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Hey guys, I recently decided to do the 3x3 mod on my 19 drz400sm. For the first couple of days I ran the new jetting setup without cutting a hole in my air box. It was fine, but felt relatively stock still (power wise). I went ahead and cut the 3x3 in and then the cold start issues occurred.

 

When I pull the choke out completely it’ll start right up as usual. But after a couple second the bike will begin to idle slower, then die. I’m constantly having to readjust the idle to compensate for lack of.. Air..? Fuel..? After getting past the cold starts the bike runs flawlessly. It leaves me to wonder if the bike is running too rich or lean. So I’ve been light on the throttle. Any tips for deciphering a rich or lean condition? Thanks
 

Im located in Long Beach, California so I’m at sea level sometimes around 300ft above, current temp is around 60-85F. My bike has Stock pipe and carb. 
 

jd jet kit specs

Main jet - 155

Pilot - 25

Blue needle at 3rd clip 

Fuel screw 2.5 turns out 

 

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3X3 will have zero effect on idle or cold start. It only makes a difference about 3/4 throttle. Have you, after firing up., pushed the choke button in 1/2 way ? It has three positions, off, half and full.

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2 minutes ago, William1 said:

3X3 will have zero effect on idle or cold start. It only makes a difference about 3/4 throttle. Have you, after firing up., pushed the choke button in 1/2 way ? It has three positions, off, half and full.

Yes I’ve tried 1/2 position and it’s the same story 😕

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If... all is right with your carb, cold start needs choke. Choke adds fuel and air, providing a rich, fast idle. Half choke is simply a little less fuel and a little less air. If your bike runs fine once warmed then you base jetting is fine (pilot, fuel screw, needle and main). The only thing that is affecting things is the starter jet and choke knob.

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2 minutes ago, William1 said:

If... all is right with your carb, cold start needs choke. Choke adds fuel and air, providing a rich, fast idle. Half choke is simply a little less fuel and a little less air. If your bike runs fine once warmed then you base jetting is fine (pilot, fuel screw, needle and main). The only thing that is affecting things is the starter jet and choke knob.

Would you know what the stock jetting for the starter? Or is that something to be left alone. Also, how can I tell if my bike is running too rich or lean? My top end is substantially less. I used to top out at 105 now I’m doing about 87. I’m not constantly pinning it but the bike does sound like it’s lacking something on the top. It’s not sputtering, backfiring, or bogging really. 

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Starter jet rarely matters, several sizes up or down often makes little difference except in  extreme climates. Is it possible you put the wrong jets in the main and starter?

I doubt you every hit 105 with a stock DRZ. 87 is very good. You can try it with the air box door removed to see if you are too rich or tape a little of the 3X3 over to see it you are too lean.

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1 minute ago, William1 said:

Starter jet rarely matters, several sizes up or down often makes little difference except in  extreme climates. Is it possible you put the wrong jets in the main and starter?

I doubt you every hit 105 with a stock DRZ. 87 is very good. You can try it with the air box door removed to see if you are too rich or tape a little of the 3X3 over to see it you are too lean.

I’ll give that a shot. I have a extended fuel needle coming in today. Hopefully that’ll help too. I’ll post bike on any new findings. Thanks 

 

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Make sure your petcock vacuum line is properly connected. It does sound like you have a lean idle mixture.

Yes. 2.5 turns on the mixture screw is only a suggested setting. I would say your idle mixture is not optimised.

When the extended screw is installed, reset your mixture.

Check you have reassembled your carb correctly too. I notice many on this forum have not done this correctly and go on to post that this was the problem.

I have had a 400SM for 15 years. 60,000+ miles. With a 25 pilot it ran optimally at only a 1/8 turn out !

I reverted to the 22.5 with 3+3/4 turns out. It's a balancing act.

It is indeed possible to hit 105mph indicated on the speedo. It's probably out nearly 10% though. 😉 My highest is 107, with a 60mph tail wind !

At WOT on the road, pull the choke out and see if the power and speed improve. If they do, put in a main jet up to 160, 165. If it stutters with choke on, you are probably jetted ok. I run a 165 for top end on the standard carb. I change to a 145 for long distance economy.

You DO NOT need to run a jet kit.

My standard needle is shimmed/raised 1mm and fuel screw liberated and set at 3.75 turns with a 145 main. It has served me well for all these years, right from standard, to big bore and big cams. If all else fails, try those settings. ( I also run an FCR40 and TM42, with those big cams and piston....  but that's another story )

 

 

Edited by Tony Wyp
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5 hours ago, Tony Wyp said:

Make sure your petcock vacuum line is properly connected. It does sound like you have a lean idle mixture.

Yes. 2.5 turns on the mixture screw is only a suggested setting. I would say your idle mixture is not optimised.

When the extended screw is installed, reset your mixture.

