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Old 01-05-12
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105 series Spider Carb cleaning

Good afternoon,

My spider will be back on the road in the next few weeks and whilst I've given her a full service, I was wondering if the carbs would benefit from a proper good cleaning. Ive never attempted this before and was wondering what was involved and if it was difficult. I don't want to get in to a full dismantle as they were not long set up.

Also, my clutch appears to be 'lazy'.......... Whilst it doesn't slip whilst in gear and driving it seems to be a bit slack when engaging, like when you change gear and take your foot off the clutch pedal it takes a second to engage. So it sounds like it slips then doesn't if that makes sense!!??

Oh and while I'm at it my rev counter doesn't read correctly........ 0 RMP at idle....


Any help would be appreciated

Cheers

Amir
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  #2 (Post Link)  
Old 01-05-12
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Look forward to responses. I also plan to clean my DHLA 40 Dellortos and have bought a rebuild kit from classic alfa, I assume its a take them off and strip and clean whilst replacing some gasket and the diaphragm. Anyways let's see what others who have done say.
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Old 01-05-12
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You didn't say what carbs you had, but my Dellortos were pretty straightforward, check the accelerator pumps if fitted, when the carbs are off they just squirt a big gob of fuel straight out while there is still fuel in the bowls.
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Old 01-05-12
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Originally Posted by harryf View Post
You didn't say what carbs you had, but my Dellortos were pretty straightforward, check the accelerator pumps if fitted, when the carbs are off they just squirt a big gob of fuel straight out while there is still fuel in the bowls.

They are Weber carbs
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Old 02-05-12
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Webers are more or less as the Dell'Ortos. At any motor factor you can get carburettor cleaner or you can use Cellulose thinner - the latter is probably more toxin and I would use rubber gloves using it.
Erik
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Old 04-05-12
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Hi all

Busy restoring a "74 gt junior, had a mate of mine put the carbs in his ultrasonic cleaning tank, then put in new repair kit.

best results for little effort.
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Old 04-05-12
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Originally Posted by Erik Loye View Post
Webers are more or less as the Dell'Ortos. At any motor factor you can get carburettor cleaner or you can use Cellulose thinner . Erik
have Dell'ortos,, r u you suggesting use of carb cleaner without removing them and without dismantling them ??
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Old 05-05-12
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If the carbs are very old/worn you need to dismantle them as they very likely needs repair kits, but if they are only full of precipitate and coated with goop they is no need. Carb cleaner and compressed air will do the trick.
Erik
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Old 05-05-12
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Originally Posted by Erik Loye View Post
If the carbs are very old/worn you need to dismantle them as they very likely needs repair kits, but if they are only full of precipitate and coated with goop they is no need. Carb cleaner and compressed air will do the trick.
Erik
Eric, I will clean em up first. R u saying that I won't need to remove them if I spray them with cleaner?
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Old 26-05-12
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Ok chaps for what its worth, took my Dellortos off, stripped them, cleaned with thinners and blow through all the jets etc. Fitted the rebuild parts, gaskets, pump diaphragm and set the floats. Took me an afternoon and a morning as I did one at a time to always have a reference. Only problem was the ball bearings in one of the chambers falling out onto floor....found them. Polished all the brass nuts and everything now really clean. Reassembled, fitted and tuned. MPG now 25 +ish, (was running at about 15MPG before and leaks) car running smoothly, no leaks.....brill. First time strip so as opined here its not difficult just take your time and be methodical, results well worth it for £25 refurbish kit.


Regards
Robin
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  #11 (Post Link)  
Old 27-05-12
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Robin, I don't know haw briskly you run the Spider, but 25 MPG (Imp) is somewhat on the low side. I normally get 30/31 MPG in my 1750 in a mix of short and longer journeys. So maybe some fine tuning of ignition and mixture is in order.
Erik
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Old 28-05-12
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thanks for the help,, have most people scaring me off from even touching the carbs,,, thats why i am so apprehensive,,now on my winter jobs list,,, will put my 'methodical' hat on and it give it a go....
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Old 29-05-12
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MPG and tuning

Erik, agreed. I need to do a few more runs etc to get a decent average but yes a bit of fine tuning is in order. Mixture, dwell and timing. First two I can do but dont have a timing light so not sure how to check, adjust that one. The car runs and starts fine other than a flat spot at 2k revs.
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Old 29-05-12
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Originally Posted by Robintr6 View Post
The car runs and starts fine other than a flat spot at 2k revs.
That could be a couple of things. I don't know about Dellortos but the changeover to main jets is from 1,500 revs onwards for Webers. Did you balance the two carbs to be in sync? Perhaps the mixture needs some tweaking or maybe the main jets aren't right. Do you have a standard air filter?

