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Hi all! I'm new to this site and ATV's in general. I've had quite a few motorcycles in my day but never an ATV. My son (who just turned 10) has expressed interest in doing a project with me out in the garage. I thought it would be fun and a good learning experience for him. So as the title suggests, I found a 2007 TRX250EX. The owner seemed honest and said the motor was "blown". He stated his girlfriends kids overheated it out in the field one day while he wasn't home. He didn't know much more than that. It had oil but the battery was no good to turn it over. He had the rear cover plate off so we were able to crank the engine around a few times with a wrench. It definitely had a sticking spot where it seemed to grind a little. My limited knowledge I was hoping it was the top end piston or cylinder. Everything else looked pretty clean. I negotiated a price of $250 and he accepted so I figured I would go for it.

Here's what it looked like when we brought it home:
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So we first drained the oil, it was BLACK as night and had small metal shavings in it. Not surprising. So we started taking things apart starting with the top end. Once we got the head off it has a lot of carbon, but actually looked pretty good:
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So we proceeded to take the cylinder off and it didn't look to bad either (probably can't tell much from the pictures, but no scoring, heat marks, etc):
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Then we ran into trouble. The piston head moves freely but the connecting rod around the crank is pretty bound up:
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So here we are now:
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I've worked on a lot of things, but I've never taken a lower engine apart. We plan to do it and just go slow and follow the manual. I'm probably going to need a lot of help along the way though. So that's why I'm here. :)

I guess at this point I would like to know if this is common and if anyone has dealt with it before? I'm curious if anyone has a guess as to why this overheated when there seemed to be oil in the engine. Obviously until it's torn apart no one knows what is really going on, but I'm curious about educated guesses from people who have worked on these before.

We plan to proceed with removing the engine and tearing it open. This is a little intimidating though as I haven't done it before. My plan is to just take our time and ask lots of questions in this thread along the way. Hoping to get some help. So at this point does anyone see any reason not to remove the engine and open it up? Anything in particular to watch out for when cracking this thing open? Again I plan to just try and follow the manual as closely as possible. Also if anyone has any good links to videos of anyone doing this that would be helpful. I search around but didn't find any for this exact engine.

Anyways I'm looking forward to learning with my son and spending time together. I'm hoping in the end we're actually able to ride something and keep the total cost below the worth, Thanks for reading and I looking forward to chatting with you all!!
 

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Welcome to the forums , nice looking project ---- the top speed listed for a GSXR1100 is 185mph stock off the show room floor , how fast have you had yours , I take it you have one as your name suggest it
 

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the top speed listed for a GSXR1100 is 185mph stock off the show room floor , how fast have you had yours , I take it you have one as your name suggest it
I had many GSX-R1100's in my younger days, kids now and those fast impractical toys are long gone. 185 on a stock GSX-R1100 would be a very difficult thing to accomplish, you'd need to be jockey size and on a track. I'm 6'4" 250lbs so my weight slowed things down. That said I had it up to 155mph one time and one time only. It had a little more power but not much. Might have been able to reach 165 but that would have been it. I wouldn't have done it anyways because at 155 everything was a blur. Most people thing I'm lying to them when I tell them I've gone that fast. They don't know the power of those bikes though. :)
 

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When I was younger in High School in the early 70's , I rode a Kawasaki 500 Triple 2-stroke with a lot of work and money into it , back then it was about the quickest in a 1/8th mile , I weighed 120pounds , 125 was max , you hit that in a 1/8th and just rode out the other 1/8th , that was fast enough for me , I couldn't imagine doing 185 , I read the Ducati's can do 205 right off the floor ---- the reason the GSX-R1100 interested me was a 22 yr old got killed on one about two months ago on the corner of my street and the highway , 150ft skid mark , 8 ft diameter blood ring , body parts detached , knocked the 150 Ford 25ft sideways , the front wheel is touching the engine block , the Troopers said the impact was around 125mph , so how fast you think was he going to leave a 150ft skid and still hit at 125mph

what are your plans for the EX , you doing an jug job
 

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oh yikes!! Yeah I have no interest going that fast anymore. Yeah I will probably do a jug job on the EX if I can get the main issue in the lower all sorted out. Swapped a lot of motors in my day but never done any work like this before. Looking forward to learning though.
 

