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DRZ400SM deceleration sounds?

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Hi all,

Ive read a million posts about decel sounds (rich/lean) and am a bit confused as people have different opinions - I was wondering if anyone could let me know what they think on my specific set up.

DRZ400SM 2012
3x3 mod,
Full MRD Pro Comp with spark arrestor
Twin air filter
JD Jet Kit - Blue needle 3rd from top, 160, 25 and stock screw 2.5 turns from closed.
sea level and about 25-30 degrees Celsius (77-86F)

On quick gear changes there is a small pop when i roll off the throttle quick, and when I roll off the throttle slowly and decel there is a rumble/burble (which sounds nice).

Note: On the new MRD pipe, at the mid pipe joint there is a small amount of black build up after a couple hours of riding - I havent used any sealer as the instructions say not to, although Dave did say it is fine to use a little bit if needed.

I've read that black on the pipe means rich and rumble/burble on decel means lean - I am a bit confused here.

Does this seem fine? or should I adjust the fuel screw or change needle colour to red? (I do have a Kientech Fuel Screw but want to avoid drilling if possible).

If you need photos or a video of the decel I can post those.

Any advice would be greatly appreciated.

Thanks

 

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Well, i was experiencing a full set of woes, idle was stuttering and not at all influenced by turning the idle screw even all the way,

difficult start with rpms fluctuating wildly, and a lot of decel popping. Someone advised to try removing the coast enricher spring. You won't see a happier man and a happier bike anywhere soon, after weeks of confusion and pain the bike runs just marvelous. I'll be smoking a cigar this evening.

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Hi Michael,

Thanks for your advice! - I just finished reading on removing the coast enriching spring and stumbled upon suggestions to turn down the idle speed or readjust the throttle cables. I will try adjusting those two before removing anything.

I will take a video tonight of starting the bike, going through gears (small pop) and then on decel (rumble/burble).

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Jack , once you put an open pipe on you will hear all of the exhaust noises , these include popping on decel and yes the occasional pop on the upchange , aswell as induction roar now you have the 3x3 . If you still have the mikuni , you dont have a coast enrichener per say . The mikuni has a pair valve and a solenoide attatched to it . If you didnt do it during your 3x3 , get rid of them . The pair valve bleeds air into the exhaust port to pass emission controls and the solenoide allows air into the diaphram chamber of the carb , stopping it from getting full throttle in lower gears . Where in OZ do you live ? , you would only want to use the red needle for humid or high altitude conditions . If you have the quiet insert in your MRD , I think the advice is to go a bit smaller in your main jet ( 155 ) , but overall your jetting seems good for aussie conditions , greg

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Hi all,

Ive read a million posts about decel sounds (rich/lean) and am a bit confused as people have different opinions - I was wondering if anyone could let me know what they think on my specific set up.

DRZ400SM 2012

3x3 mod,

Full MRD Pro Comp with spark arrestor

Twin air filter

JD Jet Kit - Blue needle 3rd from top, 160, 25 and stock screw 2.5 turns from closed.

sea level and about 25-30 degrees Celsius (77-86F)

On quick gear changes there is a small pop when i roll off the throttle quick, and when I roll off the throttle slowly and decel there is a rumble/burble (which sounds nice).

Note: On the new MRD pipe, at the mid pipe joint there is a small amount of black build up after a couple hours of riding - I havent used any sealer as the instructions say not to, although Dave did say it is fine to use a little bit if needed.

I've read that black on the pipe means rich and rumble/burble on decel means lean - I am a bit confused here.

Does this seem fine? or should I adjust the fuel screw or change needle colour to red? (I do have a Kientech Fuel Screw but want to avoid drilling if possible).

If you need photos or a video of the decel I can post those.

Any advice would be greatly appreciated.

Thanks

 

 

Use the blue needle , clip 4

155 main jet with insert....160 without insert..

Popping is completely normal , try turning out the fuel screw to 2.75 turns to help calm the pop if it's annoying you...

With unleaded fuels the exhaust colour is not a true indicator of how the bike is running....

Edited by Craigo 485sm

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Hello,

Thanks for all the replies.

Here is a video of acceleration and deceleration - 

... mind the quality, I just needed a quick upload, its the sound that counts!

I can't upload an image of the small black soot build up around the mid join pipe, its minimal, maybe some high temp silicon would fix that up - I just thought that might be an indicator of a rich mixture.

In order:

Greg: I thought it was normal to hear noises :) with the bigger/straight pipe, I just wanted to make sure they were good rather than bad. I have the factory Mikuni carb and have not taken out the coast enricher or the solenoid, I was hoping to fix (if needed) with just air fuel mixture, needles, jets. I live in Sydney, so not too far away comes the hot/humid weather, and I am certain that I will need the red needle 3rd clip then. No quiet insert, just the spark arrestor.

 

Craigo: I am 2.5 turns out from completely closed, should i go .25 of a turn from there? or is it 2.75 turns from where the engine begin die out with the fuel screw screwed in (say 200-300 RPM)? It isn't annoying at all, I do like the sound, I just wanted to make sure I wasnt doing damage by leaving it the way it was.

 

Backyard Hack: I was thinking of those mods, but then thought again as most of the speed limits after 50, 60, 70km/h with traffic lights and speed cameras everywhere - I'd be getting to the next red light much quicker and more expensively.

Thanks.

 

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Jack , you cannot tell if your bike is lean or rich , by looking at the colour of the exhaust . The new fuels that we have nowadays burn one colour , black . It is just carbon and once there is enough in the join it should seal itself . Do yourself a favour and read the master 3x3 post . It lists how to remove the pair valve and disable and remove the solenoide , there is no coast enrichiner on the mikuni , that is the slant body keihin . With the mixture screw , warm up the engine , screw in the screw till it stumbles then screw it out till it stumbles , then go back to the halfway point , all done , greg

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Craigo: I am 2.5 turns out from completely closed, should i go .25 of a turn from there? or is it 2.75 turns from where the engine begin die out with the fuel screw screwed in (say 200-300 RPM)? It isn't annoying at all, I do like the sound, I just wanted to make sure I wasnt doing damage by leaving it the way it was.

 

 all screw settings are taken from closed position

there was nothing I heard in that clip to be alarmed about...

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