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Discussion Starter · #1 · (Edited)
I have a 1983 Honda Prelude 1.8L (dual carburetor). The number of hours that have been spent by so many (including three certified mechanics) to get this thing to idle on its own is immeasurable. Three times now I have seriously wanted to push this car into the river. My friend keeps saying "you've put so much time in it. You can't quit now". First off, I'm not a mechanic. I don't know much. I've taken over since the mechanics can't solve the problem. The facts: The car was stored for several (8 years) with limited intermittent driving until one day a few years ago it started to stall at stop signs. That owner (the first and original owner since 1983) had the car looked at by a mechanic who couldn't solve the problem. Hence, she sold the car. Enter me... yep, I bought it. I drained the fuel tank, changed the primary and secondary fuel filters (and air filter). I replaced the fuel pump (OEM-used) and the spark plugs (wires look good). We suspected a vacuum leak because acetylene at air intake and then propane at manifold/head had the car running smooth and solid (but rich). Next, pulled the carburetors and the intake manifold off. Four of six nuts I could pretyy much unthread with my fingers (as I struggled to be able to get at them), changed the gaskets (including EGR) and O-rings/siliconed up where appropriate and hooked up all the pre-marked vacuum lines. We're reasonably satisfied at this juncture that there are no more vacuum leaks. I've installed a brake booster vacuum switch (for some reason there wasn't one on the brake bosoter vacuum line) as well as a new ported vacuum switch that looked rough. The fuel pump as I think I mentioned was also replaced with a used OEM pump. Fuel is coming out of the fuel line. The car as I understand it calls for a pretty low 3 psi. Despite all these efforts, nothing has changed. Simply put, I have to pump the accelerator several times before I crank the engine to have a shot at getting it to start. Basically, when it sounds like it might start, I need to quickly and repetitively hit the gas pedal and then I can pretty much get it to start. However, after it starts running, I need to adjust (continuously) the pressure on the accellerator in order to keep the engine running. If I remove my foot from the gas pedal, the car will stall immediately and if I don't adjust my foot regularly and accordingly, the car will stall. Plugs have been replaced (yes, there is spark), oil and antifreeze have been changed and as I mentioned, two vacuum switches have been replaced. One of the three mechanic friends I have has insisted that the carburetors are not the problem. Another friend believes "maybe" the carburetors need to be rebuilt. He beleived this because when he plugged one carburetor with a rag, the car ran fine. Now in fairness, that was before I pulled the carbs and manifold and resealed them. I am truly exhausted from the numerous hours I have spent on this car and the cash I have laid out. The problem is that the car is in incredible shape. It was very well maintained by its original owner since 1983. It's a keeper IF it can get it to run. I'd be grateful to receive comments about what I might need to do. Thanks, Giggs
 

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not idling

100% the carbs they were way too complicated in the US with all sorts of extra emissions crap, in the UK they didn't have EGR, they didn't have all that crap on top of the inlet manifold and they had a 100 less vac tubes. But even then the carbs are problamtic at this age, they rely on thermostats for automatic choke and idle that use wax and degrade and to be honest mine are on a very short list of things to get binned asap!

Your best bet is to just bin them buy a pair of webers and enjoy the induction roar and the extra power! :)

Other alternative is set of bike carbs there are some with large enough bore and even 80mm spacing to suit our engines I think Mikunis from early Kawasaki Katana are ideal either in 36mm form or later more powerful 38mm

If you really want to try and keep this stock then you may need to replace the auto choke mechanism and do a full rebuild but this still may not guarantee success!

is it auto or manual?
 

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Discussion Starter · #3 · (Edited)
Thanks for getting back to me on this. It's very kind of you. It's automatic. 100% stock with all the emission and vacuum lines all over the place. At this point, I'm looking for the easiest and best solution. I don't mind changing things around but must confess I know very little (but learning...). My friends come by and tell me to do this or that and then leave and they come back when I'm done and give me more instruction. I have a manual too so it helps. But if I can buy other carbs and put them on great but if I need special skill and have to have things fabricated I suspect I am going to run into trouble. Would you be able to give me a little bit more direction on whether to rebuild or replace? I did find a guy in Toronto who said he'd rebuild the carbs for me a while ago when I thought that was the problem. Instead, I didn't and put it all back together again. Ughh. But if you think I can buy other carbs and go from there and it might be better I'd be willing to give that a try. one more thing. The seats where the carbs go into the manifold are cracked but only in the middle. They are otherwise smooth and solid around the outside where they seat in and are clamped down. My friend said that was fine because where they insert and fasten are a clean and tight fit. Before I put it back together I tried to find replacements just in case but I couldn't find any anywhere. He said not to worry about it.
 

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fitting different carbs

The easiest option then for you would be fitting Webers DCOE 40's would be big enough for an automatic and you can buy off the shelf manifold from NewZealand that will fit easy enough.

As to the insulating mounts as long as they are not cracked on the inside and sucking in air from the outside they should be fine, if your worried about it try covering them in silicone sealant to make sure it's not leaking.

I suspect you have two issues, the auto choke maybe not working, the two carbs maybe out of balance from being taken off and back on again, and simplest thing maybe that you just might need to increase the idle screw higher have you tried that? do you know where it is?

Also ignition timing affects idle have you changed the position of the distributer at all? if you've moved it and not put it back in exactly same position to within .5mm you could have negatively turned down ignition timing which will stop the engine from idling in the right spot.
 

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Discussion Starter · #6 ·
Thanks again for all of this. I am very grateful for your assistance.

Pretty sure I know where the idle screw is. I watched my friend adjust that. If not, I can find it but I think he gave that a go. And while I don't recall anybody working with me touching the distributor, that doesn't mean the guy who had it before me didn't.

Questions:

1. Where would I find "Webers DCOE 40's"? And btw, following your last post I looked on ebay and found some remanufactured Mikuni 38mm VM38 roundslide carburators for sale. Would these be what you were referring to before? And if yes, would you nevertheless suggest the "Webers DCOE 40's or these? At this point I'm looking for the easiest fix.

2. Where can I "buy off the shelf manifold from NewZealand that will fit easy enough"?

3. If the idle choke isn't working is that something to be repaired or will it be replaced with the new carburetors?

Sorry I sound so pitiful, like I said, the guys will help me if I do the work. They just don't know anything about this car. So I have to chase down what I need and they'll tell me what to do when I have everything in hand.
 

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carbs

Easiest fix would be to attempt to have your existing carbs cleaned/rebuilt but if the auto choke is broken not sure if replacements can be bought anymore.

The only way to check dizzy is in right position is with timing gun and having it pointed at the timing hole in the transmission case by the block. If you can take a picture of the dizzy as it butts up against the head there is a cast line in the middle this will at least show me if someone has completely retarded it or not, normally it will be pointing roughly at the middle of between the two bolts that hold that bearing cap on the head.

Mikuni slides are good carbs but you would have to get a custom manifold made up so would not be the easiest thing to put on, I would say the webers will be easier as all the parts are off the shelf that you need to convert. The mikunis would be cheaper to buy if you can find someone to make you a manifold.

For webers just search the internet despite being a very old design they are still one of the best performance carbs available and are still made new in Spain and are sold globally to motor enthusiasts.
 
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