Quick! What's your Dellorto jet sizes?

Gordon---I don't know if it matters (Type I or Type IV) but my engine is 2,143 cs and the carbs are Dellorto DRLA 40s with 43 mm venturis.  The Idles are 60s and the mains are 140s.  If it matters, the air correctors are 180s and emulsions are .2  I can't think of a single change to the engine's performance that should be made and for my particular use they seem perfect.  I do run some Seafoam through periodically and feel that this is one reason I never have to clean the idle jets.

The altitude where I live is 540' ---almost no matter where I drive I can't tell any difference in the performance but that's probably my lack of discernment!

I have a couple of handfulls of jets if I can send you, but I suspect you already have more jets than I do!

Good luck with your rebuild!

So the reason I'm asking, is that when I dismantled my 40mm Dells to rebuild them I found that the actuator arm for the accelerator pumps on BOTH of them was floating - neither of them had the lock-screw in place and the throttle shaft was just rotating free inside of the actuator arm - That means that neither of the accelerator pumps were ever working!!!  I remember that it bogged a bit when I first got it running and I adjusted the pumps to little effect, so I ended up maybe running larger idle and Main jets to compensate.  Now that I have identified the problem AND corrected it, maybe I can get away with smaller jets and make it all run the way Gaetano Dell'Orto intended it to run.  I never noticed this when I installed them - Heck, I had never even SEEN a Dellorto!  Always wondered why the air-fuel gauge dipped when I punched it.

I used the Tomlinson Dellorto book as a guide for the rebuild and, taking a cue from MUSBJIM, I made an accelerator pump measurement gauge from an allergy serum syringe and now have them squirting just as they're supposed to (at least on the bench) and know how to adjust them properly so away we go!

Here is the accelerator pump gauge I made up from a cut-off syringe and a 4-40 screw - works great!

And here's the bench test stand for the carbs (it's just a couple of strips of Azek, screwed together)

For you Weber guys and chasers of "Brass thingies", those four tubes sticking up in the middle of the assembly are the Idle (short) and Main (tall) jet holders.  YES!  You can access the jets from the top of the carbs!  No screwing around on the side where there is no room! 

Maybe some like to screwing around on the side ��

Just having the easy access of the Dells have me on the hunt for a set... 

Nobody knows what their 2,110 Dell 40 jet sizes are?

Jack just gave you pretty good data though, Gordy.

I'd have to dig mine out of a box, Gordon (life continues to be in disarray), but I'm pretty sure I was running 55 idles and 145 mains in my 2110. 60s are easier to drive (they don't require being fully warmed up to work well), but they aren't quite as "crisp" as the 55s. I've been as low as 52s, but they only work when it's 90* outside.

I'm a big believer in a wideband Lamba meter. It really makes set-up super easy.

Y'all know that I have Webers, but jets are jets, and fuel/air are going to flow no matter what brand is on the carb.

I run 57.5 idles and 140 mains in my 2165, and I agree 110% with Stan above here, a wideband is IT!

Thanks for the replies, everyone, and especially Jack - great description of what's going on back there.  

Since my accelerator pumps never seemed to be working (what did I know?), I over-compensated on the jet sizes so I think I'll be going to 55-ish on idle and I think I still have some 150's kicking around for the mains (I'm currently running 162.5 mains) .  Might as well put everything together right, while I still have them on the bench, as I'll be dialing them in again once they're back in the car.  I have an on-board A/F meter from CB that should at least tell me how things are working and get the final dial-in sometime in the Spring.

Thanks again, folks!!

OK, so my jet selection seemed to be (in my mind, anyway) greatly exaggerated, and I worked with what I had kicking around.

Idle Jet:  Went from a 65 to a 60, thinking that our "Dear Leader" was spot on with his advice.  Now, with working accelerator pumps it just might transition to the mid-range ports without "bogging", and I'll have an engine that is happy in everything from 25ºF to 105ºF.

Main jets:  Here, I had gone WAY, WAY overboard to overcome the bogging at speeds over 50mph, which explains why I was always running in the 12's on my A/F gauge when on turnpikes (and you could see the gauge dip WAY into the lean end for 2 seconds when moderate throttle was introduced).  I guess Dells are supposed to run a lot better than mine (without working accelerator pumps) so this should be a cool trial of how decently set-up Dells should really work;

On the mains, I went from a 162.5 to a set of 140's BUT!  Now, with real, working accelerator pumps (set slightly heavy over "stock"), the transition "bog", even on the mains, should go away, PLUS I should gain a bit better fuel mileage - maybe go from my current 25-26 into the 30's?  We'll see, and I'll report, but not until next Spring.  

