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FCR jetting help for DRZ SM. YFZ quad carb

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Hey all, Following on from this thread (FCR CUSTOM YFZ450) Which was more about the modifications and fitment of the carb I'm now after some specific help with jetting the carb.

I understand info might be a bit niche with a YFZ carb but A good base line to start from would be good.

I've done a fair amount of reading on jetteing over the past few weeks and what I've found is info mainly on MX and slant jetting for the DRZ.

I think I can disregard the slant jetting, am I right in saying this is wrong for the MX carbs? of which the YFZ carb is, just without the removable bell?

 

As a starting point I had this jetting

main jet 155

pilot jet 45

starter jet 90

main air jet??? 70

EMN needle on the 3rd clip down from the top.

 

I'm not to sure if I'm calling the main air jet the right name? its the one circled in red in this image. From what I've read about mx jetting it seems people are running 200 air jets?

is that right and why is mine so low?

iSYjmDX.jpg

The bike is an SM with E cams, 3x3, open muffler but stock headers.

 

The bike started not needing any choke at all and I had to set the idle quite high for it to tick over, other than that it ran well at WOT it pulled hard in all gears when giving it lots of throttle, however there was a lot of popping on declaration.

Also when I tired adjusting the idle mixture screw there was no change in rpm and when I wound it fully in the idle would get much faster, the bike does not bog and stall at all.

 

So at this point I guessed that the pilot circuit was too rich and possibly the main jet is a bit rich too.

So today I fitted this jetting 

main 150

pilot 40

starter jet 70

main air jet??? 70

EMN needle 3rd clip from top.

 

From cold the bike needed half choke to start, once warn it starts bang on the button with no choke.

The bike seems to be running pretty well on these jets, the popping on declaration has gone and it still pulls at WOT perhaps a little less aggressively. However when trying to adjust the idle mixture screw it sill does not differ no matter how many turns in/out I put it, and the idle still gets faster when its screwed full in. The rpm increases but not as much as with the original jetting.

 

So does this mean I need to go even smaller on the pilot air jet? It seems a 40 is small from what I've read. OR do I need to move the clip on the needle up a notch?

I was thinking to try a 38 pilot next with a 152 main. do I need a bigger main air jet also or a smaller starter jet?

 

I've also been searching for a NCYR needle as I've read this is a little leaner that the EMN but I'm not sure thats my problem, its at 0 -1/4 throttle that needs fixing I think?

I also dont have the funds at the moment to splash out on a JD KIT, can only seem to find them in America and postage is a lot.

 

Any and all help is much appreciated. :thumbsup:

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the 70 circled in red is the pilot air jet

standard setting is 45 fuel / 100 air ,  with slant body 38 fuel / 73 fuel worked fine too.

take a picture of your pilot jet,  the older type can work with emN. the newer type does not

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Ah okay cheers for clearing up what jet that is.

When you say 45 fuel are you referring to the pilot jet? and 100 to the pilot air jet?

Like I say I originally had a 45 pilot jet in there but I felt it was running too rich, but is this because I have a 70 pilot air jet?

I'll order a 100 pilot air jet if thats the base starting point for the MX carb.

 

This is the pilot jet. the EMN needle came stock with the carb. 

ZjUSBFS.jpg

 

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Been doing a bit more reading and it seems mx carbs bought before 2012 people recommended to remove the PAJ all together?

I know my carb is between 2005-08. 

I was going to order a 100 PAJ but maybe I should try removing it first?

or just drill my 70 PAJ out to 1mm as a cheaper option?

 

Any and all help is appreciated I really want to get this sorted.

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So better off replacing the 70 PAJ with a 100.

ok I'll get one ordered. 

There seems to be mixed opinion on removing the PAJ. I read that carbs bought before a certain date from TT it was recommended to remove it, cant remember the exact date but around 2012-13.

Carbs bought after then it was said to leave it in as the carb design changed.

I'm not sure if this just applies for carbs bought from TT however?

 

I've read a few post from people saying they had removed it and the bike ran well.

 

I'm of the opinion its there for a reason, its just getting the right size. 

As my idle mixture screw is unresponsive with the 70 PAJ hopefully a 100 will sort it but I also read even a 100 was not enough which is why people removed them?

 

Edited by -=fusion=-

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2 hours ago, ohiodrz400sm said:

Removing the pilot is bad information perpetuated over and over. Put it in

Amen, Brother..................

Removing the PAJ is a bandaid attempt at fixing the poor AP response of the FCR slant.

Keihin didn't tap a hole for a pilot air jet that wasn't necessary.

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thanks for the replies guys :thumbsup:

 

Just been talking to some guys over the FB DRZ page about why the idle increases when the mixture screw is turned all the way in.

One suggested that my idle is set to high giving me false readings.

