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Should I replace factory jets?

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Hey guys, out of curiosity what are your opinions on stock jets vs aftermarket (jd jetting). I was also considering a 3*3 mod on the airbox. Are both of these things worth the time/money for the performance? 

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JD kit and 3x3 mod about the cheapest and easiest thing you can do to boost the power on your Bike.  So I'd say yes!!!

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JD uses genuine jets, only the needle is proprietary. The needles and engineering/testing time is what you're paying for with the jet kit. Unfortunately, short of modifying the needle yourself(if you know what your doing and feel like experimenting), there isn't really a better replacement needle than the JD.

 

The original dirt only DRZ that the S and SM models are based off originally produced approximately 40 horsepower. The S/SM make approximately 32 horsepower. 1 of the changes Suzuki made to the S/SM was to make the airbox intake hole much smaller. The "3x3 mod" simply opens the airbox hole to the original dimension.

 

The other changes between the engines include,

 

Smaller diameter exhaust pipe

 

Less compression 11.3:1 vs 12.2:1

 

Less lift and duration on the camshafts

 

Lower rev limiter (10k vs 10.5)

 

Smaller, less performance orientated carburator ( 36mm Mikuni BSR vs Keihin 39mm FCR)

 

 

 

 

 

 

 

 

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10 hours ago, dannyrg85 said:

Hey guys, out of curiosity what are your opinions on stock jets vs aftermarket (jd jetting). I was also considering a 3*3 mod on the airbox. Are both of these things worth the time/money for the performance? 

 

A jet kit is pretty much required on these bikes if you want them running at their best. Mine ran like crap from the factory.

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Seems like the majority use JD and Dynojet. You need to look at Factory Pro. 25 years ago I used Dynojet on more than a few bikes. I'm a perfectionist. They work, but the results are inconsistent. Then, about 1999, I tried Factory Pro on my 98 Vmax. The R&D that goes into the Factory Pro kit is night and day compared to Dynojet. Mark S. tunes the bikes right on his Dyno and designs the needles exactly for the application. DJ is known to use needles for other kits as long as they are "close". FP jet kits are Mikuni jets and not the crap DJ jets. Factory Pro makes the first Eddie Current Dyno by the way.

I haven't used any jet kit in over 10 years. I just bought my '17 SM. First person I called was Marc at FP. He didn't answer but the tech was thoroughly knowledgeable of this particular kit. Did you know that the factory 142.5 is WAY to big even for a pipe? I dug for an all stock dyno sheet with AFR and it completely backed this up. I do not agree with the 3x3 mod. But, that's my View from thoroughly understanding CV carb operation.

So, many years of doing this and I get told what main jet to use. Most of the time people are clueless and just guess. I know FP is close. But my Innovate LM-2 wideband doesn't lie. I know when someone BS's me. 

I just put my kit in. I cannot believe what a difference it made. Then I installed the RS2 pipe. Even more. AND, I didn't get my O2 boss welded in yet to really determine what main to use. It now will lift the front end rolling into it. NO popping the clutch. I haven't even tweaked it yet.

Ill know exactly what main jet to use on Sunday. I had to order a SD card(non HD) version that's compatible with the LM-2. Otherwise I cant log any data....

BUY A FACTORY PRO KIT! 

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Seems like the majority use JD and Dynojet. You need to look at Factory Pro. 25 years ago I used Dynojet on more than a few bikes. I'm a perfectionist. They work, but the results are inconsistent. Then, about 1999, I tried Factory Pro on my 98 Vmax. The R&D that goes into the Factory Pro kit is night and day compared to Dynojet. Mark S. tunes the bikes right on his Dyno and designs the needles exactly for the application. DJ is known to use needles for other kits as long as they are "close". FP jet kits are Mikuni jets and not the crap DJ jets. Factory Pro makes the first Eddie Current Dyno by the way.
I haven't used any jet kit in over 10 years. I just bought my '17 SM. First person I called was Marc at FP. He didn't answer but the tech was thoroughly knowledgeable of this particular kit. Did you know that the factory 142.5 is WAY to big even for a pipe? I dug for an all stock dyno sheet with AFR and it completely backed this up. I do not agree with the 3x3 mod. But, that's my View from thoroughly understanding CV carb operation.
So, many years of doing this and I get told what main jet to use. Most of the time people are clueless and just guess. I know FP is close. But my Innovate LM-2 wideband doesn't lie. I know when someone BS's me. 
I just put my kit in. I cannot believe what a difference it made. Then I installed the RS2 pipe. Even more. AND, I didn't get my O2 boss welded in yet to really determine what main to use. It now will lift the front end rolling into it. NO popping the clutch. I haven't even tweaked it yet.
Ill know exactly what main jet to use on Sunday. I had to order a SD card(non HD) version that's compatible with the LM-2. Otherwise I cant log any data....
BUY A FACTORY PRO KIT! 

