Rich Mixture
-
tankstraddler
- Posts: 81
- Joined: 13 Feb 2010 18:40
Rich Mixture
I run a 1976 Strada with standard carburettors and clean standard air filters. It is currently jetted with 43 Idle Jets, 45 Starter Jets and 260d Atomisers but runs rich and starts from cold without the choke. Has anyone experienced this and moved to leaner jets or altered float heights from the specified 10mm as a cure? If so, what jet sizes/float heights worked for you? Thanks.
Re: Rich Mixture
Running rich where?
Idle mixture is set by the jets in combination with the mixture screws. The jets alone set the 'progression' mixture which is where the stumble pulling away often comes from (often too rich with 50s).
Corroded needles and/or atomisers will cause a rich/inconsistent idle. On my 250 someone had polished (very nice job!) the corrosion out of the needles and fuel would pour out of the atomiser at just above idle. If you're laying the bike up long term it's a good idea to prop the slides open to stop the corrosion.
The 10mm float height is difficult to measure as you have to estimate the float centre. The Dellorto manual (available online) gives a distance from carb body to the edge of the float. Float needles often leak, particularly with modern fuels and the floats can become porus. It's expensive, but an upgrade to the later (non adjustable) floats and viton tipped needles is a good move.
Plug colour can be a poor indication of mixture these days. Black plugs are just fine as long as they aren't sooty. There's an article online somewhere about modern fuels and plug colour.
Idle mixture is set by the jets in combination with the mixture screws. The jets alone set the 'progression' mixture which is where the stumble pulling away often comes from (often too rich with 50s).
Corroded needles and/or atomisers will cause a rich/inconsistent idle. On my 250 someone had polished (very nice job!) the corrosion out of the needles and fuel would pour out of the atomiser at just above idle. If you're laying the bike up long term it's a good idea to prop the slides open to stop the corrosion.
The 10mm float height is difficult to measure as you have to estimate the float centre. The Dellorto manual (available online) gives a distance from carb body to the edge of the float. Float needles often leak, particularly with modern fuels and the floats can become porus. It's expensive, but an upgrade to the later (non adjustable) floats and viton tipped needles is a good move.
Plug colour can be a poor indication of mixture these days. Black plugs are just fine as long as they aren't sooty. There's an article online somewhere about modern fuels and plug colour.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
Re: Rich Mixture
busted choke piston rubber, they should be flat but develope a profile after a while from whith fuel seeps into the system allthough the choke is closed
just replace them if any doubt, they are for sale at any DellOrto supplier
just replace them if any doubt, they are for sale at any DellOrto supplier
Re: Rich Mixture
+1 on the choke rubbers also check the other small O rings in the carbs.
If you remove the choke plungers and the rubber in the bottom is still
soft but as taken the shape of the jet it sits on by using a very small
hoked tool you can remove the rubber, "it sits in a lipped recess" without
damaging it then put them back upside down and they will last a bit longer.
If you remove the choke plungers and the rubber in the bottom is still
soft but as taken the shape of the jet it sits on by using a very small
hoked tool you can remove the rubber, "it sits in a lipped recess" without
damaging it then put them back upside down and they will last a bit longer.
Ralph
1975 Strada 3 1/2
Knott End NW UK
1975 Strada 3 1/2
Knott End NW UK