[beecoterie]

Yes, I'm starting from not even knowing what kind of bike I have, or at least not how it's represented in this forum. I know it as a 2002 Bullet ES 500cc. My goal is to ultimately find an air filter replacement.

But I'm wondering more generally how I would know if it is an Iron Barrel, Electra/AVL or one with UCE?

Bonus points if someone can help me out with a link to an air filter that would work for it!

[mevocgt]

I think it's an iron barrel.  As far as parts, you can go to http://www.classicmotorworks.com/

The host of the forum's store.

Good luck!

[Ice]

Hello beecoterie, welcome and congrats on your Bullet !

 Correct, you have an Iron Barrel !

 Some identification information to get you started. 

 In the yellow oval is your "distributor" aka Delco. Only Iron Barrel engines have those here.

 In the green circle is your four speed transmission ( five speed looks different) A 4 speed can be fitted to an AVL but none were imported to the US with one.

 Aft of the green circle, on the frame at the swing arm pivot is a large chrome nut, IIRC 2003 was last year of that style of nut.

 In the red circle is your flat top oil filler cap. IIRC 2003 was last year with those.


 Share some more with you about CMW a.k.a. "the store".
In addition to hosting this site they were the exclusive US importer & distributor of Royal Enfields.  Royal Enfield North America ( RENA ) bought those exclusive rights from back from CMW's owner & president Kevin Mahoney effective new years 2016. Kevin is bike guy and posts here regularly.
 The store has 10,000 sq ft floor to ceiling of everything we need. Only a small percentage of the stock on hand is on the website and the folks are Minnesota nice. 

 Part number 112178 should get you the air filter but call CMW to be sure.

Welcome to the fun.

*sorry for the ramble and to answer your original question, Bullet Iron Barrel section.

[Arizoni]

All of the 500cc Royal Enfields up to around 2007 were Iron Barrels.
From about 2007 to 2009 the AVL's were sold in the US.

From 2009 on, the engine is the UCE style.

For a standing back and just looking at the engine method, I look for these features.

The Iron Barrel has external lube lines running to the rocker arms towards the top of the head.

The Iron Barrels rocker arm covers are not large and their lower surfaces which mate with the top of the cylinder head run parallel with the ground.

The proportions of the height of the cylinder head looks about right with around 8 cooling fins.

The Iron Barrel has a gear train running up the right side of the engine to drive the mag or ignition points.

The Iron Barrel may have a separate 4 or 5 speed transmission bolted to the rear of the crankcase.  The 4 speed has a separate neutral selector lever near the gear shift lever on the right.

The Iron Barrel drive chain is on the left side (aft looking forward).
The AVL has external oil lines to the rocker arms toward the top of the cylinder head.

The AVL rocker arm covers lower surfaces which mate with the cylinder head are not parallel with the ground.  They are at a angle of about 15-20 degrees to the ground.

The cylinder head looks much too tall for the engine with about 12 fins.

The AVL has a gear train running up the right side of the engine which may or may not drive the ignition points.

The AVL has a separate 5 speed transmission bolted to the rear of the crankcase which does not have a "neutral selector" lever in addition to the gear shift lever.

The AVL drive chain is on the left side (aft looking forward).

The UCE engine does not have any external oil lines to the cylinder head.

The UCE rocker arm covers are large and their lower surface that mates with the cylinder head are parallel with the ground.

The UCE cylinder head looks wide with 9 cooling fins.

The UCE transmission is built into a streamlined unit construction crankcase.
The neutral selector lever is not available.

The UCE drive chain is on the right side (aft looking forward).

There are more differences but these are the ones I usually look for.

[beecoterie]

Huge help. Thanks everyone. Was interested to find out that CMW is based out of MN...as it was a MN company that sent me to India for 3 months where I became familiar with these cool bikes!

I took the advice and called the store, and was super impressed. These days, with everything online I wasn't expecting to get a human on the line, let alone a helpful one. I've got an air filter on its way! Long story about how mine got all gummed up, but suffice to say I'm waiting on it to ride again!

[Ice]

Huge help. Thanks everyone. Was interested to find out that CMW is based out of MN...as it was a MN company that sent me to India for 3 months where I became familiar with these cool bikes!

I took the advice and called the store, and was super impressed. These days, with everything online I wasn't expecting to get a human on the line, let alone a helpful one. I've got an air filter on its way! Long story about how mine got all gummed up, but suffice to say I'm waiting on it to ride again!

 That's one example of "Minnesota nice" 

[heloego]

  Congrats on your Iron Barrel! 
  The gang at CMW definitely are the "Go To" folks when you need a part! Enjoy!