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JE H/C piston dia. differences vs stock


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In looking for causes of the failure of my engine i compared the J&E high compression piston size to the stock piston size and found the the J&E piston is .0025" smaller in diameter in the same place (front to back just beneath the rings) than the stocker. Perhaps this is on purpose, but i started comparing the two as to how they fit in the bore (without rings). The J&E rocks quite a bit, where the stock one does not. I can fit a .010 feeler gauge and the J&E piston into the bore without binding, the stocker is only .0045.

Does this mean anything? I don't know. Difference between cast vs forged? I don't know.

Also, what appears as a crack doesn't go all the way through the top of the piston.. It is a surface imperfection that wasn't there before i installed it, so don't know if carbon build up came loose or what.

There is no blowby on the skirts of the OEM piston, nor is there any on the skirts of the J&E piston although the J&E piston was only run for about a total of 20 minutes and about 7000 miles on the stock.

I am tempted to put it all back together with the cam one tooth advanced as that seems to be the position that has more valve clearance, change the stem seals on the valves, and see what happens. Why it got noisier and started smoking is now a mystery to me. It's going to take someone smarter than me to figure this one out.

Thanks.

EDIT: I forgot to add that the ring gap is .014" for the top and second rings, and the oil rings are .010".

Edited by Older and Slower
Forgot to add something.
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Because of the forged piston I'm not surprised about the extra clearance as compared to the stocker. The 223 grind cam leaves plenty of valve/piston clearance even with correcting the squish band clearance. Web uses stock Suzuki cam cores so I can't imagine the valve timing marks being in the wrong place. So I'm going to say either you didn't have the timing correct with the front of the chain tight when you checked it like you thought you did or the higher lift 180 cam requires more pocket depth??๐Ÿ‘

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Mx-Rob, i did a valve clearance check yesterday (in the other thread) with the cam in the 'normal' position where it was when i originally assembled it, and also one tooth advanced. The measurements are in the other thread.

i can't figure where the oil was getting into the cylinder from. It was originally noisy but didn't smoke, hence my first thread, then got noisier and started smoking so i shut it down and tore it back down.

Now i'm headed to the shop to order a head and base gasket.

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Hey there bergman501.. Thank-you for the ring gap information. While i had instructions with the piston, it had nothing about ring gap, just ring thickness, piston groove thickness, job order no., target weight, etc. All i have is a bench grinder or an air grinder with Rol-Loc discs. to open the ring gap, you think that will produce acceptable results?

It does say to set the clearance at .0015 with some apps. requiring more .... hence my research and question above.

I'm at a loss myself. Some think i had the cam one tooth retarded. When it is lined up the best possible with TDC, the marks are very very slightly to the retarded position, MAYBE a half degree if that much, but nothing like they are advanced when it is one tooth advanced.

I'm thinking i'll try running the stock cam and see what that does, and maybe someone will want to trade the 190 cam for a 223 ... 'ya think? Nah, whose going to want the same problems. Maybe Web Cams will take it in as a core for a 223 cam.

Thanks again for the help, i appreciated it.

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Actually i decided to hell with it. I can't believe that this piston is supposed to run with that much play. Ordering gaskets and stuff from Ron Ayers (no affiliation) tomorrow and putting it back together as it were. Lapped the valves today and changed the stem seals so no surprises there.

What a waste of money.

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you can use just a flat file--just used one on my tt600 rings--had a hand crank ring filer i gave away from when i used to build s/b chevys---ya never going to use it again:bonk: yes ring gap is a big deal with forged pistons. my instructions with my dr piston had no such info also if i remember correctly, why the tt600 did?? it's amazing i spend more time modding--working on this stuff than riding--something is wrong:banghead: for me i guess it's old age:lol:๐Ÿคฃ:lol:๐Ÿ‘

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I can't believe that this piston is supposed to run with that much play.

Pistons are typically supposed to be measured about 1/2" up from the bottom of the skirt. They are tapered and smaller diameter at the top to allow for heat expansion. Forged pistons will expand more than cast pistons. Measuring the diameter at the top won't tell you anything unless you have the piston design specs on hand to compare them to.

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about your cam---maybe the regrind is wrong? don't worry about your piston clearance .010 is .005 on each side and is about right. what base gasket are you using? anybody make a copper head gasket for the dr? a little thicker? my tt600 is. where is the piston in the cyl? is it down in the bore a little? is it out of the bore? need to know where the piston at tdc in the bore. open up the ring in gap--could have been your smoking problem. are we having fun yet???

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Hey bergman, thanks. I don't know about the cam grind. It's stamped 190 and it has an E on it also. Base gasket was a Suzuki metal one and the head gasket was a Moose that came with the kit. I ordered a Suzuki metal base and a Suzuki metal head gasket today, along with other stuff (piston pin, locks, washers, etc.) to put it back together again. The piston is not down in the bore at all, it is at the top of the deck. I have a micrometer depth gauge and i guess i could measure it, but there were no signs of it hitting the cylinder head, just the valves. I definitely will not put the cam back in the head, i'm planning on calling Web and see if they will take it in as a core for a 223 grind cam. Not so sure i want to put this piston back in, the weird crack thing in the top between the valves doesn't go all the way through the crown, it looks like the piston hit something, or more correctly something hit the top of the piston. The thing was pristine when i buttoned it up the first time, but now its scratched around the piston pin hole as i had to pry the lock out to take the pin out and various light scratches on the dome.

Anyway, this whole thing has become a PITA and i'm wishing i had saved myself the money and aggravation.

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Snip...

Anyway, this whole thing has become a PITA and i'm wishing i had saved myself the money and aggravation.

That's a shame O&S..... I couldn't be any happier with my J&E piston and 223 cam in my DR650. When I ride my wife's DR650 with only the FCR-MX and the GSXR system I think what a dog!๐Ÿคฃ I hope you get this fiasco all straightened out. ๐Ÿ‘

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...and maybe someone will want to trade the 190 cam for a 223 ... 'ya think? Nah, whose going to want the same problems...

hmmmm.... Now that I got my top end worked out, I might be able to find a use for more problems...๐Ÿ‘

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