should have been in there to begin with...120's out, 125's in. but when I put the header and pod filters on the bike...did not come with an airbox... I figured to go with the larger jets as it will be breathing alot better...and boy does it! So, perhaps if this is looking for 137.5's, with the better breathing header and such, I should go up another couple three sizes....HMMMN...I wonder....See, there I go again....you know, I used to belong to a suport group for people who talk to much, it's called onandonandon. thanks for the informantion, amazingly useful as always....L8R...........The Lorax.

[John]

The 81 XS and the XJ used the drain taps on the bottom, like the carbs on the right, but the choke on an XJ is cable operated.