Honda TRX250R Forums banner

1 - 16 of 16 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter #1
My R was running well then yesterday, I took a couple laps around my property,(20 acres) it lost power and shut off. I compression tested it today but no reading at all. I started tear down and found out my piston melted. What would cause this to happen?
64532
7FECB25B-AB92-460F-A79C-8010FB870DB0.jpeg
 

·
Registered
Joined
·
370 Posts
A lean condition. If it was jetted properly then you could have lost a crank seal, base gasket, or an intake gasket. Did you have any exhaust leaks? Wrong fuel?
Loren
 
  • Like
Reactions: SandSlinger

·
Super Moderator
Joined
·
2,348 Posts
What compression are you running and how fresh was your fuel?
 

·
Registered
Joined
·
13,193 Posts
My R was running well then yesterday, I took a couple laps around my property,(20 acres) it lost power and shut off. I compression tested it today but no reading at all. I started tear down and found out my piston melted. What would cause this to happen? View attachment 64532 View attachment 64532
While an air leak of the Main Seals on the left side (or right), intake or base gasket is the most referred cause of your failure, it is unlikely for the damage seen on the piston, unless the leak is MAJOR. If it was a major leak, you can see traces/trails of the leak on the intake & base gaskets, and seals…. effectively the leak source must be very significant & noticeable.

Besides the good questions already asked:

Was the failure immediate or after a given riding time, say =>5 minutes?
How long has it been running well?
How long has it been sitting?
New, old or same gas as always, same ratio mix?
What does the underneath of the piston crown look like, Black crusty, burnt-baked oil?
Same Plug Heat range?

IMO this is an IGN related failure more than a simple leak. Possibly the CDI, Stator, Flywheel, Pickup or major timing short…. the damage is severely on the exhaust side, typical of overheating. I would get your Honda service manual & OHM meter out and start checking.

Carlos
 

·
Registered
Joined
·
8 Posts
Discussion Starter #7
While an air leak of the Main Seals on the left side (or right), intake or base gasket is the most referred cause of your failure, it is unlikely for the damage seen on the piston, unless the leak is MAJOR. If it was a major leak, you can see traces/trails of the leak on the intake & base gaskets, and seals…. effectively the leak source must be very significant & noticeable.

Besides the good questions already asked:

Was the failure immediate or after a given riding time, say =>5 minutes?
How long has it been running well?
How long has it been sitting?
New, old or same gas as always, same ratio mix?
What does the underneath of the piston crown look like, Black crusty, burnt-baked oil?
Same Plug Heat range?

IMO this is an IGN related failure more than a simple leak. Possibly the CDI, Stator, Flywheel, Pickup or major timing short…. the damage is severely on the exhaust side, typical of overheating. I would get your Honda service manual & OHM meter out and start checking.

Carlos
I ran it for about 30 minutes yesterday it’s been running good since I was on here last and you guys helped me with jetting
There is a little oil coming from the base gasket
I put fresh super gas in before I ride, mixed at 32:1
The underneath of the piston skirt has some discoloration, brownish
Still running the Dynatek cdi, still looking for an Oem one
Thanks for the info
 

·
Registered
Joined
·
8 Posts
Discussion Starter #9
A lean condition. If it was jetted properly then you could have lost a crank seal, base gasket, or an intake gasket. Did you have any exhaust leaks? Wrong fuel?
Loren
Base gasket has some oil around it. No exhaust leaks, same fuel as always.
Thanks for the info
 

·
Super Moderator
Joined
·
2,348 Posts
Back about 10 years ago my brother went riding with his buddies with our R, it had an ESR 350BB back then, and it was fast as hell! It was a high compression motor (as all my motors are). My brother accidentally put our lawnmower gas in it, 87 octane NO PREMIX, just straight freakin 87 octane. The piston in my motor looked EXACTLY like yours does! I still have that piston out on my work bench...
 

·
Registered
Joined
·
43 Posts
Back about 10 years ago my brother went riding with his buddies with our R, it had an ESR 350BB back then, and it was fast as hell! It was a high compression motor (as all my motors are). My brother accidentally put our lawnmower gas in it, 87 octane NO PREMIX, just straight freakin 87 octane. The piston in my motor looked EXACTLY like yours does! I still have that piston out on my work bench...

That hurt to read........
 

·
Registered
Joined
·
13,193 Posts
between the base gasket leaking and crap cdi i think yo have your answer.
Agreed...:)

I ran it for about 30 minutes yesterday it’s been running good since I was on here last and you guys helped me with jetting
There is a little oil coming from the base gasket
I put fresh super gas in before I ride, mixed at 32:1
The underneath of the piston skirt has some discoloration, brownish
Still running the Dynatek cdi, still looking for an Oem one
Thanks for the info
Don't know if you still can, however; it would be to your best interest to perform a leak down test now and try to identify the leak source and volume. Best to identify now, correct and move on.

I still say the IGN is mostly at fault; current aftermarket CDI's are not healthy for the 250R's, despite what some may say. The advanced timing curve found on all the aftermarket CDI's will eventually lead to failure, most kick back and let you know of the advanced timing, however; under certain conditions, they don't kick back, yet the advanced timing is always present causing overheating & detonation.

Carlos
 

·
Registered
Joined
·
1,607 Posts
Anytime you or someone you know buys a 250R from someone that says fresh rebuild. Unless you see engine disassembled in your face engine installed and ran than believe it.
but most times just do simple tear down to check work no matter what.
I ha e bought a few rebuild 250r and all were not. I tore down used OEM Honda parts assembled cleaned, leak down checked fresh fluids and off to tuner
 

·
Registered
Joined
·
13,193 Posts
It’s called ‘seller convenient remembrance’…seems all used engine sales are always more worn, smaller displacement aka bore, CC’s, run worse than stated, and need rebuilt regardless of the sellers assurances that it was fully rebuilt, with less than 5 hours of total riding time.

Carlos
 
1 - 16 of 16 Posts
Top