[luoma]

I see there i now a 535 upgraded piston available for the AVL. Any idea on how well these work? I am not currently in the market for a major modification, but I have thought about doing something like this whenever I need to do a top-end job. At a bit less than 11000 miles, I figure I am about halfway there.

[UncleErnie]

That sounds good.  I wanted one of those from the get-go.  I'm still breaking in my new engine and would hate to have to do that all over again, though.

Is it a kit?  How much?

[luoma]

The piston/rings is about $235. I think any good bike shop would be able to bore the barrel and shave the head. The shop I use is run by a guy who races vintage Brit bikes and can do something like this easily.

[UncleErnie]

Why would the head ned to be shaved?
Would I need to re-jet (again)?

[ace.cafe]

No need to shave the head.
Compression will be slightly increased anyway, by squeezing more cylinder volume into the same size combustion chamber.

And if you use the hi-compressiion piston with it, you'll get plenty.
No need to fiddle with the head joint.

[basanti]

I'm very much interested... is anyone running one of these pistons? I got the 30mm "performance" flatslide carb, SB air filter and shorty exhaust. Would i need to upgrade the carb (to maybe a 32 or 34mm) to see full potential from this piston? What else would i need to upgrade?

[bob bezin]

3 hd clutch springs

[ace.cafe]

I'm very much interested... is anyone running one of these pistons? I got the 30mm "performance" flatslide carb, SB air filter and shorty exhaust. Would i need to upgrade the carb (to maybe a 32 or 34mm) to see full potential from this piston? What else would i need to upgrade?

Apparently the AVL is already at 8.5:1 compression, according to my Google search.
So, the "potential" is the added bore size.
This amounts to about 7% displacement increase.
In a stock AVL with about 23hp, that would amount to about 1.6hp, and probably a similar increase in torque.
The result will not be nearly as noticeable as your exhaust and carb improvement, but you might be able to feel it.
It will be better, but not by alot. It depends on how much you want to pay for that horse and a half.

The clutch springs might be a good idea, as Bob pointed out, if you start to notice that your clutch begins slipping.

[t120rbullet]

I got the 30mm "performance" flatslide carb, SB air filter and shorty exhaust. Would i need to upgrade the carb (to maybe a 32 or 34mm) to see full potential from this piston? What else would i need to upgrade?

I think your 30mm flatslide will be fine.
Small carb = Low end torque
Big carb = Top end power
I think you'll find in "real life" street riding you'll appreciate low end torque a lot more than WFO power.
 

[HRAB]

When we were developing the kit, we took it to the extreme to see where it would go.

We finally settled on the 535cc kit to stay with some of the proven limits and to solve some problems we had with the 560cc test.
With the 560cc we needed to have a larger carburetor. The 535cc iron barrel bikes were running fine with the flat slide carb. The amount of cylinder wall remaing with the 560cc  piston was so thin we were concerned about reliability.

http://www.enfieldmotorcycles.com/forum/index.php/topic,150.0.html

jim

[basanti]

Thanks for all the explainations guys.

How disappointing I was waiting for someone to come up with a big bore kit for the AVL thinking i could squeeze more power from this machine. 1.6 bhp doesn't seem to justify going big bore unless you're due for an engine over haul. Hmmm, what do we do now?.....

[t120rbullet]

1.6 bhp doesn't seem to justify going big bore unless you're due for an engine over haul. Hmmm, what do we do now?.....

Ride it?

[Cabo Cruz]

"Ride it?"  t120rbullet

Amen!!!

[ace.cafe]

When we were developing the kit, we took it to the extreme to see where it would go.

We finally settled on the 535cc kit to stay with some of the proven limits and to solve some problems we had with the 560cc test.
With the 560cc we needed to have a larger carburetor. The 535cc iron barrel bikes were running fine with the flat slide carb. The amount of cylinder wall remaing with the 560cc  piston was so thin we were concerned about reliability.

http://www.enfieldmotorcycles.com/forum/index.php/topic,150.0.html

jim

Well, bear in mind that it is a "percentage" increase.
So, If you had a modified AVL with 28hp, then you'd get 7% of that as your increase, or more like 2hp. The displacement will go along to help the other mods in the package, particularly breathing mods like head, carb, exhaust.
Then, you could be looking at 30hp, instead of 28hp, and that might be enough to make people want to do it.
It's just that little bit extra that might give you the power level you want.

But, all in all, the exhaust, carb, filter, and rejetting is the most "bang for the buck".
That's good for about 5hp, and it's under $500. About $100 per hp. I don't know what they are asking for the BigBore kit, but if it is under $500, then you have about $250 per hp with that one, and there's not much else available to do with an AVL at this point.

The best other options would be aerodynamic ones. Low bars, like the Ace bars, will lower your riding position, and improve your critical frontal area by about 15%-20%, which is significant. Then a low "racy type" front fairing will help that out even more, with some streamlining.
These are things that you will really feel when you get up around cruising speeds, and the bike will cruise and pull more easily at speed, due to less load for the engine to overcome. This also makes it much nicer when you gear it a tooth higher on the sprocket too.

Just a couple of ideas.

[basanti]

Ride it?

 

Heh,heh, heh.... Regardless, i love my bullet. I live in India and have been riding a succession of Enfield 500s for the last 18 years. Tinkered with half of them beyond hope of redemption. Last year thought enough is enough and got myself a brand new Yamaha FZ1 2007 (reason being imported bikes are prohibitory expensive... 128% duty) and sold my bullet.  Swore to myself (my wife being witness) that I'd have nothing to do with Enfields again as long as i live.

Six months later i went i bought a brand new 500. Again. I just love riding the bike too much And i think i have a problem: I just have to tinker with it. Just cannot leave it alone.