Balancing carbs on a CU

[T25rc]

Helloo,
My camper's engine is very rocky, i've swapped one of the carbs today as something was up with the choke mech. What are the common causes of a very rocky engine, i assume the carbs need balancing as a start?
so how do i go about it on my CU, do you do it with the airflow like usual? I have a synchrometer from messing with my 1300 on twin dellortos.. Do they have mixture screws?

Also, i need to check that my vacuum pipes are ok and to the right place onto the dizzy, has anyone got a picture with them coming from and going to their correct locations? (there's a couple of pics in the wiki, but have conflicting ideas on where they should go...)

Thanks a lot
Rich

[Fritz]

Personally I'd be checking all the basics (Compressions etc and ignition components/ all Vacc hoses for security/splitting etc/ are the igition leads, dizzy cap all OK ?) before getting involved with the carbs unless some silly sod has been buggering about with them.....

Then once you are satisfied everything else is OK and the engine is still leaping about ONLY then would I consider twiddling with the carbs....

By the sound of things I'd be trying to get hold of a decent manual to refre to, a Haynes will do you for starters.


Regards,


Fritz,,,,,,,,,

[T25rc]

Well one of the carbs was in a bad way with the choke mechanism not working so they decided to drill the butterfly a bit, i've just swapped that carb for another which looks better condition.

Can anybody shed light on which vacuum pipes go where onto the dizzy (a pic of a correct engine would be great)

[irishkeet]

hi

there is a good photo of a CU in the wiki

irishkeet

[steve8090]

There is a lot more to balancing the carbs than just setting them on the linkage, you need to set the basic gaps with the carbs off, reset the mixture screws to make sure they are balanced, you then need to measure the flow of air through the carbs to make sure they are set to between 7 and 9 kg/m3, if this is higher then there will be too much vacumm pullng on the dizzy hold the vacumm advance open, once these screws have been set, mark them as they will not need to be adjusted again, note they are not tickover screws, then you can balance the carbs, do it at 2000 rpm and check at 3000 rpm, set the tickover on the top screw left carb then check the mixture at ickover using a decent gas analyser.