TheSamba.com :: View topic - Done research, still need carb help please

Sun Jun 22, 2014 12:53 pm

1835, .009 distributer, dual weber 44 idf's with 135 main and 50 idles.
So I went from kadrons to these. These I dialed in to the best of my knowledge. I have all the bypass screws fully closed. Set the idle at about 700-800 RPMs. Went through and tuned the carbs twice each. It idles pretty well at 800 RPMs pulling a "4" on the snail gauge on all 4 barrels. If I stomp it of idle it stumbles and wants to die. If I baby it if snaps and pops and backfires through my carbs until I reach 2500-3000 rpm.
From what I read it sounds like my idle circuit running to lean??? Is this correct? So bigger idles?
Or are my acc pumps not set correctly? They put a a good solid stream right when I hit the throttle.
Please help me. I've been doing lots of reading and research between dealing with my kads and now these giving me grief I just want to throw in the towel. I've been fight carburator problems for a year now. I would like to be able to enjoy my car on the dunes for the 4th of July, not be all bitter cause it's running like crap.
Thanks for any help.

Sun Jun 22, 2014 1:19 pm

I would strip down the carbs 1 at a time and clean them with carb cleaner and blow through all the jets starting with the idle jets. From what you have wrote it sounds like the idle circuit isn't working as it should . Could be a number of things carb related. this is were I'd start.

If you still have the old kads I'd take The tops off them to see if there is any crud in the float bowl. You may have a lot of dirt in the tank. The tank needs to be clean. So if you strip down and clean the carbs and but still have a dirty tank you will be back to square 1 very fast

Sun Jun 22, 2014 4:15 pm

My first thought is dual 44 IDF's are too big for your 1835.

What size are the venturies?

What cam and heads are you running?

What size exhaust?

What gearing and tire size are you running?

Sun Jun 22, 2014 5:28 pm

That's how I'd expect it to run. Main is probably too lean but since you have a little engine try going down on the vent size instead.
Try 55 idle 34 vents, all else the same (that is 180 air and f-11 tubes....which should be there, but make sure).
While you are inside make sure float level is set!

Sun Jun 22, 2014 7:26 pm

Well crap. Now I have to build a bigger motor:)
It has 1-1/2 exausht. Not sure on the cam. I will have to pull my oil pump and see. They have 36mm venturies in now. So you think i can dial them down enough to work with my motor? How do I get the venturies out? Thanks again

Tue Jun 24, 2014 11:21 pm

Okay so here's whAt I have,
36mm vents
50 idle
135 or 185? Mains. Hard to read. I'm assuming it's 135
F11 emulsion tube with 175 air correction jets.
I still havn't pulled my oil pump to see what can I have and don't know rocker ratio either(was a used motor I got in a Baja years ago)
Stock heads and 1-3/8 exhaust.
I would like to tune these down to work on my motor. Would 34 vents still be too big? I was thinking 28 or 30's if they make them that small. What jetting should I use for that size?
If I go smaller vents and bigger idles wouldn't that make it run too fat at idle and be hard to tune?
I'm still learning here so bear with me.
I'm trying to locate some 40 IDF's but having difficulties right now(2 people I called both sold yesterday).
I would like to have it running good by the end of the weekend. Willing to pay extra for shipping.
Also who is the best(quality and time frame) to order this from? Should I get different sizes of vents and get some jet kits?
Another thing is there any tricks to getting the vents out? Are there hidden screws or clips that hold the aux vents in?
Also was reading about the jet dr. I'm assuming that would be a smart purchase since this is a Baja.
Sorry for all the repetitive problemS you've all probably dealt with ten times over.
Any help would be awesome.

Tue Jun 24, 2014 11:31 pm

You could try 32mm vents but don't try smaller. As small as 28 exist designed for other models but just because it fits does not make it right.
Past a certain point it WILL create the problem of being too rich at part throttle. Vent size just needs to be small enough to start feeding fuel as the idle system is phasing out, which depends on both the carb and engine!

