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Joined: Thu Mar 14, 2013 3:54 pm
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Vehicle: twin locked matt black 89 zook

Post Posted: Mon May 26, 2014 6:12 pm 
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Hi all, I don't post on here much. Been a bit of a lurker but i thought i'd upload my carb experiences on my 1989 Sierra WT for anyone else who likes to tinker.

I commonly see "get a weber, they are far simpler and more reliable, but don't like hills without mods".

I decided i'd try and reduce the stock Aisin carb in the hope of to the simplicity (and therefore reliability) of a weber, whilst keeping the aisins performance on the steep stuff. Below is a write up i've done. PDF Here:http://www.auszookers.com/forum/download/file.php?mode=view&id=30189

Just consider messing with emissions and carburetors is illegal, so I'm not suggesting you do this on a road registered car/ your daily (or at all, this could be dangerous or harm your engine as everything i've written is my own opinion and may not be correct, i'm no Suzuki engineer!). I've been running this for >10 months, weekend rig. Haven't had to adjust anything since the initial setup.
This write-up might be pretty wordy, I haven't done these before but here goes...

Notes:
• I did not take photos before/during the modifications (I didn’t know if any would work!)
• I recommend completely stripping, cleaning and rebuilding the carburettor before this. Nardek/eBay sell rebuild kits.
• I used some stainless safety locking wire and snips to do all of my temporary fixings. Many of these have ended up permanent.
• Carb: Aisin 90-18(?) found on the SJ50 and SJ70 (G13BA and G13A)


These are the systems removed:

1. EGR
2. Idle up
3. Choke
4. Vacuum assist for secondary throttle.

The EGR on these cars is for emissions and does not have the cruising benefits of newer EGR systems are, I know this because the 4th and 5th gear sensors on the gearbox deactivate EGR. If Suzuki knows the engine doesn't perform well with EGR in 4th and 5th then I don't want it in 1st to 3rd either. The vacuum motor (diaphragm) on the LHS of the intake manifold below the vacuum line going to the brake booster is automatically closed.

Image

I removed the vacuum line from the EGR vacuum motor (1) all the way back to the intake manifold (4). The vacuum line passes through a thermistor below the thermostat (3) and an electronic solenoid on a bracket above it (4) (these two controls deactivate it in 4th and 5th and when the motor is cold as mentioned before).

I left the thermistor in the manifold and just pulled the vac lines off. I took the electric switch and bracket off and tied the cables off (2).

You could make up a plate to replace the vacuum motor (1).


2. The idle up solenoid uses manifold vacuum to pull a vacuum motor, to activate a linkage on the front of the carb which raises idle. The idle up is activated when you use heater fan, headlights or rear window defogger on a hardtop if you would like to test yours to see it work. I was going to reroute mine to a switch on the dash to idle up at my leisure, but the vacuum motor started fluttering so I removed it completely. There is a switch (green wire) which sensors when it is activated, I think it simply relays it back to the ECM but I removed that and snipped the wire back with no issues.

Image

Hopefully you can see from the photo, I literally just removed everything. I took all the linkages off the front side of the shaft, but kept the spring and nuts on it.
I believe the washer on the shaft may help seal the gap between the shaft and the carb housing (feel yours for lateral play) and it also makes it look like the shaft has a purpose and you haven’t just molested the carb (the spring doesn’t add any tension, it’s just sitting there).


3. The choke uses coolant temp to heat a wax motor to control a throttle butterfly in the top of the carb. Even when fully warmed up, the choke butterfly can only open so far, causing a massive restriction to airflow. I changed the coolant hose run so it only runs through the carb base bypassing the wax motor (5) You can bypass this too if you like.
I removed the choke assembly including the throttle butterfly inside the carb and plugged the hole the shaft runs through (6) – you can probably do a neater job than me here. Associated linkages were removed, vacuum lines plugged. I haven't "needed" a choke since. Cold starts are a bit rough, I just start driving and take it easy until she's warmed up. If it runs without a choke, don’t use a choke I say.

Image


4. The vacuum assist for the throttle secondary I removed, like the choke - to see how it would go. Less vacuum lines and motors = less to go wrong. This requires a bit of setting up, tweaking and fiddling. More fun!
I removed the vacuum motor and associated linkages, and all vacuum lines running back from it. These ports where they enter the carb body were plugged (8) (12) (check photos below).

There's a black box on the LHS of the carb with vac lines going into it - I removed this too (It's an air temp sensor to only allow the secondary to open once it's warm).

Once all that was gone, I then got out my stainless safety wire and some pliers and got to work. I added a return spring on the secondary, with two safety wire point so the secondary would open, only at WOT. I played around with this a bit to get the tension correct on everything (so it didn't put too much pressure on the shaft, but still moved properly) This would be the tricky part to all the modifications.

