Royal Enfield 535 GT Asbo 40 cylinder head tuning work discussed at Performance Classics.

From the third machine of this type to be tuned at Performance Classics, we take a look at some of the work done to the cylinder head, to hopefully make a contribution towards livening things up a little.

[@jeremyatkinson4976]

According to Hitchcocks the carb is a 32, the same as the Amal. There's not enough room under the frame for a bigger VM or Mk 1. There is enough room for a MK2 Concentric 34, which is a very short spigot mounting carb. However Amal no longer make the bodies for those, though they do sell all the parts. So without trying a Keihin or a S/H Mk2 the only other option is to bore out the carb to 33. This was often done when racing 32 MK1s. Whether this would improve or worsen the bike's performance, is quite another matter. SR500s used a 34 but they peaked at 6500 and stayed much the same to 7000

[@BilgemasterBill]

Nice to see a modern Continental SINGLE featured on your channel...or ANYWHERE for that matter. It just seems like since the new 650s came out all those formerly boisterous "Fast Lads" (at least when compared to us other thumper jumpers) have taken some weird vow of silence. On the Enfield Forum I follow, mostly you just hear crickets in their cobwebby section nowadays. So please do go ahead and make that Conti really bark, OK? 'Cause it's getting a bit spooky in that 535s lounge.

[@paulhenshaw4514]

I know the forum you mean, Bill - I am featuring this job there as well as in a couple of other places and will update the project with videos as it moves along, hopefully culminating in a quick ride video once those cams have arrived and been fitted!

[@piearm1271]

Be very interesting to see how that runs after. Funny but when you said it’s all simple stuff I couldn’t help remembering the quote genius makes the complex look simple.

[@paulhenshaw4514]

Wow, thank you!

[@GrampsD63]

I've done the same work on my FT500 Ascot head. It was breathing much better at the mid- to high RPM range. Of course I had a couple extra valves..

[@silktvPDR1]

I loved my GT but it had to go to make way for a rather nice MZ Skorpion and sadly it puts the GT to shame in every field. Will watch with interest though 👍

[@sajivnair78]

Paul! Very nice video and appreciate the clear and simple way you go about explaining the modifications...Helps folks like me who are attempting to do this for the first time!! :-) I had a question, if you would be kind to help out, on my UCE 500 head I plan to reduce the cylinder height to increase the compression by reducing the squick height(?)...In my eagerness to get the head and cylinder off to the shop (a little ways from home), I missed getting the mm by which the chamber needs to be shortened (by putting the piston at TDC); side note: the piston I plan to use is a flat head piston (from RE AVL 500cc engine) For this specific modification, you mentioned reducing by 1mm and also retarding the intake by a tooth... For my application - since I don't have the actual height measurement from the TDC to barrel edge -- what would be a conservative reduction in height? 1mm or maybe 0.8mm ??? If I do a 1mm reduction, will I have to retard the intake and probably measure the squish as well? (if less - I may have ruined the barrel) Apologies for the rather long-winded question!! :-) Thanks in advance!

[@Taurim]

Thanks Paul ! I have a lot of grinding work in front of me :-D We discussed that in FB yesterday ;) Serge (hoping to build a faster 535 too !)

[@paulhenshaw4514]

You can do it!

[@thefastelephant94]

Did this tonight. Lets see what the coming weekend brings.

[@thefastelephant94]

Just did this work. Had to have shims under the rocker bearings as my valve seats needed to be cut thanks to my sloppy hands when porting the head. Runs really well and pulls too hard.

[@amelierenoncule]

I like those two set pins, 180 degrees from each other.. Make haste to ask me not...but, a new, or just machined, 'Top End' has a rather sensuous allure about it. The time I had my A65's head done, I stared at it, drinking in its' charm, for almost a full week 'fore I torqued it atop the cylinders. i.imgur.com/vlBaLo8.png BTW, to the left of 'your' Hd., lies a magnifying glass. For what purpose do you employ it...besides cleaning your fingernails ?

[@paulhenshaw4514]

Ah, the magnifying glass - my eye sight has held up well enough after 56 years for me not to need glasses, but occasionally I use this when inspecting valve seatings, carburettor jet sizes and piston rings for orientation marks, etc. Here, I would have been using it to check the valves and seats, while grinding them in.

[@Ginga7r]

My 535 is ticking away and I'm thinking of this exact mod how much roughly are you talking to complete what Awesome work you have done here Sir.

[@paulhenshaw4514]

Thanks - it is quite expensive with the carb kit, cams, exhaust etc, then my work on top. You could buy a good used Honda XBR 500 for about the same as getting the best from one of these will cost!

