fresh built top end blown up

[rodknee1231]

Well I.just rebuilt my top end and after about 4 hours or use it lost power and seized up on me, I used the cheap namura piston and cylinder kit and I filed the ports possibly not enough I think it snagged a ring but not sure I can't kick it what so ever, do u guys know any other reason this thing would seize? My tranny fluid was just changed and I run a 28 to 1 mix in case my jetting was off its stock bore with a 230 main jet stock pipe rps silencer

 

[rodknee1231]

Btw I filed the ports because I heard they were not chamfered enough from the factory

 

[Blaaster]

Did you make sure the engine was leak free before you started it.

Running a 28:1 premix, could have leaned out the fuel contention the mix to cause a lean enough condition to fry the piston.
Adding oil reduces the fuel content in the mix., not a good idea.

Although adding extra oil provides more lubrication, it robs the engine of fuel!

I am unfamiliar wit a RPS silencer, but if it provides less back pressure than the stock pipe you may need to have re jetted for it.

Did you heat cycle and re tension the head and cylinder nuts?

Was the float set at the correct level and the idle set before riding?

What oil do you use?

 

[Awk08]

oh rodknee
so many things could have gone wrong....
IT WAS NOT THE PISTON CHOICE.
what was the piston to cylinder clearence ?
filing ports - did you get absolutely every filing cleaned out ?
was it leakdown tested ?
was it heat cycled and retorqued ?
28:1 just created a lean air/fuel ratio of that stock 230 main jet....IMO, NEVER PLAY WITH THE MIX RATIO,
32:1 HAS PROVEN TO WORK 150% OF THE TIME. PERIOD.
was it held wide open for 65 miles ?

 

[joeak47]

Its not the piston. I've ran MANY namura pistons with zero issues.

 

[Bluesman]

As well as everything mentioned, what was the reason for the new piston? Was there an unexplained, catastrophic piston failure? The crank could have used up 8 of it's 9 lives. There could have been piston debris in the bottom end. The crank seals could be trashed. The list goes on. I'm really surprised Blaaster didn't light into you about a leakdown test, like a preacher standing in front of a Planned Parenthood clinic.

 

[Blaaster]

Blues man needs to read posts properly.

I did mention about a leak test, and Awk got in second!

Read the first line of my reply.

The main reason an oil ratio should be changed to provide more oil is to allow long periods of WOT.
It is perfectly fine to alter the ratio provided you change jets to suit.

 

[Bluesman]

I read it. I just thought that was a bit on the "give it to him easy" side. LOL

 

[dirtysquared]

There is alot that could have gone wrong. That cylinders kit could have not been in spec's. , bad jetting, air leak, almost every thing is on the table now.

 

[benharcombe1985]

locked solid to kick over says heat seized mains to me my 98 kx did this halfway up a jump very sketchy shall we say lol which as said above could have been caused by many things time to strip down in afraid mate

 

[rodknee1231]

Didn't leak down test it ....I know I know I should have, I did go through the heat cycles and re torque everything I'm gonna tear into it, the company I bought the cylinder and piston from said they would replace both if it snagged a ring, when I.bought it the piston and cylinder were junk and looked like they had melted but I found the oil inlet on the carb was left unplugged after they did a oil injection delete so I been fighting getting my pilot jet where it should be.

 

[Bluesman]

So, are you gonna do a leakdown test before you tear it apart?

 

[98blaster]

You shouldn't have to mess with the pilot jet at all, the stock 32.5 works for 99% of all blasters the 1% left run a LRD pipe which works best with a 30 pilot. Your are screw should be about perfect at 1.5 turns out, if your having low speed issues im betting you have a crank main seal leak

 

[Blaaster]

A small air leak, accentuated by the diminished quantity of fuel in the mix by adding extra oil could have been your demise.

 

[rodknee1231]

Well guys I tore apart the cylinder was smooth as a baby's ass piston and rings looked new the connecting rod bearing at the crank is shot it won't even turn so that was binding the top end up so now I guess I have to split the case and find the metal pieces in it ?

 

[98blaster]

Its time for a complete bottom end rebuild, with new crank or yours sent to KOR for a rebuild with a pro-x rod kit, a set of all balls main bearings, a seal kit, an a OEM base an head gasket, or I use OEM base with vito's high compression head gasket.

 

[rodknee1231]

I have a new oem jug on it now I just want to rebuild it stock I don't have a lot of money laying around to do so I'd like to just replace the bearing and all necessary gaskets while I'm in there is that possible or is the crank f*cked now

 

[rich1]

Seriously ? You had a rod bearing go out and you want to know if you have to change the crank bearings too ?

 

[rodknee1231]

I don't think you understand what I'm saying, and some of us have never done this before hence the post on here, the upper rod bearing is fine the lower bearing on connecting rod is bad won't turn very easily, I'm asking if I can get in there and replace the bearing and all the necessary gaskets or is there more required

 

[Blaaster]

You can get into it by splitting the cases and then you could have the crank rebuilt!

Replacing the crank pin bearing is a specialist operation, the average home builder will not have the necessary tools.