Author Topic: RD400 Carb Tuning  (Read 872 times)

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Offline 5port

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Re: RD400 Carb Tuning
« Reply #15 on: July 15, 2021, 10:40:15 PM »
Just getting to this, this weekend.

I will try 160 Mains, & 27.5 pilot.
As free flow filters should have the most effect on the tuning, vs other mods.
Needle @ #3.
They say better to start rich.

we will see how it does then.

M



Good luck.  I would still suggest getting back to standard with it running correctly first.  Think that would just be needing the standard paper filter without baffles for you?  If you can only get the USA baffled filter with the metal tubes, just cut out the metal plate with the tubes.  At the moment, your symptoms could indicate other possible problems like an air leak.  Far better to start with the basic bike right, you know where you are then. 
Cheers

5port
5port

Offline Milan

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Re: RD400 Carb Tuning
« Reply #16 on: July 20, 2021, 09:38:22 PM »
Worked on the carbs friday nite.
Another mandatory inspection for all who open up their carbs.
I attached a pic 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.

Offline Milan

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Re: RD400 Carb Tuning
« Reply #17 on: July 20, 2021, 09:41:25 PM »
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 adjusted 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 heard 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.

As it is now, it has no crossover pipes on the intake rubbers.
Thinking of fitting them?

M

Offline 5port

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Re: RD400 Carb Tuning
« Reply #18 on: July 21, 2021, 09:39:33 AM »

As it is now, it has no crossover pipes on the intake rubbers.
Thinking of fitting them?

M

What?  No point wondering about standard jetting if you run a non-standard set-up.  The x-over can make a lot of difference.

5port
5port

Offline 5port

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Re: RD400 Carb Tuning
« Reply #19 on: July 21, 2021, 10:09:09 AM »
Overall, like all standard set-ups, you use standard set-up and it works standard.  ;)
The 2R9 has the small x-over alloy tube and that matches the jetting.  You are getting farther away from the standard settings and really, you are re-jetting the bike to a different set-up.
If you want to do that, you might be better to refer to a jetting set-up guide.
You also should consider the fuel you are using.

5port       
5port

Offline Milan

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Re: RD400 Carb Tuning
« Reply #20 on: July 21, 2021, 02:48:57 PM »
bike came stock from PO.
He is reputable, so I dont think he changed anything.

Crossover was not there when I got it from him.
All manifold bolts look unmolested.
So maybe the Canadian 3J7 model came like this?

Looking to source some of the crossover rubbers, and the pipe.

I found some on Ebay but the guy wont ship to USA.
Can anyone here help me get these?
I will just send you funds via PayPal.


https://www.ebay.co.uk/itm/133652936769?epid=652524292&hash=item1f1e55f841:g:La0AAOSwniZgFusJ

https://www.ebay.co.uk/itm/133652735128?hash=item1f1e52e498:g:La0AAOSwniZgFusJ]
[url]https://www.ebay.co.uk/itm/133652735128?hash=item1f1e52e498:g:La0AAOSwniZgFusJ
[/url]

I will take all (4) of them.

Crossover is hard to find.
Maybe someone here has one?


Milan



M

Offline 5port

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Re: RD400 Carb Tuning
« Reply #21 on: July 21, 2021, 06:01:59 PM »
bike came stock from PO.
He is reputable, so I dont think he changed anything.

Crossover was not there when I got it from him.
All manifold bolts look unmolested.
So maybe the Canadian 3J7 model came like this?

Looking to source some of the crossover rubbers, and the pipe.

I found some on Ebay but the guy wont ship to USA.
Can anyone here help me get these?
I will just send you funds via PayPal.


https://www.ebay.co.uk/itm/133652936769?epid=652524292&hash=item1f1e55f841:g:La0AAOSwniZgFusJ


[url]https://www.ebay.co.uk/itm/133652735128?hash=item1f1e52e498:g:La0AAOSwniZgFusJ]https://www.ebay.co.uk/itm/133652735128?hash=item1f1e52e498:g:La0AAOSwniZgFusJ]
[url]https://www.ebay.co.uk/itm/133652735128?hash=item1f1e52e498:g:La0AAOSwniZgFusJ
[/url]

I will take all (4) of them.

Crossover is hard to find.
Maybe someone here has one?


Milan


M


No, the 2R9 power unit is a complete system.  The 3J7 Model with the 2R9 engine has all the 2R9 engine parts, carbs, exhaust, air filter, reeds, rubbers, small alloy x-over and CDI ignition.
The Tourmax brand pattern rubbers are good.  The small alloy x-over tube is the same part as the 250/350LC  4L1/4L0 European bikes and it is usually available at about $20 used.
Avoid the later large x-over from the 350YPVS  31K bike or similar large x-over, unless you wish to go non-standard. 
The parts for your 2R9 engine etc will be in the 2R9 Manual in the tech, although you really need a copy of the 3J7 Manual and the 3J7 Partslist for your bike.

5port   
5port