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General Category >> Rubber Side Down! >> Attempt at carb tuning failed, need some help.
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Message started by sexombob on 12/10/10 at 00:04:43

Title: Attempt at carb tuning failed, need some help.
Post by sexombob on 12/10/10 at 00:04:43

While drilling the hole in the brass plug to get to the low speed mixture screw. My screw broke while inside the hole and i tried to just drill the entire plug out. Needless to say, that was a big mistake on my part and now i have this mess:
http://img405.imageshack.us/img405/4897/20101210024458.jpg

How can i get access to the low speed mixture screw now? I'm beginning to dislike this bike in terms of ease of "hacking". My Honda is so much more compliant... *sigh*. Also i probably deserve some flaming for being a noob, so lay it on me. :'(

Title: Re: Attempt at carb tuning failed, need some help.
Post by sexombob on 12/10/10 at 00:27:15

Would using these forstner bits work without damaging the screw?

http://www.harborfreight.com/7-piece-3-8-eighth-inch-shank-1-4-quarter-inch-to-1-inch-titanium-nitride-coated-forstner-bit-set-1903.html

I would prefer to do it without buying anything if that's possible. I'm on a tight budget, so if there's a different way to do this, i would love to hear it! Thanks!

Title: Re: Attempt at carb tuning failed, need some help.
Post by Routy on 12/10/10 at 04:30:33

Yours is not the first horror story of hacking this part of this carb.
This is the "idle mixture" screw, not the low speed mixing screw, as many believe.

I can't help on getting it out, because I never took one out,....because I never had a good reason to take one out. So my question would be,....why are you taking it out ? If the screw behind the brass plug has not been turned, maybe you can just leave bad enough alone, and not completely ruin a $400 carb.
There are other ways to adjust the low speed circuit in this carb. But if you were having a problem w/ "dead idle" then and only then would you have a good reason to hack this part of the carb,....IMO

Title: Re: Attempt at carb tuning failed, need some help.
Post by Routy on 12/10/10 at 04:40:47

7A6C7166646B666B090 wrote:

These bits are made for use in a drill press or milling machine only. And depending on the quality, they are probably made for wood only.

Title: Re: Attempt at carb tuning failed, need some help.
Post by verslagen1 on 12/10/10 at 07:33:06

I had a similar situation with another nuub's bike.

It actually doesn't look too bad. Your hole is center and you haven't gone too deep.

Can you drill straight? Do you have a good drill motor that will go slow? If you do, you might be able to save it. Pick a drill size that's just a little smaller than the plug. You want to leave a thin wall on the plug to make sure you don't nick the carb. If you have a drill stop, now's a good time to use it. Not sure how thick that plug is, but guessing about 1/4". Set you drill stop for 3/16". If you don't have one use tape wrapped around the drill. With a slow speed, drill into the plug. If you're lucky, before you bottom out the drill stop the plug will catch on the drill and spin out. If not set your drill stop just a little deeper and try again.

If your hole is a little off center and the drill you selected is going to touch the carb body, back off and use a smaller drill.

Only thing you don't want to do is mess up the head of the idle mixture screw, makes it hard to adjust.

Title: Re: Attempt at carb tuning failed, need some help.
Post by Bubba on 12/10/10 at 07:40:24

Bummer, but what routy said can be true. I was helping my brother with his savage over thanksgiving. we pulled the brass plug and discovered that his screw was ALL the way in. No adjustment clockwise at all! whenever we turned it ccw it would start backfiring like crazy...even 1/4 turn out. performance was slightly better but the backfire was terrible when you shut the thottle down. A friend of his said he thought someone was shooting squirrls in the park... ;D

Anyway, everyon's different. he lives at 700 ft elevation in humid Missouri. you may not need to adjust that screw at all depending on what it's doing

Title: Re: Attempt at carb tuning failed, need some help.
Post by Baldeagle on 12/10/10 at 07:54:20

How I did my idle mixture screw and plug.........used a very small drill bit on low speed.........deep enought to screw in a small sheet metal screw.....then took pliers and pulled plug out..........final adjustment was 2 1/2 turns out on the idle mixture screw and adjusting the other idle screw. This was four years ago and have had no problems.

Ride safe!!

Title: Re: Attempt at carb tuning failed, need some help.
Post by sexombob on 12/10/10 at 07:57:12

Thanks guys, i'll try the drill again.

The reason i am doing this is to get rid of the backfiring and get better idling.

Title: Re: Attempt at carb tuning failed, need some help.
Post by justin_o_guy2 on 12/11/10 at 04:54:25

If I want a drill bit to not go all the way in, I wrap it with tape.

