Author Topic: Hi-Compression Piston (Read 15107 times)

geichal · **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 · **Reply #1 on:** November 22, 2007, 12:09:25 am

Quote from: geichal 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

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 · **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.

Bullet500Dude · **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.

Kevin Mahoney · **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 · **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 · **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,,,,,

LJRead · **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 · **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.

RagMan · **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.

geichal · **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 · **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 · **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 · **Reply #13 on:** November 26, 2007, 02:15:22 pm

Quote from: geichal 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. 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

t120rbullet · **Reply #14 on:** November 26, 2007, 04:59:40 pm

Quote from: geichal on November 26, 2007, 01:56:35 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

geichal · **Reply #15 on:** November 26, 2007, 11:56:33 pm

I do have a RH shift kit and the "improved" clutch pack yet to install. I have been considering a larger countershaft sprocket, but figure that I had better run her first to really appreciate the difference.
geichal

Peter · **Reply #16 on:** November 27, 2007, 01:09:21 am

It may be helpful to actually look at the stock Bullet piston.
What I pulled out of my 2003 didn't look very convincing.
It's got cuts in places where people once believed that they were helpful.
Pay particular attention to the circumferential cut under the oil ring.

Just looking at the thing makes me laugh.
No wonder that there are reports of the piston crown separating.
There is no better way to improve your engine than to put a decent modern piston in.
An alloy jug is a close second.
It just happens that the available pistons have higher compression because who would want to put up with the issues of a TOO LOW compression engine when already there.
The "Accralite" looked decent to me and is performing well.
You can always use compression plates if compression turns out to be too high.

I don't know if they have changed piston design since 2003.
If you have one like I found in my engine you will need to be verrrry careful.
Talking reliability while leaving such a thing in place makes no sense whatsoever - IMHO

Peter

indian48 · **Reply #17 on:** November 27, 2007, 01:42:49 am

To the question LJR asked, what is performance?
My 2 cents:
To the best of my knowledge the IC engine converts just about 25% of the energy in the fuel into mechanical energy, the rest of it lost as heat mostly. And if you take the power losses between the engine and where the tires hit the road to impart motion, I have no idea what more is lost,,,I would guess that in riding the bike, we waste 80% of the energy in the fuel we buy. I would therefore define my performance objective for the Bullet to be to get those figures moving upward as high as they can, and the fun in the Bullet is that it affords the owner a lot more opportunity for those moves, than the modern bike or car, where the only real option one has to walk and not use the vehicle to conserve energy( exaggerating here for drama!). I would define any move that gets that number up to be progress, in my book.
The second objective would be to get the bike to deliver that energy conversion on an on going basis, without intervention other than to keep moving that number upwards( routine/preventive maintenance not defined as intervention here). Which means working on its ability to do what it does on a sustainable basis - in other words, reliability.
How does that sound Larry? Good enough?!

LJRead · **Reply #18 on:** November 27, 2007, 04:29:12 am

Well, I'm not sure if the answer I give will fit in, but today I have been doing some thinking about gear ratios. When you look at Specifications, the different bike models just say 5-speed gear box, they don't seem to give the gear ratios. Now all this emphasis going on in the forum on getting that little bit of extra speed without harming the engine has me thinking that maybe someone should think about either going to a 6-speed gearbox accessory or else some sort of kick in overdrive. Don't know enough about what ratios are used in various bikes, but do know from recent reading that 6 and even 8 speed gear boxes are sometimes used.

Either that or perhaps a change in gear spacing might be in order, giving the ratios typical of the older 4-speed gear boxes for the first four gears, then having a step up to the fifth gear, making it an overdrive. I can probably cut, modify, or make gears on my equipment, but it would take me years to do so, but looking at the R E gearbox in the parts manual I got from CMW indicates that the outside box is roomy enough and the inside gear arrangement is simple enough, so that maybe an after market gearing system could be produced. Would there be a market for it? Don't know. But one of those whiz bang modern factories in India should be able to design and produce one in a weekend or so.

The R E seems to have plenty of raw torque to handle more gears. If it had a still higher gear than the fifth one, or if the fifth one were made higher, then it would seem to have the torque to handle it just fine. It wouldn't have to be that much higher to handle an additional ten miles per hour speed. At a time like this I wish I knew what I'm trying to talk about! But someone on the forum may have that sort of knowledge - hope - hope!!!

RagMan · **Reply #19 on:** November 27, 2007, 11:01:18 am

That would be a way to go, but with bikes you can seriously mess with ratios by changing the front and rear sprocket; works out a lot cheaper. My oversize front sprocket, stock rear makes for 65 mph all day.