Check you have reassembled your carb correctly too. I notice many on this forum have not done this correctly and go on to post that this was the problem.

I have had a 400SM for 15 years. 60,000+ miles. With a 25 pilot it ran optimally at only a 1/8 turn out !

I reverted to the 22.5 with 3+3/4 turns out. It's a balancing act.

It is indeed possible to hit 105mph indicated on the speedo. It's probably out nearly 10% though. 😉 My highest is 107, with a 60mph tail wind !

At WOT on the road, pull the choke out and see if the power and speed improve. If they do, put in a main jet up to 160, 165. If it stutters with choke on, you are probably jetted ok. I run a 165 for top end on the standard carb. I change to a 145 for long distance economy.

You DO NOT need to run a jet kit.

My standard needle is shimmed/raised 1mm and fuel screw liberated and set at 3.75 turns with a 145 main. It has served me well for all these years, right from standard, to big bore and big cams. If all else fails, try those settings. ( I also run an FCR40 and TM42, with those big cams and piston....  but that's another story )

 

 

I’ll try this out tomorrow evening! I’ll let you know how everything goes, thank you!

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I have installed a 25 pilot in my carb just now.

I will put it on the 400 and see if I can emulate your problem.

Its 10.30pm here, so will try tomorrow 🙂

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Well Ive just been in the garage tinkering.

Temperature here is 10 deg C/50 deg F.

It will not run on choke with the 25 pilot jet for more than 10 seconds. Changing the mixture made no real difference. Nor did covering airbox etc.

I replaced the 22.5 pilot, 3.5 turns and it runs on choke as long as you like.

Go figure ?

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23 minutes ago, Tony Wyp said:

Well Ive just been in the garage tinkering.

Temperature here is 10 deg C/50 deg F.

It will not run on choke with the 25 pilot jet for more than 10 seconds. Changing the mixture made no real difference. Nor did covering airbox etc.

I replaced the 22.5 pilot, 3.5 turns and it runs on choke as long as you like.

Go figure ?

I never got around to doing it earlier lol, my air fuel screw flew off the bike and I was pissed off all day hah. I have a new one coming in today, should be here around 3 or 4 pm. 
 

Before the incident I did try the full choke at full throttle method, it didnt seem like bike felt any different to be honest.
 

I’m currently at 155 main/25 pilot, should I try 155/22.5, 160/25? Or 160/22.5?

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Put in the 22.5 at 3.5 turns and begin testing main jets.

If still no good, put in the standard needle, raised 1mm and test again.

Also try smaller jets than 155 too, right down to your original jet.

My carb, in the specs I have...22.5, 1mm needle  145 main, suit my bike from standard cams and bore, thru to 440cc and 2 x DRZ400E B cams, 9.3mm and 243 degrees.

I only need to change the main as desired for the purpose.

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1 minute ago, Tony Wyp said:

Put in the 22.5 at 3.5 turns and begin testing main jets.

If still no good, put in the standard needle, raised 1mm and test again.

Also try smaller jets than 155 too, right down to your original jet.

My carb, in the specs I have...22.5, 1mm needle  145 main, suit my bike from standard cams and bore, thru to 440cc and 2 x DRZ400E B cams, 9.3mm and 243 degrees.

I only need to change the main as desired for the purpose.

Will give it a go, thank you! It’s 3:35 am and I’m ready to hit the hay 😂

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Here are some pics of the FCR40 and TM42 on my bike.

Both add more power, respectively.

20200620_183623.jpg

20200612_222152.jpg

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1 minute ago, Tony Wyp said:

Here are some pics of the FCR40 and TM42 on my bike.

Both add more power, respectively.

20200620_183623.jpg

20200612_222152.jpg

My mind says go big or go home, but my 3 year unlimited mile warranty says no 😪 They allowed me to rejet the carb, I’m not sure how they’d feel about the big hole I cut in the air box though haha! 

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No worries. I ran my bike for 13 years with standard carb, opened up standard muffler and airbox holes. 

They go extremely well in this spec !

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Just now, Tony Wyp said:

No worries. I ran my bike for 13 years with standard carb, opened up standard muffler and airbox holes. 

They go extremely well in this spec !

I have considered going with fcr39mm, but I couldn’t justify spending, 600+ on one. I’ll have to keep in touch to see about cheaper alternatives. Im fairly new to the Drz game, been building foxbody mustangs for a couple years and that’s all I know. 

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Yes buy one off an MX bike

You can probably buy one for $100 - $200 USD, I guess.

I buy and sell them here in NZ.

Check my link

 

https://www.trademe.co.nz/2683627571

oh and i did ford capris for 20 years, if you can see my profile pic 🙂

Edited by Tony Wyp

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A slight rethink:

Suggest you return your carb to bog standard and start from there.

When you jet it the best you can, put in the JET KIT and retune again.

See which combination feels/performs best.

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