Image

(10) Is your fuel shutoff solenoid. This is for safety, keep it working.

(9) Is a redundant linkage I tied off to stop it rattling. I kept all these redundant linkages as spacers, you could make up some spacers to tidy it up.

(7) Is a spring I relocated to help the throttle return closed completely, I was finding it wasn’t shutting properly and giving me a high idle. There is a kink in the safety wire as I had to get the tension of this spring right so it worked smoothly. If it’s too stiff the throttle will rap shut hard, you can get a feel for what’s right and not abusing this equipment.

Image

(11) is just a screw I added to hold the spring.

(12) is to be blocked off

Image

(13) Is a wire attached to a bracket on the secondary throttle shaft, and the carb body. This is so the secondary can return when throttle is lifted; once again the angle of this rear spring bracket needs to be played around with so there is not too much or too little force.

Image

(14) Is a wire attached to a long spring attached to the base of the throttle to assist it in returning. This spring works in conjunction with spring (7) above. As they are both at different angles, both springs can run at much lower tension yet still ensure the throttle returns properly, minimising wear on the carb body. I will make a bracket to drop this spring even lower one day.

I have also highlighted the ports to be blocked off.
If you are wondering what the small vacuum line is coming from the intake manifold – it is for a vacuum gauge.
Once this is done, in my eyes you have yourself a weber. You should have a vac line (fuel vent) to charcoal canister, (from venturi) to distributor, intake vac to brake booster. You should still have a pair of wires going into the carb, this is the fuel shutoff solenoid to stop fuel leaking anywhere when it's parked up. I’ve added a few more photos below:

Stay safe,

Will.

Choke removed frees up so much airflow!
Image

Image


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Joined: Tue Jan 17, 2012 2:10 am
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Location: Darwin, NT
Vehicle: WT sierra, GU CRD

Post Posted: Mon Jun 02, 2014 2:22 pm 
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Good read mate.

Doing similar except keeping the idle up and vacuum secondary.

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Post Posted: Mon Jun 02, 2014 3:34 pm 
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:goodjob: Will, thanks for sharing

sounds similar to how shep fixed his carby, but you probably used less rocks & hammers. :lol: viewtopic.php?f=5&t=4574&hilit=carby+fix

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Joined: Tue Jan 17, 2012 2:10 am
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Post Posted: Thu Jun 05, 2014 7:55 pm 
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Yeah, I forgot to suggest moving this, good idea.

Maybe the threads can be merged.

Mine's copping bigger jets as per Santos and Zook_Fan as well. I heard shep's carby worked well so decided to do the same.

Edit: I hate auto correct sometimes.

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Joined: Thu Mar 14, 2013 3:54 pm
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Vehicle: twin locked matt black 89 zook

Post Posted: Fri Jun 06, 2014 12:59 pm 
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Cheers guys,

Marko - good point about the jetting, I've completely overlooked this as she runs well.

My engines freshly rebuilt, overbored, port matched, port + polished head and cammed with a 2" exhaust. I'll definitely have to experiment with jetting see what gains over stock there may be with these mods.

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Post Posted: Sat Jun 07, 2014 7:39 pm 
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Great read thanks

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Joined: Thu Mar 14, 2013 3:54 pm
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Vehicle: twin locked matt black 89 zook

Post Posted: Tue Oct 28, 2014 10:19 pm 
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Minor Update: I've been playing about with jetting a fair bit, i'm going to settle around 102.5 primary 130 secondary at the moment.

Going bigger in the primary (say 115) seemed to create idle tuning difficulties (not sure why it was having any effect it may have been other issues) and the 140 currently in the secondary is just too rich at WOT, i'll drop it down to 130.

Definitely gains to be had over the stock 99 primary 102.5 secondary though. Upping the jetting in the secondary actually gives a bit of a kick when it opens up, you can hear a difference in note.

Another note as a knock on effect of these mods; bypassing the water choke and carb base with the coolant lines and connecting the manifold directly to the water pump intake seems to divert too much water flow away from the thermostat, it wasn't seeing the heat quickly enough to react and I actually managed to boil the motor over before the thermos kicked in/ radiator got warm on one occasion. I'd recommend blocking off the port or adding in some sort of restrictor.

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Joined: Wed Oct 29, 2014 7:23 pm
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Vehicle: Suzuki SJ80

Post Posted: Wed Oct 29, 2014 7:29 pm 
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Willis, how has this affected your fuel consumption?

I'm running a stock carb and rebuilt engine on 31s and getting 7kml.

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Post Posted: Wed Oct 29, 2014 7:33 pm 
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Sandboarder wrote:
Willis, how has this affected your fuel consumption?

