ESE's works engine tuner

[husaberg]

The limit used to be around 106cc I thought. When did it change?

When its is air cooled and has a 24mm carb Jason...................

As i have said before there Kevin Orrs is that size or bigger.....and legal... Thing is it is still giving away cc's
Grumph will confirm but is'n't it 117cc or close to that.

[F5 Dave]

. . .
I'm surprised it went to 54mm. Dave Diprose tried boring an MB out to 54mm years ago and went through the sleeve to aluminium in places.
. . ..

Actually I think he tried to get 125 & went through. I believe you can get out to about 118 with a 56, but then you go through. Yes Kevin's was undersize as is D.Cottons.

. . .
Dave has reduced the stroke to 48mm with the help of Yow Ling. His motor is now the same stroke as mine and he's running KT100 pistons around 52mm
. . ..

wrong Mike Mike, this Mike is in wgtn.

[husaberg]

Actually I think he tried to get 125 & went through. I believe you can get out to about 118 with a 56, but then you go through. Yes Kevin's was undersize as is D.Cottons.


wrong Mike Mike, this Mike is in wgtn.

Its not a very common name Dave.......

[TZ350]

Posted because someone asked where to find it all, so a recap on the basics of the Beasts Engine. Using Thread Tools and the View Thread Images option is a good way of finding interesting posts.

The exhaust open point has very little to do with creating power due to "pressure" on the piston for "longer" with lower timings.
The gas pressures soon after TDC ,that creates the real power, is up over 80 bar, the pressure at Ex open is a couple of bar at best.
Moving from 200* to say 190* creates jack shit extra exertion of pressure on the piston to create torque, that then creates HP.
But the real issue is that down at 190* duration we get a huge amount of superposition of the gas pulse exiting the exhaust, on top of the residual pressure at the port.
This adding of a new pulse on top of an existing residual pressure means the wave front running down into the header has a huge relative amplitude, and this creates a huge depression at the port around BDC.
This also means we have port/pipe resonance over a much wider range and at a much high higher level than can be achieved at 200* duration.
In a conventional design we are forced into a corner by needing to create as much BlowDown STA as we can, and raising the timing is the only available route.
This pushes us away from the ideal port/pipe interaction timings, but is a compromise we are forced to accept to create the + 200psi bmep's needed, to be competitive.
Just another small detail that many overlook, or are unaware of.

Some old links, to when we were setting up the port timing for the 30hp Suzuki GP125.

EngMod2T

For something different Page 400 is going to be the basic info for building a 30+hp Suzuki GP125 taken from the EngMod2T simulation files.

You will have to go to the original post to see all of the pictures and the complete text.

Ok .... this is where the simulated rubber hits the road.

We are going to see if we can make this.

Red line is my efforts with EngMod2T, Blue line is after Wobbly polished it up a bit and replaced the RS pipe with one of his own design.

Wobbly can provide the pipe dimensions or even one already cut out ready for welding.

Wobblys rule of thumb is, low and wide for the transfers to maximise blowdown time area which is usually in short supply on a single exhaust port cylinder like mine and if you have multiple exhaust ports Low and Wide allows a low exhaust port which helps keep the pipe in resonance for longer (wider power spread).

All the port timings are in this post

Ok ... ported the exhaust port.

I was able to clean up most of the damage around the exhaust port that happened a while back when a peg came out and allowed the ring to turn and catch in the port.

Exhaust timing on this one.

Next move is the inlet

Now to setup the compression ratio.

All the basic info for everything is displayed in the EngMod2T sheets.

I was thinking about more ordinary things like getting the transfers staggered just like Wobbly wants and the port entry windows in the correct ratio of 1.3 -1.2 and 1.1, and curved nicely. The inlet system the correct length and shape without humps and bumps and the workmanship for making a first class expansion chamber and all those imperfections that creep in, just basic stuff.

Here is a first shot at the GP125 with triple Ex ports Vs the single port version. You can see the big jump in blowdown pressure entering the transfers of the single port engine when in the overev region.

The single port is short on blowdown STA.

Wob, thanks for looking at my EngMod2T files.
I am not sure what I should allow for losses, I have used -12% on the RS graph and get 32 rwhp. I should get a chance to put it on the dyno in the next day or so, so fingers crossed and we will see how it works out.

