Why?

If you're going to spend that, at least go for higher compression. It's the only reason to.

Service providers and resellers' businesses are to make money out of you. Some do so whether you need to spend it or not. The biggest tool in their toolbox is a "FUD wrench". Exploiting individual's 'Fear, Uncertainty & Doubt' is a great way of making more cash. Especially when they themselves don't really know.

Ask Scott, "If I am going to buy new set of quality pistons to set off an EV27 nicely, should I buy stock compression or higher compression?" (... and set the squish tighter).

Half the trick is knowing the right question to ask, the other half is knowing about the various options that exist to ask about, and knowing when not to freak.

That $180 will do you and your bike no more good than taking an aspirin will. No more good than those $30 pistons or spending $30 (est) on having your old ones notched.

Again, ask an expert who's sober, got integrity, and does not just want to make money from you. If they say you need to buy something, ask them "Why ... Show me ... Tell me ... Explain". Don't just believe them.

Otherwise, just light a candle and say a Hail Mary and stop worrying ... it's on the same level (but cheaper). Or send me $100, and I'll say a prayer for you and promise nothing bad will happen to you. It'll still save you $80.
I don't know. Sometimes I cannot work out if he is 'Typing Under the Influence', or just struggling with his iPhone and getting cranky.

 

You said yourself pistons need valve relief for the 27 cam . Not going to notch mine, rather buy new. As far as compression goes, not looking big horses to strip my tapered tranny shaft or look like a fool trying to kick start my high compression evo.
So am I wrong? If I install an ev27 I most likely need valve relief. = new pistons.....

 

No, I don't say that. I would not do so unless I knew it to be true. Part of knowing it to be true, would be knowing the measurements. I say it's mathematically impossible, without some other factor being involved.

What I found ... and pointed out/corrected myself ... was that it was just a general disclaimer for *all* cams copy and pasted from a reseller of a resellers' catalog. And, as I said earlier, you can't trust them, and should not be worried by them into spending what you don't need to.

Choosing 9.5:1 or 10:1 pistons (or even higher), and setting the squish tighter, wont make it harder to start. Quite the opposite, it'll make it nice and crisp, reduce any tendency to detonation or premature combustion, and limit carbon build up. It will add efficiency and performance.

You also won't be running at whatever the published piston compression level is (so don't freak), you'll be running *at least* 1 point below because of a number of factors,

a) your deck height/loose squish,
b) the size of your combustion chamber, and
c) your cam's timing (link) ...

Again, get a second opinion from Scott (and I'll bill him for sales pitch), i.e. if you put in 10:1 pistons, you'll probably be getting a real world 8.8:1, which is just modest and healthy. (Stock is meant to be 8.5:1 ... but never is).

How and what to measure ...

Firstly the Piston Deck Height; the distance between the piston top and the top of the cylinders (just don't use bare metal grips on the shaft like those guys are! Wrap it). If the pistons are below the top of the cylinder, which I bet they are, you have nothing to worry about.

Assemble the cylinders using whatever base gaskets you have ... is it 10 thou? ... and torque down to spec. Place a flat edge across the top and turn the engine around to TDC. Measure the gap using feeler guages or a guage. If you get that far, I'll give you other hints of what to do.

My guess is you've got a 15 thou base gakset, and it's going to be more than 15 thou down the hole.

Then check valve travel to see and satisfy yourself. This way you will learn, save money, and end up with a better bike. Do you have a dial guage or caliper?

Stick the valves in the guides, move them the TDC lift given about, measure the distance between the cylinder head face and the lip of the valve. Again, hints on howto available.

Lastly, consider measuring your combustion chamber (and then we will remove all fears about compression ratios). Rough is good enough for this level of work, e.g. using a measured syringe. My guess is it's going to be 82 cc or more, i.e. low compression. You're probably running at less than 8:1 at present.

Using the calculator linked to, and putting in the stock figures you say you have, using an EV27 will give you corrected compression figure of 7.65:1 and Cold Cranking Compression (CCC) of 150 psi ... which is road kill poor.

