ESE's works engine tuner

[TZ350]

Thanks, the wings are easy to understand, I just couldn't see how the double bellmouths were meant to work.

[husaberg]

Thanks, the wings are easy to understand, I just couldn't see how the double bellmouths were meant to work.

I couldn't even see the Double bell mouth...

Here's an exploded view :

Attachment 269328

The double bellmouth must be a Yoshi add-on.

http://shop.yoshimura-jp.com/en/prod...ai.php?id=1385

[dinamik2t]

I haven't neglected your post Husa, I was pointing out that it was an aftermarket part; not a mikuni part. That became obvious though in the following posts..

[husaberg]

I haven't neglected your post Husa, I was pointing out that it was an aftermarket part; not a mikuni part. That became obvious though in the following posts..

No worries just added it in case it was missed

Ok here is a Amal concentric MK1 modified to push pull with large (read huge) float bowl of a Valiant (Chrysler car)which i guess makes it a Strongberg?
its on a stinkin diesel tractor on alky

[speedpro]

This problem reminds me of an issue I had with my TS/RGV motor years ago. On the dyno at certain times you could see flames dancing round inside the carburetor. This was a full crankcase reed conversion. After a long time, over a year, in an attempt to fix the problem I just advanced the timing as far as it would go. The flames disappeared and it starting making modest power.

It seems from what people have been saying that this problem of detonation is evident on all(?) high performance 2-strokes. There may be a small number of cures but for whatever reason they have never been implemented. Thinking about it this could be what stopped my bike at Taupo. The piston was certainly hammered with cracks all over and Dave did say he was cruising in the corners which probably created the conditions needed for the problem to manifest.

The simplest answer seems to be to ride hard, maybe even changing down shift patterns - letting the revs drop as you brake and then dropping the gears as needed from lower revs.

[TZ350]

Jan Thiel. At part throttle there is less transfer flow, causing detonation (auto ignition)
The entering fresh charge is ignited by the remaining, hot, burned gases!
You can see very severe damage to the piston after maybe 10 seconds at 20% throttle.

Frits Overmars
Like Jan wrote, a shorter exhaust duration will worsen the detonation. What happens is this:
During normal operation, the blowdown time area of the exhaust ports is sufficient to drop the cylinder pressure below the crankcase pressure before the transfer ports open, even at high rpm. At part-throttle that cylinder pressure will drop to the same level, but now the crankcase pressure is much lower and exhaust gases will enter the transfer ducts, contaminating and heating the fresh mixture even before it enters the cylinder.

Hi SpeedPro, TwoTempi has suggested a possible solution to me that seems very simple, hopefully he will post it.

[Fooman]

Casting integrity is best achieved with pressure die casting. The "other" Ned Kelly in Timaru has been low pressure die casting pistons for years so it is possible in the home workshop. Hot isostatic pressing is not avilable in the Southern Hemisphere to my knowledge - but there was for years an outfit in Aussie doing high pressure resin sealing of castings...
An option for your case filling is metalspraying - whichever way you do it, it WILL distort so be prepared for that.

Best sort of casting process for mechanical integrity - in terms of strength, near-net shape, and little or no porosity, is squeeze casting. Best way to describe it is "liquid forging". The combination of high pressure, low feed rates, and high heat transfer during solidification from the mold result in porosity free and fined grained/dendritic microstructure - best for (low temperature) mechanical properties. The most common application for squeeze casting, that I can remember, is mag (aluminium) wheels. Toyota first started using it in 1978 on their alloy rims, mainly to prevent leakage of the air through the rims. Also used for casting pistons. I wrote something about squeeze casting a wee while ago if you want to read bit more about it.

High pressure die casting is good for surface finish, but does entrap a lot of gas during the casting process - the high velocity of the feeding results in "spraying" of the metal into the mold. So behind a nice finish, the casting can be a bit swiss cheesy.

Low pressure die casting is more sedate, meaning less issues with porosity than HP die casting, but has lower heat transfer rates that squeeze casting, giving a smaller supercooling effect, resulting in lower hetrogenous nucleation, and ultimatly coarser grains/dendrites than squeeze casting - lower mechanical properties.

The "Cosworth Process" is another good process for casting, used to cast engine blocks in sand. Mold is filled from the bottom, under very low pressure and velocity, to make sure defects like porosity, entrapment, lapping and segregation are minimised. But does not match the heat transfer of permanent mold casting techniques, hence lower mechanical properties. Was patented by Cosworth, but those have probably run out now.

