RD400F Main Jets

[Milan]

Took apart my 2R9 carbs.
They had #140 mains & needle clip in #2 from top.
Does not match books with #145 & mid clip.

I put a K & N filter in the stock airbox
Mark said for sure #145 or maybe even a #150
Any other thoughts?
What about pilot jet increase from 25 to 27.5

Thanks

[Milan]

Anyone have any thoughts on the jetting with a K & N?

M

[Striker1423]

Start high, work low.

Say 160 and go down from there.

[hayduke]

You've got to jet to the bike, not the book.

That said, a less restrictive air filter would indicate the need for bigger jets.

Is the rest of the machine stock?

I wouldn't change the pilots until you see how the mains are working, the pilots have a little adjustability with the air screws.

So yeah, start in the 150-160 range.

[Milan]

All stock 2R9 bike.
Just the K & N.

The pilot air comes thru the filter as well, although it is that small orifice.
So I was reading that if the air screw is < 1 turn out on idle, then go to a bigger jet.

I would also think if a bigger pilot jet could be used, then use it.
The pilot does contribute when the throttle is staring to open, so may help with take-off by being able to supply a little more fuel at the different injection point

I will give it a try this weekend.

Anyone else running a free flow filter with stock?
How did that jetting turn out.

[scully]

I don't have the 400f, but a 400c, put in a uni. went up 30 pilot and 132.5 main. Originally 25 pilot and 120 main. 1 1/4 out on airscrew. Should mention too, I removed the rubber snorkel on back of airbox as well.

[Bullockcm]

2R9 would be different than a Daytona which most people would associate with 400f, at least in the US.  I do not have a stock bike but you don't want to go huge.  Maybe start 3 (160-170) mains bigger and then work back from there.  Air screw and idle will let you know if the pilots needs to be changed.

[Milan]

Worked on the carbs friday nite.
Another mandatory inspection for all who open up their carbs.
I attached a puc of my float contact plate.
As you can see the needle stem put a divot on it.
This would hinder the smooth movement of the float, & in my case i had a dripping overflow.
Sanded out with 1000 grit & Q-tip with polishing compound.

Reinstalled & set float level to 22 mm, still in spec, but wanted higher level.

[Milan]

27.5 pilot went in with 160 MJ.
5J6 needle at #3..
Slides also had divots in them from the idle screw.
So replaced the slides & idle screws.

Put carbs on, did the popsicle stick throttle cable adjustment with the idle screws backed out.  Then adusted idle screws to 3.5 out.
This then gave me the 2mm cable slack.

New clear poly gas lines & the rest put on.
40 to 1, 93 octane ethanol free gas put in.

So. The moment of truth.

Pulled out to driveway.
2 kicks, fired right up.
Sounded better than anything i head since getting it.

I knew then that it was not setup right prior based on the nice oil show from the right pipe on my driveway.

That burned off & idled great at about 1200 rpm.

Took it out to the street, went up to second gear & about 5000 rpm.
Felt good, maybe just a little buck at about 4000 rpm.
Very little smoke coming out pipes, looked good.
I will try another longer ride tomorrow.

So the bucking could mean to rich?
So i can try #2 needle clip. Or go to 155 MJ

But will ride it at high rpm"s first to see how it does.

M

[Milan]

Driveway

[m in sc]

try the needle on leaner. oil spots interesting. 

[teazer]

According to my notes and not to be taken as gospel, C&D models came with 115 main jets, but in Australia our 400F with carbs marked 2R9 came with 145 main jets in #284 series needle jets which are the ones with tall spray tubes and create a different fuel curve than earlier carbs.

LEDAR used to recommend 240 main jets which I think measured something like 1.4mm and that caused some confusion back in the day. We ran #40 pilot jets with lightly ported cylinders, foam filters and what I think were DG pipes but that's far from sure.  Might have been Aussie copies.

We ran fJ6 needles in 3rd slot and that's all my notes say.

Are you running oil tank(pump) as well s premix or just pre-mix?  That oil spray suggests an oil build up in the crankcases and pipes that needs a few hard miles to burn clean.

[m in sc]

fyi, in a pm i suggested the 160s a few days ago as well.  Seems to be a consensus as that as a starting point. That being said, until there's a WFO plug chop done, he wont know. 

the oil puddle seems like there was mixture sitting in the crank case that got puked out. Unrelated to tune id say. (but maybe a sticky float as mentioned above).

[SoCal250]

All stock 2R9 bike.

If your bike is a Canadian '79 it's technically a 3J7 not a 2R9. Although it does utilize 2R9 carbs.

You may already have it, but here's a Data Sheet (see attached) I copied a while back from a Yamaha book I have for all 1979 Canadian models.


EDIT: changed attached file from PDF to JPG.

[Milan]

Yes.
It is a 3J7 model.
But most parts are the 2R9

Has no crossover pipe either.
Should i be lookung to put one on?

Funny thing is 1 carb is a 2R9.
The other is a 1A1.

Although the 1A1 seems to work

Both were jetted identical.
So looking for a 2R9 non-choke carb
since bike is stock, to try & keep book correct.

M