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3 x 3 jetting help please? (pilot/fuel screw)

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Hi all. ive just done the 3 x 3 mod as follwows.....

4 x 2.25 hole

DJ needle + spring

4.5 clip ( surging problem)

142.5 main

25 pilot

Full CRD exhaust

CRD air filter

Problem is i cant get the mixture set right. At 2.5 turns on the fuel screw the bike tends to stall very easily but as i turn the fuel screw out (now at 3.5 turns) revving off idle or on decel becomes very sluggish and delayed. On the stand it becomes more and more sluggish with repeated revs, with black smoke and resulting in a massive backfire complete with very impressive flames!

Im out of ideas really because turning the fuel screw has problems in each direction. Is this delayed sluggish response rich or lean? im guessing rich due to the fireworks but as i said, inwards makes the bike stall alot? Ive never seen it here but would it be worth trying only 1 turn out to see what happens? Its just i dont want to be running lean too much more incase it does damage.

Thanks guys, any help would be a godsend

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First, a drz won't run so lean as to damage the engine according to a well known mechanic around here. That is the case with most modern four strokes.

It sounds as if you are rich because of the bog. What is the 4.5 clip??? When my bike is rich it will not go as low on the rpm's without cutting out. When it is right I can just about come to a complete stop in first or second and then accellerate cleanly away (before I installed my rekluse of course).

I have a fcr on my bike and set it a little differently than most, I just go in (leaner) until it starts to cut out and then back out just til it smooths out. That seems to work well for me at least. I and the few other people that have ridden my bike seem to think that the jetting is really good, FWIW bronco is one of those people. I think that some bikes/carbs are just plain less picky about jetting, mine was almost,,,no it was, unridable when stock. It would bog and die every time I tried to lift the front wheel. Once I jetted it to burned's specs it got a lot better. Then it was just a matter of being able to tell burned what it was doing, not as easy as it sounds, and following his directions to fine tune it. Not sure if he realizes it or not but he was able to teach me what to look for and which direction to go with which needle/jet, also not as easy as it sounds 🙂, so now I feel comfortable knowing what to change and which way. Of course I still go back and reconfirm it with the man 🙂

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Thanks 10 guy. Sorry, with 4.5 clip i meant, circlip on the fourth notch from top with a shim underneath. This seems to help the surging im getting with steady throttle at 74mph. Its still surging a bit though.

When i got the bike from new it would stall all the time the second i opened the throttle from idle. The mechanic at the dealers said these bikes are allways lean from the factory and that he had richened up the fuel screw a bit. (UK by the way)

So i cant understand why i turn out the fuel screw and its too rich and bogs and backfires. And i turn it in and it stalls as it did when new but theres no in the middle where it doesent do either?

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((((3.5 out on 25 pilot and 4.5 clip would be horable on my bike with 142.5main, similar to what your are saying,))))

What gearing you running? 15/44 at 75 mph is just at half throttle, lower gearing at half or slightly more.

Maybe you try going back to 2 3'4 out on fuel screw 4th clip and go 1 larger on the main like 145

Just a thought , cause no reason for your bike to behave with black flames and such, oh and new plug also

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Tarka, I don't know where in the UK you are.

But I am running the following settings, as the Burned set up was too rich for me,

3x3 and stock, bit drilled exhaust

22.5 pilot jet

136 D/J main jet

needle is 3 1/2 down (3rd clip & washer)

fuel screw is 3 turns out

Bike is running very well, top speed is the same as it was with the 140 m/j

but the pick up is faultless, no flat spots or surging, and it will lift the f/wheel in 1st or 2nd, at will on stock gearing.

Neil. 🙂

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Thanks for that Neil. The bike actually rides pretty dam good. Pulls very strong. Much better than stock. I think im close but with limmited knowledge, miles off! So are we all ageeing that its running rich on the pilot circuit?? Hence the black smoke and fancy flames??

If so would it be an idea to go back to the 22.5 pilot as it seems its low down that has all the problems??

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Thanks for that Neil. The bike actually rides pretty dam good. Pulls very strong. Much better than stock. I think im close but with limmited knowledge, miles off! So are we all ageeing that its running rich on the pilot circuit?? Hence the black smoke and fancy flames??

If so would it be an idea to go back to the 22.5 pilot as it seems its low down that has all the problems??

Yes go back to the stock 22.5 it worked for me, it was what made me start to experiment with the rest of the jetting. Mine ran pretty good on Burned's jetting, and pulled strong as well, but it was not perfect. I have now probably given up about 10 % of what I gained, but the bike is now much more ride-able, or tractable if you like. Before I re-jetted, 2 weeks or so ago when it was very hot and muggy, and the bike was so rich it was blowing black smoke every time I got on the gas, it was also only doing

70 miles to reserve, now it averages 97 miles to reserve.

Neil.

