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2008 DRZ400Sm surging,hesitation, at 1/4 throttle

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Hello TTers. 

 

I need some advice and help with ideas and things to check and look for on this problem please. 

 

I have a 2008 DRZ400SM in the workshop at the moment and is has an issue with hesitation when cruising at 100 kph. Also if the throttle is held at 1/4 in netural it pops and has a slight back fire.

I understand these bike run better with the 3x3 mod and a jet kit and I also am attempting to understand more about the leaning effects.

It is running the BSR Mikinui CV carb.  

He is what has been done to it. 

It has the 3x3 mod done and it has a DJ kit in it from what I can understand from the jets inside, not the JD jet kit. It has the original fuel mix screw, 155 main jet, 22.5 pilot jet,165 air jet and a new needle in it with 5 clip positions. The clip is currently on the second groove from the top. It has an aftermarket exhaust and K&N filter. The pair valve has been disconnected and the pair valve exhaust return pipe has been blocked off. It still has the solenoid connected to the carb and the solenoid vacuum pipe to the the top of the carb.

The bikes was recently taken into a local dealership for it's 12000 k service. The client got it back and now it is running rough. Prior to this it was running fine according to the client. 

The local dealership is well known for crappy workmanship. 

Here is what I have found after it's service, The HT lead from the coil was not secured into the plug cap correctly, as in it fell out of the plug cap......Not even screwed in. The dealership replaced the plug with a CR8E plug and it was loose not even torqued properly. I sorted these things out hoping it woulf fix the issue but it did not. The K&N filter does not really fit well and I am planning on sealing the base of the filter with sponge rubber so axcess air does come in from under the filter, as I am picking this could make it run lean.

The original fuel screw position was three turns out from lightly seated. I tried it at 3.5 - 4 - 4.5 - and 5 turns out and the best was 4.5 turns out but still really rough running. I marked the throttle with tape to check the throttle position while carring out the checked and it is right on 1/4 throttle or just a little over at 100 kph.

The valve clearance was checked according to the client as part of the 12,000 k service but this I am yet to inspect my self.

I have removed the carb and check all the carb parameters according the Clymer manual and I have cheked the TPS function. I have run it without TPS connected........No difference. I have chec TPS resistance and it is operating at 4.98 Ohms closed and 3.277 ohms open but not quite fully open.

I cleaned the carb out and all the connecting orifices and venturies with carb cleaner and compressed air. There was a little sediment in the bowl but not much. The float level is at 13 mm. I have chanaged the needle clip position to the 3rd groove. I have not yet installed the carb to see if it has made a difference.

 

If anyone has any advice or help for things I can check please let me know. I have been researching on TT, and other Forums and I understand it is a common complaint..........But I am all ears as I only know what I know and any and all comments are welcome. 

 

Here are some pics of the carb and the bike below. 

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Here are some pics. 

 

Q1.jpg

 

Q2.jpg

 

Q3.jpg

 

Q4.jpg

 

Q5.jpg

 

Q6.jpg

 

Q7.jpg

 

Q8.jpg

 

 

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More pics

 

Q9.jpg

 

Q10.jpg

 

Q11.jpg

 

Q12.jpg

 

Q13.jpg

 

Q14.jpg

 

Q15.jpg

 

Q16.jpg

 

Q17.jpg

 

 

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no expert here, but its rough going behind someone that may have not known what they were doing .. i'd guess youre on the right track with the carb, the only thing is this carb has alot of little parts in it that can get misplaced if youre not familiar with it .. it would be a nightmare for sure if someone else aced it up .. anyway  i think the going setup is 160 on the mainjet and 4 grooves down on the 'blue' needle for a bike with a pipe .. pilot is 25 i think for the stock fuel screw ..

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That 3x3 looks a little on the big side.  Fix your air filter then try a 25pj - 3 turns out - leave the needle alone - 160mj.  If that doesen't work try clip # 6.  If it's getting better try a 165mj.  Sometimes jetting just doesen't go by the book (unfortunatley).  Hell, my mods are similar to yours and before I got an FCR39 I ended up with :

 

JD Jet Kit

175mj

Blue #5

25pj

Stock fuel crew

2.875 turns out,

 

I know someone will trump my post but just keep trying different suggestions till it works.  :banghead:

Edited by billdirt1
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That 3x3 looks a little on the big side.  Try a 25pj - 3 turns out - leave the needle alone - 160mj.  If that doesen't work try clip # 6.

