RZ350 , 421 athena conversion tuning????

[Younmar]

Hi Guys... new to the forum, I`ve read a lot of posts on do`s n dont`s building these things. Im trying to finish a project for a friend they started too long ago. all parts were sourced through TTS in Cairns. Atheena barrels and head, stroked crank. motor was assembled before my time, as far as i can tell done properly. have fitted standard pipes up for now(fully cleaned and new silencers), running RZ Mikuni standard carbs. Money short hope to get running then improve. also has adjustable timing at stator. I need to jet it up more i know, but seems odd i have trouble keeping it running? can get it to start but even with air restricted seems to run out of fuel?, and starts easier if i retard ignition a bit..... Sorry bout big speil just wondering what some of u blokes might think ? Im limited with this level of modification..... thanks in advance...

[mkane]

Gummy petcock

[Younmar]

Na running a remote fuel tank for access while getting it going. cheers

[mkane]

Did the bike have gas in the carbs before you started working on it? If so how long did it sit that way. Sounds like they need a once over. Plugged pj passages will keep it from running

[Younmar]

Have fully stripped and cleaned the carbs, put new jets in from a 350 kit, but think not enough fuel for this motor. 220 main and 27.5 pilot. has been a lot of cleanup to get it to this stage as it sat for a long time and a lot of parts went missing. thanks for suggestions

[JonW]

Im no expert but I think you can safely say that you need bigger jets; 220 is for a 250 RZ or an LC350, the pilots are closer but still too small. you can run a 421 on the OEM 350 carbs, but it wont make as much power as it could, same with the OEM pipes. Does it run better on choke? if so you know you need more fuel.

[Younmar]

Thanks John, hav bn looking at your build.. nice job. I`ll definately get jets, bit unshore about advancing the ignition? guy from TSS told me 2 degrees (from stock) for runin? but seems to start easier standard? yes need choke but still stopping as if out of fuel. dont have aircleaners at present so that possibly not help[ing also......

[JonW]

Thanks for the kind words, hope it helped.
Have a look at Roger from Wicked's build on here that used OEM banshee carbs that might help as he mentioned using a slotted stator i think and I think he used +4deg, but am not sure. Personally I think you need a programmable ignition as the curve really needs more than just a blanked +n, but understand cash is tight.

[Younmar]

Has similarities to your build, Rgv front end and swingarm, want to get it running and look at performance as owner gets used to a big 2stroke..... It`s bn an unfinished project for too long.......

[Younmar]

whats best way to search for rogers build on the forum????

[Younmar]

Found some of rogers stuff, bit different motor still had stock barrels but he runing 340 main. So definately need to go up there....cheers

[JonW]

i will have a look for you when i get time, but ramped at mo. defo there is a 421 build with 26s that he did...

[JonW]

this i think:

http://www.rzrd500.com/phpBB3/viewtopic ... 4&start=30" onclick="window.open(this.href);return false;

[seahorse]

Ive been running vm 26ss mikunis Non Power Jet carbs on my 421 for about 6 months . After I gave up trying to tune out an off throttle stumble with the PWK 28 flat slides.
I dare not post what im running ,30 pilot AS 1.5 turns out, 5KI needle pos 3, Standard emulshions, I have run it on both 360 and 320 mains. Running pod filters and Kenny TSA pipes, I wouldn't come below 300 mains.
It seems to run ok, you cant be flippant about winding the power on in first second or third, a poorly timed wind on close to it coming on the pipe will result in uncontrolled skyward motion.
I still am having an off throttle 5 k sea saw issue that is resolved by selecting another gear or throttle position.
On the pipe it runs sweet. And it is easy to ride in slow traffic even with my tall gearing (18 front).

As I have the rz engine in the LC Frame I am running a standard 350 crossover, but a good friend and very good 2t builder has suggested a boost bottle may resolve the slight off throttle back and forth surge which I'm yet to try.
FYI and food for thought.
I haven't read much feedback anywhere else on 421 street tuning.

[Younmar]

Thanks for the info, sounds good, just waiting on new gasket kit to arrive and hopefully we can get it to a rideable state and start really tuning it. Keen to take it out for a run, havnt had a good 2stroke for a while, you realise how much you miss them when u start playing again......