He suggested that I turn the mixture screw all the way in until it bottoms out at which point lower the idle screw until the bike bogs and stalls. 

Next set the idle 1/8 a turn back up and set the mixture screw 1/2 turn out.

 

If the bike bogs out when the mixture screw is turned all the way back in this means the idle is set correctly.

 

From there I'd need to change the pilot jet to get the recommended 1 1/2 -2 turns out on the mixture screw.

 

Hope that made sense :jawdrop:

 

The way I'm thinking at the moment is the idle is set high as the PAJ is too small. I'm hoping a 100 PAJ with a 40 PJ and 70 starter will get me some where close.

What do you guys think?

Edited by -=fusion=-

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you need 100 air jet, 45 fuel jet and a leaner needle.

100 + 40 + emN may work , but still on the rich side.  

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I'm waiting to hear back on a NCYR needle from a uk company.  I can only see to find them from America.

I can get hold of a NCYU needle from a RMX450 which I've read is similar???

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ncyu is similar to ncyr , only much leaner from 0 to 1/4 throttle. maybe too lean even with 100 + 45

ncyr is available all over the word, it's an oem part.  you will probably need 100 + 40/42 fuel.

i'm sure that earlier derestricted rmx450 had  ncyr + 100 + 42.  an  R or S needle was  very common with 42/45  into derestricted japanese oem fcr mx.....

 

part numbers for ncyr,  from a post by bumtarder:

Honda 16203-MEN-671

Kawasaki 16187-0190

Yamaha 5TA-14916-YR-00

Suzuki 13383-35G40

 

 

Edited by 30x26

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Cheers for the info.

The company I e-mailed doesn't stock them so I'd have to go to a main dealer.

Kawasaki is closest to me so i'll give them a try.

 

On the plus side I'm getting pretty quick at removing the carb :)

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any official dealer can order it from europe or japan. faster  and safer ,  because you do not have the risk of a single little and fragile shipping.

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Next Update.

Kawasaki can get hold of the NCYR needle for around 20 quid.

After searching for ages online for the right PAJ for this carb Which is a M4.5 x 0.75 x 13mm Which is totally different from the TT FCR PAJ.

It would be the most expensive jet to get hold of, after shipping it comes in around 15 quid.

So to save a bit of money I thought I'd try drilling the stock 70 PAJ to 1mm. I know its not the Best Idea to drill jets but I didnt have much to lose, I'm going to get a new jet any ways and this gives me a better clue at what size i need.

 

So As I understand Keihin jet sizes equal to mm so a 100 PAJ is 1mm, 110 PAJ is 1.1mm etc?? I dont know if this is 100% accurate but It's what Ive read after a lot of searching.

 

So I drilled the stock 70 PAJ to 1mm, Which should give me roughly a 100 PAJ. It's not going to be bang on but near enough.

 

After fitting the 100PAJ and not changing any thing else I started the bike and noticed straight away that the idle was too high, A good 2 1/2 - 3 turns to high.

 

After warming the bike up I turned the fuel mixture screw all the way in but the bike still increases in RPM with it fully in???

With the fuel screw all the way in and the bike idling faster I lowered the idle screw until the bike bogged and died. 

I then set the fuel screw out 1/4 a turn out

And turned the idle screw up 1/2 a turn.

 

This got the bike idling pretty well, after blipping the throttle it hangs ever so slightly, if I turn the fuel screw out more this helps but the idle gets worse.

 

So at the moment I have the fuel screw 1/4 a turn out which is obviously not enough but I'm already running a 40 PJ.

However the bike idles faster with the fuel screw fully in so maybe I need to go to a 38 PJ.

 

This got me thinking about the PAJ again and the reason people suggested removing it. 

The largest PAJ I can find for this carb is 115. 

Is it possible people removed the  PAJ because they just couldn't get one large enough. 

I noticed that with the larger PAJ my idle was higher so I'm more inclined to increase the size of the PAJ before getting a smaller PJ

What do you guys think?

I can drill out the PAJ to 1.5mm again nothing to lose as I can order a 115 if its too much.

 

Other than the fuel mixture screw being too far in the bike seems to be running well.

It pulls hard in all gears, its much more powerful, gets up to an indicated 85-90 and is still pulling though the speed wobble does nothing for me at those speeds :)

Its got a very slight amount of decel pop but I think its well with in limits, am I right in saying this is a rich condition? I'd prefer to be running on the rich side than lean.

 

Just seems the idle - 1/8 throttle is not quite right.

Just to recap I have 

E-cams

3x3

open exhaust with stock headers.

150 main

40 pilot jet

70 starter

100 pilot air jet (drilled)

the main air jet is fixed and non changeable at I think 200 but again I'm not 100% sure on this, thats just what I've read.

 

Any more help is really appreciated.

Thanks.

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2 hours ago, -=fusion=- said:

Next Update.

