HarleyTechTalk

Quote from: JW113 on April 23, 2020, 04:48:56 PM

The limitation will be that playing with the timing by rotating the module affects both max timing, and timing at idle.

Yes, no and maybe. Have you considered the effect of different module positions in conjunction with the various curves and how they affect advance at idle and full advance?

Quote from: JW113 on April 23, 2020, 07:16:47 PM

Quote from: Hossamania on April 23, 2020, 06:15:03 PM
I remember talking to an old rider (like in his 60's!),

Ouch! Hey I resemble that remark!


-JW

LOL
For Maximum Performance set the Timing where it Runs the Best... I will Not share where I ended up with the timing on the DragBike... but It also runs "Race Gas"... I never understood Why improve Performance with Dual Plugs... then throttle it with reduced Timing!!! All I ever got out of Reducing the Timing, was excessive Heat!!!
But... I hear it all the Time... We Ain't Racing Here... just Improving performance a Little bit I guess...
Edit; That Ironhead Still wants some Timing... It is still an Ironhead!!!!

Dual plugging an Ironhead is not a little boost, it makes a significant improvement!

I'm sure the MoCo was aware of this and likely did not add this feature to production as a Sportster was already faster than a Big Twin (their flagship model).
If they had added it to production no one would ever by a Big Twin! (except touring guys who wanted a heavy weight bike)

Generally the high advance numbers that an Ironhead likes is due to to the crappy combustion chamber shape.
By dual plugging you are speeding up the time it takes to get the fuel in the chamber lit.
A motors need for high spark advance numbers is indicative of an in efficient combustion chamber
In the case of an Ironhead (which is an extreme example) it is so bad that a significant amount of the fuel doesn't get burned until it is way past the power making stage which contributes to the carbon buildup they are famous for.
There is a down side of the high spark advance numbers in that it puts the motor closer to detonating, combined with pockets of un-burned fuel which further increases detonation potential.
Dual plugging speeds up the peak pressure in the chamber by getting more of the fuel lit sooner, so technically the cylinder reaches peak pressure sooner it does not require near as much spark advance. This is beneficial as there are less cold spots in the cylinder and less tendency for detonation.
Detonation happens when the cylinder pressure has raised enough that the fuel ignites explosively. So you light the fuel on one side of the piston and the pressure starts increasing, the piston is still rising so the mechanical pressure is also rising. So by the time the fuel on the other side of the piston ignites the cylinder pressure has exceeded the fuels knock rating, and BOOM!
An great example of what happens is, a cap gun. If you ignite a paper cap in free air it burns like lighting a match, whoosh. But if you pressurize the cap by hitting it with a hammer it goes BANG!
(In the motor this all happens in microseconds so you have to "freeze frame" it to wrap your head around what is happening.)
For this reason you cannot compare the spark timing of a dual plugged motor to a single plugged motor
In other words by changing the spark advance you are adjusting the peak pressure timing, so technically the lower spark advance of a dual plug motor is not lowering the peak pressure. Dual plugging it advances the peak pressure so the spark has to be backed off to compensate.
Some motors with very efficient combustion chambers only need 20° of spark to make full power!

https://youtu.be/jdW1t8r8qYc

I find this one fascinating, not dual plug, but related to engine spark.
Sorry if I'm hijacking. Not meant to change the discussion.

Well I must have not got it all out of my Ironhead!!!!!
I can tell you that lots of advance at the start reduced at the top end is Very effective... not easy to do... but Effective..
And My Dual Plugged IH with a Healthy dose of Compression... wanted more timing than one would Think... to squeeze Maximum Performance..
75 Cu.In. doing 9.8 at 135MPH in a Standing Start Quarter Mile... In 1996!!!!

Well this has been an interesting day. Troubleshooting the no charge problem, so looked into the Ironhead spare parts box to see if I had a spare gene and regulator, but found a unopened box from JP cycles. Hmm, what have we here? One of those alternator conversion kits??? Don't remember ordering that, but like Hoss says, I'm old. Dementia setting in.


So spent the day putting that on, and now it seems to be charging again. Just for fun, weighed the diff between gene and alternator. 13.5bls vs 3lbs. Lighter is better, ja? So in the vein of weight loss, I ordered a Anti-Gravity battery, which is 10lbs or more less than this lead acid battery. Hey, less weight is HP, right?

-JW

This the coolest ironhead I have ever seen and possibly my favorite thread right now. I really enjoy seeing these older bikes updated and modernized.

Well I can certainly tell you that it's a real hoot to ride. Love those close ratio sporty 4 speed boxes. And I know the Prez don't like 16" front tires, but it sure changes the cornering characteristics for the better. I've had the battery on the charger for over a day, and it still will not get up to 100%. Starting to think that was my charging problem.

-JW

I guess the battery is OK, finally charged up to the "green" zone. I use one of those X-treeme pulse chargers, this battery is old school lead acid and quite large at that. Maybe too much for the pulse charger. So no miles today but it was kind of warm here, like 88F. Rather do the break in when it's below 72F at the most.

-JW

Quote from: Racepres on April 24, 2020, 11:00:15 AM
Well I must have not got it all out of my Ironhead!!!!!
I can tell you that lots of advance at the start reduced at the top end is Very effective... not easy to do... but Effective..
And My Dual Plugged IH with a Healthy dose of Compression... wanted more timing than one would Think... to squeeze Maximum Performance..
75 Cu.In. doing 9.8 at 135MPH in a Standing Start Quarter Mile... In 1996!!!!

Yeah, you need more spark when you're tipping the can!   

