Technical Advisory for the 477cc Engine Upgrade

This information is for customers who have purchased the 477 set

Please read before installation

Downoad the 477cc cylinder insertion instructions as pdf

Raw Liner kit: Please check if the liner fits into the engine housing before you do the boring. There has been a case where the housing had an “edge” where the 2 halfs meet and this edge would not allow the liner to fit. It is a RE QC issue but obviously we can’t do anything about it. If the liner does not fit use a lathe to get it to fit before doing anything else. It is possible but much harder to fit it after you have it installed into the cylinder.

If you install the 477cc piston with only one layer of bottom cylinder gasket you will achieve a compression rate which is OK for 92 RON, the standard 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. If you chose 2 bottom gaskets make sure you use one of ours and one OEM. If you use 2 of ours the timing chain will be too short if it is new. On an older bike the then elongated chain may fit even with 2 of our gaskets.

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 cylinder bottom gaskets, one exhaust gasket (copper ring). If you do the changes yourself you will need a tool to adjust the valves (available e.g. online at ebay, from RE and Hitchcock’s for 30 pounds) after installation. If you have a carby bike you may want to change to a 130 main jet and a one size bigger pilot as well.

Break-in rules should be followed religiously.
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. Full break-in is achieved after approx. 2000km. After the initial 500km an oil change (with filter) is needed. Also then re-fasten the head bolts (otherwise the head gasket may leak oil) and adjust the valves. 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 from a LS410 OEM gasket available from Royal Enfield.
Sometimes parts are not 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 using the 477cc on carbureted Himalayans as well. The UCD33 carburetor is also used on the Bullet 500 with the same 125 main jet. We have changed that to 130 and one size bigger pilot and our bike runs OK when cold now. It will run with the 125 original jet but adjusting to a good cold idle is almost impossible. If you venture into the high mountains change to 110 or else the engine will lose 50% of its power. Do not forget to change back to 125 or 130 when coming down or else the engine will run way too lean and get overheated.

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 or similar device. Some users apply the 462cc map available from Hitchcock’s. We supply our own 477 map and make it available for d/l in the forum.

While we do not offer a warranty for this upgrade 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. It may take up to 2 weeks to get a cylinder sent to us from the factory in Chennai under normal conditions (no lockdown).

If you want to discuss your experience with this upgrade in the Himalayan community there are various general bike forums and some specific to Royal Enfield out there. If you are interested in replies from us we suggest you use our own forum which specializes in the Himalayan.