310 Heat seize

[xTHUNDERCATx]

Didn't read every comment.Looks like it four corner seized mine was trashed had to be bored. Was just stating that if it needed bored or honed Eddie would probably do it for free.

Even so this one is on me, I'm not a fan of eddies for his motor work so I go elsewhere (didnt save me from my own stupidity on this one). I just used some local builder for the bore/hone on this. I may have to send it off to my actual builder to double check the clearance and maybe get some port work done before I retry it.

[Daniel370r]

I should have had the clearance on mine checked before I sent it back. I wonder if that's what normally causes a four corner sieze. Ct has a crazy heat cycle diagram I followed it and didn't do the trick for me. Still cost me another piston. I'm always nervous of seizing after every build.

[xTHUNDERCATx]

You have it up and running properly now?

[Jerry Hall]

Even so this one is on me, I'm not a fan of eddies for his motor work so I go elsewhere (didnt save me from my own stupidity on this one). I just used some local builder for the bore/hone on this. I may have to send it off to my actual builder to double check the clearance and maybe get some port work done before I retry it.

Do you know what the piston to cylinder wall clearance was set up to?  The aluminum definitely needs to be removed but the clearances still may be too tight if you just install a new piston after dissolving the aluminum with acid.  You need to find a shop with the proper honing and measuring equipment and knows how to use the tools.  You also need a shop that has a lot of experience with you type of engine and knows what clearance it needs to be set it up to.

I would find another shop if they use digital calipers for measuring tools, a ball hone or a hone on the end of a drill to bring the bore to size.  These are not the type of tools you will find in a shop that can give you the type of precision you need.

You may also have problems in other areas that caused the piston to overheat.  Do not over look fueling and exhaust system problems.  I am not sure what you are wanting us to see by showing us the view of your silencer core.  There are many variables that affect main jet size but I typically see main jets in the 190 to 200 range on the 310s with the ESR TRX 11 pipes that do not have any manufacturing defects.

[xTHUNDERCATx]

I asked them to set it up at .003'' but I dont think I ever double checked it. And to my knowledge fuel flow was good, I have good flow from the tank and carb was clean unless there was something I am missing that may affect it.

[Jerry Hall]

I asked them to set it up at .003'' but I dont think I ever double checked it. And to my knowledge fuel flow was good, I have good flow from the tank and carb was clean unless there was something I am missing that may affect it.

Fuel flow includes fuel flow into the float bowl as well jetting.  Wide open throttle involves the main jet and needle.  Different needles and clip settings often requires different main jets to get the same fuel mixture into the engine.

[udontknowme]

4 eyes is always better than 2. can usually score some decent used bore gauges and micrometers from ebay. this way if theres a problem your more likely to catch it before the engine is even fired. also a temp gauge is a must have imo. i got em on every bike in the garage. gives you some warning there might be a problem. never hurts to have plenty of oil in the gas also. i think this is where alot of people go wrong. 50:1 just doesnt cut it imo. alot of people will try to convince you that todays oils are so superior that you only need a small amount but dont be fooled.

[Daniel370r]

Mine was fine after he bored it.

[Pumashine]

alot of people follow some voodoo break in routine but its all nonsense.  if it wont go full tilt within the first few minutes then a 1000 heat cycles aint gonna make any difference. probly had your clearance to tight or something along them lines.

When is the last time you pulled the piston after 8 hours and remeasured it? You would have found the piston has shrunk .001" to .002"  The break in time gives time for the piston to wear into the shape that it will have for most of its life. This is why we use .003 clearance for bore size. In a week that will be closer to .005" clearance after the piston was wore in. You are not going to see this kind of damage with .005" clearance

[Jerry Hall]

When is the last time you pulled the piston after 8 hours and remeasured it? You would have found the piston has shrunk .001" to .002"  The break in time gives time for the piston to wear into the shape that it will have for most of its life. This is why we use .003 clearance for bore size. In a week that will be closer to .005" clearance after the piston was wore in. You are not going to see this kind of damage with .005" clearance

Yes this is so true.

An engine must have a minimum operating piston to cylinder wall clearance for the time span of wide open throttle operation the engine will experience.  The engine does not care how this necessary clearance is/was obtained. If this clearance is .0001" more than the minimum operating clearance the engine is happy.  If the minimum operating clearance is .0001" less than what the engine needs the piston will generate enough heat in the tight spots that it will seize.

