Did a 103 upgrade on my Ultra about 5000 miles back, about a month or so back coming home from a run up north I had to stop for gas (premium) at a no name gas station. only got maybe a half mile down the road and I'm hearing what I think is spark knock. First time sense putting this thing together, naw must be the wife's bike next to me, so I grab a little throttle and no It's Me. I babied it for the next 40 - 50 miles and then got some sunoco ultra. bike seemed fine rest of the way home, now, cold, it is not bad but as it gets up to temp I have a rattle tinny slap sound coming on and getting worse as the miles go. So I parked it until I have some time to pull the top end down and see what the hell happened. Cast Harley pistons, could I have collapsed a skirt maybe ? are others having issues with low grade fuel, causing damage ? the motor is nothing major build wise, Flat top pistons - 255 cams - thin head gasket .03 and No problems before that tank of gas.

 

Wow! Ya got alot of compression for them cams!

 

Warm that motor up. Get some warm water & start slowly pouring some in the throttle opening while you flutter the throttle to keep it from stalling. Around 1/2 quart should do. Now put the air breather back on & take it for a run.
I think you got some snot on your valve seats from bad fuel. This should clean that up!
Hatch.

 

Actually my compression is not that high, I have flat pistons not domed, and the SE 103 heads are a big hemispherical shape not the bath tub type, this is the older 2003&4 kit, I know the 255's don't go in the older engines, I reworked the inner bearing end to fit and put in the billet SE cam plate with the hyd. chain tensioners. (older engine brought to newer specs.) anyway, also installed compression releases and have not had to use them yet, no matter how hot it gets. I should be at around 9.3-5 to 1 on compression.

 

I get what your saying but I have had the exhaust pipes off and looked up in the exhaust ports with a scope and it is pretty darn clean up in there no carbon build up and my plugs are clean too, for grins I will try it though, steam clean that *****. the noise I am getting sure sounds like piston rock or slap, what puzzles me is that I would expect piston slap to be loudest at start up and then get quieter as it warms up this is just the opposite quiet cold noisy when warm ?

 

Maybe its just pinging. Running some known good fuel through it a few tanks and it will go away if pinging.

 

How's your idle rpm....too low and you could get a lot of skirt slapping.

 

Idle is set at 1000, I have run plenty of different fuels thru and it doesn't make any difference noise wise, the noise I have now is not ping or spark knock, it is a definite mechanical noise whether at idle or cruise, it comes on loudest after warm up. Can hear it when cold after 1,900 rpm but quiet at idle and up to 1,900 after it's warmed up the rattle slapping is present all the time, it is definitely hurt inside. when I got that crap tank of gas it started rattling and knocking so loud I wanted to stop (should have) but was about 20 miles from anywhere, thought if I babied it and stayed in a lower gear keeping the r's up and no load on it that it would be alright, witch it seemed to be once I put good fuel in. I guess with all the other noises you get along with now being in a lot of traffic, I didn't hear any thing more the rest of that ride home. I started to notice the noises riding to work early in the morning not much other traffic, cold was fine but by the end of my 20 mile trip to work you did not want to run the engine any longer. come out at end of shift fire it up and it was fine til about 1/4 of the home and same thing getting loud, people would look while setting at a light. it's a loud noise, is not primary related. I really think a piston is what I'm hearing, I do have a little valve train noise, always did (roller rockers) but this is a fast, not half rpm speed noise. Was wondering if anyone else has had this happen.

 

well...keep us posted. when I did my 103, I checked all the measurements. the only thing spooky was play in the tilt back and forth of the piston rods....the front was way more than the back...but there's no spec for tilt back and fourth play. they both checked out on horizontal and vertical play. And yes....I def hear a noise in the front cylinder that I do not hear in the back. So mechanical noise can be tricky....things could be in spec..and still make funny noises.

 

What bothers (scares) me the most is that is was as quiet as the 88 was, really good running - sounding engine until that crap gas. Bike still runs just fine, worried a piston is gona let loose and that could waste everything, will be sure to put Forged in when I take it down to see what's going on. recommendations on piston make - mfg. ? yes I know the forged will poss. make a little noise, But, there will be a reason for that noise and I'm fine with that. one of my other scoots keep eating cam chain tensioners, put in a gear drive set and yeah some gear clatter at full temp. but again, there was a reason for it and it didn't bother. It's not that it's noisy, it's that it was Not, right from the first time I fired it until the gas thing.