 

The 3x3 is a little big. It is more like 3x4. The interesting thing is that this bike was fine before it was taken to the dealership......Or so the client says. But everyones idea of fine can differ. 

Thanks for the advice. I will look into it and trythe jetting. It is a Dynojet kit and not a James deans kit.

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no expert here, but its rough going behind someone that may have not known what they were doing .. i'd guess youre on the right track with the carb, the only thing is this carb has alot of little parts in it that can get misplaced if youre not familiar with it .. it would be a nightmare for sure if someone else aced it up .. anyway  i think the going setup is 160 on the mainjet and 4 grooves down on the 'blue' needle for a bike with a pipe .. pilot is 25 i think for the stock fuel screw ..

Thanks Cowpie but I think you are referring to a JD kit and this is a Dyno jet kit. 

Thanks for the help. 

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That 3x3 looks a little on the big side.  Fix your air filter then try a 25pj - 3 turns out - leave the needle alone - 160mj.  If that doesen't work try clip # 6.  If it's getting better try a 165mj.  Sometimes jetting just doesen't go by the book (unfortunatley).  Hell, my mods are similar to yours and before I got an FCR39 I ended up with :

 

JD Jet Kit

175mj

Blue #5

25pj

Stock fuel crew

2.875 turns out,

 

I know someone will trump my post but just keep trying different suggestions till it works.  :banghead:

 

Yes I am beginning to understand what you are saying by trial and error. Looks like it will have to be the case for this type of carb and situation. Just out of interest.....what did the FCR carb cost?

Edited by GEOF
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Check the pilot jet again.

Thanks.....The pilot jet is all clean and clear. Nice hole and no dirt or debri. Looks good. 

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The spark plug is a nice light tan colour and not foulded or showing signs of running rich. 

All the spacers are in the correct position and accounted for on the needle.

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The 3x3 is a little big. It is more like 3x4. The interesting thing is that this bike was fine before it was taken to the dealership......Or so the client says. But everyones idea of fine can differ. 

Thanks for the advice. I will look into it and trythe jetting. It is a Dynojet kit and not a James deans kit.

 

I was digging up old posts one day and I remember Eddie saying.....For every additional sq. in. of air box opening to go up a main jet size or 2.  So take into consideration that your 3x3 is not 9 sq. in., more like 12 sq.in.  :thinking:

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Yes I am beginning to understand what you are saying by trial and error. Looks like it will have to be the case for this type of carb and situation. Just out of interest.....what did the FCR carb cost?

$600  :devil:

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I was digging up old posts one day and I remember Eddie saying.....For every additional sq. in. of air box opening to go up a main jet size or 2.  So take into consideration that your 3x3 is not 9 sq. in., more like 12 sq.in.  :thinking:

 

Thanks........IT still baffles me because what you are saying is correct and I can understad that but running okay before like this and now not?????? :thinking:  :confused:

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Thanks........IT still baffles me because what you are saying is correct and I can understad that but running okay before like this and now not?????? :thinking:  :confused:

Yeah.....I know the feeling, I have a hard time figuring out my own stuff out sometimes.  Just keep on looking it over to make sure those knuckle-heads didn't leave anything else loose.  Then get back to the jetting.  :doh:

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One thing I guess to consider with this bike is that I am in New Zealand and the dyno jet instruction are for US models only. 

I have read that it is better to put in a 135 air jet for our imported models and remove the 165 air jet. 

Any thoughts?

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One thing I guess to consider with this bike is that I am in New Zealand and the dyno jet instruction are for US models only. 

I have read that it is better to put in a 135 air jet for our imported models and remove the 165 air jet. 

Any thoughts?

Best advise I was given here was - is it better or worse with the airbox door off - have you tried this ? better off means your rich at whatever throttle setting observed.

 

+1 on the suggestions that you fix the air leak at the air filter, besides jetting issues if the owner rides gravel roads and we have a lot in NZ then perfect sealing air filter is obviously super important, I run a twin air and its a perfect fit.