The necessary operating clearance can be set up when it is bored or it can be set up a little tight and broken in until it has worn enough to have this necessary operating clearance.  Drag engines are usually set up loose and most other engines are set up a little tighter.  

The forged pistons ware much more quickly and will ware and collapse .0020" very quickly.  The peaks ware off the tooling marks during the break-in process then the ware slows down.

[udontknowme]

When is the last time you pulled the piston after 8 hours and remeasured it? You would have found the piston has shrunk .001" to .002"  The break in time gives time for the piston to wear into the shape that it will have for most of its life. This is why we use .003 clearance for bore size. In a week that will be closer to .005" clearance after the piston was wore in. You are not going to see this kind of damage with .005" clearance

well my '13 ktm 250 had only a couple hours on it when i pulled the cylinder and piston to swap it for a 300 jug. havent measured it but the cylinder and piston is still sitting in the garage. ill make it a point to measure it this week. service manual lists what the piston and bore diameters should be when new so i should be able to compare all the numbers and see what has happened after just a couple hours run time. ill have a update on this around the weekend

i did measure a coated wiseco from my honda after just a couple hours. i didnt like what i saw. clearance had damn near doubled. presumably because the coating had worn off. for what ever reason wiseco only coates a very few select pistons. personally i dont care for a coating and will likely remove it before the piston is installed next time

do what ever breakin you want. ive tried a few different procedures including heat cycles and full bore right out of the gate. from what ive seen theres nothing to suggest a bunch of heat cycles offers any advantage. i dont see where riding like a old lady for 3 tanks of gas will do any good either although i havent tried it and never will

[Jerry Hall]

well my '13 ktm 250 had only a couple hours on it when i pulled the cylinder and piston to swap it for a 300 jug. havent measured it but the cylinder and piston is still sitting in the garage. ill make it a point to measure it this week. service manual lists what the piston and bore diameters should be when new so i should be able to compare all the numbers and see what has happened after just a couple hours run time. ill have a update on this around the weekend

i did measure a coated wiseco from my honda after just a couple hours. i didnt like what i saw. clearance had damn near doubled. presumably because the coating had worn off. for what ever reason wiseco only coates a very few select pistons. personally i dont care for a coating and will likely remove it before the piston is installed next time

Do what ever breakin you want. ive tried a few different procedures including heat cycles and full bore right out of the gate. from what ive seen theres nothing to suggest a bunch of heat cycles offers any advantage. i dont see where riding like a old lady for 3 tanks of gas will do any good either although i havent tried it and never will

Wiseco forged pistons from the 250 s and larger single cylinders collapse rather quickly. Wossner has a lesser problem due to their thicker skirts but a typically much heavier than the Wiseco.  The German Mahle pistons seem to be about the best forged two stroke pistons but they only make OEM pistons for the European built engines.  The Wiseco KX, CR, and Suzuki LT500s will collapse .002" to .005" in one week end of hard riding.  The pistons for the big bore 250Rs have a similar problem.  I have gone round and round with Wiseco over this age old problem.  They will not admit they they have a problem with pistons collapsing.  They have tried to convince me that I or the customer is doing something wrong to make the piston's major diameter get small so quickly.  They say it is ware due to dirt, improper break-in, the clearances too tight,  the clearances too loose, the wrong oil, wrong oil mixture, the list goes on and changes each time I talk to them about the collapsing problem.  The majority of the collapsing started back when they started making the pro-lite series of pistons and making the skirts too thin.  It seems like they would revise their piston design rather than offering free tee shirts and hats, or offering me another piston at distributor prices.  

A piston collapsing problem is very easy to monitor.  Record the diameter of the piston skirt were the major diameter is located and measure the piston diameter just below the wrist pin.  Run the engine hard for a few motos or ride it for a week end dune trip with the best oils, and keeping the dust out.  Remove the top end and measure the piston skirts.  The skirts will look like a new piston with out any scratches or polished areas on any of the skirts .  Compare the dimension of the new piston and the piston with 2 to 5 hours on it and you will usually see the major diameter on the skirt decrease .002" to .005" and the diameter of the piston below the wrist pin will increase .002" to .005".