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Posted by: Petepat Dec 23 2022, 07:07 AM

So I have a 1.8L engine with twin carbs and its very difficult to start, if I put my foot on the gas too soon it just dies, I have to let it run at 2-3 hundred revs until it warms up and slowly cox it into life.It back fires a lot when I take my foot off the gas but often backfires with normal driving. I had the rockers (that's the English word!) checked for gap clearance and there was no gap on any of them!!? but it doesn't seemed to make much difference. Any thing that will stop me snapping, cracking up or popping will be gratefully received. I'm a newbe in the 914 world.

Posted by: Front yard mechanic Dec 23 2022, 08:54 AM

Stop feeding that thing rice crispies and adjust your carbs

Posted by: brant Dec 23 2022, 09:05 AM

Timing also

Posted by: ChrisFoley Dec 23 2022, 09:16 AM

Get a (Weber or Dellorto) book or look online for detailed information about your carburetors.
Open all four idle mixture screws half a turn, one at a time while the engine is idling. Do it gradually so you can notice the effect each change might cause.
Increase idle rpm as needed by screwing in the idle speed screws on the side of each carb.
Buy a Synchrometer so you can match all 4 carburetor throats to work equally. It is important that each intake sucks at the same rate, and gets equal fuel, which takes some fiddling around.

Posted by: brant Dec 23 2022, 09:51 AM

Also pay attention and look at the linkage carefully

Popping can be an imbalance from right to left bank
Or loose/worn out/ misadjusted linkage creating an imbalance

Posted by: Craigers17 Dec 23 2022, 09:52 AM

The folks that have responded know a lot more about carbs than me, but if you haven't already, I would pull out the jets and clean them at a bare minimum. Junk in the jets can also cause backfiring. As already noted, if you have done valve adjust already, then timing and carb tuning is probably next. If you have no idea of the history of the carbs, you might want to get them back to a baseline and adjust from there. There are many youTube videos on this...usually you can find one based on the brand you have....or something close.

If you're having trouble with the car warming up in general, I would also check to see that you have a functioning thermostat/bellows and that your flaps are working properly. The flaps are supposed to default to open as I understand it, which is what you want when your car gets warm, but not necessarily when it's cold. Perhaps your bellows are non-functional or disconnected. Here's a generic video on carb setup that may or may not be useful to you. Being a carb novice myself, it helped me understand some of the nuances of carbs, such as how the low idle circuit is affected by idle speed screw and the angle of the throttle plates. Note: I have Empi carbs so it was particularly helpful in my case.

https://www.youtube.com/watch?v=JvQo-akB69U

Posted by: rhodyguy Dec 23 2022, 10:36 AM

How big are the carbs? 44s? 40s? Other? 44s with 36 venturi are too big for a stockish engine. 44s are pretty big for a 1.8. Very poor vacuum signal at lower rpm. You should not lug the engine while driving around. There might be a number stamped on the mounting flange. What are you using for a distributor? Once over 3000 rpm does the engine wake up?

Posted by: 930cabman Dec 23 2022, 10:38 AM

Did this condition just arise? It could be as simple as clogged jets.

Posted by: Petepat Dec 30 2022, 06:20 AM

Thanks guys, I'll have a fiddle with the carbs and see how that goes. Cheers

Posted by: CCE Dec 30 2022, 01:25 PM

Look for a full time mechanic, he will solve the issues in less than an hour and will make your life beautiful again… or, try lo learn, solve frustration, buy books, spend hours watching videos, and do a half good tune-up… it will be cheaper too… jejejjeje and drive…

Posted by: Petepat Jan 8 2023, 07:36 AM

So I have bought myself a Flow meter and it read 3.5 on one side and 2-2.5 on the other so I have brought it up to 3.5 BUT watching a YouTube the guys doing a tune up and his reading is around 8.0 on both sides, should I be thinking of raising mine a little? Somebody mentioned did the carbs kick in around 3000rpm, well in that direction, they do but seems a bit starved at the lower end.
It's also true I could take it to a pro, but getting to know my car feels good and yes it's a steep learning curve but you guys have already gone before me so that's a great support.

