Which way round does Dellorto throttle return spring fit

[SilverBeast]

The Europa is finally back on the ground, but I'm having an issue with the throttles not fully closing giving an intermittently high tickover. I was wondering if the throttle return spring was the wrong way round.

I've seen pictures with the coil mounted both towards the manifold and towards the airbox backplate (as mine is in the picture  below). I just wondering which way round is correct. I tried fitting it the other way round (breaking part of it off while removing it!) and it was the same the other way round. Can anyone confirm which way round it should be fitted please?

Bending the spring so it exerts more pressure seems to close it properly, but I suspect the issue may be either I have got the throttle cable too tight, or there is too much friction in the cable, so I'll be lubricating it later in the week and adjusting where the outer cable mounts from below.

I have a new return spring on the way from SJS which I'll also fit as, without the bit I broke off it can slide sideways and catch under the idle screw fitting in the carb. This then holds the throttle open. I feel a 6,000rpm idle is probably not ideal!

There was an extra spring fitted when I got it hooked round the inlet manifold (see scratched paint on manifold below). 

[jbcollier]

The throttle return spring is to aid throttle return against friction in the throttle pedal and cable.  With the throttle cable detached, the carbs should snap closed smartly and firmly as they have internal return springs.  First make sure that this is so. Then check that there is virtually no friction in the cable and pedal.  Fix that next if needed.

Throttles can also hang because they are way out of sync with one "closed" carb acting as a "springy" stop for the other carb.

[SilverBeast]

The springs on the carbs shut the butterflies properly. I've just partially rebuilt them. I didn't seperate the carbs (left them on the airbox backplate) or adjust the synchronisation.  I cleaned them out thoroughly and replaced diaphragms, o rings, needle valves where I could. Didn't do idle mixture screws as I can do those with carbs fitted one at a time without having to worry about messing things up. I've only stripped a lawnmower carb before! I've got the Des Hammill Dellorto/Weber book
 
I suspect the adjuster where the cable outer mounts to the plate is possibly the issue as I didn't pay much attention to it when putting it back together. I've also tie wrapped up so it's not dangling under the car after connecting it up again, which may have added a little stiffness that means the pedal would be against the stop. I've got a cable oiler, so I'll lubricate if with silicon when I get the new spring.

It's my mothers 80th on Sunday, so organising for that is current priority, but I have next week off work too....

[jbcollier]

D. Hammill's book is one of the best and very helpful when dialling in carbs in an application, or tune, not covered by the manufacturer.  A few comments:

- not sure what you are using behind your carb mounting nuts.  Can't tell if they are rubber or springs.  They do look too tight though.  The carbs need to flex a wee bit so they can properly deal with engine vibrations.

- DHLA-E carbs have fine graduated progressive circuits and fine threaded idle mix needles.  80+% of the time the engine is running, it is on the idle and/or progressive circuits.  Remove the carbs, mix screws, idle jets, progressive access screws, and flush with cleaner, thinner and blow everything out (jets, passages, etc) thoroughly.

- not disconnecting the two carbs from the airbox does not keep the same throttle sync.  Slight variations in how the carb mounting nuts are tighten will change the sync between the two carbs.  After you sort out the carbs flexible mounting system, you need to resync the carbs.

- if you do not know the history of the throttle cable, just change it.  You can make up a new one using bulk, teflon-lined, bicycle brake housing and tandem length brake cable.  Lined housing makes a huge difference.

[fotsyr]

The spring should face outwards. You have more issues than that, see above.

[SilverBeast]

Main reason for stripping carbs was a fuel leak from a pump diaphragm. The only thing I couldn't get out was the pump jet as I didn't want to risk damaging it and the needle valve/adjusting screws (77 in TC manual exploded diagram). Everything else was thoroughly cleaned. Reassembled with new o-rings/gaskets/needle and seat (fuel inlet to float chamber) and banjo fuel filters. Basically a Dellorto rebuild kit. Below is a picture of the pump body before it was cleaned.

Carbs are mounted with new 'O' rings on the spacers and Thackery washers top and bottom withe the requisite 0.040" gap between the coils and the carbs can flex on mountings without leaking air.

Main reason to get this sorted is so I can run it enough to tell if clutch is still slipping after adjustment and determine the next thing to tackle.

As it's mainly been run on choke in the garage for last year or so it had started running very rough. Plugs were also heavily sooted and gaps were at 0.030". These have been cleaned and regapped to 0.025". Car fires up as soon as it cranks and will idle OK, even as it is now.

I was just checking that the return spring was the correct way round, which it looks like it was. There is wear on the spring where the coils have rubbed together, and against the plate from the airbox backplate (see second photo). New spring (ordered from SJS yesterday) is next to it. You can also see where old spring has been formed to exert more pressure to close butterflies/retract throttle cable.

I will disconnect throttle cable and double check butterflies are closing with carb return springs (also new from rebuild kit) before I fit new throttle return spring. I'll also be lubricating throttle cable as I started above.

Thanks as ever for the prompt responses and guidance.