Hi all

[KwakKwak1]

Thanks for the add.
A potted history: I've had my Zephyr 750 since 1997 (!) and after little use decided since 2003 decided to re-commission it and ride it to the Cafe racer meet at Montlhery. On the way back it started to run v rough and only just got me home (it died on my drive). Since then, i've been fighting it to get it to run, cleaning the jets multiple times, re-setting everything (float heights were wrong, jet needles changed, all jets out and cleaned. All this and it was still as rough as a badgers...
..... but now it runs as sweet as a nut. Reasons and lessons:
- as mentioned, float heights.
- blocked jets
- old petcock (blocked)
- Airbox intake baffle foam was non-existent (they are essential!)
- The rear airbox (air filter housing) did not latch into the front airbox.

Lessons:
- do the basics first; clean the carbs and be sure that each jet is not blocked. That means taking them all out and clean, checking all the holes (suggest one carb at a time). Clearly, check the strength of the spark.
- chances are, the plastic lugs on the rear airbox / filter housing will not fit into the slots in the front airbox. If they dont fit, there will be a gap between the two, and the bike will never run well. On mine, the filter itself prevented the lugs engaging, and i had to cut them with a knife to fit. This was the breakthrough for me.
I see that Richard (legend on this forum) used a sealant to bridge the gap described in his build diary.
- Boil up a full kettle for a nice brew just before you put the rubber intakes back in. Leave them in the hot water for a few minutes to soften them up. It took me ages to realise this !
- check and replace the intake baffle foam as a matter of course.
This stuff you probably know, but snippets of info are always useful.
It's time for me to enjoy mine then tidy up further over the winter.
- after-market float chamber valves can be out of spec; check the length.

[Ivor]

Hi and welcome, and thanks for the info. And like you say after I rebuilt mine i tried for ages to start it up with out the air box on, it just wouldn't run right or not start at all. Once the original air filter was on and the carb rubbers fitted it was much better

[Freddy]

Certainly worth highlighting the importance of the roam surround on the intake noise baffle (the white thing in the air filter intake lid).

If someone hasn't replaced it, there is near zero chance the original very light form will still be intact. It does make a performance difference. Take the 'white thing' completely out and the bike will barely run past half revs its that important that it needs to be in place and correctly sealed by the foam surround.