[tooseevee]

Boy, I'm really impressed with you guys. You really know your shit!

Reminds me of some of the discussions back when Tom Lyons was on the forums every day.

[mcplorer]

Paul Henshaw had a compression boosting modification for the 500 AVL which involved machining 2mm off the base of the cylinder flange, and a 2mm deep by 10mm wide band off the top of the 84mm piston crown, might this be adaptable to the UCE, even with the Baleno piston? As the latter has a dished crown this mod would give you something like a flat-topped piston instead of a dished one. I don't know what the Baleno piston has by way of valve pockets, but you will want to check for valve head to piston crown clearance if you do this.

Also - VERY IMPORTANT - make sure your new Mikuni is jetted to suit the higher compression, particularly if you're keeping standard valve timing, don't ask me how I know this...

The other trick - again, from Paul Henshaw - used on high compression IB and 500 AVL engines is to retard the inlet cam by one tooth on the cam gear, apart from giving the engine an easier time and reducing vibration and any tendency to pinking it gives a better top end performance at the expense of some of the lower down grunt. This might not work so well on a UCE as the cam gears have 36 instead of 40 teeth if I'm correct, so the retarding would be more pronounced, but it is something you could look into.

A.

@Adrian

I have been following Paul from pretty long time and just watching his videos and reading his post gives so much knowledge

Shaving off base of the cylinder flange even if deck height is zero? Paul indeed talks about shaving off 2mm but will it apply to a UCE motor as well?

"and a 2mm deep by 10mm wide band off the top of the 84mm piston crown" - This I never understood before also and now is no exception either. Please explain a bit. I am confused. If we make a cut 2mm deep and 10mm wide won't it actually increase the volume of the combustion chamber actually?


This is Baleno piston, in attachment

Jetting the Mikuni? For sure, 100%. I have really got my hands dirty during jetting the CV carb and then VM28 and have also tried UCD33 Bullet 500 carb on a friend's bike.

Retarding inlet cam by a tooth? Yes have followed Paul closely on this as well and he suggested this might not be that effective on a 350 (in my case it will be 400cc) unless it has higher compression ratio

Please do let me know few more pointers. What is threshold for cylinder sleeve thickness? Was reading on Hitchcock's website that nothing less than 1.5mm

[AzCal Retred]

The UCE head & cylinder top are flat. Shaving a bit off the cylinder base makes the piston protrude into the combustion chamber more raising compression. Creating a flat band around the top of the piston to match the head surface creates a "squish band" with attendant good effects on combustion. See attached articles.

Shaving off base of the cylinder flange even if deck height is zero?
"and a 2mm deep by 10mm wide band off the top of the 84mm piston crown" -

https://en.wikipedia.org/wiki/Squish_(piston_engine)
Squish is an effect in internal combustion engines which creates sudden turbulence of the air-fuel mixture as the piston approaches top dead centre (TDC).[1][2]
In an engine designed to use the squish effect, at top dead centre the piston crown comes very close (typically less than 1 mm[2]) to the cylinder head. The gases are suddenly "squished" out within the combustion chamber, creating turbulence which promotes thorough air-fuel mixing, a factor beneficial to efficient combustion. Squish effect may be found in side-valve, OHV and OHC engines, including engines with a Heron cylinder head. Squish effect may be found in any fuel type internal combustion piston engine. Squish piston engines are also found in both two stroke and four stroke engines.
Turbulence in the combustion chamber due to this squish helps with air-fuel mixing, cylinder wall heat transfer, thermal efficiency, and overall engine performance. Heat transfer is aided when the combustion gasses swirl around and heat the cylinder wall, allowing the cooling system to work more efficiently.[3] This efficiency and swirling can also reduce the amount of soot production.[4]

https://www.cycleworld.com/2015/08/07/tech-essay-kevin-cameron-how-close-can-a-motorcycle-piston-come-to-the-cylinder-head/

https://www.cycleworld.com/blogs/ask-kevin/optimizing-motorcycle-ignition-timing/

[mcplorer]

Why Baleno piston is an automatic and great choice

[AzCal Retred]

Dimensions are necessary when making useful comparisons.

