engine and drivetrain carb Q: I know its been asked 1m times-BUT

[jetboy]

i need some help tuning dual side draft solex and thought id put it out again in case some expert has come along recently.

i keep having troubles above 3k, but its not vacuum (as far as I can tell) and the jets should be close enough - but not sure (is there a way to test without getting other jets-- cause i got no others)

here is where it stands- took it out today and I can rev the engine to 3 k while standing, drop the clutch and peel rubber off my tires- (just to show it works well under 3k) but as soon as it hits there-- it sputters and misses and dogs-- and develops smoke which i assume has to be gas which is not burning - or oil that only shows up after I push it hard for a while -

so the question is, if this was you and you didnt want to *just switch the carb idiot" because you love punishment, what would you start with - ?

[KFunk]

whats the fuel pump situation?

[jetboy]

stock mechanical pump, which is sufficient if its in good working order. that is one thing I have not tried-- if you suspect it then its worth a shot-

now that you say that I do have another one that looks like crap - but maybe it works fine. ill try that!

thanks-

[KFunk]

Maybe, I dunno. Lots of people swear by mechanical pumps, but I never had any luck with mine. It wasn't getting enough volume for some reason, and cuttin out under load with just my single 32/26.

Just wondering if maybe you got a weak stock pump as well, which isnt getting enough volume at high RPM.

Correct me if I'm wrong someone, but if lack of fuel is the problem, then the engine should rev up a lot better if you're sitting still with no load on the engine, just pushing the gas. When you put it under load, the lack of fuel issue will make it stumble and cut out. Atleast thats what happened with mine.

Really though, I'm no expert on this subject at all, and just a beginner as well. I'm just trying to get the ball rolling a little since nobody else is saying anything right now.

[jetboy]

its certainly worth a shot- !

[mikeS]

Hmmm...please clarify...

1. Will it go over 3k when you're revving it in neutral?

2. If (1) is 'yes', can you get it over 3k while moving if you're on flat ground and you're just BARELY cracking open the throttles, e.g. not flooring it?

3. What size venturis, jets, etc?

4. Does it backfire out the tailpipe, or backfire/spit out the carbs?

Mike

[jetboy]

1. yes

2. yes, but it takes some effort because it starts to miss

3.idle jet is 55, the rest I am not sure as I cannot reach them easily when installed- but I was *told* that they are speced to a stock engine and worked well on a stock before. 55 is a little large for idle, (52.5) but I was told that as a solex ages it needs slightly larger jets due to wear -

4. it spits a bit of fire when its cold out the carbs, but not when its warm - none out the tailpipe. i can adjust the timing to stop this, but advancing too far seems to make the missing/smoking worse. i have adjusted the valve clearance-and am running a petronix with new plugs, wires, and distro cap. could it be the dizzy?

[napa02]

Check your Pertronix, replace with properly adjusted points and see if condition changes.

[mikeS]

I would agree with napa...rule out ignition problems before digging any deeper into the carb. I could be the distributor, Pertronix, the coil, or ---don't wince at me--the firing order (I've done that myself before, drove me nuts...idles fine, revs in neutral, won't rev in gear). Also, make SURE the throttles are opening fully, and aren't sticking at about halfway. Once you're satisfied that it's not the ignition or linkage, I'd play with the main jets--at 3k you should be getting off the idle jets and onto the main jets. They could be just clogged, too, or the float setting could be wrong.

Usually Weber sidedrafts have the opposite problem...they go great at the high end, but the low end dogs out. This is usually because of poor vacuum at the low end, when the throttles are open and there is no air velocity.

Mike

[jetboy]

thanks!- and have some new info for you all:

today i took it out for a bit and found out this:

in first gear I can go past 5k no problem -

in second 4k- cant quite hold smooth but does it

in third i can do 3k, but not well

and fourth sucks---

when i hit a slight down grade i could go to 4k in third and no missing, but as soon as a hill started-- missing---

i picked up a free fuel pump today, give it a whirl--

[FL02]

Napa's probably right. I had the same issue on my car before I installed the pertronix sytem and new wires. It was like the car would break up over 3k just like yours did. I thought the points got wet once and were bad. Then I had some slight similar issues with the pertronix EI but it was because one of the little screws came loose and the sensor was vibrating, now everythings is tight and it runs like a champ and revs through the full range. The ignition system with the new hi-perf wires helped out alot, good luck.

[boxy02]

subscribing to thread...

[jetboy]

i switched the fuel pump- no great difference->

but i have to pospone other tests as I was revving and driving - and punched it off a stop sign and chopped the bolts on my rear axle-> yaih!

[jetboy]

well, fixed the axle-- so back in business->

and it looks like the new fuel pump is helping, when i first threw it on my carbs were all strangely set to try and compensate for the fuel - so its actually running better now that i made some adjustments -

I have yet to change the distributor - but ill see how far i get with just tuning and if it still doesnt work quite right all switch the petronix out. with these type of problems it seems its often mroe than jsut one thing out of whack - everything just a little wrong makes for a big wrong result - yah

for those trying to tune these beasts, i have recently had luck getting the engine all warmed up, then pulling the spark plug wires one at a time and listening for the change-- and then adjusting the idle/mixture screws until the change is consistant no matter which plug i pull. its not perfect but gets you within a range that you can work from.

[jetboy]

Well: its getting better slowly-- each thing i do seems to be an improvement:

this time: I dug around in the parts that came with the car and found what looks to be an OEM coil- all covered in grease and gunk - cleaned it up as best i could- threw it in in place of the "firebreather" the PO had installed- and damn if that doesn't help quite a bit!!!! this thing looks like its from the 70s- but i can hear it clicking away quite clearly when I remove a plug wire-- i never could hear it so nicely with the firecrapper, as i will now call those coils from now on! its workign so nice, i got to get me a nice new OEM one and I bet thats gonna help quite a bit!

it always takes a bit to see how much it reallyhelps cause i got to re-tune everything everytime i change something in the chain of power-- but i think its close-

its only stumbling the slightest bit now, and that might just be timing - NO LONGER THE INSTANT DOG! who would have thought the old greasy ugly black coil would rock the sleek silver beast!

for those with PHH solex, i have also found this interesting fact: the two idle screws between 1/2 and 3/4 do not have lock nuts on them (at least mine don't) and as yo drive-- they vibrate and begin to turn. feck! a bit of driving and all teh tuning im doing is getting erased and im wondering what the hells going on.

so got to get some lock tape or a little nut to put on there!