Title: Re: Attempt at carb tuning failed, need some help.
Post by elecdonia on 12/12/10 at 08:27:04

477067676434353D36050 wrote:

I don't think the engine should run at all with the idle mixture screw turned all the way in. The typical setting is 2 1/2 turns to 3 turns. My bike backfired a bit at 2 1/2, but this stopped when I went to 3.

I have a 2001 LS650, 7000 miles, OEM air cleaner and muffler. Fortunately the brass plug had already been removed by a previous owner. And they did a good job too. Nice and clean.

I've heard that Suzuki put loctite on the idle mixture screw after adjusting it at the factory, then they put the brass cover plug over it. Maybe your bro's idle mixture screw just needs some exercise to get it moving freely? Be careful: Don't overtighten it and don't mess up the slot in the brass screw. Turn it counterclockwise first. Then turn it clockwise until you feel resistance. Turn it back and forth several time. Maybe this will loosen it up.

The idle mixture screw in my bike turns very freely. Perhaps too freely? I am more than a little bit concerned that vibration will make it rotate all by itself, maybe even loosen up and fall out?

If the idle mixture screw really is all the way against the stop, could it be that the petcock on you bro's bike is leaking through the vacuum hose, resulting in a very rich mixture?

According to other posts here, there shouldn't be any traces of fuel in the vacuum hose at all. This is the smaller of the two rubber hoses that go from the petcock to the carb:

Small hose: Vacuum source to turn on the fuel while engine is running

Big hose: Fuel supply to carb.

Have you checked the spark plug color? If it's totally black then you have too much fuel (over rich mixture).

I'm not sure about the backfiring, perhaps either too lean or too rich can cause it?

As for my bike, with the mixture screw at 3 I rarely get a backfire, and when it does happen, it's always on de-acceleration in 2nd or 3rd with the throttle shut. Also, my bike often gives one little "putt" in the muffler after I shut off the ignition. This happens AFTER the motor stops rotating. Question for the board? How common is this?

Title: Re: Attempt at carb tuning failed, need some help.
Post by verslagen1 on 12/12/10 at 09:41:05

typical setting for the idle mixture screw is 2 turns out ± 1/2.
at 3, you're in danger of losing a screw. Time to go up in size.
I've never heard the comment about locktite before.

Hard to get rid of the backfire at shutdown completely, I always tune for a poof. no sense in getting too rich as when adjusting the idle mixture screw per lancer's instructions, I generally get a bang on shutdown. An 1/8 to a 1/4 richer tones it down to a poof.

Title: Re: Attempt at carb tuning failed, need some help.
Post by sexombob on 12/12/10 at 12:02:58

Just an update on my particular issue.

I'm waiting to borrow a better drill. My old Skil drill starts to smoke when i go slow pushing the drill against the brass plug.

Title: Re: Attempt at carb tuning failed, need some help.
Post by Bubba on 12/13/10 at 08:01:52

elecdonia - I've done the air mix adjustment on mine so I kinda know what it feels like. All I know is that his definately felt bottomed out. Plus we turned it quite a few turns out (maybe 2 1/2) and it was still in there so I'm thinking it was bottomed out under the brass plug. I was pretty surprised too becuase I would think it could barely run with the screw bottomed out.
Anyway, he has complained about some surging when it's cold and I know that was cured on my bike when I swapped out to the raptor petcock...

Title: Re: Attempt at carb tuning failed, need some help.
Post by verslagen1 on 12/13/10 at 11:37:21

It's possible your friend has a defective idle jet.

I'd swap it out and see if it improves.

Second possibility, if the idle speed was set to high to begin with, it might never get to the idle circuit.

Title: Re: Attempt at carb tuning failed, need some help.
Post by Bubba on 12/13/10 at 12:10:37

I gave him my 55 pilot w/ bleed holes and told him to throw that in if he wanted to try something different. Overall, his bike runs well, it just seems to take awhile to warm up when the temps are around 50 or below. He's always had a mild poof on shutdown but never any backfires when riding...

Title: Re: Attempt at carb tuning failed, need some help.
Post by feelinjunky on 12/13/10 at 19:33:38

26302D3A38373A37550 wrote:

Thanks guys, i'll try the drill again.

The reason i am doing this is to get rid of the backfiring and get better idling.

Have you tried adjusting your idle SPEED screw to around 1100 rpm? FYI, for me, stock carb intake exhaust, this COMPLETELY eliminated backfire upon shutoff and even when on the road.

EDIT: after reading verslagen's post, I have to add that I also do not get a poof. Complete silence after shutdown. I should record it, if it really is that rare for a Savage to do that...