11.5:1 pistons....

[benny hedges]

these are the ones ive got on order for an upcoming rebuild...
thought i'd put a link to them here in case anyone else fancies a go.
their shop has changed name which is why you probably wont find them under atvparts

http://cgi.ebay.co.uk/140537380314?ru=h ... 1100wt_754

quote "Check out eBay item number 140537380314 at our other eBay store, racepartsplus.
We also can sell you all 20 shell bearings.
I can do the whole thing for $525 (£327 incl postage) shipped to the UK, and we can mark it as a gift for postage."

if you are running standard cams there are some porsche pistons that will fit & raise the compression to a massive 12.5:1 - i'll post a link to them if i can find the shortcut to them lol.
didnt want to risk them with the cams i have in mine.

[AMCQ46]

I will watch them for my engine rebuild when I swap to the spare over the winter

[mik_str]

FWIW, I am running these same basic pistons (mine are 0.5mm oversize) along with Yoshimura Stage 1 cams, which, if I remember correctly, have more lift than the Moris, albeit less duration. MY heads are also decked 0.015" and all is well with the world.....

[tony.mon]

A pair of these nestles gently in my own engine, but be aware that you will also have to budget for rings, standard Honda ones fit fine; just need gapping to fit the bores.
Silvers got 'em.

From measuring the clearances, I think you can skim (deck) the heads a fair bit with them fitted, I rebuilt the engine with just the outer springs on each spring and checked clearance throughout the camshaft rotation, there's plenty of clearance.
But don't just take my word for it, measure it yourself before having any work done......

I think from memory that you could skim 1mm off the heads without clearance issues, that should make a fair difference.
You may need to re-profile the edges of the head to clear the raised crown, though, but even so a benefit should be possible.

[mik_str]

FWIW, I did a rough calculation and found that the 0.015' milling of my heads bumped the compression ratio by slightly over half a point (now in the area of 12.1:1).....

[benny hedges]

I think from memory that you could skim 1mm off the heads without clearance issues, that should make a fair difference.

wont be skimming mine bud as i have no idea how high the lift is on the cams im running, but side by side with the original ones theyre a lot higher...
thats why i wanted to see if you fkt yours up before i invested in a set

[VTRsquid]

Any gains to be had from running more compression on an otherwise stock engine? More down low? more everywhere? Nothing much at all?
Seems it could be pretty cost effective mod just to skim the heads since stock compression is pretty anaemic and have access to 98RON at pretty much every bowser..

[8541Hawk]

Any gains to be had from running more compression on an otherwise stock engine? More down low? more everywhere? Nothing much at all?
Seems it could be pretty cost effective mod just to skim the heads since stock compression is pretty anaemic and have access to 98RON at pretty much every bowser..

More compression will give more bottom end at the expensive of being able to rev at the top end. That is where the matched cams come in

[Stephan]

Any gains to be had from running more compression on an otherwise stock engine? More down low? more everywhere? Nothing much at all?
Seems it could be pretty cost effective mod just to skim the heads since stock compression is pretty anaemic and have access to 98RON at pretty much every bowser..

you have to skim quite a lot to get some reasonable CR. I did the search in the past and can post exact numbers later.
Add the fact you need to check piston to valve clearance, and retime the cams.

Not so easy, if the cylinders are ok, just put JE Pistons is better.

[Chris58]

Any gains to be had from running more compression on an otherwise stock engine? More down low? more everywhere? Nothing much at all?
Seems it could be pretty cost effective mod just to skim the heads since stock compression is pretty anaemic and have access to 98RON at pretty much every bowser..

Je's will make a difference..on their own you will get a bit more low end. You may lose some up top.
They are best used with longer duration cams, they make up for some of the compression lost at low rpm due to the intake valves closing later, and give higher compression at high rpm.

Usually skimming the heads or block is best left for flattening the surfaces, but I suppose you can raise compression a bit that way. As Stephan said, you would need to check clearances first, and after.

but not sure the $$ and effort vs. gains are worth it when done by themselves..Unless your like most of us here and enjoy modifying your bike as much as you like riding it.

Probably the best, and most noticable mods I made was: lightening the flywheel (E Marquez has great reveiws with that), and fitting aluminum clutch plates..Which btw I still have one extra set.
makes for a fun ride, but may not be for everyone.

[E.Marquez]

fitting aluminum clutch plates

What was the weight difference between 9 driven steel plates and the 9 aluminum driven plates?
How many miles on the aluminum ones so far? and have you looked at them for condition and measured them for wear?
One off custom made or are they from a different application?
Are you an innie or an outie? Do you like slow walks in the moonlight?....LOL ok enough with the questions I guess...

[Chris58]

fitting aluminum clutch plates

What was the weight difference between 9 driven steel plates and the 9 aluminum driven plates?
How many miles on the aluminum ones so far? and have you looked at them for condition and measured them for wear?
One off custom made or are they from a different application?
Are you an innie or an outie? Do you like slow walks in the moonlight?....LOL ok enough with the questions I guess...

they are supposed to be 65% lighter. I had lost my scale, but it seems like 2 or 3 steel plates are about the weight of the whole pack of aluminum ones.
Ive only had it out once so far, but as expected it is like lightening the flywheel more. Im in Canada and our Igloos are just melting now.

They are cryogenicly treated, so they shouldnt have wear issues. Barnett Clutches sell similar plates for other bikes that describe what they are.
http://www.barnettclutches.com/cryodized-plates.htmlp

They were made specifically for the VTR by a company called CryoLabs. Can't find any info on the company...packaging looks old. there still good (new in package), not fossilized yet.

Outie, and I love moon lit walks ;) LOLOL

[VTRsquid]

Ok so theoretically, If i went JE pistons and longer duration cams (are these available?) what would the dyno plot look like next to the stock one theoretically? What kind of gains and where?
Not 100% sure i would want to go lightened flywheel and clutch at this stage - wouldn't this start to introduce bad road manners?

[Chris58]

Ok so theoretically, If i went JE pistons and longer duration cams (are these available?) what would the dyno plot look like next to the stock one theoretically? What kind of gains and where?
Not 100% sure i would want to go lightened flywheel and clutch at this stage - wouldn't this start to introduce bad road manners?

I just did pretty radical cams with je's, 99mm bore, o/s vavles, porting etc... havent done a dyno yet. I would think my torque at low rpm will be close to stock and it should make more power everywhere... especially up top.

every build is different though.. hard to say what a dyno will look like without doing one.

you are right about road mannors lol

[AMCQ46]

its weird when a benny hedges thread pops up .. good to be reminded of his wisdom