 

Are you sure the service didn't include the poor fitting filter issue you describe ?

 

I have not yet identified the needle in mine, it has five clips pos which I originally though was stock - wrong.. and it is not red or blue, a local dealer told me that the yosh RS3 was shipped with a needle ? I don't know anything about that needle or if that is what is in my bike but I do have a RS3 open pipe and a 5 clip needle in the stock Mikuni BSR carb, runs sweet as for me with #25 pilot at 2 turns out (not extended screw) and a 157.5 main with a 3x3, cams now HC stage 2, stock cams wanted #160main. I have never looked at the air jet.. changing to a big carb soon.

Edited by mike500
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Best advise I was given here was - is it better or worse with the airbox door off - have you tried this ? better off means your rich at whatever throttle setting observed.

 

+1 on the suggestions that you fix the air leak at the air filter, besides jetting issues if the owner rides gravel roads and we have a lot in NZ then perfect sealing air filter is obviously super important, I run a twin air and its a perfect fit.

 

Are you sure the service didn't include the poor fitting filter issue you describe ?

 

I have not yet identified the needle in mine, it has five clips pos which I originally though was stock - wrong.. and it is not red or blue, a local dealer told me that the yosh RS3 was shipped with a needle ? I don't know anything about that needle or if that is what is in my bike but I do have a RS3 open pipe and a 5 clip needle in the stock Mikuni BSR carb, runs sweet as for me with #25 pilot at 2 turns out (not extended screw) and a 157.5 main with a 3x3, cams now HC stage 2, stock cams wanted #160main. I have never looked at the air jet.. changing to a big carb soon

 

Okay I will try the Air box suggestion. I have not done this yet. 

So you are saying that on standard cams you ran better at 160 main with a 25 pilot. I have an extended fuel screw on order from the states to try and i understand these are better with the 22.5 pilot and the standard screw is better with the 25 pilot jet. I would also like to get some jets from a supplier here in NZ. Can you recommend anyone?? Only supplier I can find is Motoone or Motozone. 

Just out of interest what part of NZ are you in??

Also were you experiencing similar problems before you made the changes?

 

And poor fitting air filter could have been the trouble but I am yet to establish.

 

Oh and thanks for chiming in. And any other ideas will be greatly welcomed.

Edited by GEOF

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Okay I will try the Air box suggestion. I have not done this yet. 

So you are saying that on standard cams you ran better at 160 main with a 25 pilot. I have an extended fuel screw on order from the states to try and i understand these are better with the 22.5 pilot and the standard screw is better with the 25 pilot jet. I would also like to get some jets from a supplier here in NZ. Can you recommend anyone?? Only supplier I can find is Motoone or Motozone. 

Just out of interest what part of NZ are you in??

Also were you experiencing similar problems before you made the changes?

 

And poor fitting air filter could have been the trouble but I am yet to establish.

 

Oh and thanks for chiming in. And any other ideas will be greatly welcomed.

Airbox door tells you a lot... when I needed this idea and it was suggested by the more experienced DRZ people around here it was like pennies from heaven yes really, it was night an day and the bike ran so well with the airbox door off I wanted to leave it like that but we do have fords around here and that would never work.

 

I am in the south island near the foothills of the alps mid Canterbury, the gravel roads here need awesome air filters with no leaks, plenty grease on the intake seal.

 

My bike has never exhibited  the 1/4 throttle surging/hesitation your looking at. mine had a 3/4-full throttle issue and it was sorted by a main jet change down one size. as its now winter here that could be another size by summer.

 

Leaking air filter sounds bad - after fixing that as to the jetting on what sounds like the needle at 1/4 throttle your probably going to need help from those with experience on that for the stock carby.

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GEOF

ASK the Client which DJ jet kit.? stage 1 or 2 (DJ3109 or DJ3110)....settings are different for each jet kit

AS it's surging on clip 2 I would take a guess that you have the stage 1 kit....

if so ,the needle needs to be on clip 4 and the main jet a 142.5 with open pipe....

Stage 2 settings are clip 2 and 160 main jet

 

Common to both kits are the pilot circuit settings

22.5 pilot jet with extended fuel screw or 25 pilot jet with stock fuel screw

2.75 turns

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