What don't you agree about the 3x3 mod. ? I know carb venting needs to be improved to an area where there is more "still" air. And the biggest problem seems to be the lean needle (fat section/small throttle opennings)
Interesting you talk about the rich main cuz as i go leaner on the main with my stock pipe, stock carb 434. It keeps running better and i now get around 110 miles from full to reserve with stock tank.
Interested to hear your results with the wideband sensor.

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Just installed my JD Kit with the 155 main and the red needle and I gotta say it feels good. Feels like its finally opening up. Also cut the 3*3 in the airbox. 

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Morning,

Still waiting for my SD card to arrive. Its out for delivery. I have everything hooked up. Boss was professionally welded in. Damn weld looks way better than anything Yoshimura did. I agree with all that you said. Yes, it seems that the factory deliberately tunes these "non-emission" friendly bikes lean from idle to 3/4 throttle with fat needles and an anemic pilot fuel jet. Then, they over compensate with a MASSIVE main jet to make it run. Its fun playing with Carbs. My wide band shows I'm at 14.7 at idle with a p25 and 2.75 turns out. That's were I got the fastest idle. It starts easily now with NO choke.

As for the 3x3, it's not for me. I don't agree with it. It will take a lot of typing to explain it. This mod will work just fine on a FCR or conventional slide. Messing with an air box with Constant Velocity can get really tricky. Again, from experience, screwing up brand new bikes in the 80's and 90's, I learned from my dumb mistakes. I had to take a set of CV's off a brand new Nighthawk 750 to a machinist to fix the plugs I extracted by mistake. My father watched me screw it up when he was visiting. Long time ago. He always told me "why cant you just leave it alone?" He beat my a$$ 40 years ago when I took apart his lawnmower. Probably the most tricky bike to tune was the Gen 1 Yamaha Vmax. You messed with that airbox, opening it up or "Removing the Y", you'd better be ready to deal with pain for awhile. The CV's did NOT like change. 

OK, this CV BSR is way more forgiving to change. I honestly don't know why. I'm thinking the bleed circuit was moved closer to the venturi so that its more responsive to throttle movement. I once opened up my airbox on my 87 ZL1000 Eliminator. It absolutely KILLED my motor. Again, on a FJ1200 with poor results. So, what happens is you MUST have a pressure differential between the venturi and bell.(engine side/air box side) As you open the throttle, you pull vacuum across a port that bleeds to the CV chamber. When you open an airbox, the pressure difference is less. This not only slows slide response, but affects the carbs ability to pull fuel from the bowl.  So, we OVER compensate to fix this mistake with massive main jets. OK, we can increase the CV air jet ONLY if it has one or we can change the slide spring rate. That's a partial fix.

There really is  a fine balance for air volume, pressure and maintaining velocity. Leave pulse timing out of this discussion. So, I believe a more subtle air box opening will reap higher benefits. Again, this carb is WAY more forgiving from all that I've seen in the past. I cannot tell you how many times I've been on the dyno and proved this with street bikes. I eventually stopped making this mistake. Dyno Jet Stage 3 Kits and Stage 7 kits ALL tried to compensate for this. Yeah, it kinda worked but never was it perfect. So, when I see a bone stock dyno of this DRZ bike with an AFR of 10:1, with a 142.5 main, it got me thinking. The guy at Factory Pro was DEAD CORRECT. He gave me the jets in the kit that I wanted, not what I was told to use. There results showed most power with a m122.5 or a m125 with just the snorkel removed. AND, I believe them 100%. 

