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Orville538

Need help identifying piston size

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I got this Honda TXR EX300 but I suspect it has a big bore that someone made fit without machining the cases...apparently the person grinded down the cylinder bottom sleeve and fit the cylinder head somehow,I will post pictures of the sleeve tomorrow possibly,for now I have this and need help whti the size of piston needed,looks like the camshaft is a bit rough to...maybe? Piston skirt has this scratches...piston is Niche brand like cylinder head sold @ Ebay or Amazon 

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Hmm now thats a real odd situation. I dont see anywhere to get a 79.5mm piston. The 330 kit is 80mm i would think that sleeve could easily be honed out to make a 80mm piston work. Saying they didnt clearance the cases has me concerned though. They would have had to do some lathe work on the outside of the sleeve then and if its that thin i would be weary of making it any thinner. But the 330cc or 80mm piston is by far the easiest to find piston to get it running again. The cam is rough no doubt. For multiple reasons. Cam sprocket bolts look terrible. The one lobe is pretty pitted and roughed up. How do the rocker arms look? I can only imagine they will have a wear shelf in them. Which will make getting them adjusted or keeping them adjusted near impossible. Welcome to the forums!

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Ihave gotten a custom piston from J+E Piston 1-714-898-5114

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9 minutes ago, Fishfiles said:

Ihave gotten a custom piston from J+E Piston 1-714-898-5114

You got one up on me fish. I couldnt get JE to respond to me at all. I called them a few times and never got to anyone who could help. I sent them emails. Which kinda stunk cuz they are a local company to me. There is one of there headquarters in mentor ohio. Which isnt but maybe and hour and a half drive. I ended up going with CP. They responded and were able to do my piston. From what i found all the places would only make 2 or 4 though. Unless you wanted to pay more than 500 dollars for one piston. I had CP make me 2 for 425 shipped. Which is kinda nice. I have a back-up if i need it.

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I guess I caught him on a good day , cause he really went out the way to help me with my project ----- I guess you and me are just little peas in a pot of vegetable soup , they be scooping for the meat 

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Slammed have you ever used Total Seal rings ? Good or bad ? Any draw backs ? ---- I have had people tell me they don't last in a dirt bike or atv used for mudding , they are for racing applications !!! 

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9 minutes ago, Fishfiles said:

Slammed have you ever used Total Seal rings ? Good or bad ? Any draw backs ? ---- I have had people tell me they don't last in a dirt bike or atv used for mudding , they are for racing applications !!! 

I have not. I did some research on them at one point. Never found anything that really sold me on the idea. And my custom pistons came with rings so im just gunna run them. Sorry OP were kinda hijacking this thread.

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18 minutes ago, SlammedRanger said:

I have not. I did some research on them at one point. Never found anything that really sold me on the idea. And my custom pistons came with rings so im just gunna run them. Sorry OP were kinda hijacking this thread.

No biggie slammed,I appreciate the help also Fish I want to thank you for your time and info as well,I don't like wasting no ones time because time is valuable you cant give time back to no one,BTW as yoy guys know I'm new to this forum!!!! I have some knowledge about atvs but not to your level,with that said I researched Wiseco they have a 79.50 mm 8 8:1 but is for 350cc rancher? and a 78.50mm 8 8:1 

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If someone put a 350 rancher piston in there i would be very shocked. You would have to do extensive measuring and clay it and measure again. The chances that all the valve pockets would line up and everything would just work would be extremely slim. Niche is a kind of generic brand. They dont really make things with tight tolerances and doing a custom build with there piston would be something i would be very skepetical of. I would be measuring the thickness of the sleeve down at the bottom and see if going to a 80mm 330cc bore would be feesable. That would be easy for alot of reasons. But if the sleeve is to thin you are in a situation. I would probably at that point get a niche cheap kit with a cylinder-piston and gaskets and go back to a smaller bore to not have to mess with case milling. My .02

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Welcome to the forum.  You have a 300EX correct? ( If so we can move this into the sport section that needs more threads.) I would have to dig up specs and research to help out. Piston pin size is the first step when trying to figure out backyard big bores. Once you know which motorcycles and atvs use that piston size then the real search begins. I'll need to be on the computer for that to make it easier for me and right now I'm mobile. 