[@Ginga7r]

I did think that mate especially when you look at the prices Hitchcocks is asking for some parts. I might not have much of a choice though but it depends if its going to be covered under warranty as I have been waiting well over a year just to get the dealer to look at it and they don't seem to have a clue where the noise is coming from, but its obvious where to look either the valve and guide or the hydraulic pushrod or the rocker cap has slackened off, but as the bike has only covered 1475 miles fingers crossed its something minor. Thanks for responding keep up the awesome work mate.

[@keesstam909]

Hi Paul, why throw the throttle body away and use a carburator? regards Cornelius

[@paulhenshaw4514]

Hi Cornelius, the fuel injection system is tuned for economy and emissions, rather than performance, and although there are ways of adjusting it, it is easier for most - including myself - to fit a carburettor and tune it to suit the rest of the engine's set up.

[@thefastelephant94]

Hi Paul, Doing this here in India this weekend. Just a few quick questions. Your help would be genuinely appreciated. - The Inlet and Exhaust port enlargement, do they taper out towards port? - Does this need to be done on a lathe alone or will a dremel work? - Mirror Finish on Exhaust Port will be helpful if am correct but it should be avoided on intake port as its a port injection design, is that correct?

[@davidvardy8582]

Paul I presume you remove any sensors etc and block the relevant holes when fitting a carb conversion. Will you also alter the exhaust system.

[@paulhenshaw4514]

Yes, all in hand.

[@bsatrialsguy9095]

good advise and finding love to see asbo 40 efi type engine please make video of crank tunning

[@paulhenshaw4514]

Thanks - I will keep it in mind!

[@glaicogobbo4046]

It is necessary to have a lot of practical knowledge in addition to the theoretical for the optimizations that are being carried out in this head in addition to carburation. I have no idea how the exhaust system will be prepared for these latest innovations which will certainly give this engine a lot more claw. Soon customers will appear to further tune the engines capable of employing the new cylinder head with valves driven without rods and impellers launched from 9/11/2019 to the Himalayas, 462cc with more torque and power in the entire rotation range provided with base gasket, chain tensioner gasket and head gasket by Hitchcocks Motorcycles. I assume that this motorcycle has 5 gears which will greatly accentuate its maximum speed. It will be a great success! Many of those who purchased the new Hindu models will appear at the Performance Classics workshop requesting a similar cocktail so as not to force themselves to ride on the English superhighways jammed by today's powerful trucks. Unfortunately, England is entering a new standstill. Terrible for the economy!

[@paulhenshaw4514]

Thanks, Glaico!

[@jeremyatkinson4976]

Paul Lives in Wales. They don't know what a recession is, as they've never come out of one.....

[@glaicogobbo4046]

​@@jeremyatkinson4976 Here in Brazil, with several Lockdowns in different states with governors who are not obeying the federal government, behind their own interests they have caused a very violent recession. The President has been guaranteeing low-income, or even jobless, people since the beginning of the pandemic and extending the payment of a monthly allowance to millions of people of R $ 600.00 until December. (GBP 87.1287), greatly increasing our domestic debt. In Europe, the press is saying that Prime Minister Boris has decreed a total blockade of a few weeks, which can cause immense economic problems. The English economy is much stronger than the Brazilian. However, if these interruptions continue, there will be major economic disruption.

[@davidwilliamson9162]

No decomp 🕳 hole

[@paulhenshaw4514]

That's correct - the decompressors on these machines is built in to the exhaust camshaft and is automatic.

[@hermangibbs8163]

Fantastic. Thanks Paul.

[@paulhenshaw4514]

Thanks again, Herman!

[@davidforsdike4343]

Do you know why Hitchcocks have stopped selling the cams.

[@paulhenshaw4514]

I am not sure, but I hope they will be getting more in the future.

[@davidforsdike4343]

I have spoken to Hitchcocks. They are waiting for a new batch of cams.

[@andrewholden4812]

Avidly watching Paul , I'm really taken with this type of machine , very interesting thanks for the videos

[@paulhenshaw4514]

Glad you enjoyed it

[@wdhewson]

Is the brass fitting with wire a knock sensor?

[@paulhenshaw4514]

I think it is probably a heat sensor, but I am not entirely sure.

[@wdhewson]

@@paulhenshaw4514 Yes, the copper based alloy would be good for heat conduction and the fuel injection system would have to have temperature for mapping. Thanks.

[@davidwilliamson9162]

Excellent work,is there 1 cut on the valves or do you 3angle them?

[@paulhenshaw4514]

Thanks - just the one cut.

[@davidwilliamson9162]

Are the 535 gt heads the same as the Indian bullets?

[@paulhenshaw4514]

No, they are totally different.

[@davidwilliamson9162]

@@paulhenshaw4514 could I request at sometime a video with the back to back,or name the main differences?