Dellorto 36 idle mixture screw not working?
- Thread starter dubdubz
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dubdubz
Well-known member
ok still confused
the carbs have been swapped - the manifolds and the bakelite gaskets have remained on the original side.
the compressions have been checked and all at 150psi or there abouts
BUT I still have a non responsive idle mixture on #2
so it can't be the carb - or idle jet as this was on #3#4, the entire carb has been swapped across.
the only thing - which I'll remove tomorrow is the bakelite and gaskets, obviously I'll need to put a gasket between the manifold and carb.
So the problem is still on #2, but compressions ok, the plugs have been cleaned and the plug that is now in #2 was in #1, so I can't see it's that. I may try the original sp lead back into the mix, but can't see it's that.
So really the only thing that hasn't been changed is the bakelite spacer and the gaskets, guess that's the thing to change then.....
the carbs have been swapped - the manifolds and the bakelite gaskets have remained on the original side.
the compressions have been checked and all at 150psi or there abouts
BUT I still have a non responsive idle mixture on #2
so it can't be the carb - or idle jet as this was on #3#4, the entire carb has been swapped across.
the only thing - which I'll remove tomorrow is the bakelite and gaskets, obviously I'll need to put a gasket between the manifold and carb.
So the problem is still on #2, but compressions ok, the plugs have been cleaned and the plug that is now in #2 was in #1, so I can't see it's that. I may try the original sp lead back into the mix, but can't see it's that.
So really the only thing that hasn't been changed is the bakelite spacer and the gaskets, guess that's the thing to change then.....
dubdubz
Well-known member
I might try that again....but my mind is set on removing the bakelite and gaskets.......
I recall on my dells a simular issue. took out the idles, and mains. now looking fron the top of the carb, you see the idle hole has another hole next to it.. about half way down the idle hole is a lil hole that joins these 2 together.
mine was blocked proper tight. took careful work with some .7 steel wire. once unblocked it idled n could be dialled in right.
worth checking of not.
Sent on tapatalk pro.. Making a free forum a paid for app
mine was blocked proper tight. took careful work with some .7 steel wire. once unblocked it idled n could be dialled in right.
worth checking of not.
Sent on tapatalk pro.. Making a free forum a paid for app
dubdubz
Well-known member
it can't be the carbs - as they have been swapped over from left to right - the entire thing [ well apart from the throttle arms as they are handed ]
it can only really be the gaskets around the bakelite spacer or some weird valve issue - the compressions are all the same and good readings.
I basically get the same issue [non responding idle mixture screw - can screw it all the way in and not get the cyl to stumble or drop revs] on a carb that worked fine on the other side, ie the mixture screws operated exactly as expected.
I am truly suspecting the bakelite bits - which is why they are coming off in about 10mins. If that doesn't fix it then I am stumped and will probably drop the engine. I suppose the only other slight possibilty is both pushrods got bent? and the valves aren't opening correctly, the actual compression when valves are shut are right, it could be the valves aren't opening to have that cyl as functional as the others.
If the gasket removal doesn't fix it then - that is my next port of call - to swap the rockers and check pushrods....
exciting isn't it......... :lol:
it can only really be the gaskets around the bakelite spacer or some weird valve issue - the compressions are all the same and good readings.
I basically get the same issue [non responding idle mixture screw - can screw it all the way in and not get the cyl to stumble or drop revs] on a carb that worked fine on the other side, ie the mixture screws operated exactly as expected.
I am truly suspecting the bakelite bits - which is why they are coming off in about 10mins. If that doesn't fix it then I am stumped and will probably drop the engine. I suppose the only other slight possibilty is both pushrods got bent? and the valves aren't opening correctly, the actual compression when valves are shut are right, it could be the valves aren't opening to have that cyl as functional as the others.
If the gasket removal doesn't fix it then - that is my next port of call - to swap the rockers and check pushrods....
exciting isn't it......... :lol:
i still say put new plugs in,also swap lead say with no4 lead to see if thats ok .have come across whiped out cam follower as well so not opening valve check lift against 4cyl with rocker cover off see if same
dubdubz
Well-known member
had to go on a trip - thanks for the suggestions
I intend to;- [when I get back]
remove bakelite spacers and install a new gasket [no spacers]
install new coil - the one I have is old and consider it worth doing
I'll also install a new rotor and cap, again preventative maint really and just to be sure
I'll also triple check the static timing, and the strobe as I've made a few changes - it'
s again worth having the baseline.
then if still not playing ball - I'll look into lift and checking rockers, pushrods etc
how fat should the spark be - it's quite bright but possibly too thin?
I also loosly wonderd if there was anything distributor wise that may cause this, sticking shaft?
I intend to;- [when I get back]
remove bakelite spacers and install a new gasket [no spacers]
install new coil - the one I have is old and consider it worth doing
I'll also install a new rotor and cap, again preventative maint really and just to be sure
I'll also triple check the static timing, and the strobe as I've made a few changes - it'
s again worth having the baseline.
then if still not playing ball - I'll look into lift and checking rockers, pushrods etc
how fat should the spark be - it's quite bright but possibly too thin?
