Bike siezed - Broken valve spring

2010 TXC 250

Was riding some single track on Friday. Idling through some tight and twisty stuff, and the bike burbled and died. Tried to turn it over with the e-start & it just clicked. Tried to turn it over with the kicker and nothing, totally seized.

Pushed her out of the woods put her on the trailer and made the hour drive home. Once I got home, I tried the electric starter again, and it was totally free. As a matter of fact, it was too free, no compression at all.

Turned it over a few times. If I left the throttle closed, absolutely nothing. If I opened all the way while cranking it would puff smoke and cough, but that's it.

Pulled the head and saw the problem right away. One of the exhaust valves was open. Grabbed it and pulled it right out, not even fastened. Turned it over and the springs fell out in my hand in 4 pieces.

This is my first time doing major engine work, all me experience is with smaller RC Airplane engines.
I'm obviously going to replace the valve that let go, and while I'm in there I am going to replace the springs and keepers on the other 3. Since the head is off, I'll probably get new rings as well.

The bike is a 2010 TXC 250 with 156 hours.

I'm worried about the fact that when it first died it was seized, I'm wondering if there might be some damage to the crank bearings or conrod. Everything down low is turning freely right now, and there doesn't seem to be any strange noises or binding, so I don't know.

I honestly don't know if the spring broke first, or if the engine seized, somehow causing the spring to break.

It was a very wet day, deepish puddles everywhere. I'm wondering if maybe I sucked in some water that caused the piston to hydrolock. Seems unlikely, but who knows, the bottom of the airbox was definitely wet.

Any guidance, tips, or suggestions are welcome as always.

So no impact on the piston crown? good. Look for chunks in the lower end too.

Is it possible the bike was way-overheated (bad impeller, t-stat, etc)? Burnt oil smell is sometimes a clue. I would do the head- with 4 new springs too, possibly. Maybe do the rings (and piston?) while you're in there.

Sorry, I don't have anything direct to offer; but you may have dodged a bullet.

As far as I can see, the crown looks perfect.

It's funny you mention the impellor, as I just fixed it a few weeks ago. I had two days out where the bike was definitely running hot. Boiled it twice. Turned out that the impellor nut had let go, and the impellor mounting surface was totally bored out. There was no coolant flow at all. I replaced the pump, along with seals and gaskets.

When the bike seized this time, the first thing I did was check the temp. It was 71 degrees C (160 F) so it definitely wasn't hot. Perhaps the spring was weakened from the two days it was run hot with the busted impellor?

I'm definitely going to change all of the things you mentioned. Both local dealers I spoke with suggested that I do the bottom end as well as it is past due ( according to the suggested husky service schedule ). I don't have unlimited funds, so I have to decide.

I have had a few valve springs break. Usually the inner spring breaks and the bike will idle and run a little crappy. I never had the inner and outer break. Supposedly Zip Ty has better valves and springs...

That's good to know. I'll give Zip-Ty a call and see what they have. I am definitely planning on replacing all of the valve hardware, might as well go with the good stuff.

I have a question about the crank/conrod. I haven't split the case, but with the cylinder off and the piston at TDC the crank is right there. when I rotate the conrod front to back everything seems smooth, so I'm hoping the bearings are fine. However if I rock the conrod laterally side to side, there is a little play. Not much, but it is noticeable. Since this is my first time working on major engine components, I'm not sure if a little play is normal or not.

I also sourced a used head with valves included off a low hour TE250 (approx 1000 mi) for $600. That could be an easy option for the top end. I doubt I could buy 4 valves and the mounting hardware for any cheaper than that.

if your cylinder head is repairable I would just fix it with new parts. buying a used head is a gamble.

I hear you. I just need to get the bike fixed by the 5th of September. I'm signed up for training with Chris Birch that weekend. As it stands now I'm going to have to go on my mountain bike!

I also sourced a used head with valves included off a low hour TE250 (approx 1000 mi) for $600. That could be an easy option for the top end. I doubt I could buy 4 valves and the mounting hardware for any cheaper than that.[/quote]
If the 1,000 miles was put on by a soccer mom it would probably be fine... if it was a pro rider i'ts probably worse then the one you took off.

Your con rod should have lateral movement.

Brought the engine to the shop yesterday to get a professional opinion on the overall condition. He used to sell the old huskies, so has a lot of experiences with the engines. He recommended I do an overhaul as most of the tolerances of the major parts are out of spec. Since I've got it torn down and I'm out of commission for a while anyway, I figure it's just as well to do it right. So, Looks like a rebuilt crank, case bearings, piston set, valves, timing chain, etc. are all on the shopping list.

It's only money... Right?

Maybe. 'specially if you're talking radial runout of the crank or excessive lateral movement of the rod (I'm slightly incredulous but...) . AND if you're doing it yourself then the money thing isn't hugely huge ($500us vs $900).... but- if a shop is doing it then I don't know. You could be talking serious bucks ($900 top end vs $2200 rebuild; I'm pulling these numbers outta thin air). And (I CRS) is your engine an x-lite? because the older generation motors have a very solid rep; 156 hours wouldn't be shit. Hell, I'd be surprised if an x-lite was bottom end was due at that time even (component failure: maybe... but everything due??)

looks like you "un-dodged" the bullet I spoke of earlier. did you ever figure out if the motor got cooked?

good luck.

It is a first generation X-Lite. The engine definitely wasn't cooked. The valve dropped, but did no damage to anything on the bottom end. The only metal I found in the case was a part of the broken valve spring.

The valve job was a must. All of the valves were a little sloppy and had too much play in the guides.

The conrod was also way to sloppy on the crank. Since he has a rebuilt crank, ready to go, I figured I'd do it. Then I figured why change everything and leave the old bearings.

He did say that other than the valve job, the other parts could possibly last for another who knows how many hours. I don't think any of the other parts were near failure, but are showing enough wear to warrant replacing them. Especially since I've already got it all a part.

I plan on keeping the bike for another couple of years, and hopefully after this I'll be good for another worry free 150 or more. Since I usually ride 50 - 60 hrs per season, I'd rather do the work now while I'm down and hopefully get away with an incident free season next year

Well, I just put the engine back together and went for a test ride. Engine feels good as new. Definitely a noticeable boost in power.

I decided to do a full rebuild in the end. All new valve train, rebuilt crank with wosner conrod and vertex piston, new case bearings, and timing chain. Hopefully I'll have another worry free 150 + hours.

Nice, smart plan. Good thing the cases weren't damaged. Re built internals will obviously prevent this too.