Modded B2200 questions..carb/jet settings!!!??? - Mazdatruckin.com Truck Forum and Tech Site

vanessa_valium · #1 (**permalink**) 12-30-2009, 01:42 AM

I just bought a Mazda B2200 with a Weber "36 synchro" carb on it. I know nothing about carburetors, nor do I know how to tune one, but I am looking for a diagram or something on one that I can look at and figure it out.

I went to a shop and the guy supposedly tried to dial it in, but said it was "running rich" and he wouldn't really tell me what was going on.

The truck runs like ****, it's got a rebuilt engine in it, but this carb, everyone is telling me is the "wrong" one for this model...that it belongs in a v6 or v8. I looked at the Weber site, and it lists this carb for the B2200.

I'm so confused..I've posted on EVERY Mazda forum I can think of or find...hopefully someone can help me tune this stupid carb.

The guys at Weber said, "It should have a 35-40 idle and 120-125 main." I have NO idea what that means.

Can someone PLEASE help?? PLEASE PLEASE PLEASE!!!

briankmizell · #2 (**permalink**) 12-30-2009, 02:02 AM

These things can be tricky to get jetted correctly, I have worked on my several times and still dont have it right.

Dont let that scare you away from doing it. Dealwithit, Kyrasis6, and several others on here can give you more info than I can.

Below is the diagram of the Weber 32/36 (AKA Holey 5200)
Weber Assembly Diagram - Mazdatruckin.com

Below is info on the Holley 5200 which is almost identical to the weber.
Holley 5200 Info & Conversion - Mazdatruckin.com

vanessa_valium · #3 (**permalink**) 12-30-2009, 04:26 PM

I checked those images, but they're different from what's in my truck. I have what's called a 36-36 or so I've been told.

I took it to a shop the other day to get it worked on and to see if this guy could maybe tune it, but he messed it up more. Now the truck runs so badly, I can't get up even the simplest of hills without being in first gear and slamming the gas pedal to the floor. I'm taking it back there today and telling the guy to set everything where it was before. He messed something up.

The guy I bought the truck from said that the timing is "advanced" because of the aftermarket carb and "a new header". I am not familiar with "headers" nor do I know what they do. If someone could help explain this, I'd be thankful.

Why would that have anything to do with advancing the timing? The guy at the shop said "it shouldn't matter what header or what carb you have on that engine, it should still run fine with stock timing". But it doesn't obviously.

He also said the compression in the engine was bad, said it should have been at about 100psi, but it was only at about 80-90psi after he advanced the timing belt.

I am clueless. I have no idea what I'm dealing with here.

briankmizell · #4 (**permalink**) 12-30-2009, 08:29 PM

I am pretty sure when you advanced the timing the compression will increase. I personaly would not have messed with the timing belt unless it was not on correctly in the first place.

Cusser · #5 (**permalink**) 12-30-2009, 11:25 PM

Quote:

Originally Posted by vanessa_valium

The guy I bought the truck from said that the timing is "advanced" because of the aftermarket carb and "a new header". Why would that have anything to do with advancing the timing? The guy at the shop said "it shouldn't matter what header or what carb you have on that engine, it should still run fine with stock timing".

Aftermarket carb or headers shouldn't require any change in either ignition timing and valve timing. I kept my timing stock when I added my Weber 32/36 DGEV.

Quote:

Originally Posted by vanessa_valium

He also said the compression in the engine was bad, said it should have been at about 100psi, but it was only at about 80-90psi after he advanced the timing belt. I am clueless. I have no idea what I'm dealing with here.

I agree with Brian, I wouldn't do anything to the timing belt unless is was incorrect, and if incorrect, I would replace the belt and do it right. An "off" timing belt might keep a valve open at when the pistin reaches its top, so I understand that such compression might read lower. But I think compression values are useless if the timing belt isn't correct. And usually equivalent compression is more important than the actual numbers.

Xulf13 · #6 (**permalink**) 12-31-2009, 04:32 AM

Quote:

Originally Posted by Cusser

Aftermarket carb or headers shouldn't require any change in either ignition timing and valve timing. I kept my timing stock when I added my Weber 32/36 DGEV.

I agree with Brian, I wouldn't do anything to the timing belt unless is was incorrect, and if incorrect, I would replace the belt and do it right. An "off" timing belt might keep a valve open at when the pistin reaches its top, so I understand that such compression might read lower. But I think compression values are useless if the timing belt isn't correct. And usually equivalent compression is more important than the actual numbers.

Cusser, she knows nothing about carbs. I think it's best to take her thru the basics. The carb she has is the off brand weber like the 34/34 syncros you see for sale on ebay.