Another issue may be the distributor, I had a bad flat spot that I found to be a broken spring in the mechanical advance/retard mechanism.
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Old 30-05-12
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Cosmo

thanks, carbs are balanced. I'll have a peek at the jets and see if I can get a timing light from somewhere. I'll also have a peek at the dizzy and ensure that its all in one piece. Many thanks
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Old 31-05-12
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Did you check or change the float levels when you had the carbs apart?

The float level will influence the point at which the transition between the 3 different circuits happens. I Don't know about Dellortos, but its an easy check on the Webers, and if incorrect will give the issues you describe.

Jonathan
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  #17 (Post Link)  
Old 31-05-12
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yep did the floats as per the Brooklands book...16.5-17mm between top of float and base of cover. I'll have a go at some of the other diagnostics like opening the air screw when its missing and see what that does. Bothe floats were set the same and the problem is only on the carb nearest bulkhead which suggest something to do with that carb only , maybe the jetting is different (something I should have but didnt check)....
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Old 31-05-12
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One point to note about the rear carb is that it is on the manifold where the vacuum take off for the brake booster is attached. Worthwhile checking the hose and valve. Another possible leakage point is the rubber carb mounts. They tend to develop cracks and can let air in - check by pulling the air box up and down and see if there is any change in engine note.

Although you checked the float height did you also check the weight of the floats and their buoyancy. And you say you balanced the carbs but do you have a 4 way dynamic tester that will show you any problems when off idle?
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Old 31-05-12
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Cosmo,

good points, will add to my checklist. Had bought a new hose anyways so will fit and try the to verify no air leaks at manifold

BTW nope, dont have a 4 way dynamic tester but followed the Brooklands book, also have had a carb balancer on them, anbd a vacumn gauge so I think they are close. I have adjusted them (balance) in both directions on many occasions and test driven, generally makes the symptoms worse. I also assumed that if it was babance it would tell at idle and she idles smoothly and theres no engine vibration or any of the other 'unbalanced butterflys symptoms'

In general she runs well accelerates and pulls hard, idles well, starts easily ...and MPG is improving, its just the 2k revs issue

BTW thanks
Robin
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  #20 (Post Link)  
Old 01-06-12
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In the good old days experienced mechanics (like my dad) used a tube and listened to the carb's trouts when balancing multi carbs.
Likewise, they adjusted the ignition by setting the timing at the stationary mark and started the engine; when warm the they turned the distributor till they got the fasted idle and then adjusted the idle to a correct speed.
To check whether the vacuum tube or valve is leaking simple block the the tube with a suitable sized bolt and check the balance. If the balance is correct them order a valve or renew the tube accordingly.
Erik
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Old 04-06-12
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BTW its a 1972 2ltr GTV (carb update)

Ok, progress report. Changed the vacuum pipes, they were tired. Took the rear carb top off and checked the floats. Ummmmm, when I adjusted them they were not both parallel , ie 1 float was slightly higher than the other so no doubt the reading would have been compromised. Anyways, reset them so the are both parallel and the distance is 16.5 and a bit mm as per Brooklands book. Also checked main and idle jets and the are to spec as well at 50 and 135. Hopefully today I'll be able to take the car out for a test drive and report back.....Thanks so far chaps.

BTW Erik have tried various solutions to balance, tubes , carb balancers, following teh book re setting butterflys at rest and then tightening other carb throttle adjuster till it just touches....I am sure its very close but still not perfect. In any event its is probably only the cause of a little roughness if you pull away from idle with a very, very light throttle, if you accelerate normally its not noticeable. (thanks)
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Old 04-06-12
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Originally Posted by Giulia Cyprus View Post
thanks for the help,, have most people scaring me off from even touching the carbs,,, thats why i am so apprehensive,,now on my winter jobs list,,, will put my 'methodical' hat on and it give it a go....
Good luck Thomas. If you need any help with anything let me know! Its always fun trying to be a mechanic
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Old 20-10-12
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Hi giulia cyprus. If you live in nicosia, as a friendly gesture, I can help you rebuilt the carbs and also set them up to maximum effect. call me at 99698987.
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