Quote from: Burnout on April 27, 2020, 08:19:23 AM

Quote from: Racepres on April 24, 2020, 11:00:15 AM
Well I must have not got it all out of my Ironhead!!!!!
I can tell you that lots of advance at the start reduced at the top end is Very effective... not easy to do... but Effective..
And My Dual Plugged IH with a Healthy dose of Compression... wanted more timing than one would Think... to squeeze Maximum Performance..
75 Cu.In. doing 9.8 at 135MPH in a Standing Start Quarter Mile... In 1996!!!!

Yeah, you need more spark when you're tipping the can!   

LOL... Legal Racing Gasoline... they dipped us every Pass!!!!! But, should one "Tip the Can" more lead yet is a requirement!!!!

My Anti-Gravity battery showed up this week, so spent the day putting that in and then some more break in miles. My god, the weight difference between the stock battery and the AG is off the charts. The AG feels like a little plastic box with nothing inside it. But I tell you what, it spun that motor over like the starter was on steroids. Wow. Might have to think about one for the RK now, which will barely start on a good day.

So I ditched the stock gene for a alternator, have the AG battery, am now pondering one of the Tech Cycle starters that use a Nippon-Denso gear reduction motor and are about 1/3 the weght of the stock Bendix. Weight reduction is good, yes?

-JW

Weight reduction must be a very good thing, my doctor brings it up all the time. What's up with that?

Just remember the old rule of thumb when it comes to acceleration: 10lbs/HP. You can make the bike faster, and save money on food at the same time!


-JW

To install seals on those, you machine the guide prior to installation, and then modify the lower collar.
None leave here without that being done.

My machinist told me he was not able to add seals to the guides he used. He said between the already little space, and the higher lift cams, there was just not enough room. He did however use manganese bronze guides and clearanced the intakes on the tight side. So far it's not been a problem, it does not appear to be using oil and the plugs look nice and clean.

-JW

Quote from: JW113 on May 11, 2020, 09:25:27 AM
My machinist told me he was not able to add seals to the guides he used. He said between the already little space, and the higher lift cams, there was just not enough room. He did however use manganese bronze guides and clearanced the intakes on the tight side. So far it's not been a problem, it does not appear to be using oil and the plugs look nice and clean.

-JW

Never been a problem on mine... Trust yer guy!!!

Yep, I do. He's a far better machinist than I. Although valve seals are nice to have, they are not a must have.

-JW

Quote from: JW113 on May 11, 2020, 09:25:27 AM
My machinist told me he was not able to add seals to the guides he used. He said between the already little space, and the higher lift cams, there was just not enough room. He did however use manganese bronze guides and clearanced the intakes on the tight side. So far it's not been a problem, it does not appear to be using oil and the plugs look nice and clean.

-JW

The lower collar needs to be modified in a lathe, in order to install seals.
As I mentioned, we do that on every job here, and the lift of those cams is a non-issue.

Quote from: Hillside Motorcycle on May 12, 2020, 04:17:56 AM
The lower collar needs to be modified in a lathe, in order to install seals.
As I mentioned, we do that on every job here, and the lift of those cams is a non-issue.

If I was getting paid for it... I would do them all also... On My Bike, it ain't necessary...

OK, 400 miles of easy riding, today time to drop the hammer & dial in the main jet. I had a 185 in it, and first WOT's this morning was yielding 11.6:1 AFR. Too rich. I swapped in a 170, tested again, and now is around 12.2:1. Better, but will try a 165 and see what that gets. Trying to hit 12.6:1.

On thing has me a little confused. This thing is eating oil like crazy, like 2 quarts in 400 miles. And I can't figure out where it's going. It does not smoke at all, does not leak, exhaust does not stink like oil. I pulled the plug in the case, and got maybe 5 oz of oil. Dunno.


I pulled the plugs, they look 'OK', a little dark but I've see far worse. They look more like carbon from fuel than ash from oil. Looking into the plug holes, I can see the piston tops are still mostly shinny, not an oily mess. All I can figure is there is a bit of oil getting past the rings or guides and just getting burned. But don't understand why I can see or smell it.

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About all I can do for now is keep an eye on it, and the oil tank full.

-JW

Any drops on the case breather tube?

I have the case vent into the air cleaner, with an in-line Krank vent valve. No oil up in the A/C or on the air filter element.

I made these just now. A trick I heard about long long time ago. Ironheads tend to get too much oil to the top end, they have two oil supply lines unlike Shovelheads. You can drill and tap one of oil line fittings to accept main jets, then restrict the oil flow. Maybe this will help. Or, maybe not...

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-JW

Did a little more main jet tuning today. I thought I had a 165, but no. So I used a 160 for today's test. It must be awfully close, as the AFR is now 12.7 at WFO. I think I'll leave it for now, and let the dyno shop dial it in with better equipment. But it must be close, it no longer surges slightly when backing off the throttle from WFO.

And I think I've found a possible cause of the oil consumption. I think I'm overfilling the tank. This is the first XL I've owned with this kind of oil tank, and I think the oil cap on it is from a Shovelhead. The cap has a dipstick, but it does not match the picture in the owner's manual.

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The full mark on this dipstick is right up at the flange in the cap. In the manual, it appears further down, perhaps a half inch or more. Comparing where I've been filling the oil to, and where the oil tank vent line is on inside of the tank, I think I've been covering the vent hole with oil. I'm going to drop the oil and put in exactly 3 quarts, and see where that puts the oil level mark on the dipstick.

If anybody has a stock oil cap with dipstick, I'd sure love to see a picture of it.

-JW

I don't have one, but I know they were longer that what you have there.


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