CB should sell vents for good price.
Should have a set-screw on the side of the carb that holds them in. If they are old carbs they may be glued in with some combo of oxidation and fuel gunk

Wed Jun 25, 2014 12:19 pm

cool thanks. What about Jetting? should i leave the mains at 135 and up to 55 on idle?? just guessing here. thanks

Wed Jun 25, 2014 12:34 pm

For reference, I did an 1835 for a close friend. w120 cam, heavy port work 35x32 with matched manifolds, 9.2 CR and 44 IDFs w; 36 vents. Jetting ended up at 60/150/200 F11. Its pushing around his 65 panel.

A good start would be 55/145/200s. I would suggest going to your local vw parts supply and purchasing jet drills and use your caliper to measure as you step cut them up. This is the only way I do it. Rarely is a stamped jet perfect.

Wed Jun 25, 2014 4:38 pm

chubby53 wrote: cool thanks. What about Jetting? should i leave the mains at 135 and up to 55 on idle?? just guessing here. thanks

main jet should be about 4 times the venturi size so....
32 vent (times 4) is 128

36 vents would need 144 mains.

It's not a hard rule but it's a good starting point for sure, better than the too lean jets that it came with.

Sat Jul 12, 2014 10:38 am

So I ran it last weekend on the sand with 32 vents, 50 idles, and 125 mains. She ran good. If I snapped the throttle hard off idle it would still want to stall, but if I went smooth it went fine. I noticed it did not have much torque between. 1000-2,000 RPMs though. It was hard to get the paddles spinning off the line. Even with street tires cruising at 1500 rpm then punching it it was slow going until around 2K rpm. Never really had a problem with it leaning out and wanting to stall. I just put 30 vents in it and 55 idles and left the mains. Didn't seem to change much.
Why would I have not much torque/snap in lower RPMs? I know I should get 40's(I'm trying to find some for a good price). But in the mean time I would like it to do better if possible. Any help would be great here. I was happy from how she did, but it would be really nice to have that "snap" off idle instead of a slow build up on rpm until about 2k. Thanks.

Sat Jul 12, 2014 1:20 pm

The carbs being large for the engine is most likely what is causing your low rpm power to suffer. Get some 40's and I bet it improves.

Sat Jul 12, 2014 1:26 pm

Most of the engines that we run dual 44idfs don't really come alive until 2500 rpm or higher. At lower rpms we just open the throttle about 1/4 of the way and it runs on the idle circuit.

If the rpm range you want is 2000-4500 rpm then a single carb may actually run better and make more overall power.

It has to do with runner length and diameter. Dual carbs are usually 13-15 inches from intake valve to stack. This is ideal for a 6-7k rpm shift point. and of course the carbs and manifolds are much bigger than kadrons too.

So.... I guess it depends what you want to do. If you want to have strong torque at 1500 rpm then you got the wrong carbs. But why such low rpms??? maybe you got those carbs on the wrong engine :wink:

Sat Jul 12, 2014 1:32 pm

I just didn't know if that was normal. I've only ran 1600's Til now and just wanted to make sure that there wasn't power that I was missing. For torque, it would be nice to just hit it and it rip and snort., but I guess I would need a bigger and/or stroked motor for that. Top end does great.
It doesn't help that I would ride my yamaha 700 that has an insane amount of torque then drive my Baja.

Sun Jul 13, 2014 8:00 am

I think what you may need to do to get the torque and hp at the bottom end of the rpm range is change the cam. I have three sand rails with the big paddles on them and ran cams like the 125, 120 and the FK 8. Had to be doing 3,000 to 3,500 rpm in order to get any hp. Changed the cams in two of them to an Engle 110 and one had the bugpack like a 110 cam and the cams came in at just off idle. What a difference it made. All my engines use the dells and range from 1976 cc, 2276cc and 2388cc. I also use the Canadian 009 distributor from CB with compufires in them. My dual carbs are 40mm, 45mm and the big 48mm.

Sun Jul 13, 2014 9:51 pm

something else you may check, your timing!

what distributor are you running, what is your base timing, and what is your total timing? this can affect your low rpm acceleration also.