ESE's works engine tuner

**wobbly** · 22nd February 2014, 15:08

The theoretical MSV of 38M/Sec you are achieving will work OK, but for only 12200 rpm with 54.5 stroke the squish gap should be down at 0.6mm.
0.65 is useable in a normal 125 spinning to 14000 all day, but your piston is obviously heavyer.
The limiting factor should be that at the peak rpm used, the piston should be just shy of clipping the head.
Thus for the best squish action we end up with virtually zero clearance, so in effect the theoretical MSV becomes irrelevant.

**richban** · 22nd February 2014, 17:38

Originally Posted by wobbly

The important things to see from the above is that the Aprilia drawing shows a VERY flat bathtub and was found to be the best design for a domed piston.
The Toroid became into being as an adaption of the bathtub and proved to be the best design for a flat top piston from a huge amount of testing I did for
a Belgian company making Honda after-market cylinders.
Both are trying to get the spark gap down very close to the piston.

Ah, good to have some background on the 2 shapes. Ta.

With the crank I have I had to build some safety into the equation. Its always a pain to build an engine that has second hand bits. It should be going very soon. Like tomorrow if I get my shit together. Still need proper pipes. Hint hint.

**mr bucketracer** · 22nd February 2014, 19:01

Originally Posted by richban

Ah, good to have some background on the 2 shapes. Ta.

With the crank I have I had to build some safety into the equation. Its always a pain to build an engine that has second hand bits. It should be going very soon. Like tomorrow if I get my shit together. Still need proper pipes. Hint hint.

good stuff rich , heap it reliable and you will win race's

**speedpro** · 22nd February 2014, 19:41

Interesting link

https://www.google.com/search?q=2+st...%3B2770%3B3986

**dmcca** · 22nd February 2014, 23:26

Originally Posted by F5 Dave

Last night I encountered the most inconsistent bike I've run on the dyno; my GasGas EC300 (with road tyre fitted of course)
......
.

What year GG300? I've dynoed a couple and they definitely have a dip when the PV opens (too early and too fast) but they werent as bad as you described so I think you're right to look for something playing up or not working right. I've seen a few with very sloppy powervalves

**richban** · 23rd February 2014, 07:15

Originally Posted by mr bucketracer

good stuff rich , heap it reliable and you will win race's

Well the first step of reliable will be a trip to your house for some tuning me thinks. From what I have seen of the 2 strokes that have going through the shed I would be silly not to.

**Forgi** · 24th February 2014, 01:13

Originally Posted by wobbly

No I havnt seen any 3 port designs for the gear class karts at all.
What is the homologation number where you have seen this.
Very surprising if someone has done a 3 port, but as it stands the Italian kart factories are still well behind in detail areas
that were so successful in the Thiel inspired Aprilia cylinders with 5 ports.
Makes it easy for me to build engines that are faster than anything TecSav can come up with.

Well, maybe I'm wrong Wob! I can't find that homologation form. It was a BMB engine, I saw a outline of it in the form,but of course it was a pic of the version with 5 tranfer ports. But it had to be a misunderstanding!

By the way in my opinion these ICA/FA engines are interesting. 27-29 hp 100cc, calculated on 125cc is 35-36 hp. I think it ain't no bad taking into account the fact that tehy are low-controlled (Ex 172-178 deg, STA 0,0125-130 , blowdown 0,0060-65) , have a small carburator and a "bad" exhaust pipe etc. I think it could be easily +40 hp out of 125cm3.

What do you think what is the reason that these engines became like this? I mean they have only 3 transfer ports and such a huge boost transfer. I suppose that these characteristics are in connection with the wide power band somehow, but the old ICA-J (piston controlled inlet port) engines had similar characteristics althought they had 4 old-school transfer ports. In the last few years they were barely weaker than ICA engines.

**wobbly** · 24th February 2014, 06:53

In a 100cc bore the 3 ports give plenty of area to suit the power being generated.
More port divider walls would dramatically increase the flow friction with no real gain in directional control to increase the scavenging efficiency.
The porting developed over time to enable a very wide, but low , power spread and the biggest advantage came from being able to use very short gearing
that allowed a big torque multiplication for drive off turns, this then combined with a high terminal speed enabled by pulling 22,000 rpm.
All worked around the best way to manage direct drive in a single ratio.

**F5 Dave** · 24th February 2014, 09:24

Originally Posted by dmcca

What year GG300? I've dynoed a couple and they definitely have a dip when the PV opens (too early and too fast) but they werent as bad as you described so I think you're right to look for something playing up or not working right. I've seen a few with very sloppy powervalves

Hi Dave(?), hoped you'd pipe up as I know you've dyno'd some. Mines an 07, but I've 10*'d the head (was 14) & brought the squish down to 1mm (72mm bore & forged piston). Man its cleaned up low end response fantastically. But the dip I noticed riding it yesterday as the terrain had some wider sections. PV is next on the list for some attn. After rebuild of two buckets before the GP in 2 weeks time of course.

**2T Institute** · 24th February 2014, 11:37

Originally Posted by wobbly

The theoretical MSV of 38M/Sec you are achieving will work OK, but for only 12200 rpm with 54.5 stroke the squish gap should be down at 0.6mm.
0.65 is useable in a normal 125 spinning to 14000 all day, but your piston is obviously heavyer.
The limiting factor should be that at the peak rpm used, the piston should be just shy of clipping the head.
Thus for the best squish action we end up with virtually zero clearance, so in effect the theoretical MSV becomes irrelevant.

That is when a RS makes the most HP with a 'shadow' left on the piston from the squish band.

I'll post some pics tomorrow, roll pins for ring pegs creating deto.

**richban** · 24th February 2014, 15:16

Well the 300 fired into life today. Its taken 3 months to completely rebuild the engine and the bike. Now it just needs to be tuned and ridden hard.

My guess on the power stakes is a fat 80. We will see. Its been heaps of fun building my first proper 2 stroke race bike. Lots of info came from the people that frequent this thread. A gold mine to be sure. Thanks. Its an MC21 SE.

I have lots of picks on the engine build and porting that I will post later.

Cheers RB

**TZ350** · 24th February 2014, 15:23

Originally Posted by richban

Its an MC21 SE. I have lots of picks on the engine build and porting that I will post later.

Good work, please post your pics on here, I would love to see them.

**TZ350** · 24th February 2014, 17:58

Click image for larger version.

Name: Stator 002.jpg
Views: 95
Size: 237.7 KB
ID: 294109

5 days from ordering the new stator from Ricks Stators and receiving it, pretty good I recon.

Scotts F5 bike

Click image for larger version.

Name: Scotts F5 Dyno.jpg
Views: 181
Size: 231.1 KB
ID: 294111

Red line is where we were, blue is where we are at now after cutting 30mm out of the mid section, still a little more work needed on the pipe but will give it a run at Mt Welly this weekend and if it survives we will bring it to Tokoroa.