Carb setup Cota 349...drinks like a sailor

[potto]

Drained my tank today after a short ride recently,I used 500ml of fuel which seems too much,I'am aware its a bigbore 2S but think that's a bit much IMO.

My jetting isn't stock as the main jet is #150 and manual says #145 don't expect that is helping,plug colour indicates rich and I guess it is a bit smokey but runs crisp on throttle.

Noted the following,needle rather worn @ tip,aircleaner clean,choke shutting properly,bike idles well after startup,running 25:1 on conventional 2S oil.

Plan to replace needle........any other suggestions would be welcome thanks.

[cleanorbust]

How many turns out is the mixture screw?

[lineaway]

 Yeah, I bet a bit smokey at 25 to 1. Fuel consumption is totally dependent on what type of riding. If you are trials riding the bike barely gets on the main. If you are out trail riding all the time, it will suck down alot more. At least the old Cota has a big tank.

[potto]

Mixture screw is set @ 1.5 turns out from memory,I will add I never touched the timing as I found it to be correct just cleaned the points and checked the gap as correct.

Will start of with a new needle as mentioned and replace main jet  for correct size,I would say if the needle is worn the jet will be too.

I'am not prepared to get carried away with such an old carb and may go to a Japanese carb.

 

[cleanorbust]

Sounds like you're on the right lines with current set-up.

Depends how short your short ride was, but half a litre really isn't much to use on any ride worth getting changed for.

[oldaz]

If it's got an Amal carb, you can download their "Carburettor tuning guide" which takes you through all the steps needed to get it right.

[b40rt]

Amal tuning guide simplified, place in :-

 

[potto]

Thanks for the reply,I'am all good setting up this type of carb but I'am starting to thinks its not economical to go much further...it is old and rather worn,shame Amal didn't use a brass or hard chrome slide.

I can purchase a Keihin 26PWK which is in good used condition and its genuine,I have researched and the Chinese knock offs and they can be a mixed bag,jetting is something I will have to face.

Will update when I decide what to do as I may carry on with the Amal for a while and continue setting up the rest of the bike.

[potto]

8 hours ago, b40rt said:

Amal tuning guide simplified, place in :-

 

Yes I know,not like they were made very well....your answer made me laugh,cheers

[pschrauber]

If you want to stay with the AMAL and have a worn out needle please replace the needle jet too because it will be likewise if not even more worn out.

Another improvement is to replace the slide against one with chromed surface thus the slide and the bore of the carb doesn't eat up against each other.

Hansjörg Pfahler has made a batch of chromed slides fir AMAL carburators for Bultaco and Montesa bikes. You might give him a call for one, his Website is:

www.bultaco.de

Beat improvement is a dump against something that is not AMAL or BING.

Here  Dell'Orto PHBH or a Mikuni VM will improve everything and too gas consumption.

OKO's as Mikuni clones can be OK too.

I switched from AMAL to Dell'Orto and the bike runs much better / crisper.

[potto]

Well what another day brings,bought new slide,needle and needle guide,slide was wrong a #2 instead of a #4 my Amal carb guy said reason for fuel consumption,carb was basically mixed up,put it back together and it started first kick and much less smoke.....result.

It tuned up easily I think it will cause less air leaks @ the slide,old needle was SO worn almost no taper left @ the end,my Amal carb guy mentioned the slide was the biggest issue being the wrong one (rich) and the fact they wear out faster than the carb body,@ this stage I won't be changing carbs and happy ...as is the bike.