In the end, I might finally begin to get close to Jack Crosby's performance and mileage figures. And even if I don't, we both have white cars with comfortable seats, so that's something.

Thanks for the input, everyone!

Hey, I know I'm late to the game but since I just got a set of Dells installed last Saturday I couldn't answer your question. So in my stock 1915 cc engine with 36 DRLA Dells Pat Downs installed 135 mains, 60 idles, 35 pump jets, with 180 air correction. Now I don't know what any of that means other than Pat did it and now it runs A LOT better than it did before. But I am trying to learn.

Gordon:

Here's whats in my 2110  

Dual 44 IDF Weber carbs with

32mm venturies, match ported intake manifolds

.60 idle jets, 200 air correction jets, 135 main jets

1.   Attitude and Altitude are everything!!! (we are 308 feet above sea level here in Fresno, CA)

2.  Is your 2110 engine getting  enough carburetion  with the 40mm's?

3.  Do you like baloney sandwiches?

Tebs

Jetting all depends on Venturi size and if the carbs have had any updates like the jet doctors or update kits. If they are bone stock 40mm DRLA carbs, the tried and true starting point is 180 a/c, 140 mains and .60 idles. Jet doctors can sometimes require a larger idle jet do to the direct air inlet from the idle jet holder. Update kits can require a whole new jetting combination do to the fact that the spray bar isn't as efficient as the stock booster Venturi. A wide band a/f gauge is your best friend if you can get ahold of one and your exhaust type allows the installation of the 02 sensor. Another thing to keep in mind is the inlet valves, "needle and seats". Dellortos are notorious for running the float bowls dry of fuel. The float bowls are small and the floats can only function with 2.5-3psi of fuel pressure. I would install a minimum of .200 needle and seats in 36-40mm drllorto carbs and .250 in 45's and 48's. Make sure your fuel pressure is no higher than 3psi. 2.5 is allot safer. 

DAMN!!!!

I was just going to say the same thing Gordon

   Pat Downs beat me to to punch!!

Thanks Pat!!

Tebs

Teby, 40 DRLA carbs should be fine on a 2120cc engine but it all depends on how it's built. A mildly built 2110 is perfect for 40's but with a higher flowing set of heads, more cam and valve lift, larger exhaust, they could become restrictive 

Hi, Pat

These are 40mm Dell DRLAs I got from CB back in the mid-1990's, but I installed the Horizontal Discharge tube kits before I ever used them.  That's all that has been done to them.  They are otherwise bone stock with .60 idles, 140 mains, 180 air corrections and the new venturiis from the horizontal kits. The engine is a 2,110 with MOFOCO 044 heads, the CB/Dell intake manifolds for the 40's (I opened up the manifold runners to match the heads - they were originally sized for stock DP ports) an Engle 120 cam and a Berg extractor (a older 907DP - I think it's 1-3/8" pipes with dual mufflers).  Not sure about the bowl pilot valve size - I used whatever comes in the CB/Dell Rebuild kit for 40mm's and I'm running a CB fuel pump at about 3 lbs.  This set up has been OK for me, although running rich most of the time (12.8-14-ish on the gauge) with a bog spot between 2,500 and 3,500 rpm that would swing lean to over 16.5 for a couple of seconds - THAT should be cured now with working accel pumps.   I set the pump strokes to about 6cc's per 2 strokes, using Pat Tomlinson's book and now I know how to adjust them properly.

It seems that either the accelerator pump actuator set screws were never installed to lock them to the throttle shafts, or they fell out along the way, because they weren't in there and the pumps were never working (and I never noticed, but these were my first Dells).  I overcorrected the idle and main jets to compensate and it has run OK (with that bogging) ever since.  I'm hoping with the combo above, which gets me back to a stock starting point, and with working pumps it'll be a lot tamer-running.

I also have an older, on-board CB air/fuel monitor gauge and will be using that to fine tune them once running again.  I have the O2 sensor between the collector of the header and the muffler flange:

Please let me know if I need to tweak anything before I fire it up - That should happen Monday or Tuesday.

Thanks for the input, guys!

The bog you are experiencing is in the transition area from idle to main circuit. If the problem persist after the accelerator pump issue is fixed, I would move up one size on your idle jet and maybe bring the air correction down to a 160. 

I have never been a fan of the update kits. Yes they do make more power but sometimes can cause driveabilty issues like you are experiencing. 

