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Message started by firechicken on 07/10/18 at 20:17:47

Title: 2006 s40 jetting issues
Post by firechicken on 07/10/18 at 20:17:47
Hi everyone, I'm new to the forum and recently bought a 2006 s40. It has quickly become my favorite bike in the stable but I'm having jetting issues. I know there are a lot of jetting posts on here which I have explored and I have read the tuning guide and have a manual but I need a little extra help.

The bike has a jardine slip on and a 3 inch hole cut in the airbox cover, stock clean air filter. And I added a raptor petcock and replaced the exhaust seals. The previous owner installed a "stage 3" jet kit and needless to say it was rumming very rich and backfiring a lot when I bought it. I don't like aftermarket jets so I installed a proper 152 main and a 55 pilot, which from what I've read seems appropriate. I'm still getting significant loud backfiring on decel and when shifting, and a loud after fire during shutdown. I have the mixture screw turned 1.5 out, much more than that and it doesn't idle smoothly and at 1 turn out it shoots flames while revving in neutral. It has an adjustable 5 notch needle with the clip on the 3rd notch. The spacer is missing and has been replaced with several small washers. I'm guessing my issue is in the needle jet position, but I may also need to install a stock pilot Any insight on how to determine if the midrange is rich without chopping a bunch of plugs? I usually don't have trouble with jetting but this bike is really testing me.

Title: Re: 2006 s40 jetting issues
Post by batman on 07/10/18 at 23:36:14
I'm not sure how much back pressure your muffler has ,but I assume it's less than stock. drilling holes in your air box will not increase air flow to the carb , you have a stock air filter (restrictive) and an open muffler( less restrictive) which will cause the bike to run rich. what jets you use, and the number of #4 steel washers you use on the needle will be determined mostly by your elevation above sea level(and your muffler if it's loud )which you have not stated , (need more info) you should also reread about tuning the fuel mix screw (which only involves the idle circuit)

Title: Re: 2006 s40 jetting issues
Post by Dave on 07/11/18 at 03:39:54
Good carb jetting is done based on how the bike runs when the throttle is opened - not on what happens when the throttle is closed.  When you close the throttle completely and the engine is decelerating, it creates a high vacuum and pulls a lot of air past the slide/butterfly - however the only fuel is coming through the pilot circuit.....as a result the mixture goes very lean and the spark plug cannot ignite it in the cylinder - so the unburned fuel goes into the exhaust system where the hot header/muffler can ignite the unburned fuel/air mixture.

This is not a fuel injected bike, and your choice in mufflers makes the situation far more noticeable than a quieter muffler would provide.  You can learn how to ride the bike and reduce the condition that causes the noise.....this primitive bike does require a bit more skill from the rider.  When you shift you should not let the throttle slam all the way closed - roll the throttle off a little bit but don't close it completely.  When you are decelerating and down shifting.....hold the throttle just slightly open to allow a bit more fuel flow.  You don't have to open it up so much that the bike accelerates - just enough to make the noise go away.

And......DragBikeMike has come up with a modification to the Transient Enrichment Valve that may help you.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1523820886

This is not unique to the Savage, and the bigger the size of the cylinder the more likely the noise will be noticeable - how many Harley's with loud mufflers have you heard popping and banging as they slow down?  (Harley riders seem to like the noise). ;)

Title: Re: 2006 s40 jetting issues
Post by LANCER on 07/11/18 at 06:36:41
In addition, the Jardine muffler is notorious for its high airflow, which on this bike does not give nearly enough back pressure and very often results in back firing.  I suggest you swap the Jardine for a Dyna/Sportster muffler (very cheap on eBay or at a local HD shop...there are thousands of these take-offs laying around) which will work much better for this engine.  More people with this bike run this muffler than any other, and you will be able to take your jetting down to 52.5 and 152.5 and it will run quite happily.
Be sure to recheck you head to header and header to muffler connections to ensure there is no air leak, which will cause backfiring as well.  You can check this with a candle, holding it just under those connections when the engine is running, and the smoke trailing up.  If there is an air leak you will see the smoke being blown around.  If no disturbance then you are good to go.

