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Author Topic: Hi-Compression Piston  (Read 5026 times)

geichal

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Hi-Compression Piston
« on: November 21, 2007, 11:01:17 PM »
Anyone use one?  What kind of performance gain with a larger carb and open pipes?  How hard to kick over with one?  Just wondering...
geichal

Peter

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Re: Hi-Compression Piston
« Reply #1 on: November 22, 2007, 12:09:25 AM »
Anyone use one?  What kind of performance gain with a larger carb and open pipes?  How hard to kick over with one?  Just wondering...
geichal

Don't do the large carb. The 8.5:1 Acralite piston gives you a nice performance gain throughout. Kicking it is not any harder than before because you are not kicking through the compression stroke anyways. You may have to kick a little faster though.

Peter

dewjantim

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Re: Hi-Compression Piston
« Reply #2 on: November 24, 2007, 05:16:31 PM »
I have a big 8.5:1 535 piston and 34mm mikuni carb (both purchased from CMW) for my RE 500. Am planning on installing them this spring, will let you know then....Dew.
If it hurts, you're not dead yet!!!!!

Bullet500Dude

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Re: Hi-Compression Piston
« Reply #3 on: November 25, 2007, 06:46:15 PM »
    Well, I have the 9 to 1 piston that CMW offered a few years back, and an Amal 32mm MK2 carb.  <> BOTH ARE JUNK !  I HATE THEM !  I TOTALLY REGRET EVER MODIFIEING HER. <>  The carb has to be constantly fussed with, and never idles right. <> The hi-comp piston makes her run hot riding around town in the summer. <> Fuel is a nose bleed.  The only way she really runs good is with expensive hi-octain racing gas.   I did install the stiffer advance spring from CMW so I could run premium pump gas with booster, but I still have to retard timming to keep her from pinging.  <>  Soon as income tax return comes in.  I'll be installing a compression plate to reduce compression, and the flat slide 30mm carb from CMW.
 
Take CARE, be BAD ;-) and ride SAFE ....... D.B.

Kevin Mahoney

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Re: Hi-Compression Piston
« Reply #4 on: November 25, 2007, 07:09:55 PM »
The point about the AMAL is interesting. Someone once told me that there is no such thing as a bad carburetor as long as they are set up right, I disagree!! Over the years we have sold lots of AMAL carburetors. They are probably the most "period correct" carb for the Enfield, but they can be problematic. They can be fussy (some people swear by them though). The slides wear out fairly quickly and I think they react poorly to a hot engine. We think a more modern carb is a better carb, but at the end of the day to look precisely correct an Amal is probably the right choice.

LJRead

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Re: Hi-Compression Piston
« Reply #5 on: November 26, 2007, 12:42:53 AM »
I try to look objectively at all these performance modifications.  In another thread on this forum there is the idea of adding oil coolers and coating pistons and rings (whatever that means).  This was a good suggestion, whether it would work or not, because it would try to improve overall running, instead of concentrating on performance (speed) alone.  Isn't that what much of this about?  Don't we equate performance with increased pickup or top speed?  And is that really the desirable thing we need?The questionable thing about some of this is, 'is it going to overheat?' which many of these modifications, it seems, will cause, overheating. Or is it going to increase internal stress, which will reduce engine life?

I think I would approach the question from a different angle.  That is, what can I do to make the bike run smoother and cooler, and what can I do to make it more robust.  If the modification is going to cause heat problems or put strain on something, then it wouldn't seem a good idea.  I don't know enough about the subject to say what would help Bullets simply to run better without causing "side effects" as they say with drugs or medications.  Sometimes the cure might be worse than not doing anything at all.

If you were to make it run smoother and cooler and be more robust, then you might also increase cruising speed.  And the question needs to be asked, what are we talking about when we talk about "performance increases"?

This is coming from someone who isn't really knowledgeable about performance modifications, but who seems to detect some wrong thinking in the whole thing..  I think I would look at things like bearing modifications, or balancing, or maybe even modifying valve or lifter configurations.  At this point I'm wayover my head - just thinking out loud!


indian48

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Re: Hi-Compression Piston
« Reply #6 on: November 26, 2007, 12:56:00 AM »
LJR, I was thinking exactly the same thing, reading the posts, then I read yours and went Amen!
If I was to use an analogy from another field, do we want to enhance isolated parts of the body by pumping iron, or worse, by using steroids? Having gone through my body building vanity phase, I have now realised that instead of using machines or free weights even, what one needs to do are things that enable the body to be used more effectively, working together as a whole, as it needs to do in real life. Some of the best exercises tend to be the good old bodyweight exercises, that build and strengthen the core. After all it is the core that allows for individual body systems to deploy their capabilities. I see the act of putting in a bigger piston as the equivalent of building bigger biceps!
And finally, does one want to develop body capability for just that end - you can't take it with you - or for doing the most one can with the capability, as long as possible.
This takes us back to the good enough thread discussions!!
You are not over your head, you are at the core of the subject,,,the rest are just technicalities.
I suspect I am asking for trouble by posting this,,,,,
If anything is worth doing, it is worth doing well

LJRead

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Re: Hi-Compression Piston
« Reply #7 on: November 26, 2007, 01:18:34 AM »
That seems a good analogy since a motorcycle is very much just a mechanical body.  I made my post quickly, other wise I might not have made it at all.  From my science days I learned that many of the break though discoveries come from strangers to a discipline coming in and looking at it a different way.  I'm sure it isn't new to refine bikes as opposed to simply adding brute power, But the obvious disadvantages to the latter have been pointed out by many on this forum And simply being careful to keep everything in balance might be important. 

