Author Topic: WTF?? three torched pistons (Read 30418 times)

rjt500r · « **on:** July 20, 2014, 11:28:34 AM »

pulling my hair out trying to figure out what is going on here. Have an 88 250r , started out as a stock motor, cylinder, first ride burned a hole in the top of the piston within ten minutes. Tore it completly down different set of cases, new bearings, new seals, LED ported and o-ringed the head. New V-force reeds new UPP intake, 38mm PWK 50 pilot, 180 main, DDJ 3rd clip, AV gas 32:1 w/HP2. Second trip same results ten min ride not even full throttle burned a quarter size hole in the top of the piston. Thought maybe not pulling enough fuel changed the petcock setup to the Honda CRF250x did the petcock mod to pull from both on and reserve, new piston ran 110 race fuel thinking the AV gas was the problem nope!! another less than ten minute ride 1/2 to 3/4 throttle at most torched the piston. Air leak ?? Going to try a leak down test not sure if the hole in the piston will effect the results but i don't know what else it could be even though it has all new seals. Any insight would be greatly appreciated.

The_Steve_Man · « **Reply #1 on:** July 20, 2014, 11:44:43 AM »

Is there any coolant in it?

hickwheeler · « **Reply #2 on:** July 20, 2014, 11:47:07 AM »

I would lean towards a airleak.

KASEY · « **Reply #3 on:** July 20, 2014, 11:53:58 AM »

I am leaning towards YOU don't know the sound of a very hot lean running motor,,,, listen to the motor,, it will tell you when its that close to burning a hole ,,,, it doesn't sound or feel right...

jcs003 · « **Reply #4 on:** July 20, 2014, 12:34:25 PM »

sounds like an air leak for sure. get a pic of the piston so jerry hall or rss396 can see it and they will more than likely tell you by the piston damage.

john

Daniel370r · « **Reply #5 on:** July 20, 2014, 12:46:27 PM »

Does it have the stock ignition pvl ignitions are good for doing that

udontknowme · « **Reply #6 on:** July 20, 2014, 01:19:48 PM »

i have no experience burning hole in pistons but maybe the cdi is going bad.

jcs003 · « **Reply #7 on:** July 20, 2014, 01:29:48 PM »

check this out:

http://trx250r.org/threads/767-piston-failure-chart

john

rjt500r · « **Reply #8 on:** July 20, 2014, 05:10:29 PM »

Quote from: the_steve_man;39474

is there any coolant in it?

yes

rjt500r · « **Reply #9 on:** July 20, 2014, 05:21:10 PM »

Quote from: KASEY;39477

I am leaning towards YOU don't know the sound of a very hot lean running motor,,,, listen to the motor,, it will tell you when its that close to burning a hole ,,,, it doesn't sound or feel right...

I'm leaning towards YOU don't have a clue what i know!! I'm fully aware of what a lean engine sounds like, i have burned up pistons before because of my mistakes. Maybe you should read the post again, this is happening in less than ten minutes. The damn thing is not even warm yet. There is no warning.

rjt500r · « **Reply #10 on:** July 20, 2014, 05:31:05 PM »

Quote from: Daniel370r;39481

Does it have the stock ignition pvl ignitions are good for doing that

Stock ignition, two different ignitions, the first i pulled out and ran it in another bike with no issues.

rsss396 · « **Reply #11 on:** July 20, 2014, 05:33:08 PM »

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

rjt500r · « **Reply #12 on:** July 20, 2014, 05:33:53 PM »

Quote from: jcs003;39480

sounds like an air leak for sure. get a pic of the piston so jerry hall or rss396 can see it and they will more than likely tell you by the piston damage.

john

I will post a couple of pics

2ndmoto · « **Reply #13 on:** July 20, 2014, 05:41:12 PM »

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

Grande huevos · « **Reply #14 on:** July 20, 2014, 06:50:16 PM »

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.