Are you clear on the tuning procedure ?

Title: Re: 2006 s40 jetting issues
Post by firechicken on 07/11/18 at 11:24:24

7271647D717E2428100 wrote:
I'm not sure how much back pressure your muffler has ,but I assume it's less than stock. drilling holes in your air box will not increase air flow to the carb , you have a stock air filter (restrictive) and an open muffler( less restrictive) which will cause the bike to run rich. what jets you use, and the number of #4 steel washers you use on the needle will be determined mostly by your elevation above sea level(and your muffler if it's loud )which you have not stated , (need more info) you should also reread about tuning the fuel mix screw (which only involves the idle circuit)




I'm located in Asheville Nc at about 2,100ft, I should have mentioned that. I know how to tune a mixture screw by starting at about 1 turn and slowly turning it out while hot until the highest idle is reached, when the idle begins to fall you turn it back in a tad. When I reach the highest, smoothest idle it is at about 1 turn out and the bike backfires while revving. If i turn the screw out to 1.5 it will backfire on decel but not during a rev. The pilot I am running is 1 size over stock, I have a stock pilot which I will try next. I agree about the hole in the airbox, it was like that when I bought it and I don't think it is doing much of anything for flow.

Title: Re: 2006 s40 jetting issues
Post by firechicken on 07/11/18 at 11:33:23

03383522333F242239313C23500 wrote:
Good carb jetting is done based on how the bike runs when the throttle is opened - not on what happens when the throttle is closed.  When you close the throttle completely and the engine is decelerating, it creates a high vacuum and pulls a lot of air past the slide/butterfly - however the only fuel is coming through the pilot circuit.....as a result the mixture goes very lean and the spark plug cannot ignite it in the cylinder - so the unburned fuel goes into the exhaust system where the hot header/muffler can ignite the unburned fuel/air mixture.

This is not a fuel injected bike, and your choice in mufflers makes the situation far more noticeable than a quieter muffler would provide.  You can learn how to ride the bike and reduce the condition that causes the noise.....this primitive bike does require a bit more skill from the rider.  When you shift you should not let the throttle slam all the way closed - roll the throttle off a little bit but don't close it completely.  When you are decelerating and down shifting.....hold the throttle just slightly open to allow a bit more fuel flow.  You don't have to open it up so much that the bike accelerates - just enough to make the noise go away.

And......DragBikeMike has come up with a modification to the Transient Enrichment Valve that may help you.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1523820886

This is not unique to the Savage, and the bigger the size of the cylinder the more likely the noise will be noticeable - how many Harley's with loud mufflers have you heard popping and banging as they slow down?  (Harley riders seem to like the noise). ;)



Thank you for the insight. I have been practicing rolling off the throttle while shifting and on decel which does make a huge difference in the noise polution. I just assume that this kind of loud, flame throwing backfire is inappropriate. I own other big thumper dual sports that do not backfire like this, but they do have actual mufflers. I will look into the enrichment valve and let you know how it goes. I'll be going back into the carb to play with the needle position when I get home from work. Being that it is an aftermarket needle, and the stock spacer has been replaced with washers, it is challenging for me to estimate where the needle should have been stock.

Title: Re: 2006 s40 jetting issues
Post by firechicken on 07/11/18 at 11:38:28

48454A4741561613240 wrote:
In addition, the Jardine muffler is notorious for its high airflow, which on this bike does not give nearly enough back pressure and very often results in back firing.  I suggest you swap the Jardine for a Dyna/Sportster muffler (very cheap on eBay or at a local HD shop...there are thousands of these take-offs laying around) which will work much better for this engine.  More people with this bike run this muffler than any other, and you will be able to take your jetting down to 52.5 and 152.5 and it will run quite happily.
Be sure to recheck you head to header and header to muffler connections to ensure there is no air leak, which will cause backfiring as well.  You can check this with a candle, holding it just under those connections when the engine is running, and the smoke trailing up.  If there is an air leak you will see the smoke being blown around.  If no disturbance then you are good to go.

Are you clear on the tuning procedure ?