Maybe the easy modifications are those like increasing the bore, adding more compression - things that add power.  Other things, adding refinement, may be more difficult to achieve, but may be more valuable.

indian48

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Re: Hi-Compression Piston
« Reply #8 on: November 26, 2007, 01:28:35 AM »
As in pumping iron for quick, visible, but superficial gains - as opposed to yoga that is exactly the opposite.
Btw, I still haven't the patience to do yoga in the spirit it has to be done with. I have progressed ( if backward motion can be called that) to bodyweight exercises - if anyone is interested, google Matt Furey. He has marketed what essentially are very simple exercises, that have been practiced in India for the last 2000 years or more. Ironically, modern Indians look down on these and pursue the latest craze that comes in from the West in the area of physical fitness as well.
It took a Matt Furey from the other side of the world, for someone like me to discover the value of what was available to me at home. I hope to progress to an even more effective,  simple, but hard to do system in time - hard, because it works slowly, and works on the inside of the body more than the outside, and involves quietening the mind - yoga.
From pistons to yoga,,,my apologies for hijackijng this thread. I will keep the next posts on this subject in the Good enough thread.
If anything is worth doing, it is worth doing well

RagMan

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Re: Hi-Compression Piston
« Reply #9 on: November 26, 2007, 01:57:18 AM »
I have modified a lot of vehicles in my time - I had a 200 mph Lincoln MK VIII - like a rocket, but the performance killed the engine in 10,000 miles. A truck I modified with thousands of dollars worth of engine mods, died before half the mileage of a stock engine. Another I modified at great cost - the very expensive and highly complex fuel system worked for 6 months, and impressed all who saw or raced the truck, but after 6 months, it was shot. Now I go for reliability instead of the fast track, the only mods I make are to get the air and gasses flowing properly.  Even if I could afford the performance modifications, I would not longer go down that path. The simplicity of the Enfields is what I like - to complicate them with performance is something I would feel very uncomfortable with.
aka Indiana Bulleteer.
''99 Classic Bullet. '05 Ural Tourist sidecar rig, converted to 2wd. '05 Harley Davidson Sportster.
Jefferson County, WA

geichal

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Re: Hi-Compression Piston
« Reply #10 on: November 26, 2007, 04:43:40 AM »
My ultimate goal is to have a reliable bike that I can put some mileage on.  A modest performace gain wouldn't hurt, but by the same token I don't want to kill reliability.  So far, I had a top notch shop redo my head with the larger Kibblewhite valves and Ampro guides with good springs as well as throating the intake for a smooth airflow with my larger carb.  I am using a Mikuni 34mm TMX flatslide with a velocity stack.  Not quite period correct, but simple to tune and very reliable.  I was thinking about a perkier cam and maybe a big bore kit, but have talked myself out of them for now.  The same with the electric ignition, I'm trying to simplify.  I may go to the AL jug when I wear the iron one out.  If I can cruise all day at 60-65, I'm golden.  I'm trying to get as much info as possible to get the most bang for my buck.  Thanks to everyone for your valued experience!
geichal

LJRead

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Re: Hi-Compression Piston
« Reply #11 on: November 26, 2007, 07:20:21 AM »

Well, geichal, at least it seems you are trying to take a rational approach and not just pile things on.  Question - how close to the 60-65 mile per hour easy rider are you now?

geichal

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Re: Hi-Compression Piston
« Reply #12 on: November 26, 2007, 01:56:35 PM »
I bought the bike used with front end damage to use for a builder.  I have run the engine, but no mileage (no front end).  A testament to the Enfields reliability~ the engine ran when I got the bike even though she had 2 broken valve springs, a damaged valve guide, a nonfunctional compression release, the top end so carbonised that I couldn't believe there was even room for fuel, 1 bent pushrod, tar for oil, and a very plugged long muffler.  (I told the guy I would buy the bike if he could prove to me she ran ~ she did)  The good news!  For a "95" she only had 2000 miles, the big end looked good, the tranny & clutch were also good, and she was cheap!  I figure when I'm done, I should be under the $2K mark and still have a tight, built by me Enfield.  Most importantly, I am having a blast working on her!   I do have one question, was a domed piston stock on the "95" 500's?
geichal

hutch

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Re: Hi-Compression Piston
« Reply #13 on: November 26, 2007, 02:15:22 PM »
My ultimate goal is to have a reliable bike that I can put some mileage on.  A modest performace gain wouldn't hurt, but by the same token I don't want to kill reliability.   If I can cruise all day at 60-65, I'm golden. 
geichal
   
Geichal, My 2005 Iron head Bullet will cruise 60mph (radar checked)all day. All I have done is rejet and pipe. I even have a stock air box. You should have no problem with what you have already done and a good freeflow pipe.   Hutch
« Last Edit: November 26, 2007, 02:22:09 PM by hutch »
You learn from your mistakes, and I have LEARNED a lot.

t120rbullet

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Re: Hi-Compression Piston
« Reply #14 on: November 26, 2007, 04:59:40 PM »
I do have one question, was a domed piston stock on the "95" 500's?
geichal

Yes, and still is.
http://www.royalenfieldusa.com/enfield-500cc-motorcycle-piston-complete-assembly-p-7169.html

Good luck with the 95, a good year. If you go with a right shift consider going to a
20 tooth countershaft sprocket and leaving all the hot rod stuff off. You might be pleased with the outcome and still retain the reliability of the stock engine.
CJ 
1999 Enfield 500 Black Deluxe "Silver"
2012 Concours 14 (no name yet)
2013 Royal Star Venture S  "Jelly Roll"