Topic: 79 CB550 has rebuilt carbs but always starts will difficulty

[jturner8]

Just got the bike back from the shop and I'm so unhappy with the service and beginning to question the quality of the work.  Carbs were rebuilt but the bike will only start with the kick start using lots of throttle (and even then you have to do this for 5 minutes) then the bike wants to shut off.  After keeping on the throttle for 5 more minutes, it will idle and run like a new bike; however, once you get to your destination and turn it off (even for just five minutes) you've got to go through the whole process again.  Any ideas?  I had a CB750 and it always started with the electric start almost immediately.

[Triffecpa]

I'd double check the float heights.  If they aren't set correctly, then the small amount of vacuum generated with either the kick starter or electric starter will have trouble pulling fuel up into the carbs.  If you can get the airbox or pods off, open the throttle and spray in some starter fluid.  If it starts right up with the electric start with starter fluid, then you have a fuel delivery problem.

Tracy

[TwoTired]

Look at the headstock and tell us what the model the tag says.  (no such thing as a 79 model Cb550)

What is the tune-up status of the bike?

What modifications from stock have been made?

[jturner8]

OK - it's a 78 CB550K.  Thanks for the idea to remove the airbox and start with some starter fluid.  I guess I can move onto checking the float height from there.  Any other suggestions.

Oh, it's 100% original with 9500 miles - rebuilt carbs, new battery, new fluids, rebuilt front caliper, new tires and tubes, new o-ring chain, new tubes for the airbox and carbs, directionals and horn repaired.  Until yesterday, it had not run in nearly 20 years but was stored well and looks like a museum piece.

[TwoTired]

You can't run 530 oring chains on the 550 without modifications.  The wider chain will chew into the engine cases.  If not when new, then it will after the chain and front sprocket wear some.

Cold run issues could easily be choke related problems.  You are using choke, right?

I would check that the choke butterflies were closing fully when actuated.  And, that the fast idle adjustment is holding the throttle open enough during warm up.

Choke can be time consuming to adjust at the shop.  Because, the engine has to be cold to fine tune those idle speed adjustments.

Think about it.  Rebuild carbs, get it running and adjust the carbs to run while warmed up.  Can't adjust choke now.  Gotta wait till tomorrow morning.  Then next day, start bike, make some adjustments and, well now the bike is warm again.  Did you make enough adjustment?  Gotta wait till tomorrow morning again to find out.

Anyway, it could be that the choke cable slipped from vibration and you can't apply full choke.  Simple to check, actually.

Another thing could be the spark plugs.  If the shop thought an oring chain would work like it does on a 750, they might have put in 750 plugs, too.  This will make the 550 into a cold blooded beast.  Won't want to start and has to be totally warmed up to be ridable. 550 plugs are a hotter heat range than the 750's plugs.  You should have D7EA plugs in the Cb550 (NGK brand).  And, there should be no R in the spark plug number!  Your spark plug caps have all the resistance needed for the ignition.  And, putting more resistance in the spark plugs themselves will just make spark weaker for starting.

Finally, I'd like to know where you got new rubber couplers between the air plenum and carbs.  These have been un-obtainium for years now.  There's a LOT of us that would like to get new ones.

Cheers,

[rachet]

You always impress me TT with your knowledge!  Keep it up and  I'm looking forward to how this progresses and ultimately turns out.

racthet~

[jturner8]

Thanks TwoTired - that's a wealth of knowledge you just dropped on me.  Can't wait to get home and check things out.  Will post when I know more.

Yeah, those intake tubes are hard to find.  Used ones are available at http://www.northcityvintagehonda.com/servlet/StoreFront and new ones with the airbox are available at http://www.davidsilverspares.co.uk/.  Neither site has posted the tubes online so you've got to call or email.  North City returned my email within a couple days while David Silver Spare's returned the email immediately (and the tubes are new).

I was happy to find the tubes b/c I did not want to put pods on the bike. 

[TwoTired]

Those rubber couplers for the 77-78 models are different from the earlier model bikes.  You can get the earlier ones from DSS.  But, the 77-78 tubes aren't available.  (Or, so I'm told)   Used is the only avenue available AFAIK.

Totally agree about the pods choice.  EEEEEUUUUUWWWW.

 


Cheers,

[oldhondarider]

Just got the bike back from the shop and I'm so unhappy with the service and beginning to question the quality of the work.  Carbs were rebuilt but the bike will only start with the kick start using lots of throttle (and even then you have to do this for 5 minutes) then the bike wants to shut off.  After keeping on the throttle for 5 more minutes, it will idle and run like a new bike; however, once you get to your destination and turn it off (even for just five minutes) you've got to go through the whole process again.  Any ideas?  I had a CB750 and it always started with the electric start almost immediately.

BTW... where did you take your bike for servicing?