Peter · **Reply #20 on:** November 27, 2007, 12:29:36 pm

Quote from: LJRead on November 27, 2007, 04:29:12 am

The R E seems to have plenty of raw torque to handle more gears. If it had a still higher gear than the fifth one, or if the fifth one were made higher, then it would seem to have the torque to handle it just fine. It wouldn't have to be that much higher to handle an additional ten miles per hour speed. At a time like this I wish I knew what I'm trying to talk about! But someone on the forum may have that sort of knowledge - hope - hope!!!

I bought my Bullet from somebody who had improved the exhaust system, put a 30mm Amal in and changed the sprocket to 18 teeth. Then the piston seized and he sold it to me. That's at more than 4000 miles. I rebuilt the top end with an alloy jug and high comp piston with one 2mm compression plate and it has been running fine with no oil consumption since then. It will cruise at 60-65mph all day long.

The short answer is: You overgear the stock Bullet, you are risking overheating and demise of your piston unless you ride it very carefully and don't torture it in too high a gear.

Peter

Sam · **Reply #21 on:** November 27, 2007, 04:34:38 pm

More gears are good when the powerband is narrow; the idea is to keep the engine in it's happy zone. What passes for a powerband on an Enfield is pretty broad, I don't think more gears will do anything besides allow for more neutrals. The other reason for more gears is fashion; that's why HD has gone to a 6 speed overdrive on bikes that don't really need more than 2 speeds.

I'm sure the ratios in the 5-speed are available somewhere; for sure, in my shop manual and certainly elsewhere, I've definitely seen them. The 5 speed is more evenly spaced than the 4 speed, doesn't have the big hole in the middle.

cyrusb · **Reply #22 on:** November 27, 2007, 08:38:16 pm

When I read about possible hop up schemes for the RE my first reaction is to ask yourself"Why did I buy this motorcycle?" Certainly not for its performance level. I bought mine because I love the "living antique" aspect of it. No other new bike that I know of can provide that.If I was looking for high performance, or just plain performance I would have picked another. Its more than just a bike its a"TIME MACHINE"

RagMan · **Reply #23 on:** November 27, 2007, 09:02:22 pm

That is so true - I love the time machine aspect of the Bullet - it is a nice, easy ridden, safe feeling bike. I have tried some of the crotch rockets, and never felt comfortable on them. One, a Ninja, I felt very unsafe. Compared to the Sportster I have been riding, the Bullet is like a comfortable old chair.

GreenMachine · **Reply #24 on:** November 27, 2007, 09:17:55 pm

Ragman has it right on the money...A Time Machine and if u have one, u know what that means...not about speed but pleasure of a time long gone...If u want more speed..purchase a second bike for that endeavor...

dewjantim · **Reply #25 on:** November 28, 2007, 12:17:31 am

Hey guys, know when auto racing first started? The first time two autos got together. Do you know when hot rodding was first invented? It was by the guy that got beat...... If you have to ask, you just don't understand......Dew.

indian48 · **Reply #26 on:** November 28, 2007, 12:59:29 am

Different strokes, Dew, different strokes!

LJRead · **Reply #27 on:** November 28, 2007, 01:03:20 am

yeah Dew - it is like sailboat racing, some take out their killer instincts on the race course, some prefer to slowly drift around the pond. And, like bikes, the racers burn up a lot of gear and money to replace it. I understand Albert Einstein's friends bought him a boat in appreciation and he would drift out and go to sleep on it - now there was the smart one.

indian48 · **Reply #28 on:** November 28, 2007, 01:13:27 am

I will attempt to clarify my comment on performance in another way. When the RE that we ride was designed, it was meant to meet certain performance criteria. As the design was handed over to manufacturing, and then on through the years with value engineering ( mostly a fancy word we corporate guys use for cost cutting by cutting corners), and with impact of poor quality in the Indian supply chain ( being an Indian in India, I am entitled to say that for sure!), and because of legislation due to emission and noise standards, the bike is delivering performance way under the design spec. My effort on performance, if I could, would be to get the bike to perform back to the original design spec in concept.
A separate but related point on emissions and noise control. RE has to do what it does to comply with the legislation, and that's fair enough. However, there are not many of us RE riders around ( the Indian annual bike output is a few million and that of RE India is 35000), and even if all of our bikes had emissions the way they were in the fifties, it is not going to make any impact on a global scale to the warming issue. Likewise, if we rode responsibly, the little increase in db also will not be a big issue - for instance when I go on my very early morning rides, I push the bike to a place where it will not wake up the neighbors before I start it. With this background, even if it may be illegal for us to roll back the emission output and the db levels restrictions imposed on the bike, would that also be unethical? Or would we be being poor citizens by doing so? I do not believe so, but I would like to hear what others feel.