Yes ... I found much the same, the triple port was not much better than the single when they both had to suck through a 24mm carb but when a biger carb was simulated the tripple produced more power up top and significantly more drive down low.

If they are both limited to a 24mm carb and similar power curves, then a good reason for making a tripple port cylinder would be for mechanical reliability with the triples main ex port width at 62% of bore diameter instead of the singles 75%.

Making progress
Measuring the squish clearance with a depth mike.
Skimmed a bit out of the head and got the clearance volume to 9.0cc spot on.

I was having a look at some Kart site about honing and they go a few steps further than I did

They bolt torque plates onto the cylinders and leave them for a few hours to let the cylinder distort
bolt an old header pipe and inlet stuff if applicable, and some hone the cylinder hot at about 350° F

http://www.ekartingnews.com/viewtopi...er=asc&start=0

Torque plates are always a good idea - the aim of course is to finish up with as perfectly round a bore as possible.

Think it's even more gooder idea where there's bolts threaded into the cylinder, you've got the axial distortion from friction in the thread, it forces a sine wave shape into the cylinder wall.

Just washing in a cleaning bath is not good enough for long life and reliability.

How to clean a rebored and honed cylinder properly and know you have got it right.

Striped the engine down today after the Taupo GP

Tonights dyno effort ....



OK so now we have joined the 30RWHP Club

The big hp engine has yet to prove itself.......

[Grumph]

When its is air cooled and has a 24mm carb Jason...................

As i have said before there Kevin Orrs is that size or bigger.....and legal... Thing is it is still giving away cc's
Grumph will confirm but is'n't it 117cc or close to that.

It's around 115cc - that's enough at present.

I've been given another pipe to compare so it may be quicker yet....

[Buddha#81:Me]

It's around 115cc - that's enough at present.

I've been given another pipe to compare so it may be quicker yet....

Have you stripped it after Grey? It wasn't overly fast at the S/R there were at least 3 4T's faster

[husaberg]

Okay i alluded to this earlier on as per usual when i put something a side for later i can't find it

It was a piece written about 500 gp's
the FIM had asked two boffins to prepare and present a paper around the mid to early 90's one i think was dutch the other was English i think.

The formula they came up with was that given equal number of cylinders and open carburetors the fair size of engines 2 stroke vs 4 stroke was this.

360cc two strokes.
500cc 4 strokes.

If we were to break this down and compare to the current F4 sizes it gives this.
current rule.
Rule 24.2 3 F4 2 stroke max capacity for rebored engines 104cc
F4 4 stroke max capacity for rebored engines 158.09cc (note this was initially 130.5cc the 145cc then 150cc previously)

So to be fair, it should be 158.09 cc four strokes vs 113.82 cc 2 strokes of unlimited carb size.


Sorry TZ and other aircolled 125cc restricted carb 2 stokers. You can get plenty of 56-57mm pistons at the moment anyway.

As i said earlier this will allow the use of cheap, freely available KT100 pistons that are available in a number of sizes without the need to destroke.

These strike kt100 pistons are readily available in a huge range of sizes and are incredibly inexpensive.
We all should be using them except for the cost of destoking plus the engine will be less efficient as a non close to square bore and stoke.
Simple fact is 50-50.5mm 2 stroke pistons are not really manufactured any more and it is killing wallets and engines.

Dave had what 2 or was it 3 failures with NOS yz100 pistons these pistons have not been listed by Yam since i was at school.

I doubt Suzuki still makes RG400 pistons, either that only leaves kart pistons (but all the usable size ones have Dykes rings)
and other std road bike (not generally up to it)and Wiesco which are f-ing expensive.and not available freely or in oversizes.

[Bert]

These strike kt100 pistons are readily available in a huge range of sizes and are incredibly inexpensive We all should be using them except for the cost of destoking plus the engine will be less efficient as a non close to square bore and stoke. Simple fact is 50-50.5mm 2 stroke pistons are not really manufactured any more and it is killing wallets and engines.

Hold fire: you don't start a LC100 project with your eye's shut (it does require a little bit of preparation to resolve this).

Plently of Engines that would allow easy transformation to 100cc.
RG150: Bore: 61.00 mm Stroke: 50.60 mm (truck loads of these around).