I'm running a stock carb and rebuilt engine on 31s and getting 7kml.


Fix your gearing. Oh and your speedo will be under reading by around 20%

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Joined: Wed Oct 29, 2014 7:23 pm
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Post Posted: Wed Oct 29, 2014 7:49 pm 
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shep wrote:

Fix your gearing. Oh and your speedo will be under reading by around 20%


Already did the SJ410 TC swop with 12% lower gearing and even at 20% speedo correction it seems a tad heavy driving on they highway compared to other guys running VW golf carbs around here.

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Vehicle: twin locked matt black 89 zook

Post Posted: Wed Nov 12, 2014 8:33 pm 
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I don't really monitor fuel consumption as i only take her out on weekends and ride a 250 during the week so it balances out! I did this for reliability and power purposes only.

Hard to compare to before as I did heaps of engine mods, gearing, new tyres and never kept a record.

Highway flat out 110kmph loaded up was about 12.5L/100km average on my last 1000km round trip. Last weekend trip was 13.4L/100km. (all adjusted to be true)
I'm running 5.14 calmini gears and new 31" bighorns.

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Joined: Fri Nov 06, 2015 10:27 pm
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Vehicle: Suzuki Samurai

Post Posted: Wed Nov 11, 2015 4:28 am 
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Hi All.

Hope you guys don't mind a thread revival here.

I also have the same Carburetor. but mine is Automatic Choke, ive followed the instructions as mentioned here, and my carb is running bad, still cuts out on idle, sometime idle is 2000rpm, sometimes it idles nice at 900rpm or so, then also starts cutting out.

Ive tried setting it, but just cant get it right,
Ive got the same vacuum ports blocked off, the Choke is deleted, I don't have the EGR Vacuum motor on mine, but I do have the electric system that controls the idle when the Lights are on.
Ive managed to keep all the normal spring location points to keep the springs in their places, with out needing to use wire etc to hold them in certain places.

But seeing as my Samurai is not running so well, do these sprint tensions held by the wire make that much of a difference?

these are the photos I currently have of the carb back on my Samurai.
Image
Image
Image
Above you will see in the back that my secondary vacuum setup is in, and with the vacuum plugged, its holding the secondary arm up to allow the secondary butterfly to open mechanically. has not moved since doing this.
Image

Some pics just after the delete
Image
Image

I hope this is enough information, im not Carb conscious so to speak, as this was the first time I decided to strip it down, and put it back together, as well as decide on the delete while it was off.

Have I done anything wrong? as it scurrently a total pig to drive, feels a bit more sluggish than it did before, and I feel i don't have the climbing power I felt before doing this mod.

please help.

thank you
Justin

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Location: Northern NSW Australia.
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Post Posted: Wed Nov 11, 2015 8:44 am 
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Emission era carbies are a nightmare once they get a few K's up,best left to carby specialists and they often get it wrong.
My brothers 1980's Celica carby went to 3 different Sydney specialists for rebuilds in a 2 year period,costs were over a grand and despite assurances it was all fixed it never was,poor fuel economy and no power under load on hills(same as yours).The final fix was trawling wrecking yards until we found a genuine smash write-off and standing there while the wrecker unbolted the carby,it took $200 and a lot of talking to get him to split the carb off the motor but at least it got the car going again.

Sorry,not much help but thats my experience after playing around with carbs all my life.

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Joined: Fri Nov 06, 2015 10:27 pm
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Vehicle: Suzuki Samurai

Post Posted: Wed Nov 11, 2015 2:37 pm 
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Thank you for the reply mate.
I know alot of guys go the Weber route, I've considered it, but I see alot of people say not to.
With regards to Emissions, I really couldnt care about it, as we have no emissions laws here IN South Africa.
So if there is a way to by pass that crap and just have a regular carb. That would be a bonus.

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Joined: Tue Jun 27, 2017 9:48 pm
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Vehicle: 1995 Suzuki Sierra

Post Posted: Tue Jun 27, 2017 10:40 pm 
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Looks like its time to do this mod. Have had a 95 Sierra for about 10 years. Worked OK for a few years then choke problems so I got rid of the auto choke. Rigged up a manual choke but it starts OK without it, just have to use the foot to give it a few revs for a minute or two.
Couple of years ago wasnt idling that great so got a carby rebuild kit.
Worked OK till a few months ago. Pulled carby to bits, adjusted float, gave it heaps with a can of carby cleaner. Worked great for a few days.
Now when I start it in the morning once it is warm enough to keep going without the foot it revs at around 2000rpm. 25 km drive to town and its still doing 2000rpm when I get there.
In the afternoon start it up and after a min or 2 its idling at 800rpm.

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