JE piston

[courchaine]

I was looking to get a wiseco 1mm oversized piston with 10.25 compression bu then saw a JE 2mm oversized piston that will gave me 366cc with 10.50 compression. Is the JE piston is good ???? will it overheat ???? will it be powerfull ????

thanks

 

[griff]

JE makes some of the best pistons in the world, cant go wrong with them. For most applications theyre my 1st choice, then Wiseco. Though these days, with JE and Wiseco merged, Wiseco pistons have gotten very good thanks to JE's experience.

The JE 10.5 366 is what I am doing also, its a solid setup, will give more power, and run on pump gas with no problems.

 

[courchaine]

thank you.......i can't wait to put everything back togheter ......

 

[yamarider]

I don't know why anybody would want to do a 2mm over piston, unless it's a last resort before re-sleeving. That's as far as you can go on a stock sleeve, so the next time it needs rebuilt, you gotta spend more money that could have been avoided. That's only 18cc's, which is pretty much no power gain at all, and you end up with thinner walls so there will be a little more heat built up too. It only makes sense to me to do the smallest overbore possible.

 

[dave76]

I liked the JE piston, I don't know if JE is making a different piston or if they rate the compression different, but when I got mine it was 11.1 compression back in 2002, 2 mm over, from Four Stroke Tech, anyway I ran that setup for 4 years without a glitch, oh and I also have an oilcooler. Yes the next time you got to rebuild if you have to bore the cylinder over again, you will need a new sleave.

 

[griff]

I don't know why anybody would want to do a 2mm over piston, unless it's a last resort before re-sleeving. That's as far as you can go on a stock sleeve, so the next time it needs rebuilt, you gotta spend more money that could have been avoided. That's only 18cc's, which is pretty much no power gain at all, and you end up with thinner walls so there will be a little more heat built up too. It only makes sense to me to do the smallest overbore possible.

The sleeves are pretty stout on this engine, even at +2 OB, heat and strength are a non issue with mild to medium CR.

During a rebuild, all you should be doing is a hone & de-glaze and new rings anyways.

Only time you would need to do another over-bore is if the 1st over-bore was done incorrectly and is out-of-round. You'd be burning oil and there'd be power loss from the get go.... and you'd need a new sleeve at the expense of the idiot at the machine shop who didnt bore it correctly to begin with

 

[yamarider]

I've seen quads on the stock bore end up out of round just from wear and tear. I couldn't imagine they came from the factory with the wrong size bore. My recon was getting pretty egg shaped when I got it rebuilt, to the point that the piston was slapping around inside the cylinder.

 

[griff]

I've seen quads on the stock bore end up out of round just from wear and tear. I couldn't imagine they came from the factory with the wrong size bore. My recon was getting pretty egg shaped when I got it rebuilt, to the point that the piston was slapping around inside the cylinder.

From wear & tear? If the initial bore was good, then no way... Not on these sleeves with the rings Yamaha uses. If they were already out-of-round from the factory (and that does happen sometimes), and it would get worse over time - rings would wear all fooked up, piston slap, cylinder-wall scoring, etc.

A buddy of mine bought an FZR600 used a few years ago, it only had 1900 miles on it. The original owner didnt ride it much, and never addressed the oil burning/usuage issue it had (it started smoking a lot eventually). Stupid dealer kept telling him "oh thats normal".... my ass....

Needless to say, he sold it to my friend because it went out of warranty. I pulled the head and jugs to see wtf was going on, 3 of the 4 cylinders were out-of-round from the factory! It was clear the boring machine had a bad bearing in it (they have to be replaced fairly often), and that it was corrected on the 4th cylinder (it was perfect). Ended up buying a Wiseco +1mm piston kit, had the bore done at my bro's shop. Ran beautiful then, the big thing we noticed besides the power improvement was how much quieter the engine was at idle.