I would love to keep the Jardine since it came on the bike, but if I can't dial it in I will likely change it out. I have read about several people running jardine mufflers and reducing the backfire to a healthy crackle. I replaced the header-muffler gasket (it wasn't there when I bought the bike) and I will try the candle trick to make sure it is sealed properly, though I am confident that it is.

Title: Re: 2006 s40 jetting issues
Post by Dave on 07/11/18 at 11:55:13

39362D3A3C37363C343A315F0 wrote:
When I reach the highest, smoothest idle it is at about 1 turn out and the bike backfires while revving. If i turn the screw out to 1.5 it will backfire on decel but not during a rev.


The idle fuel mixture is the only thing you adjust while the bike is still.  You don't tune/jet a carb by revving the engine when you are not moving......you tune it for how it accelerates and runs when riding.

Your Jardine is really not suited to use on the Savage.  If you insist on using that noisy thing.....you then must accept the noise issues and popping/banging that come with it.

Title: Re: 2006 s40 jetting issues
Post by Yoshi on 07/11/18 at 17:45:26
From your original post i would recommend 52.5 pilot and 152.5 main and check for air leaks in your exhaust

Title: Re: 2006 s40 jetting issues
Post by batman on 07/12/18 at 00:14:07
I think based on your current muffler ,Yoshi is right , but if you change to a Dyna muffler (and 3 # 4 steel washers ) then,  you could try a main jet 150 /152.5  But you'll still need a less restrictive air filter. I highly recommend(use)  Öldfeller's filter , because of cost,   low maintenance, it can be reused,    and the fact that it filters better than any K&S . ( It's in the Tech Section)

Title: Re: 2006 s40 jetting issues
Post by madmikesmech on 07/12/18 at 09:47:10

7A796C7579762C20180 wrote:
I think based on your current muffler ,Yoshi is right , but if you change to a Dyna muffler (and 3 # 4 steel washers ) then,  you could try a main jet 150 /152.5  But you'll still need a less restrictive air filter. I highly recommend(use)  Öldfeller's filter , because of cost,   low maintenance, it can be reused,    and the fact that it filters better than any K&S . ( It's in the Tech Section)

Batman, great of you to recommend oldfeller2 's air filter mod! At first i had a tough time finding it but finally read the post.
Thank you,
Mike

Title: Re: 2006 s40 jetting issues
Post by ohiomoto on 07/12/18 at 10:06:07
You're at slightly higher altitude and your bike should need LESS fuel than one with a similar set up in say NY.   There is a lot of good advice here but I'm thinking you might be better off going leaner.

Jetting 101:

HIGHER altitude, temperature, and/or humidity = LESS air which will require LEANER jetting.

LOWER altitude, temperature, and/or humidity = MORE air which will require RICHER jetting.

I ride between 600-1100 feet.  I think  I have a 147.5 main and a 50 pilot with a Dyna muffler.  So I'm slightly richer on top and slightly leaner on the bottom compared to a stock 96.  My bike hardly backfires at all, runs clean and strong throughout the powerband, and averages over 50 mpg.  

When I bought it, it had a 155 main with a 55 piot, got horrible fuel economy, and it ran like a turd.

I'm not sure your muffler is helping matters, but I would go back to stock and try again.  You may find that you need to down a size in the pilot.

Title: Re: 2006 s40 jetting issues
Post by madmikesmech on 07/12/18 at 20:02:44

0D000F0204135356610 wrote:
In addition, the Jardine muffler is notorious for its high airflow, which on this bike does not give nearly enough back pressure and very often results in back firing.  I suggest you swap the Jardine for a Dyna/Sportster muffler (very cheap on eBay or at a local HD shop...there are thousands of these take-offs laying around) which will work much better for this engine.  More people with this bike run this muffler than any other, and you will be able to take your jetting down to 52.5 and 152.5 and it will run quite happily.
Be sure to recheck you head to header and header to muffler connections to ensure there is no air leak, which will cause backfiring as well.  You can check this with a candle, holding it just under those connections when the engine is running, and the smoke trailing up.  If there is an air leak you will see the smoke being blown around.  If no disturbance then you are good to go.

Are you clear on the tuning procedure ?



Great tip Lancer, i too have the Jardine turnout,

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