Possibly in this location.

Thank you, Mike.  I appreciate you responding to me, the newbie.  I can tell you have a wealth of knowledge and experience!

I need to get a service manual.  I’ve been winging it so far and without this forum, I’d be pretty lost and probably dangerous to the bike and myself.

I have very little experience with CV carbs.  I had one on another bike, but never really fiddled with it.  For such a simple bike as the Savage, it seems the Suzuki engineers felt compelled to insert something complex and sophisticated to keep the average Joe grease money entertained and dropping F-bombs.  Burying the air/fuel mix screw under a Welch plug as if there is a perfect setting for all environments is just proof they have a warped sense of humor (I digress).  But, I’m going to keep dealing with it for now.  Having much more experience with round slide carbs, and how I ride, I’m am seriously considering a swap out, but I want to see what I can accomplish with the stock CV carb first.  I still don’t have a good overall feel for the performance of this bike - owned it for 5 months now and I’ve mostly been focused overdue maintenance and ‘clean up’.

The issue bothering me is afterfire on “harder” deceleration.  Bike is stock except for a Jardine Rumbler series exhaust (virtually open pipe with a wrapped core).  I’ve rejetted to #150 main and #55 pilot and did a spaced mod to 1/3 thinner spacer (0.11” down to 0.067”).  Mid range performance improved and the bike runs very well, but the afterfire is virtually unchanged.

I think Versylagen said I’d never get rid of the afterfire with the Jardine pipe, but I’m stubborn and don’t listen sometimes.

The TEV is now in focus after reading your article and research.  I’m also considering thinning the spacer some more.  I’m also wondering if I have a weak diaphragm under the dome on the slide or a crapped out TEV. The way you researched the vacuum tells me that there is very little margin of error for the TEV to do it’s job properly.

Very interested to hear your thoughts.  Also, what brand/size of round slide carb might you recommend for a bike with my fairly stock set-up?  Thinking about easy of installation with minimal mods.  The stock 40mm CV carb seems huge, but maybe that had to do with being a cv carb.  Makes me wonder about slow air velocity, but it works and I have to respect whatever the Suzuki engineers were thinking.

Thanks for your time!  

DragBikeMike wrote on 09/02/22 at 19:45:28:

I do enjoy being the guy who works out the answer. And when I see it done, I get a kick out of it and try to learn, so if I see a problem one day, the cheap, easy answer is InThere somewhere. So, I'm understanding your setup okay?


had that Monkey Wards vacuum gage since I was a teenager.


It's a treasure.

Paul, seems to me you have an excellent opportunity to learn and share.  You have an exhaust system that is afterfiring with vigor, and an emission compliant carburetor with an afterfire mitigation device that can be tuned and adjusted.

I’ll be the first to admit that I didn’t have this TEV thing figured out completely when I wrote this report back in 2018.  At that time, I thought there was only one pilot air jet in the early model carbs.   Now I know there are two.  After more consideration, I also think there is a good chance that under certain conditions, manifold vacuum works on both sides of the TEV diaphragm.  I’m thinkin there’s a lot more to this issue than meets the eye.

Food for thought:

The idle circuit gets bleed air from three different sources when the throttle is closed, pilot air jet (PAJ) #1, PAJ #2, and the transition port just upstream of the throttle plate.  When you crack the throttle, the transition port changes from an “air bleed” to a “fuel supply port”.

When PAJ #2 gets closed off by the spool valve, vacuum will develop in the chamber on the left side of the TEV diaphragm too.  That vacuum will assist the TEV spring and help offset the manifold vacuum applied to the right side of the TEV diaphragm.  That makes analysis very complicated.  What the heck is it doing as throttle position changes (idle, cruise, coasting, decel, WOT, etc.)?  Not as straight forward as I previously thought.

The pilot jet does not utilize emulsification ports in the periphery of the jet.  It is simply an orifice.  The air bleed is introduced downstream of the pilot jet.  How the heck does it ever develop enough vacuum to lift fuel out of the float bowl.  The idle fuel port and transition port are at the top of the carb bore, so the vacuum has a long way to lift fuel.  With three sources of air bleed (PAJ 1, PAJ 2 & transition port) breaking vacuum, how does it lift the fuel that high?

I’ve been able to pretty much eliminate the afterfire by simply installing one-size larger pilot jet and raising the slide needle about .05” to .06”.  It still afterfires if I don’t raise the slide needle?  Why?  The slide needle should be offline when the throttle plate is closed.


On 9/3/22 you wrote:

“The TEV is now in focus after reading your article and research.  I’m also considering thinning the spacer some more.  I’m also wondering if I have a weak diaphragm under the dome on the slide or a crapped out TEV. The way you researched the vacuum tells me that there is very little margin of error for the TEV to do it’s job properly.”

Yes, I would reduce the spacer thickness and try it.  Use washers so you can restore things if you don’t like the results.  I have had good results and it’s a zero risk modification.

