Should not be surprised... Most all shops that I know of when building a performance motor try to set the squish low to help prevent detonation.. It's used to improve Increase turbulence in the combustion chamber to create a quicker burn.. It's all about flame travel.... I've had my squish as low as .027" in a high compression build with 213 ccp and no issues... A lot depends on the tune...

 

Shops that know what they're doing. With the wrong head gasket, the squish was under 0.010".

The original build was a Head Quarters kit. HQ did all the machining, and supplied the gaskets, cams, etc... When I had that done, HQ was using compound decking for the heads, meant to be used with HD 0.052" head gaskets. The assembly work was done by my local HD dealer. When the first top end job was done, the shop (my local HD dealer) used 0.030" MLS head gaskets. And for the entire time after that until I did the top end in 2020, I was chasing pinging, the starter clutch eating issue, etc... I went to colder plugs, played around with the jetting in the carb, played around with the maps on the DTT TC88A ignition. I was able to get some improvement, but never a resolution. It never occurred to me that the wrong head gaskets had been used.

Since the top end in 2020, there's no more pinging, and no more kick-backs on startup. I had a shop remove the compound decking, so that with the 0.030" MLS head gaskets, it's back to being 0.030" squish.

Cheers!

 

I think I'm a little ignorant here.. I've never heard of compound decking.. Can you tell me what that is?

 

HQ called it "spin dropping". If I understood the concept, as I was told, what they would do is machine the area around the combustion chamber to lower it into the head gasket. So, to achieve the 0.030" squish using a 0.052" head gasket (assuming the cylinders are zero decked), they would machine the head so it would drop into the head gasket the 0.022" needed to get a total of 0.030". IIRC, I was told they did it that way because at the time, 0.030" head gaskets, for the bore sizes, needed to make an 88ci into a 95ci or 98 ci, weren't available. When the local dealer did the top end, the 0.030" gaskets had become available, and HQ had stopped doing the compound decking, so the dealer used the 0.030" MLS head gaskets without thinking twice. They really should have checked since they were a Head-Quarters dealer, and they must have installed hundreds of compound decked heads. Makes me wonder how many are now running around with crazy high compression due to the same error.

Cheers!

 

So who payed for the extra machining? Pretty elaborate way to make a head gasket work.....

 

All the machining was included in the price of the head work (porting, larger valves, guides springs, etc...), and spin dropping was their standard practice for all Twin Cam heads they did at that time (not sure about Evo or other heads). I had the heads done in 2006, but I have no memory of what I paid at the time.

Cheers!

 

Finishing up the ditrio led light install. I'll be fine if I can figure out which wire is the brake wire R/Y or O/W. It's a scavenger hunt to find anything for my 04 Duece

 

I've got manuals for both my 2014 Fatboy and 2012 Streetglide. Both wiring diagrams show the R/Y as being the brake light. Hope that helps.
Jerry

 

Used the power polisher and buffed up the HD windshield that came with my FatBoy. Popped it on in 30 seconds or less - those quick-release design fasteners HD has are super ****. Now I need to take it for a spin and see if the ugly factor is worth it for the comfort at speed.

 

Added color to my perch mount today. Fully done with stage one and now adding some accents. Next step is suspension!

Red perch mount!

Full bike