WTF?? three torched pistons

[fearlessfred]

when changing ignitions out, was there anything left unchanged  and what had been done to motor before the hole burning started ,was it rebuilt new crank

[hontrx265r]

The difference between a 50 and 52 pilot should not be melting down though, and if your riding not idling it really shouldn't be. I always thought it was a pain when I was younger, but I dont think there is any smarter thing you could then leak down your motor after any work has been done that could compromise sealing. I just did mine today. Thankfully it was a sealed up sunday

[rjt500r]

Here are the pistons. The first pic was the completely stock motor with a PWK 38mm. The second one is a completely rebuilt motor different cases, cylinder work by LED, new V-Force reeds, new UPP intake, new bearings, new seals, different crank. Also here is a brand new plug completely melted down. I just did a leak down has an air leak at the stator side crank seal ( a brand new seal ). Is there more going on here though? would an air leak do that to the plug. I can't stress this enough this is happening in less than ten minutes at 1/2-3/4 throttle.

[rjt500r]

What ignition is on this bike? What carb and jetting? Typically a hole in the center of the piston points to ignition being to far advanced

Stock 87 oem ignition. Carb is a PWK 38mm AS 180 main 50 pilot and DDJ needle 3rd clip. these are what Arlan recommended for jetting.

[rjt500r]

In all my LRD/LED motors, I have never ran that small of a pilot down at the Oregon dunes. The main seems to be a bit large too.

Typical jetting with no airbox lid
52pilot
DDJ in the 3rd or 4th position from the top
172-178main

Best Regards
-Jason

The jetting is per Arlan at LED. He did the port work on my cylinder. It will probably need some fine tuning, but can't really do that when it's burning up pistons in 5 to 10 mins.

[rjt500r]

Is it possible that you aren't burning holes in the pistons?? Instead you don't have the proper clearance and the spark plug is beating a hole through them??   Also do you have a temp guage?? I wouldn't think you could burn a hole in a piston before the bike has even warmed up.

No it's clearly burning through the pistons. No you would not think it would burn up a piston before its warm but thats exactly why i'm posting this. Any of the Oregon riders would be familiar with Sandlake, I was parked at the west wind parking lot, started the bike rode through the parking lot to the sand went half way or less to the beach turned around and went a short distance back and then towards the beach again and lost the piston. This all happened in a few minutes 5 to 7 no more than ten. At half to maybe three quarter throttle.

[rsss396]

The porcelain is broken off the spark plug so some detonation was happening but that more than likely was caused from to much timing and/or to lean of needle

I would try a differant CDI and a richer needle

[rjt500r]

when changing ignitions out, was there anything left unchanged  and what had been done to motor before the hole burning started ,was it rebuilt new crank

 I bought the bike in Feb it has never ran longer than ten minutes without burning up the piston. Yes it has been rebuilt, my original post states that. At this point the only things that have not changed are the carb and cylinder.

[rsss396]

the piston exhaust side skirt on the left piston does not show major signs of being lean so I tend to believe that ign timing is advance possiably because of a bad CDI.
This does not mean you dont have to add more fuel also, but IMO it sure looks like it may have to much timing

[rjt500r]

The difference between a 50 and 52 pilot should not be melting down though, and if your riding not idling it really shouldn't be. I always thought it was a pain when I was younger, but I dont think there is any smarter thing you could then leak down your motor after any work has been done that could compromise sealing. I just did mine today. Thankfully it was a sealed up sunday[/QUOT


Agreed I will make it a point to do a leak down every time i do an engine rebuild. Cheap insurance for sure.

[rsss396]

the piston exhaust side skirt on the left piston does not show major signs of being lean so I tend to believe that ign timing is advance possiably because of a bad CDI.


This does not mean you dont have to add more fuel also, but IMO it sure looks like it may have to much timing

[rjt500r]

The porcelain is broken off the spark plug so some detonation was happening but that more than likely was caused from to much timing and/or to lean of needle

I would try a differant CDI and a richer needle

You can't see it in the pic but the plug is white. I did find the stator side crank seal is leaking air. I do have another cdi to try.

[atvcrazy]

I think it's ignition and your air leak.  The normal Arlan jetting is 50-52 pilot dej needle in the 4 clip and high 160' to mid 170's on the main. Even at this a bit leaner needle still wouldn't do what's happening like Dave said the rings are free on the piston and the exhaust side of the piston doesn't show scuffing.

[rjt500r]

I think it's ignition and your air leak.  The normal Arlan jetting is 50-52 pilot dej needle in the 4 clip and high 160' to mid 170's on the main. Even at this a bit leaner needle still wouldn't do what's happening like Dave said the rings are free on the piston and the exhaust side of the piston doesn't show scuffing.

I will change the cdi and replace the seals. The jetting is directly from Arlan, the 180 is the high end but the range he gave me was 175 - 180 on the main. Like i said it will probably need to be fine tuned but i can't do that until i can keep from burning a hole in the piston.

[GO OVRIT]

I know you said "stock" ignition, but is it all "oem"?  Some of the aftermarket CDIs have really bad advance curves.