High Compression Cast Pistons : V-Twin Forum: Harley Davidson Forums

backinthesaddle · 09-15-2005, 07:58 PM

I was a little naive when I purchased my FLHTCUI this spring. My last bike, a 2K RG had a stage 2 big bore upgrade done to it by its previous owner so I wanted the same thing on my new Ultra. I held off on the cams but did opt for the dealer's advertised Stage 1 Big Bore upgrade along with SEII slip-ons. The dealer told me the sale they had during the winter was over but said they'd give me the same deal because I was incorporating it into the bike purchase. When I took delivery, the parts weren't itemized on the invoice, it just said Stage 1 Big Bore. I knew up front I was getting bored stock cylinders vs new HD ones but everything else is new SE items.

You might have read my posts in the EFI forum about my dyno results and my questions about a SERT. Hals speed shop recommended a DFO after my dyno run because the SE Stage 1 1550 download had it running pretty lean. I told them that I wanted to upgrade the heads and cams next year so I was more interested in a SERT. They asked what kind of pistons did House of HD use, flat top or domed? Huh? I assumed flat tops because that's what every one on the forum here seemed to have. I went back to House and asked for the part inventory of my upgrade. Turns out they used the 22661-99A High Compression cast piston kits. No wonder my bike is pinging. 10.25 to 1 compression ratio. I have to change them if Iwant to go to Hal's custom heads adding 350 to my already high upgrade quote.

Now I'm reconsidering the head work. Anyone else have these pistons in your build? Are you happy with the results after you got them dialed in? I'm kinda lost as to which way to go now. My goal is low end torque instead of high horspower. I want it to pull hard from 2500 to 4000 RPM. That's where I have the most fun. Here is the thread I posted on my Dyno run.

Advice please. (Thanks grock and megaglide for your help in the EFI forum)

springer- · 09-15-2005, 08:53 PM

I like the SE 10.25:1 Cast pistons. The stock combustion chamber is suppose to be 85cc. Most of the ones I have measured are in the 86-87cc range and very few are actually at 85cc. When figuring your compression ratio it will drop it to around 9.9-10:1 They are designed to work with the stock combustion chamber. Add head work and a good cam and I think you would be happy with the torque. We have lousy gas around here and don't have a problem with pinging.

Kags · 09-15-2005, 09:13 PM

I did not like the HC S/E pistons when they where in my Dyna. They are many grams heaver then the flat tops. Flat tops are many gram heaver then stock. IMO that shop could be sued or something. The Harley street legal 95" kit calls for flat tops. If you push the point you could make the dealer take them out & put in what you paid for. If any damage was done from the HC pistons they should make good. If your happy with what you have them plan to do like Springer said.

uspatriot · 09-16-2005, 07:52 AM

I like mine. I have them with stock heads SE203's, V&H side shots, stage 1 air cleaner, SE Tunable Ignition and a Mikuni 42mm carb. Never had trouble with pinging. Never even had to adjust the carb. Runs good with around 87hp and 94tq.

dentman · 09-16-2005, 11:24 AM

does your bike start hot ok with that set up? i had the same set up exept a thunder header two into one and that bike was a bitch to start when it was hot, i went through a 1.6 starter and one day when it was like 105 out and i was 200 miles from home i pushed the buton and exploded the twinky shitt rind and pinion gears. i put a bdl 66 tooth set up in there and just recently put a woods 6g in there and now i feel the compresion from the pistons is being used for something constructive.

uspatriot · 09-16-2005, 12:18 PM

Nope, no problems. Once in a while I might need to bump it, but, I ride stop and go (turning the bike off and on) all the time and things seem to run fine.

dentman · 09-16-2005, 01:49 PM

thats interesting. maybe like springer says these heads varry and mine are closer to the 85cc range.

uspatriot · 09-16-2005, 02:00 PM

Yeah, maybe so, I am definetely not that technical. I do get some compression built up once in a while and get a backfire when I try to start it, but, next try, it starts right up. Sometimes things just are the way they are. I don't know why or how. Maybe if I was grock or doc things would make more sense. Just thought about this. I have the SE tunable ignition with a carb. I have the ignition set to the #3 curve with a spark advance of 5. Maybe that helps. The gurus would probably know more about that as well.

dentman · 09-16-2005, 02:14 PM

with that cam i ran the same carb and ignition on the 3 curve but with the initial timing strait up. on my bike changing the initial iming did not help the hot starts as much as it would make the bike a litle lazy. i think the machanical timing even with chain cams on these bikes vary from one bike to another. and that would change the valve timing enough to be a problem on one bike and not a nother.

uspatriot · 09-16-2005, 02:49 PM

Yeah, that could be. I just tested the #2 & #3 curves and the set the advance settings from the negatives to straight up to positive and found that the# 3 curve and +5 setting gave me more seat of the pants torque. My dealership had it set to the #2 curve straight up and I just didn't feel like it pulled enough there. Like I said, I did not have it dynoed at the current setting, but it was a noticeable boost in torque at the setting I wound up with.