Jetting time

rd400canuck · March 26, 2020, 03:52:04 PM

Hi guys,

I managed to get the RD400c together enough to drive it up and down the street fumigating it.

I have 27.5 pilot (stock 25) 5L1 needle on middle clip and 120 main (115 stock) and 1-1/2 out on air screw. Bike started right up and ran 'ok' in the little jaunts I did in 1st and 2nd. It seemed rich to me so I leaned the needle 1 position. Very nice improvement. Wanted to wheelie even more so and it felt like it wanted to in 2nd. But of idle it didnt feel as good since i leaned it out.

Everything is 100% stock aside from air filter element. I kept the bottom plate with the two venturis and sat a trimmed uni filter on it.

Question is... is it possible my bike wants a 30 pilot even though the stock was 25?

m in sc · March 26, 2020, 03:53:29 PM

YES. def go up on the pilot

rodneya · March 26, 2020, 09:58:59 PM

Warm up engine, set idle slightly higher than normal.
Start at 1.5 turns out in the air screw and adjust in and out in small increments until you get the highest idle speed. Give it a moment between adjustments to settle.
When you find the highest idle speed check as setting. less than 1 turn out go bigger in pilot. More than 2.5 turns out go to a smaller pilot
Change pilots if necessary and then set as for best throttle response.

You are jetting, not brewing magic in a cave. You dont need to do it by trial and error

SUPERTUNE · March 27, 2020, 12:21:21 AM

Quote from: rd400canuck on March 26, 2020, 03:52:04 PM
Hi guys,

I managed to get the RD400c together enough to drive it up and down the street fumigating it.

I have 27.5 pilot (stock 25) 5L1 needle on middle clip and 120 main (115 stock) and 1-1/2 out on air screw. Bike started right up and ran 'ok' in the little jaunts I did in 1st and 2nd. It seemed rich to me so I leaned the needle 1 position. Very nice improvement. Wanted to wheelie even more so and it felt like it wanted to in 2nd. But of idle it didnt feel as good since i leaned it out.

Everything is 100% stock aside from air filter element. I kept the bottom plate with the two venturis and sat a trimmed uni filter on it.

Question is... is it possible my bike wants a 30 pilot even though the stock was 25?

How are you going to buy fuel made in 1976?

Absolutely you will not run stock jetting, unless using canned fuels...not fuel from a pump unless you have a local track nearby that sells race fuel from a pump.

rd400canuck · March 27, 2020, 07:57:36 AM

ok thanks again guys...

I never thought about the gas... does the ethanol in it affect affect jetting?

SoCal250 · March 27, 2020, 12:23:58 PM

As a follow up to what rodneya posted above, you should download the Jetting Guide from The Tech Library if you don't already have it. It will help lead you through the jetting process so you're not making hit or miss random guesses.
THE TECH LIBRARY »CARBURETOR - FUEL/AIR DELIVERY

Quote from: rd400canuck on March 27, 2020, 07:57:36 AM
does the ethanol in it affect affect jetting?

yes

SUPERTUNE · March 27, 2020, 11:55:40 PM

Jetting can change a little by temp you ride at and if using stock RD round hole pistons or the Banshee Pro-X pistons I use now.
30-32.5 pilot, 127.5-130 main, 175-P2 needle jet, stock 5L1 needle on #2 pos using stock airbox with Uni filter. 1 1/2 air screw
I disconnect the bowl vent air jet tubes to the air box also.
2.0 mm ignition timing.
Chuck

RdsOnly · March 28, 2020, 01:15:03 AM

Check out this site www.rdsonly.com - now owned by Economy cycles.
click the about todays gas link. great info.

Hope that is helpful.

JT

rd400canuck · March 31, 2020, 04:42:54 PM

I'm wondering if it's even worth my time jetting when it's not even 50f outside and ill be riding in 78f on avg.

Jspooner · March 31, 2020, 10:13:41 PM

I have mine jetted so they run in all temps. They run a little on the rich side when it's really hot and humid but they run the best when it's 50-60f. I don't change my jetting with the seasons or extreme temps. I ride when it's in the high 30s as well as in the 90s and humid. I think 50-60 is the perfect temp to jet for.

Greaser Greg · March 31, 2020, 10:20:01 PM

Quote from: RdsOnly on March 28, 2020, 01:15:03 AM
Check out this site www.rdsonly.com - now owned by Economy cycles.
click the about todays gas link. great info.

Hope that is helpful.

JT

Thank you so very much for all that info!

Striker1423 · March 31, 2020, 11:07:55 PM

Quote from: Jspooner on March 31, 2020, 10:13:41 PM
I have mine jetted so they run in all temps. They run a little on the rich side when it's really hot and humid but they run the best when it's 50-60f. I don't change my jetting with the seasons or extreme temps. I ride when it's in the high 30s as well as in the 90s and humid. I think 50-60 is the perfect temp to jet for.

Plus you have the added benefit of a crisp throttle response when its in the 50's out. Although it gets cold riding home in those temps. I've done it a few times with my summer gear on. Nice when its 75 and sunny, but when the sun goes down it get's my legs shaking lol. Worse when it rains haha.

pdxjim · March 31, 2020, 11:50:11 PM

Quote from: Jspooner on March 31, 2020, 10:13:41 PM
I have mine jetted so they run in all temps. They run a little on the rich side when it's really hot and humid but they run the best when it's 50-60f. I don't change my jetting with the seasons or extreme temps. I ride when it's in the high 30s as well as in the 90s and humid. I think 50-60 is the perfect temp to jet for.

Same.

m in sc · April 01, 2020, 11:16:36 AM

depends where you live. for me, i try to tun around 70f this seems to be good for the temps i ride in, typically 52-55 to 100.

rd400canuck · April 02, 2020, 02:44:28 PM

Thanks for all the input, guys.

I think I'll have to wait till it's warmer regardless. I tried zeroing in on the correct pilot yesterday and the cold got to me. I just want any fun.

Perhaps in a few weeks it'll be warmer and I can take my time and enjoy the process.

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Jetting time