 

The condition of the parts, do you need the big bore? Possibly you could find a used top end and start from scratch and know exactly what you have. 

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There should be a size stamping or etched on the Piston, but since you have your head apart, you maybe able to use bore size to roughly tell. A good machine shop can help you out. But I'd find out what a stock size is for it and try to go from there. 

 

Good luck bud.

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Hope you not mad about me high jacking your thread either. Always think the more traffic the better.  Sometimes it takes someone to say something stupid for another to think of and say something smart —- I am full of stupid 
 

I think I would start over.  Would be a bummer to sink mo money into it something that you are not even sure what it is and have it fail again.  

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2 hours ago, Fishfiles said:

Hope you not mad about me high jacking your thread either. Always think the more traffic the better.  Sometimes it takes someone to say something stupid for another to think of and say something smart —- I am full of stupid 
 

I think I would start over.  Would be a bummer to sink mo money into it something that you are not even sure what it is and have it fail again.  

No not mad at all, actually entertained, more folks talking better off. I can't hardly get folks to understand my point sometimes cause I'm a tad backwards things don't get read how I want em to by the other person, and that was my bad I should've said use that to see what you have then start over from scratch. Oops lol brainfar. 

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14 hours ago, SlammedRanger said:

If someone put a 350 rancher piston in there i would be very shocked. You would have to do extensive measuring and clay it and measure again. The chances that all the valve pockets would line up and everything would just work would be extremely slim. Niche is a kind of generic brand. They dont really make things with tight tolerances and doing a custom build with there piston would be something i would be very skepetical of. I would be measuring the thickness of the sleeve down at the bottom and see if going to a 80mm 330cc bore would be feesable. That would be easy for alot of reasons. But if the sleeve is to thin you are in a situation. I would probably at that point get a niche cheap kit with a cylinder-piston and gaskets and go back to a smaller bore to not have to mess with case milling. My .02

Hey Slammed I forgot a major detail this honda would tick tick tick loud....and this came from a trade I did...long story short the guy who sold this to the guy I made the trade with told me that the guy told him "I just rebuilt this engine and is ready to rip" and the ticking on it is normal on this Honda's!!!! All this is coming from the original owner.... anyway when I heard it and saw the grey gaske goo coming from the valve cover and missing bolts and bolts loose I knew right away that it was a hack job....and the cherry on the top was I noticed the bottom of the sleeve shaved down all around.... and the rod has alot of play if I wiggled it side to side....I will post pictures when I come home later on,I'm at work now.... I do new construction homes in Fl.

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14 hours ago, toodeep said:

Welcome to the forum.  You have a 300EX correct? ( If so we can move this into the sport section that needs more threads.) I would have to dig up specs and research to help out. Piston pin size is the first step when trying to figure out backyard big bores. Once you know which motorcycles and atvs use that piston size then the real search begins. I'll need to be on the computer for that to make it easier for me and right now I'm mobile. 

 

The condition of the parts, do you need the big bore? Possibly you could find a used top end and start from scratch and know exactly what you have. 

If you can move the thread go ahead.... I just don't want to loose the help please....

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300ex's do tick. But not super loud. Your tick was almost certainly the cam and rocker arms are worn out. Most likely they were adjusted wrong aswell. You have to readjust the valve lash anytime the valve cover comes off. Since the rocker arms are in the valve cover and the thickness of sealer will very. Rod side to side play isnt a big concern. But any up and down play is bad news. And in all honesty the sealer is what is used for the valve cover on a 300ex. No gasket. Which i always thought was crazy. Alot of atvs dont use gaskets for the case halves either. Just hondabond. Or yamabond or what have you. I personally like gaskets. I always spray both sides with copper spray for good measure.

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6 hours ago, SlammedRanger said:

300ex's do tick. But not super loud. Your tick was almost certainly the cam and rocker arms are worn out. Most likely they were adjusted wrong aswell. You have to readjust the valve lash anytime the valve cover comes off. Since the rocker arms are in the valve cover and the thickness of sealer will very. Rod side to side play isnt a big concern. But any up and down play is bad news. And in all honesty the sealer is what is used for the valve cover on a 300ex. No gasket. Which i always thought was crazy. Alot of atvs dont use gaskets for the case halves either. Just hondabond. Or yamabond or what have you. I personally like gaskets. I always spray both sides with copper spray for good measure.

