RZ250 main jet size

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jools
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RZ250 main jet size

Post by jools » Tue Sep 26, 2017 4:24 pm

In my efforts to pin this RZ250 down perfect... (it's running pretty nicely, but I'm still chasing a slight lack of power under load at WOT - feels 'heavy' - sound rich to you?). Thinking maybe I need to change the main jet. It pulls cleanly through the gears. Smokes a bit when cold but no smoke when warmed up.
I know I'll need to re-check float height and needle position, but because everything is factory standard, the standard MJ size should be right. (But what is standard?)
The bike has standard air filter, exhaust, new pistons and bores fitted about 400ks ago, so I guess it's almost run-in.
Everything else is good, temp etc. First-kick starter.
I'm sure I'll need to do a plug chop to fine tune it, but what is the STANDARD MJ size for a '64 RZ250? -I see varying figures quoted... from 155 to 250.
Whaddayareckon?

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JonW
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Re: RZ250 main jet size

Post by JonW » Tue Sep 26, 2017 11:38 pm

standard sizes are listed in the parts books for each market, the Jap/USA market uses diff carbs for the 83/4/5, and even ours change to power jets for 86-on. Thats why the jets change size in ours, PJs use smaller mains as they use the PJ as well.

When you say '64, do you mean its a 1984?

jools
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Re: RZ250 main jet size

Post by jools » Wed Sep 27, 2017 9:03 am

Brainfade, sorry. It's an '84 model of course. Oz market, Pre power jet. I have a Haines manual but it's for RZ350 only.
I'm running 180mj (I have 155mj that I could try)
Also, float height... I set mine to 21mm but that was referring to the later 350 carb specs so could be wrong, any ideas on this? I am getting some leakage out of the LH overflow pipe.

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mboddy
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Re: RZ250 main jet size

Post by mboddy » Wed Sep 27, 2017 11:48 pm

I have the parts list for the Australian 1985 RZ250RN.
It has a powerjet and the main is 155.
So don't try 155 in a pre-powerjet carby.

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Re: RZ250 main jet size

Post by jools » Thu Sep 28, 2017 10:46 am

Yes, the last thing I want is a holy piston or two!!

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