HarleyTechTalk

Quote from: Shep236 on April 16, 2024, 08:05:52 PMThanks for the replies.  I ended up scoring a pair of 2017 xl 1200 heads for 300 bucks for the pair.  I'm gonna utilize those along with the 1275 big bore kit, and a hsr42 Mikuni carb.  Just haven't decided on what cams to run with it yet.  Was thinking the andrews n4 or n8s.  Just for ease of use really.

Either of those cam grinds will work with the 10ish:1 compression ratio you get with stock EFI 1200 heads over a flat top 1275 kit. But keep in mind that both of those are very old cam grinds, designed around the small valves and much inferior 1986-2003 hardware. The later heads have larger valves, 7mm stems, and a factory beehive spring pack, with an entirely different set of capabilities and limitations.

Let me give you an example. The last Buell product to use the old hardware was the 2002 X1 & S3 models. They came from the factory with "B" cams (.497 lift) and a 6800rpm rev limit, and at 6800rpm, the valve train was already starting to lose control, it was really marginal.

The very first HD product to use the new 7mm/beehive hardware was the Buell XB9, which came out in 2003. It had a factory 7500rpm rev limit and a two year warranty and valve train failures were almost unheard of, it was stable all the way into the limiter. This despite the new springs having roughly the same spring pressure as the old stuff. The "E" grind cams (.551 lift) in those motors had a lot to do with achieving this, with a lobe design that took advantage of the higher lift ceiling to ease the transitions between the ramps and the nose, making for a more stable valve train.

HD really showed the way on this, but they are not the only ones making cams like this for the new hardware. I'll stop there because I don't want to sound like an advertisement. My main message is that when you use cams that are made for the old hardware, with heads equipped with the new hardware, you're leaving a lot on the table.

But yes, using low lift cams does simplify installation with respect to cam box clearances. Clearancing a cam box is not difficult however and personally I would not let that deter you. It's just not that big of a deal.

You cannot see attachments on this board.

Found this for the Wood Performance WM-22XD

This topic has been moved to The Shed.

https://harleytechtalk.com/htt/index.php?topic=121671.0

This video may help understand the physics or ring rotation too.  One good takeaway is the description of how the common 45 degree crosshatch angle is calculated.  the other is what deviation from the prescribed angle does. 

I picked up several of these gauges at their SEMA booth about 10 years age.  They have a thin pad on the back to stabilize then while you inspect the angle.

This topic has been moved to Source An Item or Vendor.

https://harleytechtalk.com/htt/index.php?topic=121668.0

I had a phone conversation with one of the techs at Total Seal last summer. He confirmed that rings do rotate by design. He said if for no other reason to keep from having a score mark in the cylinder if the gap of the ring never moved. I do remember that two cycle dirt bike motors that I owned as a kid were pinned to not rotate. But I always assumed that was to keep the ring end from grabbing a port in the cylinder.

This was just the first video I've ever seen that just spells it out. Like the link to the Motortrend article, they speak to ring rotation if you read down to about halfway.

Cool quick video. My first thought before watching was: "Then why does it matter that the ring gaps are oriented they way they are when being assembled". They addressed that.

Zach

Quote from: FSG on April 16, 2024, 09:25:32 PMa good pic is worth a 1000 words   

Speaking of pictures...I measured the old vs. new rotor and found the below numbers.
When I installed the new rotor a couple weeks ago, I left the shim in and therefore the sprocket would have been 0.020" more outboard than the previous rotor..... Would that have been enough to cause the knocking I was hearing? or is it still more likely tied to the comp either being too little torque or the nut bottoming out?

Regardless, I'm going to shorten the comp nut today. Then I'll reinstall, torque properly, and make doubly sure the sprocket alignments is correct.

You cannot see attachments on this board.

I came across this video this AM. It speaks to the myth of piston rings don't rotate, as they commonly do in all motors where the rings aren't pinned.

As well taking a cylinder off the piston and rings and then putting the cylinder back on poses no problems to the motor. The rings will rotate anyway. The crosshatch is what drives the rotation.

https://www.motortrend.com/how-to/1803-the-science-behind-piston-rings-and-grooves-explained/