Cheers,
FM

[Grumph]

Interesting...been a while since I talked to Ned about his setup but I seem to recall it involved two people, one of whom swung on a lever attached to some kind of old stirrup pump arrangement which directly pressurised the melt...but only to the extent of the pressure the person swinging on it could exert.
Sounds a lot like a squeeze process.

[Fooman]

Interesting...been a while since I talked to Ned about his setup but I seem to recall it involved two people, one of whom swung on a lever attached to some kind of old stirrup pump arrangement which directly pressurised the melt...but only to the extent of the pressure the person swinging on it could exert.
Sounds a lot like a squeeze process.

Could be. LP die casting generally used gas pressure on the melt to slowly feed the molten metal into the die. Once sufficient material has solidified, that gas pressure is generally not enough to continue feeding into shrinkage regions or maintain pressure in the solidifying casting.

HP die casting uses a ram to rapidly force the melt into the die, through a nozzle.

The squeeze casting die I adpated for my research was originally built for use under a hydraulic shop press. With squeze casting, you really need quite high pressures - on the order of 50 to 150 MPa to get the best results. Fat bloke on end of lever may not be enough, generally hydraulics are used - One configration of my casting rig was designed to have 200 tonnes of force going onto something the size of a small can of V - never actually cast anything that way however. Most of my casting was done between 50 to 100 MPa, using a 10 tonne cylinder acting on the end of a 25 mm diameter mold.

Cheers,
FM

[husaberg]

Best sort of casting process for mechanical integrity - in terms of strength, near-net shape, and little or no porosity, is squeeze casting. Best way to describe it is "liquid forging". The combination of high pressure, low feed rates, and high heat transfer during solidification from the mold result in porosity free and fined grained/dendritic microstructure - best for (low temperature) mechanical properties. The most common application for squeeze casting, that I can remember, is mag (aluminium) wheels. Toyota first started using it in 1978 on their alloy rims, mainly to prevent leakage of the air through the rims. Also used for casting pistons. I wrote something about squeeze casting a wee while ago if you want to read bit more about it.

High pressure die casting is good for surface finish, but does entrap a lot of gas during the casting process - the high velocity of the feeding results in "spraying" of the metal into the mold. So behind a nice finish, the casting can be a bit swiss cheesy.

Low pressure die casting is more sedate, meaning less issues with porosity than HP die casting, but has lower heat transfer rates that squeeze casting, giving a smaller supercooling effect, resulting in lower hetrogenous nucleation, and ultimatly coarser grains/dendrites than squeeze casting - lower mechanical properties.

The "Cosworth Process" is another good process for casting, used to cast engine blocks in sand. Mold is filled from the bottom, under very low pressure and velocity, to make sure defects like porosity, entrapment, lapping and segregation are minimised. But does not match the heat transfer of permanent mold casting techniques, hence lower mechanical properties. Was patented by Cosworth, but those have probably run out now.

Cheers,
FM

Thanks Great stuff the Cosworth/GKN process is discussed here.
The third attachment

[SwePatrick]

Complete differ from what you are discussing right now.. but i have to share it with you.

'Elsinore' gearbox can only take a certain amount of torque.
If you reach above this, the gears inside will not take it



this is 4th gear, it shredded when pulling hard at ~11000rpm, about 68Mph

Now i will go an another step in evolution on engine.
More revs = less torque
2 ways to go there, either tune the engine harder, or manufacture an new primary gear to rev up the gearbox.
And newer CR80 gears are much more rigid, i will use those also.

Rgds
Patrick

[Frits Overmars]

'Elsinore' gearbox can only take a certain amount of torque. If you reach above this, the gears inside will not take it.

Any gearbox will behave like that, Patrick.

Now i will go an another step in evolution on engine. More revs = less torque.

Less torque = less power, unless you raise the revs more than you lower the torque.

2 ways to go there, either tune the engine harder, or manufacture an new primary gear to rev up the gearbox.

I would prefer the third way: implement a shock absorber, preferably in the primary transmission, but it will do some good in the rear wheel hub too.
And while you're at it: your gearbox will be eternally grateful to you if you manage to fit a slipper clutch. Most gearbox breakages occur when shifting down.

[dinamik2t]

shock absorber, preferably in the primary transmission, but it will do some good in the rear wheel hub too.

Frits, would you have a photo of such a setup, to see how it's like? I haven't heard of it before.

[Frits Overmars]

Sorry, I'm on tour; can't get to my archive at home. But Google must be able to come up with something....

[dinamik2t]

You 're giving two stroke concerts??

I 've tried it before I ask, but I couldn't get something. I quick-searched 'transmission shock absorber'. You wouldn't mean the clutch cushions, eh?
Anyway, no worries, I will find it somehow.