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Message started by DavidOfMA on 09/22/13 at 06:38:16

Title: Substitute spring for TEV?
Post by DavidOfMA on 09/22/13 at 06:38:16

I remember that recently someone on this board tried a hardware store replacement for the spring in the TEV. What was that spring size and number and at what hardware store was it purchased?

I've been able to control backfiring on decel somewhat by easing off the throttle when decelerating, but I rode in a large group yesterday, and in that context, where I need to respond quickly to riders in front of me, this strategy failed and was alarming or annoying both to me and others.

I've tried cleaning the carb, replacing the 52.5 pilot with a 55 (won't idle), got the mix screw turned out three turns. This seems to be the only strategy I haven't tried.

TIA,
David

Title: Re: Substitute spring for TEV?
Post by old_rider on 09/22/13 at 06:44:08

Have you tried the "thick washer" removal from the diaphragm needle? When I first got the bike it was popping like crazy, I adj. the flow screw out to about 2 3/4 turns and replaced the thick factory washer with two 4mm washers from lowe's. It stopped a lot of the backfire and the pop on shutdown.

Title: Re: Substitute spring for TEV?
Post by Oldfeller on 09/22/13 at 06:49:00

http://suzukisavage.com/cgi-bin/YaBB.pl?action=search2

Here is your overview and feeder to all the TEV threads -- have fun and don't poke you a itty bitty hole in that $70 diaphragm while you are doing it ....

You can also find the TEVs in the Tech Index under Carb>Backfire

Title: Re: Substitute spring for TEV?
Post by DavidOfMA on 09/22/13 at 07:12:25

Thanks. I didn't find the post I'm seeking in the Tech section or when I searched using "TEV" and "spring" so I posted here, hoping the OP will see it and respond, or someone else remembers. What was appealing about the attempt I'm remembering is that the person who did it found a substitute spring in a hardware store. Easy to try without messing anything up or ordering a spare spring to cut down.

Yes, I did do the white spacer mod about six months ago. Greatly improved midrange performance but had no effect on backfiring. Also torqued down the exhaust header bolts in case there was a subtle air leak; no change.

I hope the original poster of the substitute spring idea will eventually see this thread and respond. It wasn't that long ago.

Title: Re: Substitute spring for TEV?
Post by Serowbot on 09/22/13 at 08:10:21

Are these backfires,... hard guncrack backfires that really do spook other people?... or just pops and blats?...

What muffler do you have?... too little backpressure can't be fixed with carb work...

You won't tune out normal decel pops without making your bike run really bad...
Many, maybe most, large singles and twins will decel pop....

Title: Re: Substitute spring for TEV?
Post by old_rider on 09/22/13 at 08:28:31

Went back over last years post, found it by putting in search "valve spring" selected for the "past year", it was about nine or ten posts down.

Started by apache snow | Post by mechanikhan

I got rid of 95% of the backfiring by changing the spring in the TEV to a shorter spring. The length of the stock spring has two negative effects on the valve's operation.
Having measured the pocket that the spring resides in, I came to the following conclusions:
1. There was not much room for the diaphram to move or open during the high vacuum present at full throttle, thus limiting the enriching effect the valve is supposed to provide.
2. The stock spring was stronger than necessary and was closing the valve too abruptly during the low vacuum present at deceleration, thus the backfire.

Instead of cutting the stock spring, I chose to find a shorter one. I'm satisfied with the first spring I chose, a #90 spring I bought at Ace Hardware. Listed below are the dimensions of both springs:

Stock #90
Free length 1.400 in. 0.715 in.
Wire Diameter 0.032 in. 0.035 in.
Outside Diameter 0.483 in. 0.597 in.

My bike is a 2002 model with just under 4000 miles. I installed the #90 spring at around 2800 miles. The bike is stock with one exception: a previous owner drilled out the baffle. The bike is much more pleasant to ride, and I would recommend this modification before I changed anything else.

Hope this is what you were looking for.... :)

Title: Re: Substitute spring for TEV?
Post by Serowbot on 09/22/13 at 08:40:01

5A5951475C515047350 wrote:

Having measured the pocket that the spring resides in, I came to the following conclusions:
1. There was not much room for the diaphram to move or open during the high vacuum present at full throttle, thus limiting the enriching effect the valve is supposed to provide.
2. The stock spring was stronger than necessary and was closing the valve too abruptly during the low vacuum present at deceleration, thus the backfire.

These statemants are backwards...Vacuum is low at WFO,... high on decel...
..(not sure if the OP has the wrong logic, or simple mistyped)... :-?...

Title: Re: Substitute spring for TEV?
Post by DavidOfMA on 09/22/13 at 08:40:11

Thanks, old_rider. This is exactly what I was looking for. ACE hardware, here I come!

Serow, the bike is completely stock. I do live at sea level (literally -- a block from the ocean), which is probably contributing to the problem. Goes away completely with a 55 pilot jet, but then the bike won't idle when cold. Gunshot cracks on decel and on shutoff, not pops and blats.

What I really need is a jet halfway between a 52.5 and a 55, but they don't make one, and I can't think of a way to slightly bore out a 52.5 that would give a smooth bore. If the spring works, that's a better solution anyway.

Title: Re: Substitute spring for TEV?
Post by Serowbot on 09/22/13 at 08:46:04

A between size pilot wouldn't really help... you are in effect getting a betweeny size by adjusting the idle mix...
That is,.. when you are opening the idle mix, you are adding a small flow of fuel in addition to the pilot, though an idle passage...
So,.. approx, 3 turns is roughly equal to a half step on the pilot... more than 3 turns, you should step up a size...

PS... swapping to a Harley shorty will likely mellow the gunshots to pops...
The stock muff is pretty restricted...

The TEV mod might help..(it should in theory),.. but, the OP's logic is reversed...
... and,.. you can do the same thing with your wrist, by not chopping the throttle...
I've never messed with the TEV myself...

Title: Re: Substitute spring for TEV?
Post by DavidOfMA on 09/22/13 at 09:02:37

As I said, I'm able to somewhat moderate the decel cracks when I'm riding alone by easing the throttle to a partly-closed position rather than letting it shut. But I can't do that when I'm closely following someone else, as in a group ride. When I'm decelerating, it cracks when the throttle is less than about 1/8 open.

So I'm trying the TEV trick next, because going to the next size pilot jet was too rich for the bike to idle when cold, even if I started with the choke all the way in.

Serow, I see you are in Tucson. I don't think my bike would backfire at 2000+ feet, either. Even where I was in New York State, where the elevation was about 1000 feet, if backfired a lot less.

Title: Re: Substitute spring for TEV?
Post by DavidOfMA on 09/23/13 at 13:38:54

Spoke too soon. Been to Ace, Lowes, Home Depot, True Value, Advanced Auto, and Autozone, and nary a #90 spring or equivalent can be found. Any other ideas where I might find one?