Some of you are probably tired of hearing about my woes with my recent piston failure in my rebuilt engine. Well trust me, I'm tired of writing about it.

Something occurred to me today, and this might be a stretch but I'm not savvy enough to know.

The previous owner of my bike stuck a lady's feminine napkin to the bottom-inside of the factory air cleaner cover, which was used in conjunction with a Big Sucker air filter.

AFTER tuning my engine on a dyno to 13.8 AFR at WFO, the tuner removed my air filter cover and discovered the pad, then tore it out, asking why I'd want to choke my engine like that. He didn't make any further adjustments to the tune though.

Is it reasonable to think that maybe by removing that pad (it was probably 1/4" thick, 2" wide and 6" long) that enough additional air was getting into the engine that the AFR was made so lean as to result in piston galling?

I know that's a reach but I'd just like to run it by you all to see what you think.

I got the bike back today with a fresh set of jugs and pistons, and it ran so hot after 6 miles that when I measured they cylinder head temps just in front of the spark plugs, the rear cylinder was 370 and the front about 270. While the builder agrees this is hot, he thinks it's just the natural process of the rings seating. Me? I'm not so sure.

Here;s a link to a post I made earlier about reading the plugs that were in the engine for the 500 miles it ran before piston failure, as well as for the 6 mile run when I noticed how hot the engine was.

https://www.hdforums.com/forum/engin...this-plug.html

 

 

370*,wow.you`ll be taking that apart again

 

There is a possibility if it was choking if it was blocking the air, he would have leaned it out-
But-
If it was laying at the bottom in some way,..
So it probably had no effect.
perhaps show a pic as to how it was done?

 

I would be concerned your builder built you an engine but never noticed a maxi-pad stuck to the inside of the A/C cover

But to answer your question, I doubt that would make it run lean enough to cause the head temp you are seeing on the rear. You got a 100 degree difference there, you have something else going on.

 

Yeah, something doesn't sound right about the temperature difference.

He thinks? Hmmm...

 

Hey Joe40x, it may be a dead horse to you, but to me it's a 3-month long problem that has cost me thousands so far and is still not resolved, and resulted in the cancellation of a long-planned ride from California to Alaska and back.

I have to exhaust any and all possibilities on a problem that is over my head and many people here have been very generous with their time and sound advice.

If you don't want to hear about it any more, than stop looking at my posts, but don't be dick.

 

I wouldn't expect that it would impede air flow enough to make a huge difference, but I have no experience with air flow obstructions and AFR. The pictured football is not from my bike, but it's the same style. The green shows the approx space the pad consumed.

 

That's exactly what I fear. Rode 20 miles yesterday (freeway) to get it home, then 60 miles last night when it was cool (freeway). Through the 80 miles I took a total of six measurements. The rear cylinder was 350 ish each time, the front 250 ish. Pulled the plugs this morning. The shiny electrode was from the front, the other from the rear.






To my own embarrassment, that was on me. He built the motor, I installed it. I knew it was there, but never thought of it being an issue. And thanks for your opinion, it seems most would agree.

I know its normal for the rear to run hotter than the front, but yeah, 100 degrees? And frankly, I think it's more that he's hoping / praying, and just didn't want to tear into again until the issue behind the problem finally presents itself. He said "ride it for a couple hundred miles and lets see where we are". I fear that where we'll be is with another toasted piston.

 

I doubt that patch of area blocked caused the problem.
Those air filters are good for over 6000RPM and I doubt you were seeing much of that.