Carburettor specifications - all AF1 models

 Carburettor standard specifications - all models Dell'Orto 

My bike - carb issues part 2, fixed

Following on from part 1 of my carb/ running issues I have now re-built the carb to exact Aprilia specifications. For good measure I replaced the spark plug which is a NGK BR10EG and I also had to replace the battery as mine was dead and wouldn't except a charge, I bought a Motobatt 12N5.5-3B from Busters.

With everything back together the bike fired in to life, ran sweetly and most importantly the carb didn't over flow which points to the float weight all along.

Now that I am happy that bike is running correctly I can move on to some more restoration type jobs.

My bike - carb issues part 1

 I noticed when running the bike the carb was over flowing and petrol was poring on the floor, so I decided to strip the carb and see if there was anything obvious going on.

My first thoughts were either the floats were at the wrong height or something was blocked. After removing everything, blowing the jets through and checking the floats I couldn't see anything to wrong so I assembled and left it for another day. 

My next thought was to check the carb settings against the factory set up to see if the carb was in fact set up wrong. I have looked at the settings here: this is what I found.

The idle jet, atomiser and floats were out of spec and the needle was at the incorrect height presumably to compensate for the incorrect atomiser? 

The next thing that confused me was the carb model was slightly wrong, according to the manual it should be a PHBH 28 RD and my had the BD code.

Now the RD carb should be a power jet model, but this isn't referenced in the original carb spec so I am not sure if this is correct. The BD version seems to be a generic 2 stroke replacement carb. 

I ordered the correct parts from Dellorto suppliers Eurocarb to make by BD spec carb exactly the same spec as the manual. I also managed to pick up a RD spec PHBH28 of ebay as a back up plan but the slide is huge and the jetting is odd because of the powerjet so I am not convinced this will be any help.

The next step is to rebuild the carb and run the bike. I am convinced the heavier weight floats will resolve the over flow issue, however the battery died so the test will have to wait for another day!!!

If you have any information on the carb settings for a 89 Sintesi please comment bellow.

 

Carb settings - 1989 Dell-Orto PHBH 28 RD

 Carb settings - 1989 Dell-Orto PHBH 28 RD

Here are the stock setting parts and sizes for the PHBH 28 RD as fitted to the1989 Sintesi Replica taken from the 1989 owners manual. I have added links to the UK Dell'Orto supplier, just select he variant size you need.

Main jet – 120 - order here
Idle jet – 55 - order here
Atomiser - CF 266 - order here
Needle - X4 third notch from the top - order here
Slide - 50 - order here
Air screw – 1 turn
Choke jet - 70 - order here
Float – 11.3g - order here

The idle speed adjustment must be carried out with the engine warm, proceeding as follows.

- Adjust the idle screw (fig. 17 pos. A) in order to obtain a constant rotation of the engine.

- Tighten and unscrew the air screw (fig. 17 pos. B) until the highest number of engine rpm is obtained

- If necessary, further adjust the minimum screw

Note if you buy a brand new complete carb it will need setting to the above specs as it will not be set up for the AF1, plus you will need the cable choke kit rather than the manual lever. Buy a complete carb here