Best place to get the correct parts is from dellorto.com in the UK. They ship fairly quickly and
have reasonable prices.

 

you are correct sir, that is the correct source for factory parts and the only one i have ever used.
currently working on a few mods to better the tip in transition, but results have been poor so far,

 

His user name is Alpha1750. He ships fast and has everything from idle jets to emulsion tubes to boost prep kits.

I'm currently boosting an original Racing Beat DHLA 48 using his kit.

Just trying to give anyone looking for parts *another* option.

 

Just pulled my dellorto back apart after reading about the RB mods. I thought " oh ****, Ive got a lot more to do"

.....turns out it was already done with the same exact mods and jetting specs ! Shewwww buddy.

 

My front rotor seems to be running richer than the rear rotor. The rear plug was a nice tan where the plug from the front rotor was slightly black. The engine is a 13b from an RX4 that was street ported fitted with a header and Dellorto 48 DHLA. Took the carb apart and thoroughly cleaned it, reassembled it with new O rings, diaphragm and gaskets. All the jets are the same size for the front as they are for the rear rotors inside the carb. I don't have an air flow meter to check if the front is drawing the same as the rear but will ask some friends if they have one. Is there an adjustment on this carb to adjust that? Do both mixture screws end up the same number of turns when adjusted properly or is it okay to be different? My guess is that they can be different if the two rotors have different compressions which mine does. Don't think that is unusual because all four engines I have are that way. What made me check the plugs was the way the engine idles. It doesn't have a smooth constant idle like the stock engine but has a bit of a surging to it.
Does anyone have adjustment advice for me?
Thanks in advance.

 

Yes the adjustment screws for the idle can and will be slightly different front to rear. Keep using the
plug color like you did and you can get them pretty close.

The idle will never be as smooth as a nikki. Nature of the beast. That long wrap around intake and
the 2 large barrels at low idle to not atomize the fuel mixture as well because the velocity is not
quite there. You can either run a higher idle or adjust it until its the best you can get and live
with it. The Dell idle and sound as you open the throttle is really one of its cool features.

 

Maybe your brake booster has a small leak. It contributes to a lean rear rotor if that is where the vacuum fitting is installed on your manifold.

 

I will give that a try tonight, the drive to work and back tomorrow should be enough to show. Twenty five minutes one way. Will have to see what the brake pedal feels like first though.

 

Went out and disconnected the booster hose. The car had been sitting for about three hours since I came home from work, there was still lots of vacuum on the booster. Tells me the booster is good and the check valve is good. I did put some new clamps on it while I had it apart. Good thought though!

 

The main reason I looked at the plugs is I'm trying to figure out why the engine vibrates more than usual around the low RPMs, it goes away at 4000 rpm but is most noticeable around 3600- 3900. The new motor and transmission mounts are quite solid and lots of the vibrations are transmitted into the car now as well as the steering wheel and seat. I got the mounts from Racing Beat which are Mazda competition and are suppose to be twenty percent stiffer than stock. My old ones must have been really shot because as I said earlier they almost feel solid. (Love them though) I've had to Locktite quite a few screws throughout the car that worked themselves out since I installed the engine about two months ago. It's not a drive line vibration because it goes away when you push in the clutch and does it sitting in the garage. I have also removed the belts for the A/C, alternator and removed the fan from the water pump. If that's the way these engines run then I can live with it but I just want to make sure I'm not going to damage anything over time. Then I will just keep the RPMs over 4000 and be fine.

 

edit.....I thought if the rotors were not getting the same fuel mixture there could be a vibration more noticeable at lower RPMs.

 

so, im trying to get my rx-7 with dellorto (85 12a) going again.... that hasnt run in over 8 years.....

ive replaced plugs and wires, new gas, fixed a ignitor issue, changed the oil..after soaking chambers in mmo for a few days before turning it over.....

verified fuel at the carb..verified both leading and trailing spark......but, only way i can get the engine to fire is to put a bit of gas directly into the carb intakes.....then it fires, but dies as soon as the gas is gone......

where should i start......?..

.thanks guys

 

If you look directly into the throats of the carb with the air cleaner off does it squirt gas when you give throttle...?? Obviously do this with the car NOT running. If not, the needle and seats get stuck from sitting extended periods of time. Try tapping the top of the bowl where the fuel fitting is with the back of a plastic screw driver handle. That can shake them loose sometimes. Otherwise get in there and clean it up.

 

Ok, will try this, is there a DIY for "getting in there and cleaning it up" lol....... Carbs scare me a bit.....

 

Start by verifying that you can get gas form the tank at the rate and pressure needed. This is
as simple as pulling the line off the carb and putting it on a bucket and seeing how long it takes
fill it to some known amount. Should be about 1/2 gallon a minute or so. The pressure should
be 2.5 psi or it will have running problems.

If you are getting gas then take the top off and make sure theres not a lot of gunk. If this was
stored with old gas you will need to pull and do a rebuild. Best places for a kit it in england,
dellotro.co.uk.

 

Ok, so today checked fuel pressure ( with the bucket).... Seems ok, No fuel seen in intake when accelerator pressed.... took carb top off, removed each jet one by one and cleaned with carb cleaner.... Cleaned the floats, and all associated linkages....there was a bit of foreign material here and there..... Put it all back together , and..... Same...... No run unless raw gas in intake..... So took carb off car ...... Any ideas where to go from here... Pump on the bottom maybe?

Edit.....pulled the pump cover on the bottom......ummm...is this right?..... Looks like a lot of silicone crap in the way of that spring......

 

Eww! Thats nasty. Looks like someone tried to fix a leak in the AP. I think you need to fully clean and rebuild it to make sure that gunk is not in any small orifices.

 

That's kinda what I thought.... A bit disappointing considering I had sent it away to a very reputable member on here for rebuilding.....that was 10 years ago, it never did run after I got it back, and life got in the way..... ..so does anyone have a picture or can tell me what it should look like?..... Do I need a gasket in there?

And I guess, more importantly, would that mess cause my above non running issues?

 

This site can help you with a ton of information about the carb: Gruntled.com - Dellorto Intake System

RB made a special thick gasket for the AP to give a bit more volume. You can recreate it with
gas safe gasket paper by using 2 or 3 together. You will have to cut it out yourself.

Given that mess was on there I would say yes there may be other issues that are causing it
to not run right.

 

Ya, ill be cleaning it this week,
And I knew about gruntled.com from way back......

I was just looking for a "how to rebuild your dellorto" guide,as I really enjoy doing it myself, but am hesitant when it comes to carbs.

Also, can one still get that special RB AP gasket ?

 

RB gasket is NLA, you will have to make your own.

 

What experience do you guys have running a different weight float?

MY RB Dellorto original float is a 7gram float, 7298.3.

It is due for replacement, one of the sides is starting to show sign of fuel getting inside. Don't want it sinking on me.

I looked around and it seems that 7,8.5 and 10g floats are available. I can get NOS Dellorto 10g floats for the best price. Seems you can find 8.5g floats but they are quite a bit more $$.

Heavier float will mean a different float height setting, (16.5 to 17mm).

My RB Dellorto was sitting at 15.5mm (with gasket) and 7g float. I think this was maybe a bit too low of a float bowl level.

One reference says he prefers the heavy float as it results in easier to set bowl levels and more consistent levels.

Any experience here?