Topic: CB550f with pods only runs with CHOKE *partially* on

[whoismattclark]

I have a 76 CB550f with pod air filters (a setup from PO, sync by pro shop).

The bike was not running when I bought it, from neglect.  A new battery and cleaning of carbs got it up and running without issue.  I did a full tuneup, and was happy with the results.  Response at 1/8-1/4 throttle was a little lacking, and I made a mental note to check that later, but that was about it.  Good power band otherwise.

Now: I haven't been able to ride it much, and I accidentally left the fuel on while the bike sat for about 2 weeks.  After 3 more weeks of sitting, she needed some coaxing to startup, but she did start.  Now she only runs with the choke on, but only needs the choke partially on.  The lever need only be a teensy bit open.  But if I click it into the closed position, she immediately dies.  I've tried this even at higher rpms (4000rpm, 40mph) while in motion I pulled choke shut, and she just dies.

I'm preparing to try some adjustments to the air mixture scews, but will these adjustments be acurate, since I have to do them with the choke on?  Do you think the slow jets just got clogged with gas gunk?

Also, I've noticed some smoking from the breather tube.  Looking at other posts, I'm afraid to know what this might mean.  Do you think this is related to my 'choke' issue?

So, today, I will play with air mixture settings, pull a few plugs, and report back tonight.


thanks,
MattClark

[paulages]

that "smoking from the breather tube" is probably just condensation in the crankcase evaporating as the motor begins to warm up. happens no matter what when a bike sits in the elements, and even more if it's not often run long enough to evaporate all of the condensation produced by the engine cooling from the last ride.

incidentally, it's this condensation on the cylinder walls, that causes a bike to need to run richer, as in with the choke on, when warming up. if it's dying without the choke open after warming up, then you've got something else going on, for sure. are you using inline fuel filters or are you only relying on the petcock screen?

[TwoTired]

Clean carbs only remain clean if you feed them clean fuel.
Is your gas tank clean?
Are your fuel filters intact?
The slow jets are about .016 diameter.  You can drain and catch what comes out of each carb bowl.  If you find bits larger than .016, you know the cause.

The exhaust head pipes will be noticeably cooler on cylinders whose carbs have the slow jet clogged.  You can "flash touch" a hot pipe, not get burned, and still be able to compare relative temps across the engine.

Smoke from the breather can be water vapour as paulages suggests.  But it can also be "blow by" from leaking rings.
Have you done a compression check?

The following horror senarios may or may not apply:
The bike sits and some valves are open.  Humid air rusts the cylinder walls, rust is abrasive and soon grinds the rings down to where the they can't seal.  And, if the cyclinder walls are pitted, rings will never seal.
The rings can also glue themselves into the piston grooves and not seal against the cylinders.  They sometimes free themselves after operating for a while. Sometimes not.

These things, and prehaps some others, can contribute to blow by.

Best of luck,

[dusterdude]

gee lloyd,you`re full of good news today.

[whoismattclark]

Finally got a chance to pull off the carbs and give them a touch up cleaning.  Also pulled the petcock and cleaned the screen and gave the tank a minor cleaning.  The slow jets must have been clogged because when I put it all back together she fired right up and is running sooo good.  I'm so impressed with the power and reliability.  I never thought she'd be a 'one-kick' bike (i never thought my cheap self would ever have one), but now -- after a warm up ride -- she is definitely a one-kicker.  Also, I turned the air-screws another half turn out, and that helps the lowend power even more.

So, the slow jets just might reclog, but at least I know what to do next time.  Plus, with the pod filters, I can get the carbs off and cleaned in under an hour now.

One bike down, one to go.  Got another 550 with starter clutch issues and a shredded cam chain tensioner.  This learn as you go stuff just got a whole lot better now that I have at least one running bike.


Thanks all,

MAttClark