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ZTatZAU · #1 29th June 2022

I was going to post in the "What did you do for your sporty Today?" thread, over in the general discussion section, but it seemed a bit trite and likely of little interest to report that I repaired and replaced my front brake switch and right turn signal switch (respectively), checked my valve clearance adjustments, adjusted my drive and primary chains, and changed my primary case oil & engine oil & filter; with satisfactory results.

Instead, at the risk of evoking a bunch of "DUH's!" from all the "Ironhead-ers" here, I thought it might be a bit more interesting, informative, or perhaps more entertaining to start this new thread... to report on "What I Learned About My Ironhead Today!"... well actually over the past couple of days!

First, while some may recall I recently rebuilt my front brake master cylinder and installed a new starter button switch and a right handlebar wiring harness, my front brake stop light recently failed to function.

As I reviewed the schematic, contemplating the diagnosis and repair of my stop light, I assumed the front brake light switch was a typical, normally open / press to close button switch. I was surprised to learn that this is not the case on my 1973 XLH. I learned instead, that the button switch is normally depressed (open) with the brake lever relaxed, and applying the front brake actually releases the spring loaded button in the switch, to close the circuit and light up the tail light's stop lamp.

I also discovered that the 1/4" washer under the front brake light switch was missing on my bike. With a fully filled and properly bled front brake fluid reservoir, there is very little movement in the front brake lever required to apply the disk brake. Without the 1/4"washer, this minimal movement of the brake lever was not sufficient to fully release the button in the switch to close the stop light circuit. As a result, with a new washer installed, my OEM switch is now slightly retracted and once again functioning as it should. The new brake light switch I ordered is now on standby duty in my box of "Sportster Stuff".

My second lesson dealt with running the engine without the oil cap installed, in order to monitor and assess the flow of oil returning to the oil tank.

While I have done this, with good results, a couple of times since resurrecting my Sportster last fall, I just learned that it's a really bad idea to remove the oil cap to check the return oil flow once the engine is up and running... at least on a stock 1973 vintage oil tank/filter/dipstick setup.

Once the cap is installed and tightened down, the spring loaded seal in the cap builds up significant pressure to force the oil through the filter element and back to the tank through the center tube in the filter element canister. If you open the cap, with this setup when the engine is running, you better have a lot of rags on hand to deal with the mess!

Time will tell if this thread dies a slow death and scrolls down to oblivion, or perhaps prompts others to post and share new things they've learned about their Ironheads.

ZT (Ironhead Apprectice)

Medyo Bastos · #2 29th June 2022

I’m sure I will use this post as a regular reference!

Sent from my iPhone using Tapatalk

Captain Johnny · #3 30th June 2022

I learned that setting the idle mixture screw on a CV carb using the idle drop method required 2 things.

1.) The extended mix screw. When running a magneto it's impossible to get a small screwdriver on the idle mix screw. Even using the extended mix screw it ain't easy. I JB Welded a small piece of wire into the screwdriver slot on the extended mix screw. It sticks out a little on both sides and makes it easy to turn using one finger.

The extended mix screw is almost $30 with shipping from CV Performance. They are also all over ebay for $10, free shipping.

2.) The magneto timing should be retarded. I have run an S&S Super B and an adjustable main jet Bendix/Zenith. While running those my mag was fixed at full advance. They both started, ran and idled pretty good.

Now running a CV and have the slick retard/advance timing set-up on the mag base. Even though this carb starts and runs great it idles much better when retarded. So setting the idle mixture screw with the smooth clean retarded idle is the way to go.