Attached are some pics or my test setup. I cannot get RPM. the inductive pickup doesn't seem to work. Pulse duration is too narrow I think. So, Ill have to order the analog cable and use the negative side of the coil or something. I may just buy the Dyna CDI with the tach output. Again, I really just bought this bike to tinker with it...

IMG_3403.JPG

IMG_3402.JPG

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Attached is a capture on my 2017 DRZ400SM. I've been playing all day. This clearly proved Factory Pro is spot on. And that's why I've always trusted them. I took an educated guess on the main size based on experience. Its 88 degrees out. 300ft above sea level. Pressure is 30.05. Was a good guess. Id leave the m135 main in. Tad rich but when the temps drop to 60 and 50, I wont be lean. AFR swing at start was lessened by slide spring rate adjustments. Needle is safe but a touch lean. You don't need monster main jets.  Air box is opened up to about twice that of the stock hole/snorkle removed. I'm about 215 lbs. I usually cannot hit the rev limiter in 5th. Sometimes. There is only 260 miles on my bike. Barely broken in. 

Does anyone have the OEM service manual? I cant seem to find one.

2017 DRZ400SM 135m 4th Gear WOT to redline.jpg

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Does anyone have the OEM service manual? I cant seem to find one.

598772b9cd3df_2017DRZ400SM135m4thGearWOTtoredline.jpg.21867ecde81509f68e2289cf78b2f6e0.jpg

 

It's my experience the commonly recommended jetting on here is a bit rich. What are your modifications?

 

What are you looking for in the manual?

They are online if you search. I don't want to post the link.

 

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Looking for the entire manual for reference. Can you PM me?

As for additions, I just have the Factory Pro jet kit and the Yoshimura RS-2 full system.  Airbox was slightly modified. That's it for now.

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On the DR-Z... the 3x3 mod is simply removing any restriction to airflow before the carburetor.  Your CV is being operated by engine vacuum and the only feed back to the air intake side of the carburetor, engine wise, is the crankcase breather vent line and that is just compression blow-by pulses that are negligible.  So... by doing the 3x3 mod you have done nothing but remove restriction on the air intake side which was done not only for emissions but noise mitigation.  If the carb is tuned right, the diaphragm is still going to operate perfectly fine as engine load/vacuum dictates.  If you've opened up the exhaust, same as on any engine, you should be opening up the intake side as well. On a dyno, you will see that all you are accomplishing is gaining a little bit on your top end and possibly sacrificing torque on the low end. The DR-Z's gearing really dictates needing more low end torque, especially on technical trails.  That's what you are hurting by restricting air intake, but opening exhaust.   I live atop a mountain with a 5 mile, steep grade highway.  Simply opening up the air box and jetting the carb right made a world of difference in top speed as well as giving me low end throttle response that was severely lacking from the factory. 

Not sure what you are getting at with the pressure differentials between the air box/engine side of the carb.  You can rejet a CV carb with nothing more than a cone pulling air in without any filter at all and they still have more than enough pressure differential to run just fine.  There are a ton of cafe racer builds out there running this very setup and have crisp and snappy throttle response across the full RPM range. 

On mine - the only mod has been on the intake side.  The stock main jet leaned me out badly at WOT, so I needed to move up to the 155 on the BSR36.  This was not a result of my diaphragm in the carb not pulling the needle all the way out, it was a main jet that was too small.  Point is... I think this carb from the factory was actually a bit much for the snorkeled air intake, hence the improved performance realized by so many of us doing the 3x3 mod. 

I'll probably get all kinds of flack for this, but a properly tuned carburetor should also need some level of choke even in warm weather if only for a few moments as the combustion chamber warms up.  Lacking this is a sign of running a tad rich on your primary.  However, this engine is very forgiving of this condition.

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Well,

Like I mentioned earlier, there's way more to this theory that I can possibly type. I am providing actual data that proves this. Ya gotta understand that vendors will give you what you want no matter how accurate the product is. Sure, it may work. Just because most lean to the left, doesn't mean I have to without valid data. Again,  I don't know what experience you have tuning CV type carbs on various applications and not just this bike. I don't do this for a living. Its a hobby. Quite passionate hobby since before my teens. Long long time. I struggled for years thinking I knew enough till a friend, Pro drag racer and Thermo Mechanical Engineer said to me: "You really think you know more than the engineers that designed your bike? Stop fighting it."