🙂

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What bothers me is that this mod is made out to be very simple and for some probably is if they get lucky with the jetting. But realisticly if your not lucky its a total nightmare. For 1 if you havent had a lot of experience with this sort of thing you might think your bike is running perfect when its actually not. Secondly, getting hold of different jets isnt easy as my nearest shop is 25miles away and doesnt stock all sizes, plus they arnt all that cheap either. Also pulling the carb constantly is a real pain. And im still going round in circles???

But on the plus side, like i said the bike has much more power now, just not running right.

Im gonna try turning the fuel screw out 1 turn from fully closed. It should be much leaner and if things start to improve then back to the 22.5 it is. Does this sound sensible??

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Yes and No, I fiddled with the fuel screw when I had the 25 pilot jet in, and it made a small difference. I found that when I went back to the 22.5 pilot jet it all became much easier to work out, mainly because the fuel screw mad a bigger difference. Have you replaced the float chamber screws with Cap-Heads. If you have, you can with care (not to knock the float setting out)

change the jets without removing the carb, you can also easily adjust the needle with the carb in situ.

As a generality if you have a problem when asking for power (coughing and sputtering) it is rich, and if the problem is when cruising on a steady throttle (surging or dying away) it is to lean.

Neil.

PS. where in the UK are you ? Scratch that, you already told me, got a brain like a sieve.

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HHHmmm. thanks again. Thats what im thinking, rich on the pilot circuit and lean on the main. Whats thrown me off is when i only had a CRD tailpipe as a mod i had the fuel screw 8 TURNS OUT!! to get it running right but generally it made no difference. Whith the extra air of the 3x3 e.t.c and having had it at 8 turns i thought a 25 pilot would definately be needed but this semms waaay to rich. This is where all my confusion lies........

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p.s your being a great help by the way......

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HHHmmm. thanks again. Thats what im thinking, rich on the pilot circuit and lean on the main. Whats thrown me off is when i only had a CRD tailpipe as a mod i had the fuel screw 8 TURNS OUT!! to get it running right but generally it made no difference. Whith the extra air of the 3x3 e.t.c and having had it at 8 turns i thought a 25 pilot would definately be needed but this semms waaay to rich. This is where all my confusion lies........

A CRD can on it's own, would make so little difference to the mixture, you would get away with no re-jetting. I hate to say this , but you have a problem in the carb, probably a bit of dirt in the pilot circuit.

Strip and clean the carb and start again.

I would be very surprised if a 142.5 main jet is lean, I run a 136 !! and that is very slightly rich, but should be OK when the temps drop.

Neil.

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Its only lean at 75 steady throttle (surging) which gets worse as the engine warms up. But the shim helped a bit. Other than that its great all the way up. Its just when giving it a rev between gears or from idle thats really bad, (spluttery e.t.c)

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Its only lean at 75 steady throttle (surging) which gets worse as the engine warms up. But the shim helped a bit. Other than that its great all the way up. Its just when giving it a rev between gears or from idle thats really bad, (spluttery e.t.c)

Go with the smaller Pilot Jet, Good Luck 🙂

Neil.

Have you seen this.

http://66.47.68.116/tech/carbtune,CV,high_rpm_engines.html

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Thanks mate, great help. Let you know how it goes.

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Hi all. ive just done the 3 x 3 mod as follwows.....

4 x 2.25 hole

DJ needle + spring

4.5 clip ( surging problem)

142.5 main

25 pilot

Full CRD exhaust

CRD air filter

Problem is i cant get the mixture set right. At 2.5 turns on the fuel screw the bike tends to stall very easily but as i turn the fuel screw out (now at 3.5 turns) revving off idle or on decel becomes very sluggish and delayed. On the stand it becomes more and more sluggish with repeated revs, with black smoke and resulting in a massive backfire complete with very impressive flames!

Im out of ideas really because turning the fuel screw has problems in each direction. Is this delayed sluggish response rich or lean? im guessing rich due to the fireworks but as i said, inwards makes the bike stall alot? Ive never seen it here but would it be worth trying only 1 turn out to see what happens? Its just i dont want to be running lean too much more incase it does damage.

Thanks guys, any help would be a godsend

Well, 10guy and Neil have you headed on the right road. As to the back-fires...check your exhaust system for leaks. And, it sounds like you're way rich...Good luck 🙂

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Thanks Ross. Keep you all posted. Bet ya cant wait. lol

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As in another thread, I have also been chasing a mid throttle surging. After trying most combinations I have ended up with 140mj, 27.5pj, 5.5 clip, 2 turns on idle screw. Yes it is over rich in the low mid range, but pulls hard through the rev range, and tops out about 85mph with 14/47 gears (might go faster, but would take too long to gain much more). Still has a slight surge at 60mph, but is much better. Off-idle bog was fixed with the float level correction.

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Thanks guys. I was gonna try turning the fuel screw almost all the way in to see if things improve. If so then back to the 22.5 pilot. But, as Neil probably knows, the weather is effin crap so might not get the chance tonite.

Does the plan sound good though?

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