JE high-comp install 900SS

TAftonomos · October 21, 2011, 05:20:14 PM

Question for those who have dropped in some JE high-comp pistons.

Just double checking my work/clearances, here is what I came up with.

Top ring - .014" gap
Second ring - .022 gap
oil control rings - .015"

The above is how they came.

Also...the valve reliefs appear to be the same size....but I'm double checking there isn't a "install towards front" type orientation.

I also noticed a small marking "N" on the top ring. I installed both of these up, although I'm not sure it matters.

Piston to wall clearance is .0022 - .0025" Nothing I can really do about that, but I'm hoping that will work.

Experiences/thoughts are appreciated!

TAftonomos · October 21, 2011, 05:42:08 PM

Also...I'm assuming I install the base gaskets with tri-bond?

I've been told that a lot of people toss the base gasket to close up the quench area. If I try this, I'm also assuming I'd use tri-bond between the cylinder and the case?

What about the cylinder to head surface....just clean and dry correct?

THANKS!

ducpainter · October 21, 2011, 05:52:58 PM

Quote from: TAftonomos on October 21, 2011, 05:42:08 PM
Also...I'm assuming I install the base gaskets with tri-bond?

I've been told that a lot of people toss the base gasket to close up the quench area. If I try this, I'm also assuming I'd use tri-bond between the cylinder and the case?

What about the cylinder to head surface....just clean and dry correct?

THANKS!

yes to all

Ddan · October 22, 2011, 04:15:43 AM

You may want to check your squish before you toss the base gaskets

http://www.ducatitech.com/2v/maint/rebuild/headwork.html

greenmonster · October 22, 2011, 05:07:35 AM

QuoteAlso...I'm assuming I install the base gaskets with tri-bond?

I've been told that a lot of people toss the base gasket to close up the quench area. If I try this, I'm also assuming I'd use tri-bond between the cylinder and the case?

What about the cylinder to head surface....just clean and dry correct?

THANKS!

yes to all

+1, ditched gaskets on 2 engines.
Ignition will most likely need to be altered, comp will be higher. Ignitech is good f that.
Do check that squish, around 1mm is good.

Spec chart f rings should be supplied, otherwise dl from http://www.jepistons.com/Default.aspx .
I`ve just checked I wasn`t having smaller openings than specified.

QuoteI also noticed a small marking "N" on the top ring. I installed both of these up, although I'm not sure it matters.

Correct, according to Ca cycleworks, I mailed them same q.

QuoteAlso...the valve reliefs appear to be the same size....

No, they are not. Look closer, 1 pocket is slightly wider & deeper.

TAftonomos · October 22, 2011, 05:47:43 AM

I left the base gaskets in.

Only specs on the sheet call top ring/middle ring/bottom ring.....but it's got to be a spec for the actual width of the ring......I can't imagine JE suggesting I run a .040" gap for the top ring, a .0488" gap for the middle, and a .09 something gap for the oil rings.

The valve reliefs measure up the same width/length with a mic.

JE's site suggests piston bore x a figure determined by what type of motor you have....yet nothing is listed as "air cooled". Going by this 3.622 x .0045 = .0016" so it looks like at a min the top ring will need some filing. Of course, .0045" is the smallest gap listed, which is for "sport compact" ie: honda/toyota stuff which will probably have tighter clearances than I want.

Someone out there put these in and measured up the gaps....what did you use?

ducatiz · October 22, 2011, 05:52:23 AM

I'm surprised the valve Wells are the same size because you lose some compression but then again JE doesn't know if you've upped the valve size in your engine so maybe its a OSFA design and they make up the comp with the dome.

Stock pistons definitely have a wider well for the intake.

Setting end gap is a pain

TAftonomos · October 22, 2011, 07:59:15 AM

I don't mind setting the gap..

But knowing what to set it to would make it easier for me to do.....

ducatiz · October 22, 2011, 08:36:05 AM

I would use the factory settings. I can cnheck the maintenance manual when I get home if u don't have it.

Cloner · October 24, 2011, 03:40:20 PM

Footprint of the valve reliefs are the same, but the intake relief should be deeper. Measure from the lip at the edge of the piston to the bottom of the relief and you should see a difference. Also, visually, the exhaust relief leaves a little more "lip" at the piston edge due to it's decreased depth.

Use the base gaskets if you have any illusions of using pump gas. My bike knocked badly on a 50-50 mixture of unleaded/premium at over 6000 feet elevation (my driveway is at 5400 feet). I added knock inhibitor and it stopped. As soon as I get this tank run dry I hope it'll run on pump premium without additives. (I've only got about a hundred miles on the pistons right now)

Good luck!

Cloner
ABQ, NM

brad black · October 25, 2011, 04:00:58 AM

last time i checked the piston to head clearance on a set of je it was just over 1mm, but the tightness is at the very outer edge of the bore. and as the je squish band is at a different angle to the head the clearance increases as you move toward the centre quite quickly. you could machine the edge at the same angle as the head and then take the base gasket out. i had to do that to my st2 after having the head and barrels machined to remove the warping they suffer from.

don't confuse effects of higher comp for bad chamber shaping or squish. a better squish area makes them less likely to ping, so the above machining might help in an otherwise equal situation also. but i don't think they need mroe comp.

i've machined 3mm off the top of a few sets, taking them from 11.5 to 10.8, and they've not pinged on ie bikes with the std spark map and or on carb bikes with the timing pulled back a few degrees. bikes with them as is have pinged even on good fuel.

the valve reliefs should be visually different. every set i have fitted has been.

i set the ring gaps at 0.016" (0.40mm) minimum, but try not to go over 0.45mm.

TAftonomos · October 25, 2011, 04:38:19 AM

I measured, and saw, that the valve pockets are deeper (by a smidge). Happenstance that I installed them in correct orientation.

Thanks!

I might pull the slugs back out and add a smidge to the ring gap on the first ring.

Unfortunately, I do not have the machining capabilities here to profile the piston. I asked a few places locally about it, non of which had any idea what I was talking about

. Sucks, cause as Brad said more squish helps detonation by getting rid of the places in the chamber where it can/is likely to occur.

If I'm pulling them back apart, I'm going to check on milling a bit off the top. I don't want to have to deal with pinging all over the place, nor do I want to rebuild this motor with melted pistons after a track day.

Thanks Brad for your insight/experience.

Raux · October 25, 2011, 05:08:32 AM

I'm thinking "N" stands for iNtake?

Raux · October 25, 2011, 05:09:34 AM

Why not pull the heads and do a port/polish and reshaped the combustion chamber to better match the new pistons?

greenmonster · October 25, 2011, 10:46:34 AM

Quotei had to do that to my st2 after having the head and barrels machined to remove the warping they suffer from.

Did the warping cause the heads to leak oil and, if so, did the machining fix the leaks?

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JE high-comp install 900SS

Raux

Raux