ESE's works engine tuner

[peewee]

started making some templates for the epoxy on the inside trans wall. printed them from the computer then cut it out of thin alum. they'll work like a treat

[2T Institute]

I have recently purchased a used HE-JA barrel and head , just searching for info on what piston they used with it . It's a flat top piston with the ring peg in the centre .


Cheers , Neal

measure the comp height

[2T Institute]

Does anyone have a comparison between the standard and A-kit Honda RS125 exhaust duct exit?
Wondering if the actual exit is the same meaning an A-kit spigot could be used on the standard cylinder. I know the exhaust spigot on the A-kit is tapered whilst the standard one is round (stepped with the duct).

Look up Daniel Cottu on FB he has a A kit Honda 250

[wobbly]

I would not worry at all about the distance between the ground strap and the piston dome.
Ive run it as close as 1.5 mm and seen no issues at all.
The idea with a flat top is to get the spark gap in the middle of the chamber by using a toroid.
With a dome,the best is a flat roof bathtub, so that the highest turbulent zone from the squish action points at the gap.
But I have found that the toroid also works best with a dome, in many situations like aircooled heads or for use with pump gas ie low bmep.
This is what was used on the Webco repro heads I designed.
It allows alot more advance and a leaner mixture before deto, making the head way less fussy to tune closer to the limit.
In all cases a sharp edge from the squish into the chamber is the go.

The A kit Hondas had quite alot larger exit dimensions ie 42mm wide,that was also the header diameter.
The customer RS125s were smaller width, and also had steps,but even that size is too big for a stock port setup.
So you would have to be using the 200* exhaust timing,along with the short A kit pipe length, to make the bigger spigot work properly ie making close to 50 Hp.
Then of course it would need the bigger offset bored SPJ carb and special ignition with different PJ cut etc etc.
So in a word no,you can only use an A kit tapered spigot if you are making A kit power - otherwise weld up the stock exit height and CAD an oval to round transition CNC spigot to suit.

Re port chamfers - you must put chamfers on the Ex before plating or you will grind thru to alloy before getting it correct.
The transfers dont need any chamfer before or after plating.

All genuine A kits ran flat tops with central peg, the flat tops for customer RS125 had an offset peg as the cylinder had a wide gap on one side of the boost port - dumb.
There are dozens of good 54mm single ring with center pin.
Best I have tested would be a Meteor thin ring lightweight for a TM125 - KZ10 ,has a 4* conic dome.

And lastly Husa - those cylinders arent even close to Aprilia replicas,with no radius on the bore/transfer duct, no radius on the Ex port timing edge and stupid old fashioned round ( read stupid big ) duct exit area.

[Flettner]

OK, anyone here know anything about the Ignitech IJ 12 1CH unit? I have one but can't do anything with it, for a start I need software to program it. Ignitech are not interested in replying, at all!

[husaberg]

I
And lastly Husa - those cylinders arent even close to Aprilia replicas,with no radius on the bore/transfer duct, no radius on the Ex port timing edge and stupid old fashioned round ( read stupid big ) duct exit area.

Wob I am only going by what Frits said about them...

Dolph van der Woude is a good friend of Jan Thiel and myself. In cooperation with another friend, Thijs Hessels (picture) he has developed cylinders and other engine parts that can raise the power of an Aprilia RSW production racer to RSA-level. Thijs also makes a conversion kit to fit these cylinders to Honda RS125 production racers, giving them a new lease of life:
http://www.pit-lane.biz/t1693p25-act...ship-race-tech

I am picking also they don't give away all their secrets in pictures on the net......
I am pretty sure he also said on another forum they are the closet in execution to the Aprilia bikes other than my PayKarts ones.

[peewee]

kind of a before and after of what I did. got some epoxy in the front transfers tonight and ill work on the others tomorrow. I hope this thing is making smoke soon . good thing this aint my day job or I'd be broke

[F5 Dave]

So ahh, the small holes below the ex port ? Some sort of oil reservoir perhaps?

[Frits Overmars]

So ahh, the small holes below the ex port ? Some sort of oil reservoir perhaps?

http://www.kiwibiker.co.nz/forums/sh...post1130802658

[jonny quest]

I've tested a flat top/chamfer piston against dome. All else being equal, the flat/chamfer was a full 1hp better mid on up on a 125

Has anyone tested a flat top vs domed?

I know RSA is domed piston, but for the mere mortal engines the hybrid seems best. Primarily because of excellent flow stability at EX opening.

What gives the pure flat top an advantage? Is it more even "push" on piston during expansion?

[wobbly]

I have tested flat tops Vs domed and the critical element isnt the piston at all, its the chamber shape.
A flat top with a proper toroid will make more power than a dome with a bathtub, and that is way better than a hemi.
Its all to do with spark gap positioning.
Jan tested the difference in the Aprilia but I havnt seen any comment from him anywhere about the chamber configs that were compared, along with the dome shape.

Many people ( including Yamaha ) have found that the flat top with a chamfer ( and VHM with a radius on the timing edge ) is also superior
to the dome - but again it comes back to the chamber shape, and Yamaha for sure has a well developed toroid.
I have also done the hard yards and found the " best " combination when working on the BSL500 piston.
This ended up with the piston edge chamfer matching the squish band width ( at 50% area ) then going flat, this gave the best flow regime from the transfers
around BDC and had a good chamber shape as well.

If you combine that with ceramic coating on the chamber/piston,outside the squish area, then get clever and find a trick way of cooling the squishband
you suddenly have the best elements combined in a synergistic fashion.

Mechanically the two shapes have no advantage over each other - apart from the flat top that wont lock the ring in the groove if deto collapses the top face.
If you collapse a domed piston , even a little, it automatically crushes the ring groove,leading quickly to a seizure and a DNF.

[jonny quest]

Great reply Wobbly, thank you!

I've modified domed pistons into the Hybrid design, copying Yamahas chamfer width ratio. Needed to cut .070" off dome. I had one failure out of 5 that I modified, piston cracked at dome. Didn't cause any harm, but not good nonetheless. I knew I was risking it.

I was going to try the chamfer to match squish percentage next. For my applications, that should be no problem with piston strength.

[2T Institute]

Wob I am only going by what Frits said about them...

I am picking also they don't give away all their secrets in pictures on the net......
I am pretty sure he also said on another forum they are the closet in execution to the Aprilia bikes other than my PayKarts ones.

I have seen He-Ja equipped bikes get around they are a few hp off full house RSW 125 power levels

[peewee]

I use a 1.5mm dia needle roller from a little end bearing . Material is tough and also polished so there is no fretting on the ends of the ring. Drill down from the top of the piston allowing for some interference fit (say .05mm ) so the end of the pin is 1 - 1.5mm below top of piston, then weld over the hole to prevent the pin from coming out. You may get a slight swelling of the piston diameter at the position of the pin. Dress this off carefully with a mill-cut file. With a two ring piston you will have the ring gap in the same spot for both rings but this is fine.

good job mate. in the garage found a yami needle bearing from the clutch actuator arm. 1.5mm x 10mm needles. exactly what I needed.

[husaberg]

I have seen He-Ja equipped bikes get around they are a few hp off full house RSW 125 power levels

I guess some of that maybe because they are missing that rotary whatawacallit intake thingwajig....