Wrist pin center to deck height?
Wrist pin diameter?
Dome shape & resulting CR in a 350 UCE combustion chamber? Baleno 4-valve combustion chamber shape is completely different than the 350 UCE.

If diameter was the discriminator, the BSA/Triumph pistons after 70 years of development are in the running too. They have various dome configurations, all better suited to a 2-valve design.

[mcplorer]

Dimensions are necessary when making useful comparisons.

Wrist pin center to deck height?
Wrist pin diameter?
Dome shape & resulting CR in a 350 UCE combustion chamber? Baleno 4-valve combustion chamber shape is completely different than the 350 UCE.

If diameter was the discriminator, the BSA/Triumph pistons after 70 years of development are in the running too. They have various dome configurations, all better suited to a 2-valve design.

I had already replied for all of the above questions. Appreciate if you can recheck and do not overlook

Wrist pin center to deck height? - Compression height there is no change ( I had already mentioned in my previous posts)

Wrist pin diameter? - No change (This too, I had already mentioned in my previous posts)

Dome shape & resulting CR in a 350 UCE combustion chamber? Baleno 4-valve combustion chamber shape is completely different than the 350 UCE - We did discuss and did all the math. The UCE Piston is dished too. And why are you rejecting the fact that someone has done it and rode over 50K kms and have done it on more than 10 Enfields already? Aren't the same principle apply here too about which we talk when we take names like Hitchcock or others?

If diameter was the discriminator - Did I conclude that diameter is the only discriminator without talking about other variables?

[AzCal Retred]

Why Baleno piston is an automatic and great choice
Wrist pin and deck height are good places to start. Just "most easily filling the hole" isn't all the criteria. A 2-valve engineered domed piston that perhaps just needs the wrist pin holes reamed to size might be better. You can stop at the Baleno piston and have a good runner. To have a great runner you may need to keep looking. The 4 valve pockets are not matched to the head topology and mostly serve to collect carbon deposits. A polish on the piston tops will slow that process down some. A 2-valve domed piston will give you better control over combustion chamber shape which is a large factor in creating performance.

And why are you rejecting the fact that someone has done it and rode over 50K kms and have done it on more than 10 Enfields already?
Nobody is "rejecting" anything. This thread is titled "Serious Performance Mods", not "Hey this works pretty good mods".
If adding a bigger piston and carb meets requirements and you want to stop, that's great, nothing wrong with that. It is a way better solution than recreating the wheel which was the original proposition, so you have grown some as far as I can tell. It sounds at times like part of the thread purpose was to grow your knowledge. Refining combustion chamber shape and understanding squish banding is part of that.

Did you look at the squish band information? Good stuff there.



 

[Adrian II]

"and a 2mm deep by 10mm wide band off the top of the 84mm piston crown" - This I never understood before also and now is no exception either. Please explain a bit. I am confused. If we make a cut 2mm deep and 10mm wide won't it actually increase the volume of the combustion chamber actually?

10mm wide is for an 84mm piston, you can scale it back a bit for smaller diameters.

AzCal gave you the details, but this HAS to be done IN CONJUNCTION with taking 2mm off the cylinder base flange. Modding the piston on its own makes no sense, but if you only trim the cylinder base flange and don't mod the piston as well, the outer edge of the crown will now protrude over the top of the cylinder by 2mm and hit stuff! That is why you need to remove a band of metal, but only around edge, doing so still effectively leaves the CENTER of the crown raised, resulting in increased compression.

A.

[tooseevee]

....... but if you only trim the cylinder base flange and don't mod the piston as well, the outer edge of the crown will now protrude over the top of the cylinder by 2mm and hit stuff!
A.

     When I put the ACE head back on in 2014 I think I clay tested three times I was so worried about the larger valves, especially the intake.

