2 Strokes Down Under

Had a chance to inspect the piston and bores today with the orthoscope as I had the exhausts off.

The piston skirt at the exhaust looks brand new and the useless piston skirt coating seems to have burnt right off as theres absolutely nothing left of it.

The bore looks pretty good but there are a few little singular vertical score marks near the front transfer port window. but other than that the motor has a clean bill of health.

Checked the compression with my el-cheapo guage and it has atleast 125-130psi compression which is about right for 25+ cc pump gas head domes.

so everthing seems to be looking good inside the motor

Need some opinions for paintwork

Ive been busy in MS paint trying to work out what the best paintjob will be and its mostly been playing with the yamaha speed block design.

what are your thoughts?

RZV500 insprired


TZR3ma/TZ250 inspired



Kenny insprired (but I think yellow/black is now an overdone color scheme)


yamaha M1 red/white/black inspired


british 250GP championship bike (blue)


my own take on the speed block design that blends the side panel speed blocks with pin striping on the top of the tank and tail.

I spent a few hours other night re-reading that whole build thread,was interested in how that piston skirt coating went.Now know not to bother with it lol.Thanks.
Thanks for info on Jap postage,very interesting.Will def be looking into it some more!
Paint jobs......TZ/TZR one does it for me.

L.B. wrote:I spent a few hours other night re-reading that whole build thread,was interested in how that piston skirt coating went.Now know not to bother with it lol.Thanks.
Thanks for info on Jap postage,very interesting.Will def be looking into it some more!
Paint jobs......TZ/TZR one does it for me.

The piston skirt coatings in my opinion are a bit useless, and as a far better protection is concerned, tipping a capful of racing castor oil in the tank will provide better protection for less cost.

but my pistons also have a ceramic coated piston dome, which MAY be worth a couple % hp gain. and MAY also keep the piston skirt cooler which would reduce the chance of lean seizures. but these are all just theories.

I take back what I said previously about the low friction ceramic piston skirt coatings being rubbish.

I thought that mine have been completely removed from the piston near the exhaust port. But once I adjusted the contrast on the camera and stuck a torch up to have a look with my own eyes I found that the coating is 100% intact at the exhaust port without a single scratch on it, which is far better than the coatings found on off the shelf aftermarket pistons.

But in saying that, I will inspect it after a good hard ride and see how it looks.

mate you'll have to let me know what the engine characteristics are like when u start riding the thing and how the light chassis handles the 421, i've got an aprilia rs250 with a rz350 motor in it, im trying to toss up whether to go the athena 421 or 485 or just put a 4mm stroker crank in it to put it around 380, im just nervous going to a 421 without powervalves, a 60-70hp hit in the space of 2-2500 revs isnt my idea of fun when i've got the rs cranked right over lol

sounds like you want an athena 421 cylinder, plenty of mind range grunt without having to do any crank case machining

see i thought the athena kit not having powervalves would be too peaky?? im happy to pay for an athena kit, only thing id change would prob be change the crank for a tss one because i think it would help reduce vibration a bit,

Which TSS Crank? A standard +4 unit or the ill fated 90 degree unit ?

Or... a balanced one? Does Steve still sell them? Ive ridden them and they may not be 100% right but better than a standard unit imho.

The Athena cylinders have lower ports than the Cub which gives them more midrange than the Cub. (the Athena wakes up around 4000rpm and the CUB wakes up at 6000rpm)

But the Cub has more peak hp (65-70 vs 85-90)

The athena is also more reliable as the ports are smaller and the RPMs are less so everything lasts longer, especially the piston rings!

Yes you can get more midrange by getting a cheetah cylinder with powervalves, but its added expense, complexity and unreliability, plus even less peak hp. (I've heard horror stories or poorly maintained cheetah powervalves falling slightly into cylinder and being hit by the piston!)

The athena cylinder should produce good power from 4-5000 rpms and pull all the way to 10,000. which is pretty amazing without a powervalve.

Id just get a 4mm hotrods crank with 115mm rods. my 421 felt pretty smooth with it so I dare say the balance factors dont really matter so much for the smaller displacement RZs/Banshees.
I think balance factors would be more of an issue if you were road racing it or if you went above 500ccs.

fred99999au wrote:Which TSS Crank? A standard +4 unit or the ill fated 90 degree unit ?

lol i always said when i saw him bring out the 90degree crank that it would turn to shit. but he did have some very nice +4mm 180 cranks made up with either 110 or 115 rods aswell. i've heard bad things about hotrod cranks so i probably wouldnt go them, jeram u said 65-70 peak hp for a 421 athena kit!!??? thats ridiculously low are u sure u have that right? i could get 75 with pwk28's, 4 mm stroker crank with original cylinders??

ive seen a few dyno sheets of the athena kit and they're all pretty much the same, they sit around 20-25hp till around 7 when it shoots up to 90 at 10,000 lol

hp depends completely on which dyno you use , so I cant say for sure than my hp is the same as your hp.

haha, I just checked on the WA roads website and it turns out that Ive got 9 months rego left on this bike

can anyone from WA let me know if the WA roads website vehicle rego check service is acurate? as I had thought the previous owner cancelled the rego!

Ill be getting a battery for the bike ASAP so I can take it for a test ride around the block.