Kawasaki can get hold of the NCYR needle for around 20 quid.

So As I understand Keihin jet sizes equal to mm so a 100 PAJ is 1mm, 110 PAJ is 1.1mm etc?? I dont know if this is 100% accurate but It's what Ive read after a lot of searching.

So I drilled the stock 70 PAJ to 1mm, Which should give me roughly a 100 PAJ. It's not going to be bang on but near enough.

So at the moment I have the fuel screw 1/4 a turn out which is obviously not enough but I'm already running a 40 PJ.

However the bike idles faster with the fuel screw fully in so maybe I need to go to a 38 PJ.

This got me thinking about the PAJ again and the reason people suggested removing it. 

The largest PAJ I can find for this carb is 115. 

Is it possible people removed the  PAJ because they just couldn't get one large enough. 

I noticed that with the larger PAJ my idle was higher so I'm more inclined to increase the size of the PAJ before getting a smaller PJ

What do you guys think?

I can drill out the PAJ to 1.5mm again nothing to lose as I can order a 115 if its too much.

Other than the fuel mixture screw being too far in the bike seems to be running well.

It pulls hard in all gears, its much more powerful, gets up to an indicated 85-90 and is still pulling though the speed wobble does nothing for me at those speeds :)

Its got a very slight amount of decel pop but I think its well with in limits, am I right in saying this is a rich condition? I'd prefer to be running on the rich side than lean.

 

Just seems the idle - 1/8 throttle is not quite right.

Just to recap I have 

E-cams

3x3

open exhaust with stock headers.

150 main

40 pilot jet

70 starter

100 pilot air jet (drilled)

the main air jet is fixed and non changeable at I think 200 but again I'm not 100% sure on this, thats just what I've read.

 

Any more help is really appreciated.

Thanks.

Wow, 20 quid for a needle seems a little steep. Can you order from FrankMX! in the Netherlands?

I wouldn't hesitate to drill the PAJ. I believe as the PAJ size goes up, the PJ needs to also if you maintain the same mixture, so you may be able to combat the fuel screw being in all the way by boring the PAJ again.

Popping on decel is a lean condition and nothing to worry about unless your getting 'stack fire' ('backfiring' through the carb).

Most people don't mess with the main air jet. A tiny tach goes a long way with tuning, especially setting idle speed. 1,800rpm sounds a little quick.

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Thanks for the reply Bermudacat.

No stack back firing that I can tell, just a little pop here and there on decel.

 

I'll try and drill the PAJ out a little bigger first and see how that goes before spending more on jets.

Around £20 seems to be the average for the NCYR needle from a dealership. I cant find them any where else. Frank mx does not stock them.

 

I'm not sure if I need it though, after 1/4 throttle she seems to run great.

Though I would like to see if there is a difference with it to the EMN.

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cheers for the links. I'd seen that needle before but after shipping it comes in around the same price as the NCYR.

I notice thats a ERK, not a NYCR? 

How does it compare the the NCYR? as frank mx has it for 15 quid.

http://www.ebay.co.uk/itm/OCEKR-throttle-needle-Keihin-FCR-carburetor-OC-OB-EKR-MX-DRZ-400-KTM-LC4-SMR-/190754425918?hash=item2c69d98c3e:m:mi75ljQYcfFN-PJ7fpnLaUw

 

I've also come across that chart but was unsure how to use it for 4 digit needles like the NYCR?

Edited by -=fusion=-

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this weeks update.

 

I drilled the PAJ out to 1.5mm

With every thing else left as it was the bike needed choke to start and finally the idle mixture screw is just barely stalling the engine when turned all the way in.

This happens when the idle is set to normal, if I increase the RPM to around 1800 the bike will not stall with the mixture screw all the way in.

 

When I first started the bike the idle was noticeably higher than before, so I'm guessing opening up the PAJ to 1.5mm has leaned out the pilot circuit.

I think If i open up the PAJ any more I might as well remove it. 1.5mm looks pretty big.

 

However I'm now getting crazy deceleration popping, happening in all gears as soon as I come off the throttle.

I always thought this was a rich condition but it was mentioned that its a lean condition, could someone explain how this is as I thought it was unburnt fuel igniting in the exhaust?

 

Also I dont know if its just me getting used to the added power but it didnt feel as punchy today as it has before. (too lean maybe?)

 

The way I see it now is I think I have to go down 1 size in pilot jet to a 38, this should get the idle mixture screw to respond better. however if the pilot circuit is too lean causing the decel pop does this not mean going to a 38 pilot jet is going to make it worse? 

 

I was thinking of going up to a 152 main jet, or should I just go down to the 4th clip on the needle to richen the pilot a bit?

 

Any help getting me to understand how all this adds up would be great, I think I'm pretty close now.

cheers.

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