Loss of compression in cylinder head to new engine set-up

N

Niek Okken

Active Member
Goodmorning,

Last weekend my standard royal enfield had compression loss due to 5mm slack on the inlet valve. While riding I suddenly felt the loss and heard a rattling noise followed by an engine that does not run anymore. This saturday I will take of the cylinder head and look into what is broken and what I need to replace.

I already planned on replacing the standard Cam shaft to the HT-B camshaft, K&N airfilter and a powertronic V3. I bought these parts from a fellow Himalayan 411 rider.
Now I am also thinking of upgrading to the Himalayan tools 477 cylinder. The thing is that I do not know what I will have to do for setting up the right mapping for the powertronic.

What steps am I going to have to take to find out if my mapping is right for the new setup on the bike? Because I don't want to have the bike run lean.
 
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You have a BS4 right? you must because the PT3 is exclusively for the BS4, the BS6 uses the PT4 (very few very early exceptions where a PT3 made for the BS6 was used but we never got it to work).
We have a map for the BS4/PT3 that will fit the 477 with cam setup, derived from a Hitchcocks map of the 462 that we will supply along with the BB kit.

How do you know if you have a BS4 and not a BS6? If your ECU is a single unit under the seat its BS4, if the ECU is glued to the TB its a BS6.
 
Bespoke engineering said:
What have people done in regard to head porting and polishing ? Oversize valves? Head skim (to raise compression for more torque) ?
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well, I had the polishing done once for a BS4 in the good old days, but the effect wasn't measurable. Where I live the problem is to LOWER compression bc of bad fuel.
 
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Bespoke engineering said:
What have people done in regard to head porting and polishing ? Oversize valves? Head skim (to raise compression for more torque) ?
Click to expand...
Looking at the head there is not much room for larger valves and so far they have not hit the market.
Porting to match the seats to the ports is easily done and should make a slight improvement as will reseating the Valves to get them further into the combustion chamber.
Displacement and the Cam are a good place to start, head can certainly be shaved as the Cam sprocket is a adjustable.
 
My mistake, I was thinking of the J.
If you drop the head on a 411 anyhow your cam timing will be out ,best option I have found is an OEM Sprocket with elongated holes and skip the dowel pin.
I always increased the size of my Himalayan combustion chambers by at least unshrouding the valves and sizing to the new bore.
 
Dool said:
My mistake, I was thinking of the J.
If you drop the head on a 411 anyhow your cam timing will be out ,best option I have found is an OEM Sprocket with elongated holes and skip the dowel pin.
I always increased the size of my Himalayan combustion chambers by at least unshrouding the valves and sizing to the new bore.
Click to expand...
Have you got a photo of the head unshrouding of the valves? like a before and after? Cheers
 
Valves are hard so leave them in to protect the seats.
 
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