“Very interested to hear your thoughts.  Also, what brand/size of round slide carb might you recommend for a bike with my fairly stock set-up?  Thinking about easy of installation with minimal mods.  The stock 40mm CV carb seems huge, but maybe that had to do with being a cv carb.  Makes me wonder about slow air velocity, but it works and I have to respect whatever the Suzuki engineers were thinking.”

The stock carb is actually only 35mm.  It has an oval venturi that is nowhere near a 40mm cross section.  Lancer’s 38mm VM is foolproof.  If you are adventurous and a tightwad, a knock-off 38mm PWK works real good, but it’s a crap shoot.  Never know what you’re gonna get.  This should help.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1625732492

Thanks Mike.  I really hope I can contribute something of value to the group one day.  Right now, I’m just trying to be a good sponge and absorb as much as I can.

1) Thanks for setting me straight on the carb being 35mm!  The 40mm seemed huge and I was thinking 32-36mm would be more appropriate.  I bought a cheap project bike yesterday to  use as a Guinea pig as I learn these bikes.  It’s completely missing the carb, so it will be getting a cheap aftermarket carb for starters.  I saw Lancer’s kit.  Can’t say I want to pay that kind of money.  I would like a clue though of how much exposed throttle cable would get me close for set-up.  For the carb, not to get into exact knock-off brand names, but what size might afford the easiest set-up that’ll feed the bike (36mm, 38mm, other)?  I really want to try this route on the project bike #2.  

2) The bike #1 that we’ve been talking about is a 2004 Savage.  I think it has the newer carb jetting, but I haven’t been paying enough attention when I’ve gone under the dome.  I need to check and I start taking pictures.  Assuming it is, I’ll probably move forward with the experiment you outlined.  Before I go there though, I’m going to try raising the needle some more.  This time I’m going to try a single thin stainless steel washer. Haven’t measured but it’s about 1/3 the thickness of the stock spacer (0.11”).  So roughly, the new spacer will be about 0.035”.

3) The TEV makes me think about the human epiglottis.  Doesn’t seem like a big deal, but fills a very important role.

FYI - I ordered a service manual yesterday.  Won’t help me much with the carb, but will spare the group some of my more novice posts.

Thanks again!  Very appreciative of your time and expertise!

Although your questions pertain to a Honda, they are directly applicable to the CV carb and TEV, which should help all of us Savage fanatics better understand our carburetors.  The moderators will decide whether or not this belongs in Rubber Side Down.

The approach you take will probably depend on how difficult it is to access the carbs on the Shadow.  When faced with a problem like this, I like to make large changes that are easily reversed.  You always must start from a point of knowledge, that's why the access is important.

Can you remove the TEV diaphragms without taking the carbs off the engine?  

Can you remove the float bowls without taking the carbs off the engine?

Can you remove the slides without taking the carbs off the engine?

Is it easy to take the carbs off the engine?

You want to know if the TEV diaphragms are brittle cracked, torn, or pin-holed.

You want to know if the float bowls are clean and what size main jet & pilot jet are installed.

You want to know the air bleed jet configuration and sizes.  Those jets should be located underneath the slide diaphragm.

You want to know if the slide needle is the same design configuration as our LS.  Can it be raised by changing the thickness of a spacer?

Once you have the answers to those questions, you can make some fairly big changes to help diagnose your problem.  But you want those changes to be easily reversed so you can put the carbs back exactly as you found them, and you want to make only one change at a time.

You want the changes to be significant so that the outcome will be evident.  You say the hesitation is gone when you run with the enricher on, so you already know you are lean just off idle.  So, open your idle mixture screws about one-turn and see if the hesitation goes away or is significantly improved.  See what you learn.  Don't worry if it idles lousy, just ride it and see if the hesitation goes away.  If the hesitation goes away, you might be able to correct the condition by installing larger pilot jets and readjusting the idle speed and mixture screws.  If increasing the pilot jet and adjusting the mixture screws doesn't work, put them back where they were.

The Honda specialist seemed to zero right in on the TEV diaphragms, so if they are the least bit questionable, change them.

Raise your slide needles.  Don't be shy, raise them up a good amount (like 1.0 to 1.5 mm).  Use washers so that whatever is in there now (plastic spacer, washer, etc.) can be put back in.  You want to be able to return it to the original condition if your troubleshooting adjustment doesn't work.  See if the hesitation goes away.  Don't worry if it runs a little rich, you are just trying to find out if the hesitation can be eliminated by adjusting the slide needle.

Install smaller pilot air bleed jets.  They are air jets so don't fiddle around with a one-size change.  It's controlling air which has almost no viscosity, make big changes.  For instance, if the larger jet is a #200, put in a #100 and see what happens.  Same guidance for the smaller jet.  If the smaller jet is a #100, put in a #50 and see what happens.  Only change one jet at a time.  See what happens, then put it back the way it was and try the other jet.  You are not dialing in the system; you are trying to learn how each jet impacts operation.  You can fine tune later.  

Tell us what you learn.  But hey, let's finish Woody first.