Technical Advisory for the 477cc Engine Upgrades

This information is for customers who have purchased the piston set

Please read before installation

The 477cc piston is available in cast and forged versions.

Forged pistons that are used in racing and high performance engines have a higher coefficient of expansion under heat influence compared to cast pistons. That means they need more “breathing room” inside the cylinder. This piston must have at least 0.07mm, better 0.075mm space between piston and cylinder wall. It is important to inform the boring/honing company of the nature of the piston as they may not recognize it and give you a too narrow cylinder, opening you up for a destroyed piston under load.

There are no special considerations regarding boring & honing for the cast piston.

Unlike the 450cc if you install the 477cc piston with only one layer of bottom cylinder gasket you will achieve a compression rate which is OK for Indian fuel. Only in rare occasions and countries with even worse fuel (some parts of Africa) use 2 bottom gaskets which will reduce the compression even further.

You will need the following additional items to do the update: (they may be included, depending on the kit you purchased)
One head gasket, one or two OEM cylinder bottom gaskets, one exhaust gasket (copper ring). If you do the changes yourself you will need a special tool to adjust the valves (available from Hitchcock’s for 30 pounds) after installation.

Break-in rules should be followed religiously with the forged version. The cast version is slightly more lenient but its is a good idea to follow those rules nevertheless.
It is recommended for the first 500km to never go over 4000rpm, onwards up to 1000km 5000 rpm should be the maximum. Riding conditions should vary as much as possible which means do not sit on one rpm/speed for extended periods. If you must use a highway still vary speed and rpm.

After the initial 500km an oil change (with filter) is needed. While the break-in oil can be any cheap oil from 500km onward only use full synthetic oil, the brand is irrelevant as long as it follows international norms for high quality oil, examples are:

  • Motul 7100 4T 10W-50 API SN Fully Synthetic
  • Mobil 1 5W30 Fully Synthetic
  • Shell 5w-40 Helix Ultra Synthetic

Remember that oil is not only responsible for friction control, it also serves as coolant in the LS410 engine. The 477cc is a high performance variant asking for high performance oil.

If you have not done any operations on an open engine before but want to do it with this upgrade please watch our video on YouTube how to do it BUT use a torque wrench when re-assembling the parts. Experienced mechanics can do it by hand but it is a very bad idea to emulate that without years of experience under your belt. The torque values are available in the respective manuals as outlined in the video description.

Top and bottom cylinder gaskets are supplied with the piston. Should you need a replacement order it from us or you can cut the head gasket easily from a LS410 OEM gasket available from Royal Enfield.
Sometimes parts are not easily available or dealerships are far away. In that case you can make your own foot gaskets which are really only made from thin cardboard about 0.3mm thick. Such material is available in sheets from Amazon and locally in hardware stores. Sometimes you will also find stores for automotive parts that can cut those gaskets for you (water cutting) or some print shops that cut labels and logos. We supply the layout for download in these formats in one ZIP packet: Corel Draw 2019, Corel Draw 12, PDF, [click here].

We are also using the 477cc on carbureted Himalayans. The UCD33 carb is also used on the Bullet 500 with the same 125 main jet. We have not changed that and our bike runs great. However one customer has changed to 130 main and has also lifted the needle by 1mm (putting a washer underneath) and is reporting increased power and better response.
However EFI bikes with this piston must use a device to regulate fuel flow with a mapping according to the 477 which necessitates the purchase of the Powertronic. Some users apply the 462cc map available from Hitchcock’s.
At some point in the future we will have made our own map and will make it available for d/l here.

While we do not offer a warranty for this upgrade but we will replace a broken 477cc cylinder/piston at any time with a new OEM version (back to 411cc) for 100.- € plus shipping. We will even honor this offer before anything happens should you like an “insurance package” in your garage. Just let us know. Shipping with intl. postal services is cheap but slow (2-4 weeks). It may also take up to 2 weeks to get a cylinder sent to us from the factory in Chennai.

If you want to discuss your experience with this upgrade in the wider Himalayan community there are various general bike forums and some specific to Royal Enfield out there. We can not follow all of them so if you are interested in replies from us we suggest you use the AdventureRider forum which has a thread dedicated to the Himalayan which we frequently read and write on.

Questions, ideas, any kind of input? Please contact us.