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FAQ: 477cc / 500cc Himalayan Engine Big Bore Set

This FAQ last updated: 27.04.2024

Please ask questions in the FORUM where issues are discussed in greater detail.

Q: The 477 is flagged “on back order” – When can I expect the 477cc set to ship?
A: Now

Q: Isn’t the liner too thin for a 84mm piston?
A: Not at all. With all the sets we sold nobody ever had a problem based on liner thickness. The accumulated km driven must now be well over 100.00 – that should prove the point.

Q: When can I expect the 500cc set to ship?
A: We sometimes do not stock it because it is not a frequent order. If it is on back-order preparing it will take 10 days to 2 weeks.

Q: What power increase can I realistically expect?
A: We have researched this issue in depth and verified it with Dyno runs. The naked 477 (all stock except cylinder/piston) will give you 27 RWHP, that is 6 RWHP (not BHP as RE uses) over stock. You can further enhance this with:

  • K&N air filter plus open exhaust: gains: additionally 1 RWHP.
  • A polished head with bigger inlet etc.: gains: 1 RWHP. Now you are at 29 RWHP (or about 34 BHP).
  • Further ca. 3 RWHP are available with our HT-b cam.

The numbers for the 500cc set are about 3-4 HP higher.

Q: How much does the kit cost?
A: Please check the product page for the various upgrade sets for this information. Shipping costs will be dependent on your location, they will be calculated once you check out but before you do the final payment.

Q: Do I need special fuel or octane booster for this piston?
A: No, the compression we get is only about 4-5% higher than the stock engine. It allows for running it with 95RON or better. If your fuel has lower quality you may want to use two foot gaskets to reduce the compression.

Q: What are the advantages of a bigger piston/increase in displacement?
A: Mainly these are:

  • More displacement means more mixture can fill the larger cylinder and be burned.
  • Larger bore size means larger area on the top of the piston, so the combustion pressure acts on a larger area, providing more “push”, resulting in increased torque.
  • Larger piston area creates a harder “pull” on the intake system, increasing gas velocity in the intake port, making better use of it.
  • Larger displacement, with the same cams and ports lowers the peak torque rpm and the peak hp rpm, approximately equal to the displacement increase, this giving more power at a lower range on the rpm band. 15% more displacement lowers the working power band by about 15%, or about 700 rpm.
  • More power in the useful mid range, you don’t have to rev as high for power. You ride lower rpm before lugging.
  • Larger bore size increases compression. Without being a higher compression piston by design, just by virtue that you are compressing a larger volume into the same size combustion chamber, you are getting a compression increase.
  • Although larger size pistons could be heavier, this one is lighter thereby decreasing the reciprocating mass, and causing less stress on the rod and bearings which will add to engine life expectancy.

Q: Will the 477cc sleeve fit into the engine body without widening it?
A: YES, that was the idea behind this upgrade, to keep it plug & play.
A bigger piston/sleeve combination would require you to widen the engine body which would make the work way more expensive.

Q: Will the 500cc sleeve fit into the engine body without widening it?
A: No, you need to widen the engine body by approx. 2mm all around or 4mm in diameter.

Q: Will overall reliability suffer from this upgrade?
A: Reliability is very much a function of maintenance and correct use. The 411cc engine is very robust. Well maintained it can last very long. The 477cc upgrade is a performance upgrade and requires handling as such. The correct calibration of a fuel injection control device (e.g. “Red Box”, Powertronic) plus exact timing are essential for this upgrade to run properly and not degrade due to knocking or overheating. We supply some maps in the forum in the “support sources” category.

Q: What total cost must I expect for a 477cc conversion?
A: That depends on whether you are doing the work of changing cylinder and piston or if you outsource the work – then add ca. 3-5 hours worth of a local technician’s pay to the set price. If you have an EFI version (BS4/BS6) you additionally will need to purchase a fuel flow regulating device like the “Red Box”, Powertronic or Power Commander.