Posted by: ChrisFoley Jan 8 2023, 08:39 AM

Its most important that all 4 are equal.
However, 3-4 is probably too low. You should raise the rpm a bit and get the idle flow up to at least 6. Having the idle a little high (1000-1200) while working out the synchronization is generally a good idea. Once everything is balanced and happy working together, the idle speed can be lowered to optimal (850-900)

If the carbs are unaltered since purchase they are probably too lean in the powerband, and I would be surprised if the float levels are set correctly.

Posted by: Petepat Jan 9 2023, 06:21 AM

Thanks for the quick response and the info, makes sense, will give it a try and let you know

Posted by: rhodyguy Jan 9 2023, 08:40 AM

Use one idle speed screw to raise the idle to a point where the synchro tool needle is not jumping around. The other carb should follow suit. Now, with the idle raised measure the flow on both forward Venturi. Then have a look at all 4. Don’t be in a big hurry. Even small adjustments can take a moment to take effect. It’s not like it’s a manned mission to the moon. Just a set of carbs. The ‘preset’ adjustments/setting are very important. Spare yourself the frustration and get the CB Weber manual.

Posted by: Petepat Jan 12 2023, 03:27 PM

So there is a number stamped on the carbs 3024, does that mean anything? So I've followed the advice given and tuned the carbs and there's definitely much less snap, crackle and pop so thank you one and all. Last question, between the two intakes on the same carb there is a difference of half to one on the flow meter, can you independently adjust the flow for each throat? it's hard to see much in situ.

Posted by: ChrisFoley Jan 13 2023, 04:32 AM

Air flow correction jets are located at the base of the carb. They are the ones locked down with a small (8mm) nut. Gradually back out the jet of the throat with less flow to equalize.

Posted by: rhodyguy Jan 13 2023, 08:27 AM

AFCJ=Air bypass screws in the CB manual. They are set commonly in the preinstall procedure. Get the book.

Posted by: Petepat Jan 14 2023, 06:30 AM

I'm close to throwing in the sponge! but before that what book would you recommend for Delloto carbs? I live in France in the countryside so most professional mechanics in the area are use to tuning 2CV's with a hammer!

Posted by: ChrisFoley Jan 14 2023, 01:51 PM

The Delorto Superformance Tech Book, by Bob Tomlinson

Posted by: ChrisFoley Jan 14 2023, 01:51 PM

thought you were in Florida, lol

Posted by: Petepat Jan 15 2023, 06:55 AM

Trying to find this book is more difficult than trying to tune these carbs! I have however found I think enough on the internet to proceed the only question is do I turn the mixture screw back half a turn or three and a half when tuning? it seems different on different sites.
I'm actually coming to Florida next month for 3 months Sarasota, any car meetings scheduled?

Posted by: Superhawk996 Jan 15 2023, 07:21 AM

Get the Weber book.

Webers and Dellorto are nearly the same with respect to overall layout and tuning principles. The Dellorto book is out of print and much harder to find usually only changes hands in the FS/WTB forum based on postings.

Posted by: Petepat Jan 16 2023, 04:54 AM

Thanks for that, I have ordered the book and any thoughts on unscrewing the mixture screw half a turn out or three and a half turns?

Posted by: ChrisFoley Jan 16 2023, 05:06 AM

Those mixture screws are for idle tuning only. Idle jet size is for tuning light cruise part throttle mixture.
3 1/2 seems like way too much to me. What really matters is if the mixture is rich enough at idle to prevent misfires. Idle jet size will affect how far open the mixture screws need to be. If you need 3 1/2 turns, the idle jets are likely too small.

Posted by: Petepat Jan 17 2023, 04:25 AM

That makes a lot of sense to me, thanks.

Posted by: Petepat Jan 19 2023, 04:36 AM

So, the Webber book is on it's way but in the meantime I thought I'ld show you all some photos of the fuel system, not that I think this is causing a problem but maybe in need of an upgrade!!

Posted by: Petepat Jan 19 2023, 04:42 AM

I'm thinking to replace the lot, put the pump at the front and use metal tubing all the way into the engine compartment, fewer joints that way. Any words of wisdom gratefully received.

Posted by: ChrisFoley Jan 19 2023, 04:51 AM

I offer a complete pump and lines kit for carbed cars.