TS125x/r: Bore: 56.0 Stroke: 50.6 mm
TZR125 / Derbi / Gilera: Bore: 56.4 mm Stroke: 50.60 mm
TZR150 tzm / dtr : Bore: 61.00 mm Stroke: 50.60 mm
Mito: 56 x 50.6 mm

Silly size more crank work required:
RS125 (aprilia): Bore: 54 mm Stroke: 54.4 mm
KR150: 59 x 54.4
NSR125: Bore x Stroke, 54 x 54.5 mm

these require less work in the sleeve (offering potentially better heat dissipation) but requires more work in the crank... trade-off's..

Piston wise:

Dave had what 2 or was it 3 failures with NOS yz100 pistons these pistons have not been listed by Yam since i was at school.

Was it really the piston, really??? (only Dave can answer that); and there are truckloads available if one actually go's looking (I just picked up 4 new pistons for $80 total shipped)..

including after market Wiseco & woosner for the vintage clan (early 80's RM100/KX100/YZ100 & even TS100 options); not forgetting they make a 48-51mm piston for new CR80/yz80's (for kart racing); and all these big bore options for scooters....google..... Dealing with the pin size requires finding one that fits your engine....

I doubt Suzuki still makes RG400 pistons, either that only leaves kart pistons (but all the usable size ones have Dykes rings)
and other std road bike (not generally up to it)and Wiesco which are f-ing expensive.and not available freely or in oversizes.

Yes, you can still order RG400 pistons (but you could buy 4 wiseco versions above). What's wrong with Dyke rings kart pistons??? or the strike pistons (KT100J)..

Online ordering ~70-$150 shipped to your door; while its a little more than a cheap ass Akunar for a FXR (you could order a AX100 and have the same result)....

The 2 stroke cc limit should be about 112cc lc 2 strokes vs 155cc four strokes and i have the technical data done for the FIM to support it. Infact i intend to submit a remit to the rules based on this.

Maybe submissions on rules should be undertaken via national committee.....
these larger options are already covered off with the 125cc rule and 24mm carb (weld some fins on)....
Because in reality if one was to start on two stroke, they are more likely to start with a TF/TS/DT/RX/GP aircooled engine; not start building a LC engine straight off the bat...

Unless CC reduction is in order ----> MX80's (not necessarily 85's), where there are a F##kload of parts still available cheap... while offers up a near 2:1 ratio between the 155cc four strokes vs. lc 2 strokes; with about the same power outputs (worked).

[TZ350]

Ok Popped the bonnet on the Beast to find out why it nipped up at Tokoroa



Light four corner seizure, but why???? ....

[TZ350]

Probably figured it out.

2-Stroke running an unsuitable Cam



No detonation.



No charred oil on the underside of the piston, so not running to hot.



Both Plug electrodes look ok, no melting on the edge of the center electrode and the earth strap looks ok too.



To check the mixture one has to look deep down inside the plug and its easier to cut the insulator out of the plug body.



This is what we are looking for, the area above the black line, and it looks neither rich or lean to me so I guess the mixture must have been ok for best power.

I think the seizure is due to using a piston with an unsuitable cam shape.

It looks like water cooled pistons are not that suitable for hotter running air cooled motors and forged pistons that grow more than cast ones are even more of a problem.



The piston is kept in alignment by the skirt, which is usually cam ground (elliptical in cross section) (fig.12-16).
This elliptical shape permits the piston to fit the cylinder, regardless of whether the piston is cold or at operating temperature.

I think I will have to start looking at using a cast piston with a higher silicon content and giving it a bit more of a cam on the sides.

[Bert]

Unless CC reduction is in order ----> MX80's (not necessarily 85's), where there are a F##kload of parts still available cheap... while offers up a near 2:1 ratio between the 155cc four strokes vs. lc 2 strokes; with about the same power outputs (worked).

continuation....

A good MX80cc (pre powervalves engines) engine might put out 18Hp if ya really lucky (20-21Hp with some effort), power valve engines ~20hp (26-28hp maybe with some serious effort).
Most people racing FXR's (at the pointy end) are putting on exhausts, carbs & some are doing cams; resulting in around 19-21Hp; serious effort gets to ~24Hp and all the torque under the sun (its nearly always FXRs up the front with less power than some of the two strokes)..

