Hello, I bought an old 1991 TRX 250X quad about 2 months ago, and the engine blew yesterday while the kids were trail riding it.

I have not cracked it apart yet, but I am thinking either the piston or connecting rod broke.

It was making a ticking noise (seemed to be noisy valves) and it was running with blue smoke.

I fear the previous owner "might" have had a high compression piston in it, and I should have been using higher octane fuel.

Anyway, whatta you guys think? Do connecting rods usually break on these, or does the piston just let go?

Also, does the case have to be split to change the connecting rod? I see in the parts diagram that the crank pin comes out, but I wonder if it is a press fit.

Thanks! Daniel

 

Could be any of the above.
What did it do when it blew? Did it lock up?
I'd pull the plug and see what you can see in there. Also pull the rocker box covers and see if it dropped a valve.

 

I wish I had been riding it when it blew, but it was one of my kids' friends, who does not know much about sounds and engines!

The kickstarter turned for a few kicks, but it will not now. Kids say there was no compression when they pulled the plug and kicked it a few times.

I did pull the plug, and I cannot see anything.

I have more time to work on it this week, and I will post back what I find.

Thanks!

Daniel

 

Update:

I talked to the kids again, and they said the engine made NO loud noises or bangs when it stopped running. However, the spark plug electrode was bent upward into the plug, so there was no gap.

Hope this helps!

Daniel

 

<div class="FTQUOTE"><begin quote>I talked to the kids again, and they said the engine made NO loud noises or bangs when it stopped running.</end quote></div>
I have kids; that's what they all say!!! LMAO
I have a dent in my garage door that "nobody" knows about but you can see it's an ATV tire mark.
Let us know what you find out.

 

Ok, I pulled the top end off last night.

Not pretty. Piston trashed, pieces of the cylinder broken and fell in cylinder [img]i/expressions/face-icon-small-sad.gif[/img]

Time to part it out!

Daniel

 

Where do you live?
Are you interested in selling the whole thing,instead of parting?

 

I live in NW Ohio, and I would be willing to sell whole.

It has a modified swingarm from an ATC 250R (previous owner did mods), and I have to install a brake system from a 1985 ATC 250R, that works great.

Contact me via PM.

Thanks!

Daniel