I would like to do a review of the differences between the Stock and DJ Needles.
Note: Both needles are 63mm long.
I am going to compare the stock needle in the 5th groove to the
DJ in the 3rd groove(from top down)

Stock DIA. DJ DIA.
IDLE: .0985 .096

The DJ is richer at idle. But you only have to turn out the pilot screw 2-2 ½ turns.
We have all found to reduce backfiring at a high speed slow down and for best offline performance, the pilot screw had to be turned out 4 – 6 turns and also a larger
pilot jet for the stock needle.

For all purposes, when used as above, they produced the same results.


Normal Driving Range: This covers the next 8 mm of travel
.089 .0895
As you can see both needles are delivering a very similar fuel path.


Accelerating Mid Range: This covers the next 10 mm of travel.
.077 .071
As you can see the DJ needle becomes very aggressive at this point.
This is a very critical stage. This is when you are accelerating and everything most
work together. On a cv carb THIS IS YOUR ACCELERATOR PUMP, it works great, but your slide needs to start to open quickly to supply the required air. If you do not open quickly you will become very rich and your motor will stumble.
Note for clshortt - Your jetting on your first dyno run was only rich in mid and that is why you could not rev. You needed more air. You leaned out your main to get to top range and then was too lean. Jetting is a combination of fuel and balanced air per rpm range. Your motor needed more air, not less fuel.

This is where the DJ needle is the winner. You just have to give your motor more air,
and then throttle response and torque take a good jump.


Top Range: This covers the last 12mm of travel
.0435 .048

This is where the stock needle is very aggressive. It tapers .0028 per mm compared to the
DJ at .002 per mm. For drag only, where the rpm’s are kept in the upper range, for that application maybe the best. Now you see why MrHP recommends mikuni 145 to 150 jetting. Main size jetting is both size of main jet and size of needle at wide open.

If you perform the slide/spring mods that I have proposed, you will be accelerating thru this range quickly and thus find no difference between the stock and DJ needles.


Overview:
The DS is a 2 spark plug motor that by design is a mid range torque monster. Give it a better air/fuel curve in mid range and it really comes to life.

The original aftermarket cdi only raised the rev limter. If they were to have an aggressive timing curve, the stock needle just could not supply the needed fuel. Now that the new cdi’s have changed there timing curves, if you use the DJ needle you can possibly raise the needle more and get even a bigger torque hit. More fuel also needs more air.

I hope this overview is interesting and helps you understand alittle more of how I came to recommend the Carb Mods.

 

Bombsaint,
Do not buy an aftermarket cdi till the motor starts better.
1. Put dielectic grease on battry connections and reg/rectifier connections.
2. Keep your idle 1400-1500rpm. Butterfly covers low speed orifices and causes motor to load up if it doesn't start right away. When you release starter a large amount of voltage goes to the spark plugs and because motor is turniing very slow, it will cause the motor to turn backwards. Poor starter takes a hit.
3. The early reg/rectifiers were marginal. I've tried newer and not any better results. I am presently running a ProCom reg/rec and it has been great. I bought it for better starting not the advertised HP gains, I have not noticed any gains. Some guys have purchased the units off BMW F650, they are expensive.
4. Your higher compression is only a little more load. How old is your battery?
The newer machines have made major improvments in their electical system.
What type of spark plugs are you using?

To set the rpm's without tach:
When the motor is warm and you shift into gear-
If goes into gear very smoothly and no sounds or jerking - Rpm's too low
If goes into gear and makes a light clunk sound - Rpm's just right
If goes into gear and makes a hard clank sound and motor/quad moves - Rpm's too high

Try steps 1 & 2 and let us know.

 

Oldmanracing,
Thanks again for all the information.
After all this talk I am considering the Ron Woods stage one kit. What are your thoughts about it. I will probobly not use the pipe as I already have the big gun installed.
Does anyone know what mods are done to the Carb that Ron Woods is selling?
Carl.