While F5dave (or others) is bound to post "Flogged out MX bikes" the reality is most engines now used by two stroke bucket racers start there life as flogged out anyway (its a lottery).

Stuffed mx80 Bores are the problem (but re-plating by nzcylinders is going to be cheaper for the masses than sleeving a rare 125 down).
The rest of the parts are on par with currently available engines in use.
Anyone serious about building an engine is going to do the mains, rod & piston anyway (no matter what motor it is) and its not much more effort to do the rest of the bearings in the engine (or find another gearbox)....

if people are really serious about rule changes; then I believe (and others have posted this over the years) 80's really need to be considered (with some restrictions)? things that can be measured easily; exhaust duration & carb size. simple.

Sorry TZ for filling up your thread with this...

[cotswold]

Ok Popped the bonnet on the Beast to find out why it nipped up at Tokoroa



Light four corner seizure, but why???? ....

I reckon we still had it too lean.

[Bert]

Probably figured it out.

2-Stroke running an unsuitable Cam



I think the seizure is due to using a piston with an unsuitable cam shape. It looks like water cooled pistons are not that suitable for hotter running air cooled motors and forged pistons that grow more than cast ones are even more of a problem.

I think I will have to start looking at using a cast piston with a higher silicon content and giving it a bit more of a cam on the sides.

What about re-profiling/dressing the pistons on the four corners?
reading about old two-stroke race engines; it wasn't uncommon to read about running the engine in (bring it up to temp), then stripping them down to take the high rubbing spots off the pistons (with wet and dry).

Not that long ago there was an interesting article on Hugh Anderson and his time as a works rider; he discussed personally dressing pistons due to their production shape late at night (when he thought everyone was asleep); only to have the suzuki mechanics somehow replace them before racing the next day--- resulting in seizures (due to suzuki's endless quest for tight tolerances for top housepower).

I was surprised with the clearance specs for the Wiseco pistons (YZ100 aircooled pistons) which I assumed was to deal with these issues (well larger than LC specs); forged piston expansion rates etc (I ended up splitting the difference). even then, I still need to dress mine in the TZR around the same spots.

[Kickaha]

reading about old two-stroke race engines; it wasn't uncommon to read about running the engine in (bring it up to temp), then stripping them down to take the high rubbing spots off the pistons (with wet and dry).

That's not just for old two stroke engines, even on my 95 TZ250 that was recommended

[cotswold]

Probably figured it out.

2-Stroke running an unsuitable Cam



No detonation.



No charred oil on the underside of the piston, so not running to hot.



Both Plug electrodes look ok, no melting on the edge of the center electrode and the earth strap looks ok too.



To check the mixture one has to look deep down inside the plug and its easier to cut the insulator out of the plug body.



This is what we are looking for, the area above the black line, and it looks neither rich or lean to me so I guess the mixture must have been ok for best power.

I think the seizure is due to using a piston with an unsuitable cam shape.

It looks like water cooled pistons are not that suitable for hotter running air cooled motors and forged pistons that grow more than cast ones are even more of a problem.



The piston is kept in alignment by the skirt, which is usually cam ground (elliptical in cross section) (fig.12-16).
This elliptical shape permits the piston to fit the cylinder, regardless of whether the piston is cold or at operating temperature.

I think I will have to start looking at using a cast piston with a higher silicon content and giving it a bit more of a cam on the sides.

Never would have thought of that but makes sense when you look at piston clearances on old school air cooled motors and compare them to w/c ones.

Just stole this from vintage mx site,
for an iron bore (not nikasil) .0025-.0035" clearance is good, .005" too much. Nikasil bores are .0015-.002" for motocross bikes. Measure the bore with a bore gauge top and bottom, front to back and side to side, 4 measurements to make sure the bore is within .0002-.0004" round. Measure the piston with a mic (not a caliper) at the widest point of the skirt.
Pistons are machined with a taper in the skirt so the diameter at the crown is smaller than the diameter of the bottom of the skirt. This is because when engine is hot the crown of the piston is hotter than the bottom of the skirt so it expands more and the piston becomes more cylindrical as heat removes the piston's taper. That makes it critical that you measure the piston in the correct location.