Vanessa did not say that the mechanic touched the timing belt (thank God for that) She said that the mechanic set it back to stock timing. which should run fine. BUT when you run rich, you can advance the timing as long as there is no pingin on the engine as a way to burn more efficiently.. I have my timing advanced at 12 degrees and my truck runs fine. That carb may be too much for your truck vanessa, and even though the carb is listed for a B2200 it will need fine tuning. Meaning some jets may need to be changed out.

Vanessa, it is very likely that your mech. touched the lean rich mixture screw on your weber, and he tightened the screw to lean out the mixture (meaning to make it not run rich) see if you can find the mixture screw .... ahhh the heck I'll PM you... Cusser, you're up that way just take the scenic drive to Prescott and go help her out LOL..

EmJay · #7 (**permalink**) 12-31-2009, 05:42 AM

maybe a picture of said carb would help some of us out here, especially K6, mr. carburetor himself

Xulf13 · #8 (**permalink**) 12-31-2009, 04:33 PM

Quote:

Originally Posted by EmJay

maybe a picture of said carb would help some of us out here, especially K6, mr. carburetor himself

Yeah, they don't even have a diagram with photos of it on line like they do with the REAL Weber carbs out there.

Cusser · #9 (**permalink**) 12-31-2009, 04:36 PM

Quote:

Originally Posted by Xulf13

Vanessa did not say that the mechanic touched the timing belt (thank God for that)

Cusser, you're up that way just take the scenic drive to Prescott and go help her out

Got it: even though Vanessa originally posted that mechanic advanced the timing belt, you feel that he never touched that, and advanced the ignition timing.

However, I'm in Phoenix right now (100 miles away) and not in the Chino Valley (15 miles away), and doubt that Vanessa can wait for me to take a look. Vanessa needs to post an update - she said she was taking the truck back to the shop that made it worse to have them set it back to how it was, or to fix it. At least in Prescott area there's no emission testing to worry about.

I'd agree, start with basics: make sure the firing order is correct, that the plugs and wires are good, that all vacuum lines are on or plugged, check the EGR valve, and then check the carb once it's warmed up. With my own Weber (32/36) I've found that the idle mixture screw adjustment on mine is quite crucial to power, and that just a quarter turn more "rich" adversely affects the power and mileage.

I'm also experimenting on mine how much the taller air cleaner allows more air in and leans out the mixture. Sure, I can adjust the idle mixture after changing to the larger air cleaner, but if I've left all the other jets "as is", like jetted for smaller air cleaner, seems that it would be leaner at the higher rpm range.

Xulf13 · #10 (**permalink**) 12-31-2009, 04:56 PM

Quote:

Originally Posted by Cusser

Got it: even though Vanessa originally posted that mechanic advanced the timing belt, you feel that he never touched that, and advanced the ignition timing. [/i]

I don't think she knew what she said when she said advancing the timing belt. I'm pretty sure this all had to do simply with advancing the timing by adjusting the distributor positioning.

Quote:

Originally Posted by Cusser

However, I'm in Phoenix right now (100 miles away) and not in the Chino Valley (15 miles away), and doubt that Vanessa can wait for me to take a look. Vanessa needs to post an update - she said she was taking the truck back to the shop that made it worse to have them set it back to how it was, or to fix it.[/i]

Yes she should post an update, I wonder how everything went though.

Quote:

Originally Posted by Cusser

I'm also experimenting on mine how much the taller air cleaner allows more air in and leans out the mixture. Sure, I can adjust the idle mixture after changing to the larger air cleaner, but if I've left all the other jets "as is", like jetted for smaller air cleaner, seems that it would be leaner at the higher rpm range.

Hmmm, I never did think about that. I did notice a big difference when trying to tune the carb with the air filter off. it makes sence. it's a similar issue one has when adding pods to a motorcycle carburators. you usually have to rejet for the increased air flow. Why didn't I ever think of that?

dougstrum · #11 (**permalink**) 12-31-2009, 08:38 PM

synchronous carb will have 2 mixture screws- they will be at the
bottom of carb gently turn clockwise till they stop. If idle jets are
correct 1 1/2--2 turns out should be a good setting. Make sure idle
speed screw is backed off completely when you adjust mixture screws. Once screws are set then turn idle speed screw until you get a good idle speed.
(if mixture screws are much more than 2 turns out get 1 size smaller
idle jet---if much less than 1 1/2 turns use 1 size larger jet) the idle
jets will be behind brass screws on both sides of carb; abt mid way up

once the idle is set you can check out the mains. the top of the carb
is held on w/6 screws at the bottom of the float bowl you'll see 2 jets
these are your mains; unless engine is running extremely rich or lean
just go 1 size up or down (example:145mains try 140 leaner or 150 richer)
till it's right.

on a synchronos carb both jets should be the same size
getting idle circuit right is 1st step and critical on a webber
mains will be easy once your idle setup is correct.
try to find exploded view of your carb that will help you locate
parts i've described

vanessa_valium · #12 (**permalink**) 01-01-2010, 05:19 PM

I took the truck back to the shop.

