Hello all,

I am adjusting the carbs of my mc21 ta22b.
OEM Motors with wire splice and ethos exhaust. (original air box)

my spark plugs are black, the main jet 138 slow jet 38. the air screws are at 3.5 turns to be good.

I put a main jet in 132 and it seems better.

the solenoid circuit is in good working order and original.

does this seem normal to you?why am i so rich on the idle circuit

Hello Omegawatt,

Welcome to NSR Forums. We do not allow jetting advice in the normal forum from past issues that arose. Im sure Andy will be along soon (site owner) to point you in the right direction.

Good morning,

Thank you for your reply. I looked on the previous pages and on the tuning/workshop, and I found nothing. Sorry.

I know that carburation is never an exact science (each motorcycle is different) but generalities can be observed.

thank you if you can help me

Hello "Omegawatt", and welcome to NSR-WORLD.COM! 😊

As mentioned already, we don't allow specific jetting discussion in the open/public area for historical reasons. Basically, everyone's setup is different, even if we're just talking "stock" derestricted bikes, and a setup that works for you may very well not work for someone else. It happened in the past, where someone recommended settings that [possibly] seized another members' motor, and they threatened NSR-WORLD with court action over it. Since then, I banned it.

What I can tell you is we found the standard setup is often richer than ideal. I can only speculate that this is to compensate for the varied topology in Japan, where bikes could be expected to run anywhere from sea level to up in the mountains. There was a massive mountain road riding culture in Japan back in the "race-replica" days, and I don't think manuafacturers could afford to have motors seize because of fun "at altitude".

Contrary to the above though, we have found that in recent years we've needed to increase the pilot jet size due to ethanol content in the fuels. Have you checked the 2T pump is set correctly, and not over-oiling?

Just for reference, the standard carb setting can be found in the Technical Section. I don't expect it will help you, but may benefit someone who stumbles on this thread at a later date.
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NSR-WORLD.COM

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Hi Andy,

I understand and I'm sorry to hear that you had problems because of advice...

in my case I take full responsibility for my actions on my motorcycle. anyway, thank you for your valuable advice.

to come back to my motorcycle, yes I did check the oil pump flow rate, especially when wot the mark is well aligned. I am especially surprised that with a slow jet of 38 my air screw is loosened by 3 turns, to have a correct operation but too rich.

I leave you a you tube link if you are interested in seeing the engine speed

https://youtube.com/shorts/aP98yrJ9e5o?feature=share