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DRZ400 '03 (kicker) Jetting Advice

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Apologies in advance for something that's likely been hashed out somewhere in the forums, but I'm not finding a good reference to draw from. 

 

This bike is new to me. When I bought the bike, it started with the choke on as you would expect, but would die the moment you touched the throttle. I figured the pilot was clogged, especially since the bike was ridden once or twice a year. The bike was bone stock except for an FMF-Q and the owner said he made some jetting changes when he installed the muffler (though he couldn't remember the specifics). This has the stock slant FCR carb and not the FCR-MX. The snorkel was also removed, so it's like a 3x3 mod, but no cutting is required because this model comes with the square cutout from the factory. Elevation at the previous owner's house was around 1500'.

 

I bought a service manual and went through the bike, cleaned it up, greased everything, checked valve clearance, etc. I removed the coast enrichener and capped the three fittings. I also installed an external fuel screw. My house is about 4000' and the target jetting environment is around 4000'-6000' and 70-80F. With the fuel screw all the way in and no choke, the bike started first kick today after sitting overnight and seems to run nicely, though there is a bog when you open the throttle quickly. 

 

Next I removed the two caps on the carb for the coast enrichener and connected them with a short piece of hose. This did not seem to make any difference and that's how the bike sits.

 

Current jetting specs:

OBDXP needle 5th from top (stock is 4th per manual)

200 main air jet (stock)

60 pilot air jet (stock)

165 main jet (stock)

45 pilot jet (stock)

65 starter jet (I assume this is stock)

 

I've read about removing the pilot air jet, but every time I've found info on this, they were referring to the FCR-MX carb. Should I remove the pilot air jet with the slant FCR? I'd much prefer to adjust the pilot circuit with the pilot jet and fuel screw, instead of the pilot jet and fuel screw and pilot air jet. If I should remove the pilot air jet, it looks like I need to go back to capping the fittings on the carb?

 

Obviously I need to start leaning out the pilot circuit, but I'd like to hear some advice on how to do that from here at my altitude/temperature. I figured I could try the 38/70 or 38/73 recommendation from the article on 4strokes.com, but then maybe go down a size on the pilot jet and/or up a size on the pilot air jet since those recommendations are for 0-4000'. I also read somewhere that a 45 is good to go if you remove the pilot air jet..?

 

Any advice is much appreciated.   :)

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No love from you dudes so I figured I'd experiment a little...

 

I drilled out the pilot air jet using a 1.03mm bit and did sort of a half-ass version of Eddie's mod (ground down the rivet except maybe 1-2mm and spread the fork roughly equivalent to the images and safety wired it).

http://www.thumpertalk.com/topic/793050-how-to-eddies-mod-pics/

 

I set the air screw at 1.5 turns out, opened the choke and it started after two kicks from a dry carb. Not bad!

 

The idle wasn't super smooth, but I rode it up and down the road and it felt great, though it was popping a little on decel. I wondered if it were now lean, so I slowly backed the fuel screw to 3 turns out and the decel popping was gone and it was purring happily. 

 

I'd be content to leave it as is, but it still has some bog. I went back to capping the two fittings on the carb, but the bog seemed a little worse, so I put the hose back, though they're probably not related.

 

Perhaps I'll order a 48 pilot jet so I can get the fuel screw turned in a little more.

 

And now I'm off to investigate squirt timing and duration...

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Your lean troubles sure make me happy. I've got the same bike but with an electric start. :p Sudco Slant Downdraft FCR and a corked up after-market pipe.

I haven't gotten rid of the coast enrichener circuit yet but I experience a lot of popping on decel and a hanging idle. The hanging idle is the most annoying thing.

Anyways, hearing you trying a 48 size pilot jet at least means I'm not the only one, I ordered a 48 and a 50 a couple days ago. Waiting on them now.

 

About your bog, that sounds like AP issues. Mine bogs if you snap it open too, but if your smooth it takes off. My plastic AP lever has an oval shaped hole where the pushrod goes in from wear, if yours is like this as mine is then that means your AP timing is off like mine is. There is no point in the AP shooting in gas when the engine is already stalled, lol. Anyways, after I get my pilot circuit running right then that is my next project.

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Yayyyy, a friend! Hello friend!

 

What is your current pilot air jet and pilot jet size? Being in Ohio, I assume you're close to sea level?

 

The bog, you're right, I could very easily ride it as it is, but it bothers me too much to leave alone. 

