ESE's works engine tuner

**Flettner** · 9th August 2016, 14:40

Originally Posted by SwePatrick

About HCCI ignition(i think)
I have built a new engine(not fully complete yet)
Test started it this weekend.

It´s an Kawasaki KX250 downstroked to 211.9cc(due to regulations in swedish dragracing)
However, i was so eager to hear the engine spin even though the pipe isn´t ready yet.
So i started it anyway.
And note, the exhaustvalves wasn´t in place, the guillotine therefor left a big hole downwards in exhaustport(no lid on either)

Engine started nicely but started to rev out of control almost directly.
Tried to stop it, pulled the cord to the stop button, nothing happened.
Placed hand onto the carburetor, nothing happened.
With hand still on carb and full throttle engine lowered the speed.
Had to shut off fuel to get it to stop.

Later, put back all exhaustports and started engine with no other adjustment.
It ran nicely on idle.

Quite interesting experiance

I figure the exhaustpulses drew fresh air into cylinder through guillotineport.
And even though i had hand on carb it still drew fuel enough to get a burnable mixture.
But, interesting is that what i think it almost directly triggered HCCI.

Rgds.

No doubt true, as I had a similar problem with my HCCI mudbug (100cc yamaha), hand over the inlet didn't stop it. It was getting air in again each cycle via the exhaust port. I also had no exhaust system attached, interesting isn't it.
In my case I didn't even have an electrical ignition to try to turn off. It certainly gets the heart rate up! See what happens when you dick around doing dumb stuff, you learn dumb shit:

All you need is a bit of HCCI control

https://youtu.be/9zhFsS_ocuQ
https://youtu.be/VBVMGywXVr8
https://youtu.be/OCBngYfWiTE

I guess this is a free piston engine, that last one certainly has some grunt.

**F5 Dave** · 9th August 2016, 20:06

Decompression valve should sort it out. Probably a bit abrupt but. . .

**chrisc** · 9th August 2016, 22:32

What should the deposits look like on the piston and head for a well functioning race 2 stroke?

Just changed the ring on the Derbi 50 and repacked the muffler so I shot a few photos:

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**Frits Overmars** · 9th August 2016, 23:13

Originally Posted by chrisc

What should the deposits look like on the piston and head for a well functioning race 2 stroke?
Just changed the ring on the Derbi 50 and repacked the muffler so I shot a few photos:

You might want to check the squish gap fore and aft.

**diesel pig** · 9th August 2016, 23:16

Originally Posted by chrisc

What should the deposits look like on the piston and head for a well functioning race 2 stroke?

Just changed the ring on the Derbi 50 and repacked the muffler so I shot a few photos:

With the earth strap not quite burned half way and the fair amount of wash around the edges of the piston I would say a touch rich but not bad at all.

**chrisc** · 9th August 2016, 23:20

Originally Posted by Frits Overmars

You might want to check the squish gap fore and aft.

Was thinking that but wasn't sure if it was impacted by being the exhaust side. Will do.

**Neal** · 10th August 2016, 01:53

Originally Posted by richban

I had major problems with the wire splice method when I first got the NSR300 going. We messed around for ages and could only ever get 60hp. Plug in HRC bypass loom and 72 straight away. I run an ignitech now. We never did an all gears run so could not tell you about 1st to 3rd sorry.

That's the way I understand it too

**Neal** · 10th August 2016, 01:56

Originally Posted by jonny quest

Richban, are you talking about installing the complete HRC wiring loom that eliminates the lights?

Or a type of inline small wiring setup that HRC made?

You could buy a hrc wire splice in a adaptor loom and just plug it in to get full power , the gear position splice is a different mod

**Sketchy_Racer** · 10th August 2016, 12:19

Originally Posted by chrisc

Was thinking that but wasn't sure if it was impacted by being the exhaust side. Will do.

The head needs to be dowel located to the bore. That is why the squish won't be even. Dave and I machined that head profile just before heading to Tokoroa and ran out of time to dowel her up.

**F5 Dave** · 10th August 2016, 19:05

Two outer bolts Ithink bored for dowels. We did squish test with solder front and rear at same time held with plasticine or grease. Should be 0.5.

**jonny quest** · 11th August 2016, 08:23

Does anyone know if the stock MC21 chambers have internal stingers?

**wobbly** · 12th August 2016, 10:33

Using a " normal " earth strap to read the chamber conditions is not accurate at all due to its very high thermal mass .
Fine wire electrodes give a very good indication of the combination of advance and jetting leannes.
Having the burn mark change about 2/3 of the way toward the body is spot on.
At 1/2 distance you can look at winding in some more advance if the egt is at optimum power.

Usually the rear of the pistons squish ( over the boost port ) will mark up more due to heat as when the piston rocks over TDC
this side closes the squish gap up, increasing the MSV and the retained heat in the end gases..
Here is a KZ10 that has a straight line ignition, tuned right to the edge after a 25 lap final, any more advance and the piston would be starting to deto.
The other is a 66mm piston in a RZ400 that has done 480Km racing miles, one piston is jetted slightly richer,but the squish gap is perfect.

**chrisc** · 12th August 2016, 10:47

Originally Posted by wobbly

Using a " normal " earth strap to read the chamber conditions is not accurate at all due to its very high thermal mass .
Fine wire electrodes give a very good indication of the combination of advance and jetting leannes.
Having the burn mark change about 2/3 of the way toward the body is spot on.
At 1/2 distance you can look at winding in some more advance if the egt is at optimum power.

Thanks Wob. From reading on here and a few other places that's how I've understood it too. Good to have confirmation.
The main thing for me and this bike at the moment is reliability, suspension and gearing. I won't be doing any engine development until I have some of my own baselines so it's good to know it's probably on the safer/lower power side. It shouldn't be giving me any issues whilst I sort out the meat sack on the thing. It's getting a rev counter, temp gauge and maybe an EGT, at the moment it has none of them. Whilst it might not mean an decrease in times, it'll teach me loads about set up that I can take to my 125.

**wobbly** · 12th August 2016, 16:09

PS, if the jetting and ignition are perfect with a correctly set squish and you keep on getting a hot spot in front of the exhaust, then most likely
the stinger is too small and or there is insufficient cooling of the Exhaust duct.
I cured this in the KZ10 engines by allowing water thru slots right up to, and into the back of the bolt on flange spigot.