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New DRZ400 Big bore Popping?? What gives?

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Hey guys.. Just installed my JE 434 Numara kit and am very happy with the power, awesome.. On decel I have major popping, lots (I know some is normal, but this is alot running on an open pipe.). I don't mind some, what gives here??

I am at sea level:

TT FCR39 (last month)

Fuel mixture turns at 2.5

Pulled pilot (left of bell)

3rd clip (EMS needle) move to 4th tonight, no change.

160mj

434BB w/ hot cams

Full YOSH RS3 stainless

Any advice would be great guys.. Thank you and happy holidays!

DRZRUN.jpg

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Sounds like you're lean ,but your set up is rich , the main jet should be 155-158 with he big bore.

Your dyno looks absolutly funny ,and gives no value missing afr.

Guess it's a typo when you state you have a ems-needle , the tt-kit comes with a emn.

If you do have a ems needle , it's much more lean than the emn ,and could be the issue

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you are a little lean on the pilot. What size is the jet? since you are open 2.5 turns on the screw, you could go up one size at the jet to help out... but your needle may become hard to adjust, and it will be down around 1~1.5 turns.

Does your carb have a coast enricher? Eddie specs his jetting without it... and I removed the one on my carb... but if you have it, you can put in a larger pilot jet if it's active.

Otherwise... you got to live with the popping.

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needs the EMN needle.EMS is way to lean on the straight diameter and that has a slight influence on the pilot circuit.

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you are a little lean on the pilot.

likely not.

What size is the jet?

should be a 45.

since you are open 2.5 turns on the screw, you could go up one size at the jet to help out

only if it needs to be that far open to idle correctly.if hes got it that far open to try and compensate for the lean straight diameter of the needle than no.

but your needle may become hard to adjust,

nothing do with clip position.

and it will be down around 1~1.5 turns.

and still idle with the fuel screw fully in so that you have no control with the fuel screw.not what you want.

Does your carb have a coast enricher?

the fcr-mx kits came with no CE on the carbs.

Eddie specs his jetting without it... and I removed the one on my carb

depends on the particular carb and set up.my settings are not generic to CE removal.

but if you have it, you can put in a larger pilot jet if it's active.

no,you set the pilot circuit via idle reaction to the fuel screw.

Otherwise... you got to live with the popping.

a slight pop decel is normal.

im know you are just trying to help but this stuff just creates more confusion and makes my job harder than it already is and needs to be.

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likely not.

im know you are just trying to help but this stuff just creates more confusion and makes my job harder than it already is and needs to be.

I was... Thanks guys...

Eddie, where do I get the other needle? I only have the other needle (EMR-sitting here in front of me) my TT kit came with? Also, F2 said I may have typo'd the needle, I am going to check right now (take apart).. Don't wanna give wrong info..

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:excuseme: Yes, F2 was correct, it was the EMN needle... Thanks f2.

Now?

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ok,is the head pipe gasket in the cylinder head still there? new?

And both fasteners snug... that socket head cap nut likes to back off, and the socket head cap screw does as well... once they loosen, you start sucking air at the head pipe... just like a missing gasket or damaged one.. Nice call Eddie :excuseme:

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ok,is the head pipe gasket in the cylinder head still there? new?

Not new, and I will check even if those orings are still there. I have new ones on hand. If the original ones are still there, I have replaced the exhaust three times and kept the old ones:bonk:. Your suggestion was also my first assumption, but listening to some buddies they keep saying it's jetting. I should of been checking basics like you are pointing out, but just never got to it yesterday with removing the exhaust and checking. I will work it today.

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Okay Eddie. Checked the exhaust gasket. It is intact and tight.

Yes, this is the same carb and pipe I've been running before the BBk. There was no excessive popping before the BBK. Hmm?

What is the difference between needles you get with the TT FCR kit?

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Yes, I checked it this AM. It is a tight seal...

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[Popping and up and down idle today finally made me take the complete carb off] During the inspection I found out that the Aluminum fuel mixture screw I swapped out for the brass, that the tip broke off in the meter hole and completly blocked. It was a task to get it out. I used several picks and finally had to use a micro drill bit, which I hand turned gently and tried to pick out as much as I could. Nothing else worked besides going that route. The tip was completly locked in there.

Now that I am putting back the brass one till I get a steel one- does the fuel mixture screw tip have to come out the other end inside the carb (tip showing the adjusting out)? This is what I remember with most carbs. If that is the case, it's not happening with this one.:banghead: I do not have another FCR to compare it to. I will wait for info from you guys. "Sad case I tell you, what are the odds of this happening.":banghead:

Any info would help>>> Thanks

DSCN5678-1.jpg

Edited by phynx

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glad you found the issue. I never cared for aluminum metering screws because of wear at the tip... that's why I made mine with a brass shaft. But... I've never had a tip snap off.

did you get it running yet with your stock needle yet to verify the popping is gone?

when I was doing my swap... I don't recall the tip of the OE needle sticking up through the hole in the body... if that is what you meant.

Edited by Dr Honda

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the orifice that the fuel screw seats in is precision and very delicate.

i hate to tell you this but your carb is likely ruined.

this happens all the time with those junk aluminum screws. this is why i tell people not to use them.

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Thanks Dr. Honda...

Yea Eddie, that's what I figured and very sad.. I just want to confirm that the FM scew does not go through all the way out of the meter hole? I will be putting it back today and running it.

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