So, I read some books. Internet wasn't that popular yet. That pressure differential I'm talking about? Its the definition of vacuum. The air box is designed a specific size to maintain this pressure difference(Vacuum). When you crack it open, that design goes out the window. The pulses I'm talking about are INTAKE VALVE. You get negative pulse when the valves slams shut. The GEN 1 Vmax uses this theory in its V-Boost Design. 

So, using a large main compensates for the pressure difference loss. That's a fact. My LM2, at slow throttle opening, PROVED that the slide operated slower over time with the box opened.  In perspective, don't ya think a 150 - 160 main is quite large for a carb that's only 36mm? That threw a red flag for me. But, you won't pay it any mind unless you have tuned 50 other bikes. Street and Drag Racing. I had 41mm Keihin FCR's from Sudco on my small tire drag bike. Not the easiest carb to tune from scratch. So, tuning is getting the best average for the rider. Were do you want the power? Peak numbers don't necessarily mean a fun bike to ride. 

There's so much more to this. Its an interesting read. I actually read some really interesting articles in Popular Mechanics. Well, anyways, use this info or not. Up to you. I spent most of my Sunday, family not happy, tweaking this bike's Carb. Now, my perspective it street riding and not offroad. I'm lost there. But, opening the air box slightly, slide spring adjustments, decreased main size, increased pilot and narrower needle, this little 400 pulls quite hard. Its going to work very very well when I pull out of the tight turns when riding the twisties in W. Va..

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The DRZ shares the same basic motor with the earlier Z400 quads, BSR and all. Countless bikes and quads have been uncorked at this point, there isn't much mystery left. 3x3(bike) or open lid (quad) with appropriate jetting for location results in better throttle response and better overall power, not just peak. That's all relative of course because no matter how well it is set up the CV carb still a restriction. I couldn't stand it and ordered a jet kit and pipe the 1st week I owned my bike. I ditched the stock carb for an Edlebrock after only a couple months. I have since moved on to a FCR. Compared to a stock bike, the throttle response difference is like a MX bike vs a lawn mower.

 

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The DRZ shares the same basic motor with the earlier Z400 quads, BSR and all. Countless bikes and quads have been uncorked at this point, there isn't much mystery left. 3x3(bike) or open lid (quad) with appropriate jetting for location results in better throttle response and better overall power, not just peak. That's all relative of course because no matter how well it is set up the CV carb still a restriction. I couldn't stand it and ordered a jet kit and pipe the 1st week I owned my bike. I ditched the stock carb for an Edlebrock after only a couple months. I have since moved on to a FCR. Compared to a stock bike, the throttle response difference is like a MX bike vs a lawn mower.
 
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Hey...... I kind of like my lawn mower.lol Sure you get more throttle responce with the fcr, but you'll pay for it with decreased mileage. That may not be a concern for many bit if you adventure tour these bikes, the longer fuel range can be vital. Just recently got 63miles per US gallon on a trip with some some 70 mph hiway, lots of FSR's up to7,000ft and a little trails. Could an fcr even get close to that?
Back to OP original question, most here would say YES it's worth it, even if you plan on upgrading carb cams and other power adders in the future and especially if good mileage is a concern, but as vmax says, keep the main on the smaller side.

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Hey...... I kind of like my lawn mower.lol Sure you get more throttle responce with the fcr, but you'll pay for it with decreased mileage. That may not be a concern for many bit if you adventure tour these bikes, the longer fuel range can be vital. Just recently got 63miles per US gallon on a trip with some some 70 mph hiway, lots of FSR's up to7,000ft and a little trails. Could an fcr even get close to that?
Back to OP original question, most here would say YES it's worth it, even if you plan on upgrading carb cams and other power adders in the future and especially if good mileage is a concern, but as vmax says, keep the main on the smaller side.

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There's no way I could match that mileage. My tank on holds 1.8 gallons. 60 miles and I'm looking for a fuel station to top it back off.

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