Pinging 2003 Heritage...

[bcitori]

I have 10.25 to 1 big bore pistons with Andrews 37b cams. I have a Power comander III and had it tuned at three different
places about 5 times in total, and nobody can get rid of the pining. They say they have taken timing out to the point that no more can be pulled out with the PCIII. I am told the cam and piston combo is not a good match. What are my options the pinging is driving me crazy.....

[laserp]

Did they check your CCP? My bike was pinging like a bastard at 205/210 PSI. Swapped out my head gasket adding .020", dropping it to 193/197 and the pinging is gone. Runs much better and on 93 pump gas.

[route66paul]

That could do the job, check you CCP, your static comp is only a guess if you did not CC the heads. Changing to a thicker gasket raised the squish and then it could ping anyway. Have someone who knows modified TC engines look her over, you may need a later closing cam and a thinner gasket(for proper squish). If that piston is mated with a head that has a larger than normal combustion chamber, your comp could be within the limits for the 37 grind, and tuning could do the job, a CCP will tell the tale.

[ultraplusrotax]

Originally Posted by bcitori

I have 10.25 to 1 big bore pistons ...the pinging is driving me crazy.....

It is useless to invest in high-compression pistons if afterwards you need thickers gaskets to avoid pinging.
If you keep accelerating a pinging engine you will severely damage that engine.
My Ultra Classic runs fine on 95 , but if I accidently put that 95 in my Sportster XR 1200 pinging occurs on hard acceleration.
In my humble opinion all H-D tuning is a waste of money and also origin of many destroyed engines. The only worthwile change is a richer mixture in order to cool the TC.

[genedjr]

First fire your tuners.
Second you need more reseach.
10.25 is not bad but you need to account for intake and exhaust. The AC and the cover and the pipes exact a toll on the velocity. Velocity is the big bang.

There is a fan-wave on compression. But look closely a velocity - that is where you embarrass the wana bees

...gene

[frankysfree]

Originally Posted by bcitori

I have 10.25 to 1 big bore pistons with Andrews 37b cams. I have a Power comander III and had it tuned at three different
places about 5 times in total, and nobody can get rid of the pining. They say they have taken timing out to the point that no more can be pulled out with the PCIII. I am told the cam and piston combo is not a good match. What are my options the pinging is driving me crazy.....

first off i assume your running high test gas correct? seems like a no brainer but ive seen worse.
second how do you ride? with high compression pistons and cams you cannot ride it like a stock bike and lug it. you have to keep the rpm's up especially when you have a passenger or are going up a hill. you cannot do a hard roll-on from low rpm cruise speed.
third if your riding it in hot weather and you dont have an oil cooler, get one. heat is the cause of pinging. its the fuel actually detonating when it isnt supposed to caused by superheating it to the point of it exploding.
and i agree that there is no point in adding a thicker head gasket to lower compression. it is counterproductive of adding high compression pistons in the first place.
i live in texas and have built many bikes with big bore and 10.5:1 compression pistons without any problems with pinging. it all comes down to the way you ride and the way it is tuned. period.

[Mercury]

According to Andrews website, the 37b is designed for 9 to 9.5:1 compression. You may have gone too far with the 10.25 CR. I'm looking at that same thing myself right now with some different cams. Just saying...