This is my first set of Dellortos. Never even played with a set of Webers. I cant seem to adjust cylinder #2. Mixture screw can be turned in all the way and engine runs the same. If I pull the spark plug wire on #2 engine runs the same. If I pull any of the others engine runs worse. I changed the distributor and wires and did not help. Also checked my compression on all cylinders and they were even 115 - 120. These are new pistons and rings and havent run this enough to seat them yet. I'm guessing its fuel related. Is this a common problem with these carbs? My plan was pulling the jets out and blowing them out when I get home. Any carb experts willing to give some advice?

Thanks, Scott

If the idle jet is fouled, Adj the idle air mixture will have no effect. Clean the #2 idle jet. Blow air back thru the jet. Don't loose the small o-ring.

Fouled idle jet will also cause a backfire/pop at idle in that cylinder. It's a common problem because the bypass air intake is at the "floor" of the carb and crap easily get in there.

Are these DRLAs? @914werke has some CB Performance Jet Doctors he's probably not going to use...

Thank you guys. That was my plan when I got home from work tonight. So do you just pull the jet and clean it or do you also blow air into the hole it was in?

Pull the idle jet and lightly blow air into it; watch for any debris coming out of the small hole next to the jet (that's the air inlet port). Then pull the idle mixture screw and blow lightly through there as well.

The "jet doctor" plugs that small idle air hole with a lead shot ball and replaces the idle jet holder with a taller tube arrangement like the main jet uses.

Blow the air the opposite direction of fuel flow. If you hold the jet with a paper towel you might see specks of junk. A can of compressed air works great. Handy tool to carry on trips.

well, got home. Pulled the idle jet and mixture screw. Blew both out. Blew out the carb to where gas came out of the hole next to the jet. Car did run slightly better. Still cannot adjust the mixture screw. Turning it all the way in does nothing. If I pull the plug on the #2 cylinder the engine will stumble slightly now. I swapped the jet with the number 1 cylinder side of the carb. Same thing. So am I to assume the carb is still clogged inside somewhere?

Also wanted to add. If I put my sync tool on cylinder 2 side of the carb, there is alot less vacuum or suction than on the Cylinder 1 side. Almost none at idle compared to the number 1 side. Not saying there isn't any. If I put my hand over it I can kill the motor. Just saying the reading is much less on the tool.

I have Dellortos and I have had the same problem. If I remember correctly it was a sync issue. One carb was doing all of the work and the other carb was not doing much. Pull the linkage and sync the carbs while they aren't connected to one another. Find a good set of instructions for how to sync and set idles and follow it exactly. Make sure the bypass screws are all closed.

http://www.aircooled.net/synchronize-dual-...arburetors-103/

No mention of possible fouled spark plug ?
either get new plugs or change #2 with with a known working cyl.
Then start with that mix screw two turns out

You need to balance the two throats on one carb by opening the idle air bleed screw of the throat with less flow until they match. The air bleed is the recessed (hidden) screw on the base iirc.

Good idea on the spark plug. I've had some foul after a spark problem before. I'll try swapping it out tonight. I'll also look for that bleeder screw adjustment. I've been looking for videos on these carbs and havent found much out there. Nothing that went into balancing the two sides!

Thanks!

CB Performance sells "the Dellorto bible" with everything you need to know. It's a bit disjointed, and many pages are out of sequence (and some are redundant -- it's self-published) but it's a very good book to have if you're a Dellorto owner.

http://www.cbperformance.com/product-p/0101.htm
https://www.amazon.com/gp/product/B00SLH03R4

I went through that whole thing while I was rebuilding my 40 DRLAs and came to re-kindle the love with my long-lost inner-carburetor...though I do wish I could plug in the USB port and get some error codes once in a while...

100%

I used to have DRLA40's on my old 2270. The two throats of each carb need to be balanced individually, and then the two carbs need to be balanced. Then connect the linkage and make sure the balance is still true.
If the two throats of the same carb aren't balanced, you'll get the behavior you're describing on that carb.

The air bleed screws are tiny little screws near the base of the carb, two per carb, hidden in a recess that you probably won't be able to see into. You'll need a tiny little flathead to adjust them.

Be glad you got DRLA's and not Webers! Dells are fantastic carbs once you get them adjusted. I used to go 6 months or more without tuning them, and then when I'd go to check them they'd still be in sync. Very much set and forget.

I agree with an exception. Carbs in unkown state. Seat both air bypass screws first, then balance the flow. I typically run with one seated and one open slightly.

Carlos

Update. Replaced the plug on cylinder 2 and i can now adjust the mixture screw! Strange as all the plugs were new. Guess it got fouled. I havent tried syncing the carbs again as I am waiting for a better sync tool. I've been using my 25 year old Uni sync. engine feels better already!

I tried turning the little air bleed screws before replacing the spark plug but I couldn't seem to get them to turn. Very tight! If I have the same problem when I get my new sync tool I'll give them another shot. Maybe I need to hit them with some PB blaster? Didn't remove them during the rebuild.

[/quote]
I tried turning the little air bleed screws before replacing the spark plug but I couldn't seem to get them to turn. Very tight! If I have the same problem when I get my new sync tool I'll give them another shot. Maybe I need to hit them with some PB blaster? Didn't remove them during the rebuild.
[/quote]


That's not good. I have a 45 drla body that is has a single air bypass screw cranked so tight I can't loosen it. If any one has an answer for this, I can have a backup set.


Carlos