 

oldman racing.... thanks for the tips. the battery is like 6 months old. it is a good yuasa battery. i will mess with the idle to see if this keeps happening.

 

Oldmanracing, I work Swing shift at a specialty metals plant and sometimes work over. Sometimes my posts get alittle incoherent as I stay up too late. With 2 younguns at home, this is my quiet time.
If you want to see something that will make you cry, watch guys chopping up perfectly good Titanium tubing for recycle all evening long. I think about all the bike and buggy frames that could have been built.
I'll try your tips, I was always interested in drilling the slide but never completely understood it. I gave up tuning my DS because I guessed I was near the limit of what I could do stock and I was beating everyone I raced (stock also). I did have a few other things I intended trying like the spare header I picked up and was going to try a power bomb type modification. Also, I wanted to try lengthening the intake to see if I could pick up midrange power.
Have you port matched the rubber carb intake connector? With a little sanding and carving it can really match alot better with a difference I could feel.

 

great stuff OMR if I had my stock carb in I would be trying these mods for sure. you know what would be nice is if you could link the butterfly to the slide. make it a direct action and not rely on air flow. I dont know if its possible but its a thought.

Can the moderators make this topic and the last air box lid on/off topic a sticky? this topic comes up so often and w/ all the newbies coming in this could be a big help.

 

Oldmanracing, I am trying to go step by step and make all/most of your recommended changes to the stock carb. I finally have my needle situated, and I have a few more questions:

1) I read about your modified snorkels made from the bigger tubing. I understand everything you said until the very end where you say "run new snorkels along side snorkel to carb, where old tubing ran, and install small end into the airbox". Now, I understand that one end of the tubing is going into the airbox adapter, but where does the other end (the end that will be collecting the air) go? Back under the gas tank cover like the stock snorkels are routed? I need a bit of clarification, or maybe a picture.

2) I happen to have an extra throttle slide. I went ahead and drilled two extra .125 holes at the bottom of it and opened up the existing holes to that size as well. I ended up doing a lousy job on the two new holes and they aren't "drilled in the same relationship" to the first two holes like you suggest. They new holes are off just a little bit, and not symmetrical to the original holes. Will using this slide cause me any problems, or will it give me the same advantages?

As usual, any help you can give me would be greatly appreciated.

 

On the way to work, will be brief

1) Did you buy the sump pump hosing? If not, then just remove air tubing from adapter, turn adapter around and put tubing into larger end(wd helps) and reinstall with small end of adapter going into the airbox. From inlet in measure back 9 inches and cut the tubing.
Tubing is oriented in the same location as before, just now is 9 inches shorter. Better location to draw more air.

2) As long as the center webbing in the slide was only slightly damaged, you will be fine.
The center webbing is the webbing that the needle assembly is contained in. If a crack goes to the top,
the grey plunger will not be snug to hold the needle assembly down.

 

1) So the inlet end of the tubing (whether I use the existing or buy the sump pump hose) will no longer go under the gas tank cover, but will be nine inches shorter, so I assume I will need to zip tie it to the frame?

2) There are no cracks or any other damage to the slide or the webbing inside the slide. I just drilled the new holes a bit haphazardly. I guess it will be fine, so I am looking forward to trying that slide instead of the one with two smaller holes.


Thanks for you input.

 

The tubing will lie between frame and snorkel to carb. No zip ties needed.

I will be also looking to see how things turn out.
If everything is followed, I wish I was there to see the look on your face.

It is always nice to have a good running quad, but it is awesome when they run great
and the smile on your face tells it all.

My son is mister complainer, things have got to be perfect.
He went to his first MX race last saturday and came in third.
2 450r's beat him. He was very excited cause course was tight.
If course would of been alittle more open he would of been a contender.
People could not believe that a stock DS could slide and roost that well.
My reward is just hearing success stories.
Lets hope yours is next.