cyrusb · **Reply #29 on:** November 28, 2007, 03:23:39 pm

Hey, it's just a personal choice. I'm sure in the end that some of us will have carbon fiber walkers.

hutch · **Reply #30 on:** November 28, 2007, 03:34:57 pm

There is one thing I always think about every time I hear how WE are suppose to cut back in our lives to save on the greenhouse gasses. I wonder what amount of pullution is put out from every space shuttle launch? Not to mention the hole they punch right through the ozone twice. I wonder what EPA standards are used on military vehichles, compared to a motorcyle motor. It all just seems a little lop sided to me. Quit messing with my bikes. That is what you get from the "don't do as I do, just do what I say" government philosophy. Hutch

t120rbullet · **Reply #31 on:** November 28, 2007, 04:55:58 pm

Quote from: hutch on November 28, 2007, 03:34:57 pm

There is one thing I always think about every time I hear how WE are suppose to cut back in our lives to save on the greenhouse gasses. I wonder what amount of pullution is put out from every space shuttle launch? Not to mention the hole they punch right through the ozone twice. I wonder what EPA standards are used on military vehichles, compared to a motorcyle motor. It all just seems a little lop sided to me. Quit messing with my bikes. That is what you get from the "don't do as I do, just do what I say" government philosophy. Hutch

Just be glad we live in a state that doesn't inspect them every year for that kinda stuff.
(at least yet, she might find a way to turn that into some kind of revenue)
CJ

hutch · **Reply #32 on:** November 28, 2007, 06:21:56 pm

Quote from: t120rbullet on November 28, 2007, 04:55:58 pm

Quote from: hutch on November 28, 2007, 03:34:57 pm
There is one thing I always think about every time I hear how WE are suppose to cut back in our lives to save on the greenhouse gasses. I wonder what amount of pullution is put out from every space shuttle launch? Not to mention the hole they punch right through the ozone twice. I wonder what EPA standards are used on military vehichles, compared to a motorcyle motor. It all just seems a little lop sided to me. Quit messing with my bikes. That is what you get from the "don't do as I do, just do what I say" government philosophy. Hutch

Just be glad we live in a state that doesn't inspect them every year for that kinda stuff.
(at least yet, she might find a way to turn that into some kind of revenue)
CJ

You got that right CJ, I used to cringe every time I saw an inspection set up for cars. My new "hot rods "just seem to make an abrupt u-turn whenever one was set up. Hutch

LJRead · **Reply #33 on:** November 28, 2007, 06:23:18 pm

About global warming and greenhouse gases, we do need to clean up our act, but I fail to see that heavy restrictions on an already underpowered motorcycle, with only around 20 hp, is going to do anything. Problem is, they crack down on us small guys then convince themselves they have done their job. Car manufacturers for years kept us buying big, heavy, overpowered gas guzzlers - only now starting to clean up their act when there may be a profit motive. A completely unmodified old R E is bound to pollute only a fraction of what one of these big autos does, and often both are only carrying one person. I'd like to see some actual stats of measurements from exhaust pipes, comparing the different types, to see what the picture really is.

RagMan · **Reply #34 on:** November 28, 2007, 11:10:40 pm

Eventually, everyone will know the truth about global warming, and greenhouse gasses, then maybe we will stop being ripped off by liars, cheats and politicians.

dewjantim · **Reply #35 on:** November 29, 2007, 04:15:28 pm

Quote from: LJRead on November 28, 2007, 01:03:20 am

yeah Dew - it is like sailboat racing, some take out their killer instincts on the race course, some prefer to slowly drift around the pond. And, like bikes, the racers burn up a lot of gear and money to replace it. I understand Albert Einstein's friends bought him a boat in appreciation and he would drift out and go to sleep on it - now there was the smart one.

Hey LJ, the seat on my RE is much to hard to take a nap on........Dew.

LJRead · **Reply #36 on:** November 29, 2007, 05:50:42 pm

That is a problem, Dew - maybe buy a new seat?

dewjantim · **Reply #37 on:** November 30, 2007, 05:29:06 pm

Nah, I like my seat. Had it custom made. Guess I will just sleep in the grass.....Dew.

Cafe Racer · **Reply #38 on:** December 03, 2007, 11:32:16 pm

I would like to clear up a reply I made to another tread more or less on the subject of modifications. I had stated on an early tread that in reading and finding out about the bullet engines that to help with the heat of a air cooled engine. A external oil cooler and coating the piston skirt and dome of the piston would greatly reduce cylinder and head temperatures. Which they will. My reason for saying this is to prolong the engine life and thus riding more miles than rebuilding the engine. I firmly believe that a bullet engine can be modified and performance improved if you use common sense about it.

I hope this clears up my earlier post.