   

[mcplorer]

@Azcal make sense what you are saying. And honestly I am not completely fixed on the Baleno piston. My hunt would still be a two valve domed piston but in the dearth of finding one I will go back to Baleno.
Yes agree my goalpost have moved but don't we learn and do better and more sensible things? This is how we grow isn't it? At least in the world of motorcycle modifications

I did look at the squish band information but not like I haven't looked at it before (Did read about it before and offcourse YouTubes)

@Adrian Now I could visualize. The key point here is which maybe I was failing to synchronize is this what you wrote
"but this HAS to be done IN CONJUNCTION with taking 2mm off the cylinder base flange". Now it make super sense(it always was just that I wasn't able to grab it till now)

[AzCal Retred]

Sounds like progress to me!

"Yes agree my goalpost have moved but don't we learn and do better and more sensible things? This is how we grow isn't it? "
"If adding a bigger piston and carb meets requirements and you want to stop, that's great, nothing wrong with that. It is a way better solution than recreating the wheel which was the original proposition, so you have grown some as far as I can tell. It sounds at times like part of the thread purpose was to grow your knowledge. Refining combustion chamber shape and understanding squish banding is part of that."

Still seems to be some haziness around squish, but those Cameron articles should help.

[axman88]

Somebody in the thread brought up the idea of upgrading cam profiles a page or two back in this thread, and I was curious.

Hitchcocks doesn't cover the 350 UCE machines in their database, but from listings on Ebay and things I've read here on the forum, I got the idea that 350, 500, and 535 UCE engines all came from the factory with the same, identical #571164 Intake cam, identical #570309 exhaust cam. 

I see that Hitchcocks offers a performance cam kit for UCE machines but only 500 & 535 engines are mentioned: https://accessories.hitchcocksmotorcycles.com/32705

Do the 350 UCE engines use the same physical cam gear and shaft, and / or the same identical cams as the 500s?

What does the Hitchcock performance cam kit do for the 500 & 535 engine?  What would it do for a 350, stock or modified?

[mcplorer]

10mm wide is for an 84mm piston, you can scale it back a bit for smaller diameters.

AzCal gave you the details, but this HAS to be done IN CONJUNCTION with taking 2mm off the cylinder base flange. Modding the piston on its own makes no sense, but if you only trim the cylinder base flange and don't mod the piston as well, the outer edge of the crown will now protrude over the top of the cylinder by 2mm and hit stuff! That is why you need to remove a band of metal, but only around edge, doing so still effectively leaves the CENTER of the crown raised, resulting in increased compression.

A.

So when you say shave off 2mm off the cylinder base flange you mean the one I highlighted in red color, right (taking off 2 mm throughout the circumference obviously)?

Btw the attached image is of 350 UCE

[mcplorer]

@Azcal BTW what is recommended hose/adapter length between head and carb(carb outlet which goes into head) ? Any recommendation around it?

[Adrian II]

So when you say shave off 2mm off the cylinder base flange you mean the one I highlighted in red color, right (taking off 2 mm throughout the circumference obviously)?

The base flange is on the UNDERSIDE of the cylinder barrel where it sits on the crankcase mouth, you've highlighted the TOP flange, don't machine that down in case it interferes with the cylinder liner fixing. **If** the joint face has has been damaged some very minor skimming is OK to restore the flat surface, otherwise leave it alone.

The best fitting for the carb is a one-piece rubber flange adapter, sometimes called a plate manifold. If you want an alloy adapter and a piece of radiator hose to move the carb further out that can cause problems with the throttle cable run under the back of the tank. The factory adapter for a carb model 500 UCE ought to fit, 60mm mounting stud centers, 33mm bore which is close enough for your VM32 and a 40mm diameter recess for the carb mounting stub, same as on the VM32. This sort of thing: https://www.ebay.co.uk/itm/145506459875 (the seller is in India, btw).

A.