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i like G+H for machining and upper parts , they have a good deal and do good work ------- for the rod/crank , one ight be available new for your bike , if not/or , there is Mr Crankshaft , who will put a rod on your crank for you , I don't even know if the ex needs to be pressed on or not , I am a 300 and 450 kind of guy , the 300 crank is no longer available new , so Mr Crankshaft was my only option ----- if there is play in the wrist pin journal of the crank and you do an upper without replacing the rod , it will not last 100 hours and you will be boring it again , the piston will wobble and egg shape the bore quick
 

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i like G+H for machining and upper parts , they have a good deal and do good work ------- for the rod/crank , one ight be available new for your bike , if not/or , there is Mr Crankshaft , who will put a rod on your crank for you , I don't even know if the ex needs to be pressed on or not , I am a 300 and 450 kind of guy , the 300 crank is no longer available new , so Mr Crankshaft was my only option ----- if there is play in the wrist pin journal of the crank and you do an upper without replacing the rod , it will not last 100 hours and you will be boring it again , the piston will wobble and egg shape the bore quick
Excellent information!! Thank you!! This is the kind of info I need. I will definitely check out G+H. I haven't even spec'd the jug yet so I'm not sure if it needs to be bored out. I'm more concerned with the bottom right now. It looks like the rod is pressed on the crank for the 250EX. I does look like I can buy a new rod/crank. Looks to be about $330 new. I don't want to put in a new rod/crank though if other things are messed up down there. Curious if anyone has any thoughts on what else would be destroyed down there when it got overheated like this. I won't mine putting in $500-$600 but I don't want to invest a whole lot more than that to get this thing going. I don't think I would get my money back out.
 

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I had a 2006 TRX250EX a couple of years back , I put a few hundred into it and got it running and looking good , but it really never fit in my fleet , I am into 4wd and mud , so I sold it for $1,200 , seems different parts of the country bring different money for atvs -----

I think if I were into the engine already , I would have it bored and start fresh ----- G+H ATV , will do the boring and supply Shindy piston and rings , wrist pin , clips , all the gaskets , seals and valve stem seals you need , with shipping of your jug to them which is about $15 , it will cost you about $215 , can't beat that , takes about 2 weeks round trip , seen it happen in 10 days ----- the guy at Mr Crankshaft is Vince , he is a super nice guy and he will talk with you , give him a call and see what he can do for you , ask if he has a Versha rod for the 250EX , they are suppose to be better than a stock rod , I have one in my 300 , I know it will cost less than $330 for a new crank

as far as what else you will need , you won't know that till you do it , a timing chain is a good idea while it is down , even if it looks all right , and lap the valves and replace the seals
 

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I had a 2006 TRX250EX a couple of years back , I put a few hundred into it and got it running and looking good , but it really never fit in my fleet , I am into 4wd and mud , so I sold it for $1,200 , seems different parts of the country bring different money for atvs -----

I think if I were into the engine already , I would have it bored and start fresh ----- G+H ATV , will do the boring and supply Shindy piston and rings , wrist pin , clips , all the gaskets , seals and valve stem seals you need , with shipping of your jug to them which is about $15 , it will cost you about $215 , can't beat that , takes about 2 weeks round trip , seen it happen in 10 days ----- the guy at Mr Crankshaft is Vince , he is a super nice guy and he will talk with you , give him a call and see what he can do for you , ask if he has a Versha rod for the 250EX , they are suppose to be better than a stock rod , I have one in my 300 , I know it will cost less than $330 for a new crank

as far as what else you will need , you won't know that till you do it , a timing chain is a good idea while it is down , even if it looks all right , and lap the valves and replace the seals
Once again, THANK YOU!! Invaluable information to me. I will give both of these places a call once I get into things and know a little bit more. It sounds like this might be doable and able to keep the total cost including atv under $1k. I think it would be worth it for that. Again thanks a lot and I'll keep this post going with updates (and probably more questions.. ha!).
 

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Finally was able to get the case split last night and get the crank out:

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Going to contact Mr. Crankshaft today and see what my options are. Most everything else looks like it is in ok shape so far except the case. Both halves of the case seem to have spider cracks through them:
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I'm assuming this is not good. Has anyone across this before? Are the cases usable or do they need to be replaced? I know it's probably hard to tell from these pictures. Any advice would be appreciated though. Thanks!
 

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I ended up finding a crank case in good shape on eBay for $78 shipped. I went ahead and bought that. Don't want to mess around with this case.
 
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