I remember a conversation with Chris about a Thunder Jet on some huge flash carb some dweeb spent loads of cash on. He couldn't get the fuelling right and in desperation in the end disconnected the jet and away it went. We also had a bit of a giggle over one costly hotrod Harley that made 80hp on the dyno. When it was taken off we rolled a ZZR600(stock) on to the dyno and it made more or less the same power.
Bruce Anstey used to eat all the choc biscuits there as well.
And not talk.
Last time I saw Chris was a rather messy night when he was back in wgtn quite some while back, then a few months before at Philip Island (also rather messy) when he was with Padgetts looking after Jay Vincent or someone like. Wonder where he is now?
Don't you look at my accountant.
He's the only one I've got.
Making some progress with the new fuel injection manifold.
The injectors are angled so they squirt more horizontally across the transfer port.
The small (bottom left) injector from the Ecotrons Small Engine EFI kit for two strokes has had the clips on its top cut back so the fuel barb can be swiveled in different directions.
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I will cut back all the injectors like that to make them easier to fit into the tight space behind the cylinder.
All of the injectors are in place and I found these neat little clips and hose connectors at the local hose shop for plumbing it all up.
Lots of copper of course and in the cardboard box is a new four channel temperature data logger so we will be able to get some hard data on how hot the Beast actually gets.
Hopefully get back to the dyno next week.
I've been pissing about with an AX100.
Yeah, I know they are crap...
Still, I've done some basic stuff:
Smashed a bit of the baffling out of the exhaust, stopped it pinking on long full throttle runs.
Slightly longer header, mainly for moving the exhaust for better ground clearance, also took out most of the step as it transitions from header to diffuser.
Cleaned up the terrible porting, still not perfect but far better. Clean up of Exhaust was worth almost 1 hp.
Pissed around with jetting to get it running better.
So the next thing I did was to take the standard quiescent head and cut it down to a squish head.
It went from around 8:1 to around 12.8:1 in the process.
0.8mm squish clearance, close to 50% Squish area and a real old school shape, the squish band opens up quite a bit towards the centre and it has a radius into the main combustion chamber.
I've gone this old-school was as I expect it will work better with the standard (Shit) ignition.
So, now it's pinking once it's got some heat into it, generally (as expected) only when heavily loaded.
I'm going to back the timing off until this stops.
So My Question for the experts:
Is this going to loose power over less compression/more advance?
Testing to find the best balance would be nice but I'm going to have to plug some guesses in to this too.
EDIT: Is it just that the burn time is reduced requiring less advance?
Heinz Varieties
Depends entirely on the fuel.
At 12:1 and detoing means you cant be running AvGas and you should be, in small bores 16:1 is just fine.
The close squish clearance and 50% area are OK, but having a taper and a radius in effect means the squish is doing Jack Shit, in reality this will cause deto, not suppress it.
Easy fix is to change the fuel, but keep in mind that unleaded loves advance and hates com - and max power is gained when rich.
Avgas loves com and doesnt need much advance for max power - but works best run lean, but either way you have a compromised setup that can never make good power.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Cheers.
I'll let you know where I end up.
No luck getting the timing backed of as an interim step tonight. Try again tomorrow.
I suspect I'll end up with lower compression and more aggro squish.
I currently think that too aggro with a shit simple ignition isn't so good but I'd like to prove/disprove this with some testing If the stars align
Also, should have mentioned that I'm commuting on this pile of poop, that makes AV too much of a mission.
Heinz Varieties
My good motor has the squish area and then a radius into the chamber. I bought a fancy programmable ignition only to find it wanted the same ignition timing at all revs. I understand that an edge between squish and chamber would necessitate backing the timing off at higher revs due to faster flame propagation with the increased turbulence at those higher revs. Since you are running points and can't back timing off with revs the curve would seem to be the way to go. You're building the engine to suit the ignition's limitations.
Doesn't seem to be points, think it may have a modern sensor but otherwise the same architecture and certainly the same ignition crapness.
I've seen this before, I think, with my MB100 - although the pipe design may also play a part.
I'm considering an old style chamber on that as an interim step before getting the ingitech going on it, I desperately need over rev to give more spread and the latest, very aggressive cut took it away. Currently on an old CR80 Ignition.
Heinz Varieties
Found this in Bert's links
GRP125 made into a 170 and home built EFI. Made 29hp, not extensively ported/tuned.
Unfortunately a lot of the earlier image links are dead but I think it was a carb replacement type injection rather than a transfer port injection type.
Have a look, I haven't trolled the thread much yet but man there are some idiots on that forum.
http://www.125ccsportsbikes.com/foru...c=63480&st=320
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