In the first place, the guy DID mess with the timing belt, he messed with EVERYTHING.

The truck is running decently now, he told me he just set the timing back to where it was (advanced) because it would not run well on stock timing. It's better now, though it's still sucking gas like a fiend. I am getting the most horrible gas mileage of any 4-cylinder I have ever owned.

I can post a picture of the carb, if you guys would like me to, and Cusser, if you would like to come out and take a look at the carb and the truck itself, I would be more than thankful to have the help of someone who knows what the **** is going on and knows about these trucks more than this douche at the shop.

I have yet to take a look and actually see what this mechanic did...as I watched him, it only seemed he took the timing belt off and put it back to advanced timing and messed with the carb, but like I said, it's running fine now, just sucking gas like a v8.

I appreciate all of your help. I'm gonna catch up on all your responses now and make notes.

vanessa_valium · #13 (**permalink**) 01-01-2010, 05:24 PM

Quote:

Originally Posted by Xulf13

I don't think she knew what she said when she said advancing the timing belt. I'm pretty sure this all had to do simply with advancing the timing by adjusting the distributor positioning.

Yes, I did. He advanced both the timing belt and the distributor positioning. This mechanic messed with too much stuff.

But like I said, it's running now, so now I have a good "restart point". I can adjust things and try to see what exactly is going on with this truck myself, and if all else fails, put it back to where it was before I started...? Hahah.

This is starting to look like a bit of a project... ;/

Cusser · #14 (**permalink**) 01-01-2010, 06:48 PM

Vanessa - gas mileage on these trucks seems to vary, from about 19 mpg up to 28 mpg according to what people have posted here. I myself get 19-20 mpg in my '88 Cab Plus, city and highway, and that's been pretty much the same even when mine had the stock carb from 1994 through 2004.

Remember, someone added your current carb because something was wrong, and they thought that was the stock carb and/or ECU going bad. Well, maybe that was it and the Weber helped, and maybe not - you don't have the history on your truck. Since it's new-to-you, one needs to start with the basics, and go from there. Lots of younger mechanics don't know too much about carburetors because practically all vehicles made in the last 20 years (except for "our" B-trucks) are fuel injection. You may want to take out some of your carb jets and write down their sizes, and ensure that yours are correct for the vehicle; I doubt that anyone has "reamed" the jets larger so you can "bet" on their stamped sizes.

Where to start? If your gas mileage truly sucks due to running rich, your spark plugs should be quite black. Are all four cylinders firing? You can wear a heavy glove and pull off the spark plug boots one by one and see if any do NOT show a drop in rpm. Did you look at the engine in the dark at night, even while spraying a fine mist of water over the spark wires, to see if there's any spark jumping? All of those tests are easy, and free.

If you have a timing light, you can check to see if the timing is advancing as the rpm increases (this is easier to see if you have the AC belt off or disconnected, if yours has AC). You can check to ensure that the carb is pulling vacuum to the distributor vacuum advance. The EGR can be tested with a hand vacuum pump, and be readily removed with three bolts as well for examination.

I don't know any mechanics up there, the only two I trust at all are in north Phoenix. Even though I don't use them much as I do most myself, they know me, and I feel that they're honest and pretty good.

Xulf13 · #15 (**permalink**) 01-01-2010, 11:56 PM

Quote:

Originally Posted by vanessa_valium

Yes, I did. He advanced both the timing belt and the distributor positioning. This mechanic messed with too much stuff.

But like I said, it's running now, so now I have a good "restart point". I can adjust things and try to see what exactly is going on with this truck myself, and if all else fails, put it back to where it was before I started...? Hahah.

This is starting to look like a bit of a project... ;/

Sorry but I never heard of someone advancing the timing BELT, only the timing. You can advance the timing by turning the distributor clockwise or counter clockwise after the timing belt is properly placed, and there is only one proper way unless one removes the timing belt then removes the cam gear sprocket and sets the cam gear sproket at a different setting like if you have it set on #1 then you would remove the sprocket and set it on another number like #3 then place the timing belt back on.

Did he actually remove the timing belt? then what did he do to so call advance the timing belt? how much did that cost? because timing belt removing and swaping can be quite costly at a mechanic shop.

Pictures of the carb set up from all four angles would be great bTW.

If your compression was low to begin with then you will never get great gas mileage, so that's a thing you need to think about. You mentioned your compression at 80-90 pSi. That is not only bad compression but HORRIBLE compression. If it was around 130 the yeah you have an engine that will last a while longer. A new engine will have around 171PSI or so, just to give you an idea.

I will have to agree and say that you do have a project in your hands.