Hey Slammed This is the bottom sleeve grinded down more piston pictures and the 

 

6 hours ago, SlammedRanger said:

300ex's do tick. But not super loud. Rod side to side play isnt a big concern. But any up and down play is bad news. And in all honesty the sealer is what is used for the valve cover on a 300ex. No gasket. Which i always thought was crazy. Alot of atvs dont use gaskets for the case halves either. Just hondabond. Or yamabond or what have you. I personally like gaskets. I always spray both sides with copper spray for good measure.

Hey Slammed here the pictures of the grinded down sleeve with measurements some are a millimeter thicker or thinner,piston is 90.0mm cylinder 90.5 mm head gasket 80.0mm....also some pictures of the camshaft rocker arms which feel sharp as a knife on the edges I don't think they are good anymore and the little screws for adjustment in between the valve and the bolt....

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Oh man those rockers are toast. And that sleeve is way to thin to bore anymore. Also your saying the piston is 90mm? I thought the first few photos said it was 79.4mm? Im confused!

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11 hours ago, Fishfiles said:

Hope you not mad about me high jacking your thread either. Always think the more traffic the better.  Sometimes it takes someone to say something stupid for another to think of and say something smart —- I am full of stupid 
 

I think I would start over.  Would be a bummer to sink mo money into it something that you are not even sure what it is and have it fail again.  

Look at this I think is this an OEM cylinder head....this is the hack job someone did....

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3 minutes ago, SlammedRanger said:

Oh man those rockers are toast. And that sleeve is way to thin to bore anymore. Also your saying the piston is 90mm? I thought the first few photos said it was 79.4mm? Im 

Interesting you're right,i took measurements from bottom and today from the top 2 different measurements and I knew the rockers were no good as soon as I saw them and felt them

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Good lord my man. That is some crazy amounts of banjo tuning skills that guy had. Here are your options. If your dead set on the 330 you will have to mill the cases. I think i know what they did now. They purchased a 330cc kit from niche. Hacked it into the cases and called it a day. If i was in your shoes. I would go back to stock bore or do a smaller over bore and redo all of it. Sadly thats kinda the only option here. That sleeve is scrap metal. Piston isnt much better. Good thing is you can probably save the cylinder head atleast.

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Orv' , down  here , we would call that redneck 

 

in the pic with the piston upside down and you measuring it , I can see daylight between the caliper and the skirt of the piston on the right side , so I think if you were to measure it again you might get another measurement , either the caliper is cocked or the piston is egg shaped --- I think  a bad rod wrist pin bore  will cause it to egg shape , I know you mentioned side to side play on the rod , which is ok , the up and down play at the wrist pin causes the cylinder to wear in an egg shape , so even with a new jug if the rod has play at the wrist pin  , that new jug  won't last long , 

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8 minutes ago, SlammedRanger said:

Good lord my man. That is some crazy amounts of banjo tuning skills that guy had. Here are your options. If your dead set on the 330 you will have to mill the cases. I think i know what they did now. They purchased a 330cc kit from niche. Hacked it into the cases and called it a day. If i was in your shoes. I would go back to stock bore or do a smaller over bore and redo all of it. Sadly thats kinda the only option here. That sleeve is scrap metal. Piston isnt much better. Good thing is you can probably save the cylinder head atleast.

This are oem replacement supposedly no cases dont need machining or I saw a honda brand jug made into a 330cc jug for $120-$130 o e of the 2 and I'm gonna need those rockers and camshaft as well

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To what i remember which its been about 10 years since i had a 300ex. The 330 kit sleeve doesnt fit in the cases without some milling. Anything under the 330 kit will fit just fine. The reason for this is because the 330 is a bigger sleeve. All the other bores are done on the stock sleeve. Which is similar to the 400ex and the 440 kit. Except the cases dont need milled for the 440.

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