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DRZ400SM FCR Jetting update

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I though that I would post this up in case someone else has the same setup and problems.

2006 SM

Powerbomb header and Core 2

3X3 mod

FCR 39 (TT kit) - 160 main, 45 pilot

Running 0-1000ft and 10-25C

Problems:

1) The bike would start fine but as soon as it warmed up the idle would drop to the point where it would stall when I clutched in. Turning the idle up (and up, and up, and...) would help up to a point but it still didn't idle properly.

2) The bike smelled of fuel in traffic i.e. running very rich. Sometimes you could even see the black smoke.

3) Trying to ride at a constant speed at small throttle openings would have the bike surging quite a bit - the throttle felt more like a on/off switch in slow traffic.

4) Bike chokes if throttle is whacked open in neutral, but seems responsive when riding.

Fixes:

1) TT extended adjustable fuel screw - 1 1/4 turns out

2) JD jet kit - 165 main, 42 pilot, red needle 5th clip

3) R&D float bowl with adjustable leak jet.

Result:

1) The surging is gone. Completely! The throttle is smooth at any speed, rpm's and throttle openings.

2) It idles smoothly at what I would guess is around 1500rpm, and after an hours riding including city, motorway and country roads it idles at exactly the same rpm's and never even stutters.

3) I don't smell fuel anymore.

4) It still bogs when I whack the throttle open in neutral but doesn't die instantly like it used to. I still need to play with the adjustable AP on the float bowl, but the screw is impossible to get to on the fly.

Overall I am extremely please with the outcome. 🙂

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did you remove the pilot air jet? which adjustable fuel screw.

I bought the TT extended fuel screw.

I'm a bit confused by the term pilot air jet - I though that this is the fuel screw?

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Pilot air jet is in the bell of the carb. There are three ;adjustments; in the pilot circuit.

1) Pilot air jet - this sghould be removed on a FCR-MX

2) Pilot fuel jet, typcal size is a 45 though this can vary depending on the fuel screw brand/manufacturer/ Alloy/aluminum screw typically call foe a smaller pilot jet due to the poorly machined tip.

3) Fuel screw - This is for fine tuning the pilot circuit. Best one is the Merge Racing one, then there is the James Dean, Kientech and Kouba screws, all good.

What brand was the fuel screw? Was it aluminum or brass?

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Pilot air jet is in the bell of the carb. There are three ;adjustments; in the pilot circuit.

1) Pilot air jet - this sghould be removed on a FCR-MX

2) Pilot fuel jet, typcal size is a 45 though this can vary depending on the fuel screw brand/manufacturer/ Alloy/aluminum screw typically call foe a smaller pilot jet due to the poorly machined tip.

3) Fuel screw - This is for fine tuning the pilot circuit. Best one is the Merge Racing one, then there is the James Dean, Kientech and Kouba screws, all good.

What brand was the fuel screw? Was it aluminum or brass?

I have the Kientech fuel screw.

Is the bell the same as the bowl? Do I still need to remove the pilot air jet if I have a R&D bowl fitted?

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When you got the TT kit, you had to install the bell on the intake side of the carb with two special short allen bolts. You must remove teh bell and then remove the large jet on the left side. Re-install the bell.

You really are better off with the stock float bowl with a FCR-MX. With the R&D bowl to work properly with this carb, the ALJ screw must be seated, effectively closing off the leak jet. So, there is absolutely nothing to gain with it. Better off selling it in the TT classifieds.

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OK, thanks. I think I will leave the setup as is for now as I'm pretty happy with the current performance.

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Hey William, i just read this thread and i found it interesting that you suggest removing the pilot air jet on an FCR-MX.i noticed that suggestion in other threads, but i assumed that for for the TT FCR for sale in the TT store. i'm using a 37 mm FCR-MX off an 05 KX250F. Do you think i should remove mine too? It's size is a 100 by the way, and the FCR-MX that i'm using has no main air jet. Any more input you might have would be greatly appreciated. By the way, while i have the carb off to remove the pilot air jet, i'll check my AP timing in the post that you answered for me earlier. Thanks and God Bless!🙂

tom

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Thanks Eddie. getting ready to adjust AC pump right now. This site and your knowledge and expertise have been invaluable. You too William. Again, a thousand thanks for everyone's help. this has been a challenging venture, but it has also been very rewarding and fun!

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Hey Eddie and William, and all who have been following this thread and the others that i have participated in. i adjusted the AP timing this morning along with another pilot jet change. i'm very pleased with my results.

The final setup for me is as follows.

Pilot Jet, 40, Pilot Air Jet 100, Moose Racing Fuel screw 2.25 turns out.

160 Main Jet, Stock 06 E model nozzle, EMN Needle clip on pos 4 from top.

It's idling perfectly, has no bog under load and only an occasional bog idling and whacking the throttle open. The bike is a pleasure to ride and much more torquey through the bottom and middle.

Plug is a beautiful golden tan color and i'm a happy camper. Now if it would just stop raining long enough to go for a ride. Thanks again to all.

God Bless!

tom

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Good deal. BTW, there is almost no way to eliminate the bog when nailing off of idle. You will find that in actual riding, you will never be at idle except at a stop, so this idle bog is a non-issue.

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Thanks William, that's a good word and pretty much what i suspected. After all, it is a thumper and that crankshaft has to travel a long way on it's own if it has missed or misfired at idle. Your help has been invaluable to me and i just want to thank you again.

tom

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