ESE's works engine tuner

[F5 Dave]

Whiiir.CLICK. ok we'll get to that later.


Ahh Wob, you have a way with words that makes me laugh. . usually at myself.

I'd only changed to Castrol R30 in an attempt to get better ring sealing. I thought the old bean oils were supposed to have surprisingly good film strength esp when hot (& teh bike was air cooled not that long ago).

anyways..since it has a full reed conversion I trimmed the back of the piston from 56mm to 48 as it stuck down in the way at BDC. I'd noted the old aircoold YZs had most of the piston back missing and the KT100 .skirt was reasonably long and parralel. A few pages back you indicated that the most flow isn't happening at BDC. Perhaps I should go back to full length skirts (except on saturday nights when its dark).

[Ocean1]

If the deck height of that piston is greater than the other pistons it may be just touching the head enough to flatten the edge of the piston enough to trap the ring. A look at the head and top of the piston should give us a clue.

Or the head not doweled to the barrel properly and head chamber offset in use.

Plastigauge?

[peewee]

Dump the 18th century fish and chip cooking oil and get something in there that has at least a modicum of film strength.

why dont you like castor oil ?

[F5 Dave]

Makes the crumbed fillets soggy

[wobbly]

Most of the transfer flow IS at around BDC if the pipe is correctly designed to give max depression at this time.
Inlet flow occurs when the case starts to go negative ( and helped by the inlet length if its tuned correctly, as this goes positive )
due to the pipe suction pulling the mixture in the ducts into the cylinder,and this depression eventually opens the reeds via the case,near BDC as well.
Thus piston holes, Boyesens and short skirts all help the initial flow as the piston starts to rise.

Bean oil always has had crap film strength, what it does have is the ability to give a nice smooth wear surface - as you said when things get real hot it retains this superior
wear pattern, wheras a full synthetic disassociates into non lubricating shit chemicals.
But the new generation of oils based on esters that mimic castor but have the huge film strength of synthetics are way superior to both.
The best oil from much testing by many clever tuners for the air cooled KT100 now,is Elf 909, the most castor like of the new blends.
In my testing the best oil now for watercooled engines on pump gas that get close to being overheated by 640C in the header like we used to on Avgas, is Motul Kart at 20:1.
The super oils like Elf 927 were developed for unleaded race engines, as these run fastest when alot richer than a leaded setup and they never see the temps that killed full synthetics badly.

If you want to get the best cylinder surface on a new chromed bore, then slober R30 all over the place, mix it up at 16:1 and ONLY idle the new engine for 5 minutes.
This reduces the ring tension from high cylinder pressure, and the castor oil lets the ring/bore surfaces wear in to each other smoothly.
Once this is done, dump the castor and go racing hard on a semi synthetic.
Ive won dozens of titles with engines done this way.

[F5 Dave]

Most of the transfer flow IS at around BDC if the pipe is correctly designed to give max depression at this time.
Inlet flow occurs when the case starts to go negative ( and helped by the inlet length if its tuned correctly, as this goes positive )
due to the pipe suction pulling the mixture in the ducts into the cylinder,and this depression eventually opens the reeds via the case,near BDC as well.
Thus piston holes, Boyesens and short skirts all help the initial flow as the piston starts to rise.

Hmm ok so should I shorten the skirts but a little less both sides or just leave the dam things alone altogether?

[RomeuPT]

That happens when the piston ring is stuck in its groove, at the exhaust side. If you turn the crankshaft backwards, the con rod will push the piston against the bore opposite from the exhaust side, lifting the stuck side of the piston ring away from the bore.

Thanks, this is probably the case.

Squish deck is highly on the safe side. Rod is new....

The rod angularity is at a max 1/2 way down the bore so if the lower skirt isnt supported properly the piston will cock over,dragging the ring edge into
the bore and creating the wear pattern.
Dump the 18th century fish and chip cooking oil and get something in there that has at least a modicum of film strength.

I don't know what cause the wear at the piston top ring edge. I am not sure if this answer is for Dave or for me.
I am Using Castrol 2T stroke Racing, fully synthetic at around 3,25%.

[senso]

How is the exhaust bridge?
Seems like the problem that the gasgas has, pegging the ring in the bridge, solutoin was to drill 4 holes with 1.5mm chamfered to 2mm.

Or another note, what do you guys think about the shell racing M oil?
I can't run it on the 125, fouls plugs like there is no tomorrow, A747 doesn't do anything like that, but runs great in the cast iron 45mm crm liner.

[peewee]

has somebody tried this oil. says its good to 45,000 rpm

[wobbly]

Well as I said, fully synthetics like 2T are not good when overheated in an engine that runs leaded race gas,where the normal running temp needed to
make the fuel work correctly, destroys the film strength - the only good reason to be running a full synthetic in the first place.
And at 30:1 it would struggle in any real race engine.
I had no idea you could still buy A747 - easily the best oil made for leaded fuel, many years ago.
Shell M was developed in the stone age,for use with Methanol fuels, so no reason to be using it for anything else, or at all really.
I wouldnt put Amsoil in a race engine if it was given to me, and it ran at only 5,000 rpm.
Last engine I saw on Amsoil, was a microlight that had crashed, due to a skirt dropping off.
The other piston was OK, except for the 0.012" bore clearance after 3 Hrs in the air - running 100:1 like it said on the bottle.

Every RS125 by Honda should have 2 bridge lube holes and 1 each side of the boost,unless you want to be freeing snagged rings all the time.
A T port is absolute hell on any oil trying to keep the ring off the bore, even with super trick piston shapes and properly relieved bridge geometry.

[peewee]

i wouldnt put amsoil in a lawnmower

[senso]

A747 I can it locally for 22€, or from Spain at like 14€ for each pack of 12 liters, just under 200€ with shipping.
The Racing M is very cheap around here, about 10€ a litre.
Here is the still stock combustion chamber of the crm with like 1.2mm squish after burning 200l of 95 pump gas with the racing M.

[husaberg]

A747 I can it locally for 22€, or from Spain at like 14€ for each pack of 12 liters, just under 200€ with shipping.
The Racing M is very cheap around here, about 10€ a litre.
Here is the still stock combustion chamber of the crm with like 1.2mm squish after burning 200l of 95 pump gas with the racing M.

I would say 1.2mm squish unless you have a elastic rod, or a huge bore and stroke (say 100mm by 100mm) is not squishing much at all.
It should be nearly half that I would have thought.

I have mentioned the early Cagiva injection before based on a similar set up based on the early 851 set up.
here is some pics harvested from facebook.

[husaberg]

some more Cagiva stuff

[husaberg]

I remember asking wob early on as I had heard tales of how close the Cagiva was to being a Yamaha clone looking at these crank pics gee coincidence I think not. Cagiva cranks of various years 3rd pic. The is rest Yamaha

bugger the links are dead for the Harris Yam cranks and I can't search for cached imaged on my browser (or I haven't figured out how yet )
Anyway here is a couple that don't illustrate my point properly.........