 

Regarding Eddie's AP mods, I decided to go back to square one and bent the tab back to normal and removed the safety wire. With the carb removed and connected to the fuel tank to check duration, I get to "one one-thousand, two..." and it's done. Obviously not stopwatch accurate, but definitely not in the 3+ second range. Watching the timing, you can tell it's way off. The squirt should not hit the slide, but be so damned close that you think it's going to. My slide misses the squirt by maybe 3/8", so that's no good. I noticed the slop in that stupid plastic piece too, so I wedged some safety wire above the pushrod, forcing the pushrod to the bottom of the elongated hole, and that's where things start looking good again. 

 

I'm thinking the easiest way to fix the slop issue is to drill out the hole a little bigger, then epoxy a little brass bushing in there. I think something like this could work: http://www.mcmaster.com/#8859k19/=s5l5yp  - The ID is .097", which is 2.46mm and the rod is 2.5mm, just have to stretch it out a little bit. It says the material is also used for rifle casings, so I imagine resizing it .05mm isn't an issue.

 

Stopping the hole elongation is good, but we need a method of adjustment. Maybe an adjustable rod, or maybe file away some of the plastic/metal where they meet to allow the rod to begin its movement lower in the accelerator pump volume, which is where it seems to matter. I can now see the purpose in wiring the two together. 

 

Edit: I don't know what I was thinking, I'm just going to run as much of that safety wire as I can in the gap above where the rod fits in the elongated hole. Will report back on how that works.

Edited by corndog

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Right on, thank you. I may give that needle a shot.

 

I know I'm a little fat on the main, so I'll try that 155 and maybe pick up one size above and below.

 

Coast enrichener has been remove and the two fittings on the carb are connected with hose.

 

Have the 45 pilot installed, but the bike is happy at 3 turns out on the fuel screw, I suspect because the pilot air jet is probably closer to 105 than 100. 

 

Right now it will start first kick cold with the choke on and purrs when the choke is off. So, I'm pretty happy with the jetting, though I feel like the right thing to do is order a proper size 100 pilot air jet, which may allow me to turn in the fuel screw another half turn. 

 

Anyway, back to the bog. I'm having the best results with using safety wire to push the rod to the lowest part of the elongated hole (as shown in the photo) and also using safety wire on the lower part of the plastic arm (not installed in this photo below) per Eddie's mod, but not spreading the metal fork that it mates with. When I spread the fork, it raises the rod the wrong way and causes a delay in the squirt timing, though it seems like something good to do if the squirt were hitting the slide. Right now the bog is the best it's been and though I can still make it bog while riding, I have to open the throttle at full on chicken wing goon speed to make it happen. Next step is to try the 155 main and proper 100 pilot air jet. I'll probably order that needle at the same time, but will see how the bike runs with these jets before installing.

 

HmKqcm2.jpg

Edited by corndog

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I have a 162 main jet. Unfortunately due to our altitude differences we cannot compare out jetting setup real well.

I just removed the carb from my bike again and cleaned it... again.  I just received my 48 and 50 pilot jets in the mail from JETS r us.  I'll try the 50 first... Im pretty lean on the low end.

I'm also doing the CE removal and hopefully that really helps out it's idle and low end. I'm suspicious of it's operation, it appears to bleed air right from the airfilter side of the carb directly into the pilot circuit, you can literally pop the tube off and blow air right out the pilot jet. Which doesn't seem right although I am not a fluid mechanics engineer.

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Yeah, I put the 50 in this morning and took it for a ride. Exactly the same issues.

Hanging idle and a lot of popping on decel.

Assuming it is NOT a vacuum leak, what else could it be?

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Well, I simulated an aircut off situation by kinking the hose that bridges the nipple on the airfilter side of the carb and the "secondary pilot jet" nipple.  Now my bike idles smoothly and doesn't pop like a machine gun on decel, good enough I guess.

Glad to hear corndog's low end issues are fixed.

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Your lean troubles sure make me happy. I've got the same bike but with an electric start. :p Sudco Slant Downdraft FCR and a corked up after-market pipe.

I haven't gotten rid of the coast enrichener circuit yet but I experience a lot of popping on decel and a hanging idle. The hanging idle is the most annoying thing.

Anyways, hearing you trying a 48 size pilot jet at least means I'm not the only one, I ordered a 48 and a 50 a couple days ago. Waiting on them now.

 

About your bog, that sounds like AP issues. Mine bogs if you snap it open too, but if your smooth it takes off. My plastic AP lever has an oval shaped hole where the pushrod goes in from wear, if yours is like this as mine is then that means your AP timing is off like mine is. There is no point in the AP shooting in gas when the engine is already stalled, lol. Anyways, after I get my pilot circuit running right then that is my next project.

