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Big Bore gave up on me Saturday...

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Well, looks like my cylinder gave up on me this weekend. I was riding along and all the sudden I heard what sounded like a coffee grinder in my motor. I killed the motor as soon as I heard it but it was too late. The people I was riding with said I was smoking quite a bit before it happened. Hecklerbike is now in the ICU.

At first thought I was sure it was my top end (what else) but upon inspection it seems that the cylinder on my big bore was the culprit, one of the skirts on the sleeve broke off and dropped into my lower end. I have not had the chance to split the cases to observe the damage but Im pretty sure it won’t be pretty. I need to check my crank and piston to see if it was caused by excessive play in crank/rod/piston or a failed sleeve.

A few pics below..

Cylinder 009.jpg

Cylinder 010.jpg

Cylinder 018.jpg

Cylinder 012.jpg

Cylinder 002.jpg

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I havent got the piston out yet, It's stuck at the bottom of the stroke but the top of it looks fine and the rings are still in place.

Ugh that is not good. What does the piston look like? How many hours?

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Man that looks really bad. The possibility of that kind of thing is the main reason I've stayed away from any of the big-bore kits---thin cylinder liners. Hope your bottom end isn't too torn-up.

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Well since I keep track of these things, (I highly recommend it) I installed this cylinder new with 45.5 hours on the hour meter and it is now at 189.2 hours so this cylinder has about 143.5 hours on it. And I change my oil every other ride or after any ride of 60 miles or more. I change the air filter in the dry (dusty) season after every ride and sometimes if camping I will change it mid day. I assure you there is no lack of maintenance on my bike.

I got the piston up and there doesnt seem to be any excessive play in the rod or piston but I will need to split the cases to get any true measurements.

All I know is there is a HUGE chunk of metal in my bottom end, look at the size of the missing sleeve!! :applause:

A few more pics, allthough the lighting was crap when I took them and they are kinda blurry.

Piston 002.jpg

Piston 004.jpg

Piston 005.jpg

Piston 007.jpg

Piston 008.jpg

Wow that sucks. Any idea of the hours? That's the first failure I've seen.

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Yikes, that's gonna cost you. Whose big bore kit was that? The bottom end looks like toast. I hope you didn't damage the cases too. Can you say "grenade". Keep us posted on the damage and the repairs... Good luck!

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I would say if that piston has done 140hrs it is more likely the culprit, trying to turn in the barrell (rocking) and breaking of the skirt. Is it the original big bore piston??

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I would say if that piston has done 140hrs it is more likely the culprit, trying to turn in the barrell (rocking) and breaking of the skirt. Is it the original big bore piston??

I can agree.

I have one of Eric Gorr's 262 kits (just bored) that most guys say DO Not last. Well the cylinder had 70+ race hours but I am going on piston #3.

If the piston begins to rock too much even the stock cylinder can crack.

Good luck...

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Will be interesting to know Russell(tech) 903-938-3340 or Gary Hazel's(owner) opinion at Thumper Racing as to service life in hours for their Pistons and cylinders? Heckler are you going to give them a call, and give us the low down? :applause:

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I talked to Gary yesterday, he pretty much said the same thing. It is not the original piston, I had replaced the original one after I noticed I was burning oil, probably a good 80 hours or so on it. I will most likely send it to him to check out. Im not saying it was a defect or the TR product that caused it, I need to get it torn down to check things out first, even then I may never know.

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Hey Larry long time no talk to........Sorry to hear about your BLOW UP, I was talking to my neighbor this morning and he told me about it. He was riding with you guys his name is Ron...You remember him, he towed you back ha ha ha ha I guess you shouldn't have gone so big with that BIG BORE KIT huh?

Well I won't grind you too bad. Have fun I'll catch up with you later..

BC

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WHATS UP BC!! Yea long time no talk. Yea, Ron is a cool guy, he is the inlaw of a friend of mne.

Hey Larry long time no talk to........Sorry to hear about your BLOW UP, I was talking to my neighbor this morning and he told me about it. He was riding with you guys his name is Ron...You remember him, he towed you back ha ha ha ha I guess you shouldn't have gone so big with that BIG BORE KIT huh?

Well I won't grind you too bad. Have fun I'll catch up with you later..

BC

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I wonder if the bore (& ring) was just wearing out causing the piston to rock? Does Thumper Racing use a conventional cast iron liner?

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Yeah I been busy this last year with this new /old house we bought to retire in. Was really surprised to hear that you went RED

which is no big deal ....I even got a red bike(CRF150)just turned 59 and have been dealing with a few health issues,nothing serious just getting old crap

now that the pad is pretty much together I want to start riding again.I will need to get my riding legs back before I can haul ass with you guys but I kinda want to get hooked up with you guys since we never got to meet

Keep in touch...I'm spending more time on the computer since I just bought an I-Mac and have to learn how to use the thing. Pretty increadible machine

I had no idea all the stuff Macs can do, especially these new intell chip models.....Talk to you soon .BC

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I'm curious to see what the piston to wall clearance is when you measure everything...because it looks to me from the picture that the piston skirt

has a rounded edge on it meaning too much wall clearance and letting the piston rock back and forth at the bottom of the stroke, which would put more pressure than normal on the part of that cylinder that busted away....thats why both front and rear areas were cracked...In my opinion that's whats wrong with these short skirt pistons the four strokes have gone to.....ah yes the price we pay for more HP...............

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Hey Larry I don't know what your plan is but before you split those cases

fill them with clean solvent and while rotating the crank turn the cases upside down and blow air into the case and repete till it is clean of all the pieces..

because unless there was a ton of ground up metal in there(which from the picture there wasn't)You should be ok with just washing the cases out..

I have done this before and it worked fine ....Unless you just feel better

by splitting the cases then go ahead and do it...

BC

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