  You would benefit more from tuning if you could move up to a wide and a/f meter over the old analog unit you have. Tuning would be faster and more accurate.

Thanks a lot, Pat - Good info and much appreciated.  I honestly don't have any experience with a "stock" pair of DRLA's - they've had the horizontal discharge tubes since day one, but I'm expecting that now that I have everything in them set to spec they should be easy to dial in.  I have a set of .65 Idle jets (just swapped them out for the .60's, in fact!) so that will be easy, and going to a 160 air correction is easy, too, if I need to, but I think I should be pretty close.

My son has a wide band A/F unit from his tuner days so if I need it I have one.

Thanks for the info, and have a great Holiday season - We're just breaking 50º today and the unheated shop is about 40F    Brrrrr!

Pat Downs posted:

The bog you are experiencing is in the transition area from idle to main circuit. If the problem persist after the accelerator pump issue is fixed, I would move up one size on your idle jet and maybe bring the air correction down to a 160. 

I have never been a fan of the update kits. Yes they do make more power but sometimes can cause driveabilty issues like you are experiencing. 

  You would benefit more from tuning if you could move up to a wide and a/f meter over the old analog unit you have. Tuning would be faster and more accurate.

So, are you saying the update (44 webers/2110) kit I recently bought was a waste of good money?

I was thinking of buying that update kit for my Webers, but maybe I'll just leave it alone now!

Well, my 2,110 seems pretty stout to others that I've driven (specs up above) and I have had 1 clogged jet in 17 years, so I have to say that at least the change to horizontal discharge tubes has been a good, reliable upgrade for me.  Super-easy to install, too, or remove, if that's what you want.

My drivability issues were not related to the discharge tubes, but to non-functioning accelerator pumps and unfamiliarity with the Dellorto carb to know the difference.  That they performed as well as they have for 17 years is a strong credit to their good design.  Now that I know better how they work and how to properly adjust them, I am certain that I can dial them in lightyears better than they were before, and before, they were really good.

Can't wait to see how it performs with a proper carb set-up, now.

crhemi (Bill) poboiinhawaii posted:

Pat Downs posted:

The bog you are experiencing is in the transition area from idle to main circuit. If the problem persist after the accelerator pump issue is fixed, I would move up one size on your idle jet and maybe bring the air correction down to a 160. 

I have never been a fan of the update kits. Yes they do make more power but sometimes can cause driveabilty issues like you are experiencing. 

  You would benefit more from tuning if you could move up to a wide and a/f meter over the old analog unit you have. Tuning would be faster and more accurate.

So, are you saying the update (44 webers/2110) kit I recently bought was a waste of good money?

Never said they are a waist of money. On some engines that are built mildly, they can contribute to a mid range hesitation due to the larger Venturi. The update kits are a great item, CB had sold thousands of them over the years.

I have 44 IDF's and 36mm venturies. I have a little hesitation that I think a smaller venturi would get rid of. I don't do the high rpm thing. The highest I go on rare occasion is 5500 rpms so I'm not worried about losing the performance at the high rpm range.

Pat - I have one of your 2110 engines built around 2005 for IM. Would 32 or 34mm venturies help? Would I have to re jet? What jet setup would you recommend?

Yes, dropping down to a 32mm Venturi with 135 mains, 200 air correction and 60 idle jets would clear the hesitation up completely.

Rusty, I had the stock 36's in my 44 IDF's (2110cc), tried the 32's and they were too small, the 34's were perfect with 135 mains, 185 airs and 60 idles, hesitation gone!

Each engine is different and mine isn't a CB, it was built by John at Powerhaus.

Teby, I just noticed, you have a new girl! I've always found I run too rich when I eat baloney sandwiches, car runs fine though.

Will

Back in November, @Pat Downs wrote: "The bog you are experiencing is in the transition area from idle to main circuit. If the problem persists after the accelerator pump issue is fixed, I would move up one size on your idle jet and maybe bring the air correction down to a 160. "

Yup, absolutely right.  Runs great on the idle jets, runs great on the Mains, transitioning between them is Major Bog-City.

Tried giving it a stronger Accelerator pump charge - no appreciable change.

I have a set of 65 idle jets which I'll pop in tomorrow to replace the 60's in there now, and see what that does - it's like June here in Massachusetts so I'm getting out there before the 2'nd half of Winter returns!

Just got done ordering a set of 62 idle jets and a set of 160 air corrections and, hopefully, that will dial it in.  It sure is nice dealing with the jets on Dells......Super easy to get at, even in a Speedster.