 

Does it bog with the insert removed.?.It's an inherit issue with corking an open pipe with fcr fitted, nothing to do with your AP..

What's your current set up..(engine mods ,  carb settings, riding altitude)

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The only thing that happens when I remove the insert is the bike gets louder and the lean low end is worse.

When the plastic AP arm gets all wallowed out like it does it makes the AP squirt late.  My bike handles fine, the engine is inherently a little bit peaky anyways, it needs to rev before it starts to pull in the higher gears.

I just bought the bike this year in March.  It is a third hand bike.  The previous owner is a friend of mine and he let me get it running before I bought it.  We agreed on a price before I started working on it too and he paid for the parts to fix it.  Not much though, only a battery and a fuel petcock.  The previous owner had not ridden it since 2004ish and hadn't had it running since 2008ish.  And the owner before him only had it a year.  It is a very low miles  but had some extreme garage rash when I got it.  

Obviously the carb was literally FULL of something that resembles silly putty.  Considering he left it sit for so long with gas in the tank and in the carb.

Anyways, currently it is a totally stock '00 E model except for the BIG Gun pipe and header.  AND tires.  It also has various other previous owner redneck wiring fix blues going on.  Just yesterday the electric start wouldn't work and I suck at kickstarting it...

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A knowledgeable member of the community such as yourself ought to know exactly how the CE works and what I'm doing when I do the removal mod.  Could you tell me why it has that extra jet on the nipple that bleeds air into the pilot circuit? Also why does it even have the bit in the first part if it has a Pilot air jet in the intake? Is this a secondary pilot airjet?  Does the CE block the airflow from the intake to this secondary pilot air jet when the engine pulls a heavy vacuum?

I was able to get my bike to idle smoothly and not machine gun pop on decel by kinking the hose that bridges the two nipple in the removal mod.  I'm assuming this simulates and "Air cut-off" situation and richens the low end a whole lot.  I know it's a bandaid but at least I'm not frying my bike trying to get it to idle, right?

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The coast enrichener richens the fuel mixture on deceleration to prevent backfiring...

In simple terms it's a band aid to cover up a overly lean pilot circuit...A properly tuned pilot circuit does not need a coast enrichener...

The air delivery for the coast enrichener can be fine tuned by changing the size of the pilot air jet ...Once the CE is removed there is no requirement for air the be supplied...

Edited by Craigo 485sm
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Are there two pilot air jets? 

I just took the coast enrichener apart, it looks like it just blocks off the flow of air to the second pilot air jet when it is under heavy vacuum. Really it is a pretty clever and useful device to save fuel while idling and going slow by keeping the circuit lean when not under heavy load but richening it when it needs to be richened.  It does seem like another thing to go wrong though. Like if that little metal slide valve that is not lubricated starts wearing its just gonna let air right on by and make the thing totally useless. Probably what happened to mine and everybody else who starting having problems with the thing.

Anyways, now my 50 PJ IS too rich, time to take the bike apart again....

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Are you going to be jetting with it removed now? It's too much of an unknown to sort out the jetting with it installed since you won't really know how the wear is affecting the circuit unless you replace it with a new assembly. 

 

The 4strokes.com article tells you to cap the fittings after removing the coast enrichener, but mine idles rough with the fittings capped and runs great with the fittings connected with a short piece of hose. 

 

One of the fittings is also a jet, the smaller one. The fiche calls it "JET, AIR (90)", though I suppose you could infer that it's also a pilot air jet, but I'd avoid calling it that for sake of confusion.    

 

What pilot came in your Sudco carb?

 

Mine now has a 155 main, proper 100 pilot air jet, and a 48 pilot. The fuel screw is now at 2.25 turns out. I still feel the need to work on the bog, but the timing and duration look good, plus I don't think it will be an issue while riding, so I'm not sure if it's worth messing with from here.

.    

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It bleeds air into the pilot circuit If you have the bowl off and blow air into the jet on the fitting you can feel it come out of the pilot jet if you hold your finger under there.

Your bike idles rough when you cap it because it makes your idle circuit too rich.

The K and E model DRZ's are a little peakier than the S and SM model because of the aggressive cams.  There will be bog down low no matter what you do, however it should pull hard right away when revved a little bit.

Your 155 main jet could be lean.  The sidedraft carb comes stock with a 165 I think, at least that is what mine had in it.

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My bike should have a 45 PJ but I put in a 50 while trying to get the pilot circuit figured out.  Now that I have settled on capping off the secondary pilot air jet I'm going to put the 45 back in.

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