Funny and True

 

Yes it probably did bump the compression a smidge.

After seeing this I plan to look into options for an external vent. I've seen the post on these and read a few over the years but just did not get it until now.

 

Check out DK Customs. They do a good job explaining the external venting process.

 

My OEM pistons looked similar when I pulled them @ 9K miles. In fact, carbon played a part in why I had to pull the head off in the first place. See this thread: misfire repair.

Then I did a breather bypass: stock air cleaner bypass.

That air cleaner was too small for my build, so I went to the HD Heavy Breather and didn't add the bypass. Frankly, I stopped worrying about it. I won't look at my pistons anytime soon

 

Yeah that looks dirty. But I’m sure it is normal. There is no motor that has been running carbon-based fuel that after 30k miles doesn’t have carbon crust on piston crowns. I’ve never seen one. I’ve popped the heads off quite a few motorcycle engines since 1964, never seen one yet that didn’t have a carbon crust on the pistons. And after awhile there will also be carbon crust up on the intake valve stems.

I say it doesn’t hurt anything. The designers know about the carbon. They design the engines so that they will run their entire life before the carbon becomes an operational problem.

 

Thanks - I actually watched one of their YouTube videos last night on it.



I remember that thread. Did a search yesterday and missed that one. Great information. Thank You


Thanks for the input.

 

Look inside your intake manifold and you'll see a messy stinky oily film. It's also inside the intake ports on your heads. That is what is causing that build up on top of your pistons. My pistons looked worse than the OP.

My new pistons will never look like that because I bypassed the head breather bolts.

If your intake looks like mine did, then your pistons look like the OP pistons. It might be H-D normal but that don't mean it's all good.

 

I just did a bypass on my bike last weekend. I put a 124" S&S Crate engine, from FuelMoto, in it about 3K miles ago. While doing some maintenance, I found some oil in the air filter... I'm not about to let this new motor get all caked up with carbon from the breathers....

I've done an external breather bypasses on all my twin cams... I was told I wouldn't need to do one on this 124" S&S... Well, glad I checked, because they were wrong..

The fittings and hose cost me around $25. I use good quality fuel line, not the cheap vacuum hose..... I had the small filter already. I use the filter as a visual cue for how much oil is being puked.. I clean it when it gets oily. On two other twin cams I just have the hose ending at the frame.. Someday I'll pry open my wallet and get a small catch can... I have a roll of heat-resistant chafe guard sleeving to protect the hose from the exhaust heat, and keep a supply of Oetiker clamps for the hose connections, except for the small filter... I use a removable screw hose clamp there, to make it easier to remove the filter for cleaning...

I close off the vent passages in the air cleaner back plate by threading the passage holes (6mm I think) and I then put a set screw in each hole. The screw is slathered in JB Weld... the passages are completely blocked at that point and the bypass has no where to go but to vent externally from my hose set up...

I am one of those guys who actually likes the old football covers... when I put the football cover over the air cleaner, the hose connections are totally covered....

 

Man that 124 looks awesome, and I like your simple bypass system. I have done a similar bypass on my 2018 Ultra Ltd but kept it inside the OEM ac just to keep a clean look. I believe that using a premium synthetic oil in these engines is another contributing factor as well. Usually most synthetics are superior in many ways to conventional oils, mainly in the area of flashpoint, that being far higher temps. For example my favourite oil has a flashpoint of 228C/442F. Even with a low volatility loss of 4.2% there is a little oil vapour that is present inside the engine that could be vented out during the regular running of the engine. This could create a lot of crud inside the throttle body and combustion chamber if the vapour gets sucked in, because these synthetics can take so much more heat before they burn up, if at all. So, check your favourite oil and see how it compares to other brands. Regardless of oil brand, I think that a breather bypass is a good idea. Dutchy
https://www.amsoil.com/p/20w-50-synt...mcv/?zo=331384

 

Excellent gravity will help rid the overflow when the bike gets hot.