I also loosly wonderd if there was anything distributor wise that may cause this, sticking shaft?
dubdubz
Well-known member
OK now I'm completely baffled.
I have installed carbs - checked timing and valve/tappet gaps.
new gaskets on manifold /head
new gaskets on manifold / carb
set rpm to 800 eventually - it doesn't run right pulling #2 doesn't change so running on 3 cylinders?
sprayed carb cleaner around #2 manifold base and around carb base no change in engine note, also listened with tubing no hissing at all
NOW this is weird - if I put my hand over the velocity stack and in effect reduce the airflow into that barrel, the revs pick up and the removal of #2 plug lead does drop the revs.
so what is causing this?
if I restrict the other throats the revs drop not increase they drop
bear in mind that the carb cannot be at fault as I swapped #3 carb over to #1 - the fault stayed on the same cylinder.
The comp are all 150 psi.
there is a spark that jumps 3/4" and is blue, the lead has been changed, the plugs have been moved around too, and the fault remains on #2. It isn't intermittant it is there all the time.
where do I go from here?
I think I will drop the valve covers off and see the movement on the rockers.
Oh by the way there's a reward for fixing this or suggesting the thing that ultimatley solves it.....it's doing my head in
I have installed carbs - checked timing and valve/tappet gaps.
new gaskets on manifold /head
new gaskets on manifold / carb
set rpm to 800 eventually - it doesn't run right pulling #2 doesn't change so running on 3 cylinders?
sprayed carb cleaner around #2 manifold base and around carb base no change in engine note, also listened with tubing no hissing at all
NOW this is weird - if I put my hand over the velocity stack and in effect reduce the airflow into that barrel, the revs pick up and the removal of #2 plug lead does drop the revs.
so what is causing this?
if I restrict the other throats the revs drop not increase they drop
bear in mind that the carb cannot be at fault as I swapped #3 carb over to #1 - the fault stayed on the same cylinder.
The comp are all 150 psi.
there is a spark that jumps 3/4" and is blue, the lead has been changed, the plugs have been moved around too, and the fault remains on #2. It isn't intermittant it is there all the time.
where do I go from here?
I think I will drop the valve covers off and see the movement on the rockers.
Oh by the way there's a reward for fixing this or suggesting the thing that ultimatley solves it.....it's doing my head in
jacks906
Well-known member
are you using electronic ignition?
i had similar symtoms (would run fine but on one cylinder no matter what i did i couldn't change the engine note, covered up the port played with the carb)
dave
i had similar symtoms (would run fine but on one cylinder no matter what i did i couldn't change the engine note, covered up the port played with the carb)
dave
dubdubz
Well-known member
I am using a pertronix, I was considering trying points, but I have decided to drop the engine and check a few things anyway [deck height and record it this time, cc the heads and record it this time, set rocker geometry correctly and not the way it currently is.....etc etc]
I suppose the collar on the petronix may have a weak magnet? although I do get a spark on 2, blue one and will jump 3/4"
and even if it was fixed this morning, I'd still be dropping as there's a few things that are niggling me.....
I'm running a dual thread [ so as to catch the non EB'ers ] http://www.volkszone.com/VZi/showthread.php?p=7520512#post7520512" onclick="window.open(this.href);return false;
I suppose the collar on the petronix may have a weak magnet? although I do get a spark on 2, blue one and will jump 3/4"
and even if it was fixed this morning, I'd still be dropping as there's a few things that are niggling me.....
I'm running a dual thread [ so as to catch the non EB'ers ] http://www.volkszone.com/VZi/showthread.php?p=7520512#post7520512" onclick="window.open(this.href);return false;
jacks906
Well-known member
ahhhhhh cool will go have a read over there 
an mine was a pertronix setup, worked fine then just gave up so back with points an condensor now alot better :mrgreen: but having troubles with the dells now :?
an mine was a pertronix setup, worked fine then just gave up so back with points an condensor now alot better :mrgreen: but having troubles with the dells now :?
dubdubz
Well-known member
engine out - wonder what I'll find....
Jacks906 so did your petronix stop working on 1 cylinder?
Jacks906 so did your petronix stop working on 1 cylinder?
dubdubz
Well-known member
8) just upping the thread so Jack sees it
jacks906
Well-known member
sorry dude missed it
yer totally stopped working on one cylinder :? not sure why, never had a good look at it but there was no damage to the magnet ring bit or anything just didnt fire at all on No1.
hope yours is a simple fix
yer totally stopped working on one cylinder :? not sure why, never had a good look at it but there was no damage to the magnet ring bit or anything just didnt fire at all on No1.
hope yours is a simple fix
dubdubz
Well-known member
jacks906 said:sorry dude missed it
yer totally stopped working on one cylinder :? not sure why, never had a good look at it but there was no damage to the magnet ring bit or anything just didnt fire at all on No1.
hope yours is a simple fix
thanks - did the compass trick to see if the magnets were working seem to? will check and possibly replace - the pertronix is probably 6yrs old :lol:
