TOPIC:

H guys,
I have just refurbed a 1977kz650b1 it has stock airbox and filter and standard jets as recommended in the workshop manual. I was unable to get a standard exhaust so fitted a MAC 4into 2 megaphone from Niche cycles. The bike is hard to start and runs rich, do you think i need to fit smaller jets to lean the mixture and get it running better

Welcome Ian,
What have you done to the carbs service wise? Vacuum balance sync'd, bowl fuel level, colourtuned air screw/fuel screw, which slot is the needle clip in.?
What have you done mechanically?, compression test, valve gaps, cam chain tension?
What have you done electrially, ignition timing, points dwell, primary/secondary windings coil test, voltage to coils test.
Do you have vm22 or vm24 carbs. Airscrew only or air and fuel screw?

Thanks for the response.
I have bench synced the carbs. set float height but don't have access to a colour tune kit.
valve gaps are set ok and cam chain tension is ok.
Carbs are vm24 and only have airscrew.
electrically, coils are new ht leads are new, timing is as close as i can get it with out a strobe, the only thing i haven't tested is the voltage to the coils.

Ok, good news is you have the easier carbs to tune. Set the airscrew to 1 and 3/8 out from lightly seated to start with. Where are the needle clips?
Get a volt meter and check the voltage to the coils and let us know what readings you have.
Plugs ngk b7 or equivalent?
Guessing as your posting now you are in the UK? or an insomniac.? Whereabouts?

I definitely would NOT fiddle around changing the jetting in the carbs; that will just make things much more difficult to correct. Keep in mind that the engine ran perfectly fine when it left the showroom floor - and it had the stock jetting.

You need to accurately adjust the points before you go any further. Also, since you "bench synced the carbs" you now need to adjust them properly with them on the bike and the bike running. Bench syncing is not the same as properly syncing them with the bike running because not all cylinders, valves, etc. operate exactly the same. Far too many folks fiddle around with the carbs and set them out of tune by bench syncing them when in fact the carbs were already set correctly for the engine.

BTW, I own a 1977 KZ650-C1 (pictured below) and have owned and tuned it since it was new. I've put 62,000 miles on it and have always done my own maintenance. KZ650's are really great bikes! Ed

Yep, sorry, should have said. Bench sync is not the same as vacuum sync.

thanks mate
understand what you are saying about syncing the carbs and plan to get them vacuum synced when i can borrow unit.
i was just concerned as to what effect a non standard exhaust system would have on performance.
plugs are ngkb7es. i will test the voltage to the coils at the same time and let you know the results.
I am in western australia , been here for 38years and originally from middlesbrough. it is often difficult to source services and parts for vintage bikes in this part of the world so i try to do as much as i can myself,

I have quite a bit of 650 B1 spares leftover from many builds but not too much electrical stuff or if you find any bits your after in Europe and they wont send them to Aus let me know. I can get them and send them out to you no problem as would many of the long term members on here around the world. Think heavy bits would be costly p&p though!
Theres a prolific z fan in the Z10C I'm member of who lives in Aus who presumably has a decent contact list for parts from previous restorations. If you would like his contact details let me know. Info is invaluable.!!!

ianj01 wrote: ........plugs are ngkb7es. ...................

You may want to consider using ND W22ES-U spark plugs. I switched from NGK plugs years ago on my KZ650 because the plugs were not lasting very long without getting sooty. The ND plugs seem to last forever. Ed