Adding 12ccs to the Piston Dome Volume, which is approximately what a 10:1 does, you get 8.77:1 and 180 psi, which is OK. Sticking in a 30 thou head gasket (setting the squish to, say, 35 thou) takes you up to 9.1:1. Still hardly "killer" levels. I'd say, "just nice".

(11:1 pistons equal, say, 9.91:1 ... that's about idea from a performance level, but ask John or Scott's advice about CCC at that level. I'd say it was too high for every day use).

 

Thanks for the diagram, I can do this with some measuring instruments at work, I didn't mic the base gaskets yet(James kit).
My biggest concern is figuring out how to make a spring compressor.
All this is being done completed with rings and fully torqued?
Won't ruin the gaskets if I need to disassemble it.???

 

my last post on this subject - member showed up this week and is giving incorrect info - seen jackasses like this before on this and other sites -- over the 9 years i am on this forum i have yet had anyone tell me i gave them info the effed anything up -- i have 200 evo customers alone some since the evo showed up in 1984 i dont do oil changes or tires - i dont re do you pealing chrome - i dont bolt on your new radio speakers - i am in the antique Restoration end - engines - machine work - we make wire harness for what ever if they are not available - i have nothing to prove to anyone, i answer questions correctly and with the right info on the stuff others have no idea about and stand behind what i say in a post - on this site i cant count how many have contacted me for help and services i offer in my shop on the older bikes only - been doing harleys and indains 40 plus years / again i have nothing to prove to you or anyone - BUT a small reason was behind the decision re design the entire Big Twin evo piston line with reliefs in all the pistons after the first coupe of years and it has nothing to do with bravado - you have been told by many what to do its on you what happens - and during this season i have had 2 beers with my oldest son on different days - blood sugar will do that to you

 

Thank you very much John, I don't doubt you know what you're talking about ! Put yourself in my shoes with all the contrast. It's still being discussed because I can't get my Indy to move, or boutique as you call him. Sorry for the inconvenience.and thanks again...

 

Well, thank you for admitting your blood sugar problems, and that you're starting to forget things ... but rather than sinking to insults, just explain to us how. Show us the maths and tell us the methodology.

I've actually gotten off my ***, set up a head and gauges, and measured it; and you've got a big gap to explain.

I'm happy to take a second opinion on the targets, metholody, and alternatives I've offered being wrong. But they're not.

Walk your talk, and tell us your recipe ... offer an alternative breakdown of costs, and explain why they're better.

Selling "super safe", at twice the cost, is certainly good for business. But a missed opportunity for the owner.

Here's deck height measurement ... a good steel rule will be good enough if you have not got a bar or a straight edge. I prefer to use a dial gauge above a bar rather than feeler gauges below it ... or a combination of both, i.e. putting feeler gauges under the bar and turning the engine round until you see movement in the needle.

 

I'll do Scott's work for him. From another forum we're not allow to link to from here. Your ball, John.

 

you first said this and now whine

Originally Posted by texashillcountry View Post
If John says they will hit then they will hit.

((((((((( I don't know. ))))))))))))) Sometimes I cannot work out if he is 'Typing Under the Influence', or just struggling with his iPhone and getting cranky.

2 - I'll do Scott's work for him. From another forum we're not allow to link to from here. Your ball, John. -

My opinion you would not be able to take the garbage out in scotts shop much less show him anything - did you get his permission to use him as a reference ??? NO i guess not

then you show a twinkie motor as your i know what the deal is LOOK at what i am doing

AND you lost site about what this was all about - pistons with NO reliefs

your other post option in proof - 10 to 1 pistons w/ ev 27 cam AND the guys question -- it was about stock studs pulling out of the block - reading comprehension a little lacking with you these days

one thing you missed completely is some actually do this not talk about it and some like, spanners - scott and many others own and have forever, machines they have restored, donate time to help the crew in the evo section not wreck what we all enjoy - the riding time is short for some

take a deep breath and watch what goes on for a while its not a competition its an informed group of helpfull good guys / looking out for those who ask because they dont know

 

Rightously said John.......