Q: Do you provide a map for the BS6/Euro5 477cc and the Powertronic V4?
A: We do for some configurations. Please consult the forum where these maps are made available. Disclaimer: The Powertronic is NOT sold by us and all questions regarding its operation should be aimed at the RaceDynamics Helpline. The providing of maps for it is done as a voluntary service and no warranty or guarantee of any kind, explicit or implied for a specific function is given. You use our maps 100% at your own risk. You can always assume that modifications have to be done to fit your specific configuration. Of course we are always willing to help with that in the forum as much as possible.

Q: Do you provide maps for the BS4/Euro4 477cc and the “Red Box” ECU?
A: We do. Please consult the forum where these maps are made available.

Q: I have a BS3, do I need to change the carburetor configuration or the carburetor itself?
A: The standard issue carburetor of the Himalayan is identical to the one on the 500cc Bullet. We have re-jetted to 130 main and one up the pilot as well to 18 (from 15) to be able to get a low idle and reasonable cold run. But the bike will run with the 125 stock jets as well. If you go over 2000m elevation we strongly suggest a change to a 115 main jet. If you do not do this, power loss will be likely and fuel consumption goes up.

Q: Will the 477cc bike use more fuel than the 411cc?
A: No, it will use less, given comparable driving conditions. But naturally if you use the higher acceleration provided by this engine more fuel will be used. It is mostly a matter of driving style.

Q: Do you publish measurements, Dyno charts etc. of your setup?
A: There are plenty Dyno charts done by our Australian partner available on the forum with all kinds of different configurations.

Q: Are you using the factory liner bored to 477cc or are you providing the cylinder with a new liner when upgrading to 477cc?
A: For this upgrade we use a new liner that will however still fit into the engine body without any changes to the latter.

Q: What the measurements for honing the cylinder wall?
A: Opinions differ. I do 0.09-0.1mm (4 thou), I have heard others are happy with less like 0.07mm and others even do up to 0.14mm for fear of seizing. 0.09 seems to work fine, I had no seizing pistons so far.

Q: In your upgrade set do you provide everything I need for the upgrade or do I need special tools/other stuff to do it?
A: We provide everything except the tools. But the tools you need are very common and are all listed in the “How To Upgrade” video. We did it without even a torque wrench (but we suggest to use one). There is one special tool for valve adjustment, you can order it from various online sources including eBay if you can’t get it locally.

Q: Will this piston give me a greater top speed?
A: Yes and no. If you are heavier than most or ride with pillion and luggage it will because you likely never red-lined the 411 engine in such a configuration. However, if you are a small lone driver – then no. The red-line RPM is the same. To change that you would have to change the number of teeth on either sprocket – You would want to add one tooth to the front or subtract three from the rear. Make sure the chain fits after that change. Such sprockets are available online. As of our latest test a 16 teeth sprocket does a lot for a much smoother an quieter run especially at highway speeds of around 100km/h.

Q: Are there specific break-in rules I must follow?
A: Yes, there are. The engine should not be moved beyond 3000rpm for the first 500km. Then an oil change is needed and for the next 1500km 4000rpm should only be surpassed for take over. It can take up to 2000 km to reach full free running, up to this point top speed can be used for short moments but not sustained. After the initial 500km break-in full synthetic oil should be used exclusively.

Q: My engine has run for over 30.000km, is there anything I should exchange/renew with the upgrade?
A: It is advisable to change the timing chain which is suggested at 30.000km for the older versions and at 50.000km for the newer ones.

Q: Does your piston come with any kind of warranty?
A: The warranty is limited to delivery failures or damaged delivery goods see here. This is a high performance upgrade, it requires you to handle your bike accordingly. E.g. we have no influence on how the break-in, maintenance and riding is done. For that reason we do not warranty the upgrade set as such. As unlikely as they are, failures could have any number of reasons outside our responsibility. BUT we do offer to sell anyone who bought an upgrade set from us and experiences a problem a factory new 410cc cylinder+piston set for 100.- € plus shipping.

Please ask questions in the FORUM

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