73 XLCH help

[Matteaton]

Hey everyone I’m new to this from and with iron heads, been wanting one for a while so I finally found one in good shape it’s a 1973 XLCH 1000, it’s bored .50 over, top and lower end freshly rebuild, here’s the issue, when I got it home it would start on the first kick but the idle wasn’t consistent, noticed the intake gaskets were wrong they were the tubes and really dry rotted Instead of the O rings that year calls for, so I put the o rings on it has a Keihin butterfly carb that I resealed I left the jets the previous owner had in there, did a push rod adjustment and set the timing probably 10 times by now and i can’t find a good carb setting once it does run and it kickbacks every now and then and the carb sneezes, so I’m wondering since it’s bored out so much should I have to advance the spark timing? Retard the timing, or put original jets in the carb? Is it a float level issue? It is straight piped it allegedly ran great before it sat

[JB in NC]

First, a plus .050 overbore on '73 cylinders is a no-go, as that leaves them too thin. The only exception (I think) is VERY late '73s had the later, heavier cylinders that can safely be bored to plus .070.

With that said, any overbore of this sort does not change displacement enough to affect the state of tune, so don't worry about that.

In general, if it spits back through the carb when the motor is warm, it's too lean. That could be from a vacuum leak, a clogged jet or passage in the carb, or maybe a bad accelerator pump or pump setting.

When tuning, the ignition has got to be spot-on, consistent and correct, so that you remove that from the tuning equation. (After the carb is tuned in the ballpark, small ignition adjustments are of course part of final tuning.) So, good advance unit, well serviced, points clean and adjusted, good condenser, and timing set by the book. Get that right, and then LEAVE IT ALONE while you do the carb tuning.

A Keihin carb is not original to the '73 model year; I think it would have had a Bendix/Zenith from new. Factory butterfly Keihins are notorious for having lean intermediate jetting (the EPA, you know), so a larger intermediate jet will usually cure most of their ills.

Kudos for getting rid of the intake bands. The original o-rings are SO MUCH better. Hope you got good clamps to go with the o-rings.

You will have to be more specific about the whole set-up.

Jim

[denguy]

Since you said that it sat awhile, a basic place to start would be to give the carb a thorough cleaning, imo.

[brucstoudt]

Jim '72-e73 were the cylinders with the thinner liner.most '73 had the thicker liner.the early cylinders had the threads for the head bolts running to the top of the cylinders.the later revised cylinders had the threads ending approx.3/8'' below the head deck surface.

[JB in NC]

Originally Posted by brucstoudt

Jim '72-e73 were the cylinders with the thinner liner.most '73 had the thicker liner.the early cylinders had the threads for the head bolts running to the top of the cylinders.the later revised cylinders had the threads ending approx.3/8'' below the head deck surface.

EVERY '73 that I have worked on, so far, have had the early, thin cylinders. I do not believe "most" had the later, thicker cylinders; I have yet to see one. The good news is that the '74 - up top ends are a bolt-on upgrade for the '72 - '73 motors.

Jim

[1Scooter]

Take the overbore out of the equasion, it does not matter. It kicks back - timing is advanced too much. FIRST set the timing, static and dynamic so ys can eliminate one issue. No mention if the ignition is OEM breaker points or aftermarket electronic. The simplist is a Dyna S dual fire ignition that uses OEM advance. Set the timing the 1st time and forget it. Those old carbs ar hard to find good parts for. The simplest carb to replace it with is an S&S Super E. If a decide to go that route, 285/68 jetting will work fo ya.

[bill smith]

You mentioned the sneezin, mine did that and once I rebuilt the flyweights in the ignition advance unit all was good. Pay ya to pull 'em out and service 'em.

[sungod]

Originally Posted by bill smith

You mentioned the sneezin, mine did that and once I rebuilt the flyweights in the ignition advance unit all was good. Pay ya to pull 'em out and service 'em.

Bill:
+1
Often overlooked.
TSB 652
MAY 1973
Easy check:
Early 73 = 6 point 9/16
Late 73 = 12 point 7/16

[brucstoudt]

^^^ thanks for the TSB 652 info sungod.i have a stack of them,i'll have to look to see if i have that one.

[brucstoudt]

my picture from my personal collection