athena big bore kit review..i bought one

[g0zer]

should i measure the volume with a spark plug installed? or just tape it off?

edit: found an interesting website which explains corrected vs uncorrected compression ratio so i could understand it for the first time

http://www.sacoriver.net/~red/uccr.html

The "Uncorrected Method" (sometimes referred to as the Geometric or European method) which compares the volume above the piston at Bottom Dead Center (BDC) to the volume above the piston at exact Top Dead Center (TDC). This method is often criticized because it does not reflect the dynamics that occur during the engine's actual running conditions, but, as with steady state flow techniques used on a flow bench (which also do not duplicate actual running circumstances) it has a very useful place in the planning of an engine's tuning and application.

The "Corrected Method" (sometimes referred to as the Trapped or Japanese method) which compares the volume above the piston at the point on the upstroke that the exhaust port roof is fully closed (on a two stroke, exhaust valve closed on a four stroke) to the volume above the piston at exact Top Dead Center (TDC). This at first seems to be the most sensible way of looking at the situation since how could we really begin compressing fuel/air mixture before all "leaks" are shut off, right? Well, not really...

At elevated engine speeds (rpm), the piston is moving so quickly that it will actually "outrun" the fuel/air mixture to the "leak" and "trap" a much larger volume of fuel/air in the upper cylinder than just the static volume above the exhaust port. This "trapping efficiency" improves with more rpm's.

[dplb]

how long did the kit take to arrive from go to whoa goz id say to measure the volume with one installed myself

[g0zer]

uhh i think it took about a 10 working days so not long. those domes are removable so i am hoping it will be pretty cheap to return them if they will send out a new set.

i dont think its atv unlimiteds fault, i dont believe the items were damaged during shipping. came in a sealed athena box and were still individually bubble wrapped in the box. i conclude they were damaged from the factory.

[dplb]

sorry but im an impatient mofo and im waiting on the same got your crank yet

[g0zer]

nah still waiting on the crank, its made to order with the spacing plates from NZ. Steve told me Wayne (the NZ connection) was a bit snowed under so i told them not to stress and take their time since ive been tooling on the bike a lot lately and would rather ride it for a bit. i will get all the bits together and save it for something to do during winter.

[dplb]

sounds cool dude good luck with it all

[twinrock]

well i have heard nothing but great things on the banshee forums about atv unlimited hence the reason i used them im sure they will be more then happy to sort u out..while u have the barrel off u should get a copy of the porting specs to compare thats what i should have done

[g0zer]

well i have heard nothing but great things on the banshee forums about atv unlimited hence the reason i used them im sure they will be more then happy to sort u out

just thought i would mention my replacement domes have arrived from the states

big ups to Jeff from ATV unlimited who got onto athena for me and kept in the loop with the emails to make sure things were moving forward for me

also big thanks to the guys at athena USA who were a pleasure to deal with. they ended up sending out replacements from the US to Australia at no cost to me, and didnt require me to send the unservicable ones back.

i suppose i should start putting it together now.. just ive got an rgv to tear down as well :p

[oiler]

Hi Twin rock,
Im in the process of doing the very same thing, 392 + 4mm stroker crank for 421cc.. When i got the box from USA i thought they had robbed me with the weight difference until o opened it up...would like to get the good oil on all your work mate.... save me the mistakes.... Mine going together through Steve at TSS but looking forward to the power rush with no varible timing valves.... Appreciate the update

Cheers

BW

[twinrock]

hey mate yep steve will set u straight..... as for the kit all pretty straight forward..i used a spacer plate to run my 4 mm crank easiest and cheapest way to do it..the only thing u dont get with the kit was little end bearings... and just take your time to jet it...
what bike is it going in...man i bought a stock 31k rz350 this week been a long while since i rode one.... i cant imagine putting one of those engines in it...it doesnt handle the stock one..lol.... as far as bad ideas go thats a great bad idea..lol

[oiler]

thats at the wheel power... but yeah like Lee said twice the compression, I wonder how much you could get on a stock 350 by upping the comp a bit, also how much more you could expect from the athena with some decent pipes?

Wigarus....

Well i too am working up a new motor for my RD which yes is having an upgrade over to an RZ motor.... I bought a 391cc athena big bore kit.....got it in ebay auction for a reasonable price.....the kit was a very nice package indeed, 5 mm stroker crank with heavy duty bearings which gives me 421cc combo... gone for electronic ignition for the ease of timing & tuning once its packaged.... TSS doing the build up for me....the bottom end is back together...nice

Now to the pipes... my athena kit has gone over to TSS partner in NZ to be flow speced for custom pipes to maximise horespower output...
Two possible options for pipes....custom made SS pipes out of Europe... cant recall the guys name but contact through TSS, or maybe (not sur yet) peter Gibson out of Vic may do me a set.... spoke to him and this may be a good second option.... as long as hes ok with building to a specification.... right now i have a set of near new allspeeds that i picked up out of the UK - very nice but not likley the right pipes....
should have the motor back in the frame in about 6 weeks... optimum pipe design in about 2 weeks.. so can then decide for sure....based on flow tests / motor horse power output will select the right carbs to match it all in towards the end.....

Will keep you posted as to the final outcome..... no change 5k build

cheers

Oiler

[oiler]

Hi twinrock....missed your post there.... yes spacer plates a done deal....lots othet stuff i didnt post but you get the picture.... going into an RD frame...the RZ frame is just too light on.... now how to stop it?... now thats another issue...

comments please

See my update...

Cheers....

oiler

[twobangermad]

Port work done to the Athena big bore kit, just a clean up from the boys at MMT motorcycle services in Granville, Sydney. Sent them on Thursday, Craig did them Tuesday and back in my hot little hands by Thursday (could have been Wednesday but needed to be here for courier) Very happy all i need now is a new piston (light bore scoring due to burnt piston), gasket sets, oil seals and time, then i'll be back on the road... maybe after the Holidays. Also the Nikisil was not touch when porting and a light hone was performed to take off any edges

[JonW]

I didnt know MMT did port work so that's interesting, what did you ask for with the map? I know these cyls have a lot to offer and I would be interested to know if there is someone locally who can give us more power and has knowledge of these cyls.

[twinrock]

hey mate if u need a full seal kit do a search for jmc racing they are local here..i think the whole kit it the same price as a water pump seal from yam..also if u need a head gasket kit for te athena..just go to any bearing place and buy them all as they are o-rings and will have them very cheap in stock..any other gaskets u can cut from gasket paper ur self ie bace gasket agian much cheaper

[twobangermad]

Yeah they do, but I just wanted a clean up of the ports as I was told the scoring was light and therefore replating wasn't nessesarily, nessesary. Quite happy with the performance/reliablity in it's stock form with my 35mm PKW's. The plating is out sourced to Melbourne

[twobangermad]

Thanks Justin, think with the exchange rate US wise and upgraded of some clutch parts might head down this track but i'm all fo saving some cash, keep it in mind

[L.B.]

Yeah holy thread revival.....
Couple years on,hows everyones kits going?Updates?Advice?

[aaronmvrider]

your going to have to buy 1 .... and let us know how it goes L.B

[L.B.]

Lol Aaron,Ive owned one since Nov last year,but it still sitting in a workshop in Garden Grove Ca getting some trickery stuff done to em...........