Topic: Doesn't like to start - 1978 CB550

[man-bot]

I have a 78 CB 550 that I piked up a few weeks ago.  Carbs were real bad so I cleaned them up and the bike will run great - its just that it doesn't like to start!

It probably takes me 20 mins to get it going - I have to try it and leave it for 5 mins, try again and it starts to sputter and leave it for 5 mins, try again and it almost goes, leave it for 5 mins... then it'll usually go the next time or the time after.  It is warm out so I don't use the choke - and it doesn't help anyway.  When it starts to catch I usually need to hold the throttle just slightly open and it'll go.

I have adjusted the air mixture screw to 1 & 1/2 turns out... should I open it up a bit more?  To me it seems as though the engine is getting too much gas and not enough air (thus holding the throttle open). 

I have the stock airbox on - filter is cleanish... could be better but not awful.  I have checked and have spark.  Is it flooding?

Again once I get it running it idles steady around 1200 rpm and is steady through the gears and throttle range, also will start back up fine once it runs.

Just kinda baffled here as to what to do?

[Gordon]

Valves adjusted?  Timing spot on?  You've verified good spark on all plugs? 

[man-bot]

No idea on the valves or timing - haven't touched them at all! 

I have checked spark on cylinders 1,3 & 4 (couldn't get the socket into #2 w/o taking the tank off), but all of the pipes get hot when I take it for a boot.

I guess I should look into the timing... if not firing at the right itme I guess thats an issue.  Don't notice it at all when I ride though - smooth so far (haven't run it to long yet).

[Gordon]

No idea on the valves or timing - haven't touched them at all! 

Let us know how it's starting once you've done a tune-up.  

 

[the technological J]

my guess is that you r carbs are waaayyy out of sync ... do ur tapets pionts and timing before u do the sync.... its well worth paying around 100 to some one to do if u cant do it ur self

[TwoTired]

No idea on the valves or timing - haven't touched them at all! 

Let us know how it's starting once you've done a tune-up.  

Ditto.  ... AND a new air filter.  If it looks at all dirty, it is time to replace.  Honda schedule is yearly replacement.

[man-bot]

Well I guess I need to tune it up!  Clymer manual comes tomorrow so I'll run through a tune up this weekend and hope things are a bit better.

I did bench synch the carbs and they will need ot be properly vacuum synched... for now the idle and operation is pretty smooth though  - revs stay pretty constant.

I'll post my results (hopefully with a positive response!)

Thanks

[bryanj]

Did you take out the pressed in pilot jets to clean them as what you have is typical of those being blocked

[man-bot]

I did take out the pressed in jets (slow jets).  I actually had a spare set of carbs and I used the jets from them as they were nice and clean.  With the jets that were in the set of carbs that were on the bike didn't come clean enough with the simple green soak.  Both sets of slow jets were 42s though.

Fired up fine today w/ some starter fluid and ran like a top...

Can the air mixture screws have anything to do with this?  maybe 1.5 turns is too lean.

[Gordon]

Fired up fine today w/ some starter fluid and ran like a top...

Can the air mixture screws have anything to do with this?  maybe 1.5 turns is too lean.

Really...  Stop looking for other causes and just do the tune-up.  There's a good chance that will solve the issue, and even if it doesn't, we at least have a known base point that you're starting from. 

[man-bot]

Will tune up this weekend and reply then!