LOL. That's actually what I did with the front, but knocked the peaks of with the 280s. I'll look and measure these again before I decide whether to ball or straight home them going back.

I used to buy factory pre sized OEM cylinder kits when Zanotti was selling HD online. I swear the first pair I got looked like dull chrome that'd been rubbed with a brillo pad, compared to all I'd ever seen. Measured one and couldn't believe it. Clearance was right at .00075 but they worked well.

I hope it's a sharp edge. I've built quite a few with cast pistons over the years. Have personally run mine with intake leaks, too much fuel, or timed 2 degrees high (by mistake) and every other f-up you can imagine for way too many miles at a time, but I've never had one do this to a piston, regardless of the abuse.

Pass the popcorn....

 

I would think that would effect both cylinders. ( ?)

 

Of coarse the latest plugs won't tell us much about the combustion but how about the plugs that were in the bike prior to the 60 mile run? Take the best pic you can..

 

I'll try to hook you up with plug photos in a day or 2, Hotrod.

Back to Eds thought about timing, I recently emailed Dyna with a few simple questions. During all that I mentioned I'd always run the module on dual fire since '09, but I have it wired to a single fire coil. He couldn't or wouldn't say why, but did say he was "very concerned" about that.

I had a front wrist pin stick in the rod 3 years ago (another story - I know why) and put in Wisecos and they were good for a while, but engine got so noisy I couldn't stand it when it was warmed up is why I put these cast OEM pistons in last month. Forged will take WAY more timing and a/f abuse than cast and they didn't look bad at all, despite more running clearance I thought they should have.

Got me to thinking. Wired to single fire coil but switch on dual fire - what if the module is freaking out occasionally or has become damaged. Or maybe the wasted spark is happening at the wrong time or wrong cylinder, thinking it's hooked to a stock coil but the blue wire is in the circuit. It would only take an occasional and inaudible pre-ign or det to eventually cause a problem. So on the last rides it was set to single fire and the 20-30 miles after the regular fuel (50/50 93/87 at that point) was not too bad. Only pinged around 55 (2500rpm) on very slight throttle.

Of course the damage is already done and the piston will continue erode and cause a problem regardless, even if everything else is perfect so I know what has to happen there. But I'm really wondering if maybe this was the cause of the excessive engine noise with the Wisecos in the first place and the quick destruction of this rear cast piston.

 

Yeah, I missed that. How about crappy piston casting? HD pistons are hypereutectic. Not an even mix in the metal?

Could simply be too much timing and bad gas. Rear cylinder runs hotter. I generally don't consider a manifold leak unless the idle is real crappy.

 

If running dual fire the rear cylinder would be running like a dual fire system don't know what the front does. Coils / timing should be OK on the rear as it pretty much the same as running a dual fire coil. It might cause module overheating if it wasn't set up for it. Might only be a problem is running a 2000Ki. If it's external, I'd think it would be OK.

 

Hold it, You replaced forged pistons in an Evo where you should have .004-.0045" clearance as per Wiseco and then installed cast pistons in the same bore.. Not good..? You can get away with .003" clearance but that would be the Max.. Maybe that's your problem... Poor fit piston to cylinder......

And as for running a single fire coil on a dual fire setup is not an issue. The other way around and it wouldn't run.. One cylinder would be dead..

 

No no. Started with OEM std. Front wrist pin stuck in rod and knocked. (long story why, another time maybe) That hammered the bottom of the front cylinder enough I couldn't hone it out for a std cast piston. So I put in Wiseco std at about .00029 and they still looked great on the shirts after 16k miles. Honed out to 3.503 for the current +.005 OEM pistons.

Dual fire ignition can be run on a single fire coil. Just run a jumper across the two primary trigger posts of the coil. This is an early version of an Ultima nose cone module. It has a single fire coil. I've most always run it with the switch on dual fire but the blue wire is connected to the coil instead of just the pink wire and a jumper. Single fire ignition on a dual fire coil, just use the pink wire only. Single fire ignition/single fire coil, use pink for rear and blue for front.
http://www.ultimaproducts.com/53-644_ignition.pdf

Simply a bad piston was at the bottom of my list, but certainly a possibility. Only thing I've ever know to flake one is high heat. Whether from timing or a/f or pressure, heat is the killer. Put one in a toaster oven sometime and set it to "dark" and see what happens - real quick. I've done it... don't ask

I'm just sorta grabbing at straws as to why the timing might be weird (at times) even though the install sheets say all switches off to time with a light (which makes it dual fire) regardless of the coil(s) setup. Well, that's how I've run it for years. Wired for single fire, but module switch on dual fire. So obviously the blue wire sends a signal regardless of whether set to single or dual fire. Even before the current smoked piston, it occasionally seemed like it was clacking, or pinging or something. Chalked it up to Evo normal.

Yeah, it's an old one - 53-642




Wired like this
------------------------------------------------------------

 

I don't think it's a good idea to do that. The module sees 1 1/2 ohms instead of 3.

 

Interesting thread! This may not (and should not) matter, but one thing that distinguishes the rear cylinder from the front cylinder is the timing of the wasted spark. Normally the rear cylinder gets that 'extra' spark before the intake valve opens so there's no real effect on anything. I wonder whether that would be true if some air/fuel mix was slipping through..... Maybe completely irrelevant, just a thought.