Dellorto Over Fueling after cleaning

[dave275]

Elan +2 135/S

Hi,
Hopefully someone can help or point me in the direction of any previous posts.
For a while now I have suffered from a misfire on acceleration, which is well covered on the forum. However having to take off my Dellorto's, though I would try too give the jets a clean before re-assembly. Mistake! specially as I have no experience working with Dellorto's.
Now the carbs are completely out of tune, main problem being the engine revs out of control. I have read about the cause of this somewhere on this forum, but now can't find the relevant posts. Have searched "over revving" etc, could someone point at the correct terminology.
I have reset the float levels to 17.5 which I think correct for 10gm floats.
Looks like 3 and 4 are over fueling.
I removed the jets to clean and examined/cleaned other items accessible on the top of the carbs. Assuming because they were fully screwed down it would be fine to do so and simply put them back (doohhh).
Would just like to get the engine running, so it can go off the be professionally tuned.

Thanks an embarrassed,
David.

[nmauduit]

Would you have rechecked the fuel level in each carb after reinstallation? If all is back together clean I would first look along that line (float/valve alteration ...)

[alan.barker]

Hi dave ,
have you also fitted an ALL metal Fuel Pump made in India because these produce tooo much pressure so flood carbs.
Alan

[dave275]

Hi Both
Thanks for the replies and you both are pointing me towards over fuelling through the float chambers.
Currently away so can’t check out the fuel pump. All I remember is it is metal with a glass bowl, will take a closer look.
I have reset the float levels to 17.5 because of the 10gm floats, metering needles valves are metal. When I opened up the chambers 3 & 4 did appear to be holding more fuel however. I will check them again and try to lift the lids without disturbing the fuel level, to check.
These are the parts I took out and cleaned:
Main jet @ emulsion tube.
Idling jet & emulsion tube.
Starting jet & emulsion tube.
Pump jet.
Delivery Valve.
Pressure connection and progression holes.
Starting valve.

One positive I know know a lot more about Dellorto’s than a few day ago.

Thanks for the advice.
David.

[richardcox_lotus]

Another cause of overrevving could be vacuum leaks through the orings- did you renew them when you removed and replaced the carbs.

Regards
Richard

[bitsobrits]

It is extremely unlikely that anything you did with the jets would significantly increase idle speed. Extra air certainly will cause an idle increase. Sources could be from leaking O rings as noted, or misadjusted carb balance, or misadjusted idle bypass screws, or a twisted throttle shaft. I would reccomend you get a Dellorto manual and do a complete from the beginning setup up in order to determine what you changed.

[dave275]

I did replace the O rings, but will go back to check they are sitting correctly.
Then work my way down Steve's list of possible other causes.
Good to know I might not have causes any problems with the main jets.

[dave275]

Hi all,
Still struggling, but getting good at getting the carbs on and off.
So far:
Turned over the engine to fill the float chambers and this time carefully removed the covers and checked the levels. Looked ok all around 27/30 mm from the top of the casting.
Proceeded to remove the carbs and examined the O rings. All appeared to be seated correctly inside the groove, although one jumped out on number 4. So this could have been a problem. Also noticed when the O rings are removed from the spacers, they had all expanded and would not sit back in the grooves. Have been told this is caused by too much fuel soaking them.
New o rings on order!
Re-assembled again using the original O rings, carefully setting the gaps.
This time the engine starts much better and smoother, but once the throttle is pressed and released the engine just continues at high revs. The butterflies are fully closed, so I assume the fuel must be arriving via the idling jets, driven by an air leak?
Because my head has been stuck under the bonnet, only just noticed the head lights have no vacuum to draw them down. Sealed both vacuum take offs on the inlet manifold but still no change.
Think I will go back and check all the jets are seat correctly again, as don't think its related to the O rings.
David.

[bitsobrits]

The engine can't rev without air. If you are somehow over fueling things, then the engine should die because it's way over rich. Stop fiddling with the jets and continue to look for vacuum leak sources, sticking throttle cable, unclosed throttles, etc.

Also, wouldn't hurt to make sure the distributor advance mechanism isn't sticking. Remove the dist cap and rotor and check the operation of the mechanical advance is free and returns easily to its rest position. Put a drop or two of engine oil on the screw in the center of the rotor shaft (visible when rotor removed). You're supposed to do that every so many miles (12k?) but everyone forgets to do that.

When it's idling too high, can you (gently) force the throttle plates more closed? When you had the carbs off did you verify the throttle plates close completely (hold them up to a light source)?

[dave275]

Ok the problem is solved and I'm very embarrassed, but am duty bound to fess up.
When I replaced the Carburetors, the throttle lever on the left hand side was not located between the two adjustment screws. I had simply put the right hand lever directly on top of the left. Ahhhhhhhhhhhhhhh idiot.
My weak excuse was only ever worked on SU's and that how they seat.
So the throttle appeared to be fully closed, but was partly open.

Thanks for all your advice.
Now just got to resolve the stuttering on acceleration, which I know is a hole new can of worms.

David.

[mbell]

Ok the problem is solved and I'm very embarrassed, but am duty bound to fess up.

These things happen to us all... but good of you to post so that if other look at the thread they know what happened and may have done the same.

ow just got to resolve the stuttering on acceleration, which I know is a hole new can of worms.

It quite common to have 2.5k/3k rpm transition stumble if you running standard jets. These were configured for the fuel available 50 years ago which is very different to modern fuels, especially E5/E10.

IMO you'll likely want to go to bigger idle jets, maybe smaller mains and raise the fuel level 25mm from the top of the casting as a starting point. I think people have report 50F8(?) + 120 mains working. I run my car on hypojets, but idle is 50xx equivalent and 115 main jets, works well but still some room for improvement.