Jetting advice '05 drz400sm

Hello everyone, I am a carb virgin, but i do have experience tuning fuel injected street cars. I recently picked up this bike in Phoenix and rode it 480 miles back to Albuquerque(people weren't kidding about the stock seat being a 2x4 :thumbsup: ). The PO had purchased it from another seller and did not know how the jetting was done, other than the gentleman he bought it from said it was jetted, and had lived in Las Vegas, altitude 2100ft. It seems to be rich now, which makes sense. exhaust smells like it, power is down more than expected, and response seems more sluggish.

Here are the bike essentials:

FCR39 MX carb

3x3 mod

K&N air filter

full Yoshimura RS-3, restrictor removed

Will be ridden mostly from 5,000-6,00 ft with the occasional jaunt up the mountain, that is about 11,000 ft

High desert climate.

Ridden as a commuter/weekend mountain attack vehicle

My question is fourfold:

1:How do i tell if this is a James Dean kit, and the sizes of the jets? The PO stated that there was a good chance it would be.

2: I found a video of a 37mm mx carb being re-jetted, is this carb similar, as i assume the carb needs removal, and jetting will be a similar affair.

3: To lessen spillage when i crack the bowl, would it be wise to remove the vaccum signal to the petcock as the engine runs until it dies from fuel starvation?

4: If it is a James Dean, would i be able to purchase individual jets, and what size should they be?


Edited by snailspool

Can anyone please help me out with this?

I don't have a DRZ anymore, but when I did I purchased the JD kit. It came with two needles. Unlike the stock needle, the ones from JD had either red or blue paint on the end to distinguish which one it was. Removal of the Carb will not be necessary, but I always found it easier to do it when messing with jetting. If you loosen the boots, rotate the top of the carb and remove the slide you should be able to take the slide out and check the needle. The jD kit comes with PJ, 2 needles and MJ's and a chart. If it did have the kit installed it is too bad the spare parts didn't come with the bike.

Have fun. They are a great bike, only sold mine because it isn't that good at doing a supercross track. LOL

The bug

If teh needle is a standard Kehein needle, it will have letters stamped into it. If it is a JD needle, the top will be painted red or blue. Simple.

No need to pull the carb to rejet. The main and pilot come out once the bottom cap is removed. The needle can be removed after you take the seat, fuel tank and cap of the carb, then remove the 6mm allen plug on the slide.

Before you do any changes, find out what jets are in the carb. If you can, please post clear pictures of the carb right and left sides.

Looks like i was mistaken on the jetting kit. Letters indicate a Kehein, right


Here is the pics of the carb:



Will the jets have numbers stamped on them to indicate what kind and size they are?

Edited by snailspool
wrong pics

Got my JD kit in. The jetting was 157MJ and 45PJ with a stock needle on 3rd from top but i lowered it to 2nd from top and it ran better. What are recommendations for the JD kit?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now