Topic: Smoke from exhaust.

[MAGOH]

I recently bought a 73' cb350f.  A couple things:  When I went to look at it, after he jumped it due to bad battery, it ran good when warmed up.  I hauled it home and then once I got it started it won't run with the choke off.  It runs whith the choke about half.  I took it for a ride and it does ok up to about 15mph and then bogs out when I try to accelerate.  Also, when it was just sitting and I would give it some throttle it would blow a good amount of smoke out the exhaust.  The guy I got it off of told me it was running a little rich.  With only a short amount of riding time left in the season I don't want to spend it with the bike torn apart.  Does anyone know a way to fix this problem or what the problem is?  Also, the guy told me it was a super sport, but I can't find anything online about the 350 four super sport.  He said that because it was a SS it had an alternator and that because of the alternator you can't kick start it unless the battery is charged.  Whats the point of kickstarting if the battery is charged?  I would appreciate any advice anyone can give me.  Its not my first bike, but I'm not the most experienced either.  Also, can anyone tell me why there are hoses coming off the bottom of the carbs?  The drip fuel on the ground.

[wrenchmuch]

If it won't run off choke even when warm you might have plugged idle jets . Hoses at the bottom of carbs are float bowl overflow tubes . You will leak fuel here if the float needle valves don't shut off fuel flow . The above 2 points indicate that you need to clean your carbs . The PO might have left fuel in the carbs when he stopped using the bike . The fuel evaporated and left hard deposits in the jets and carb body passages . There are many threads for carb cleaning . Start at this page     http://forums.sohc4.net/index.php?board=2.0        the SOHC/4 Bikes page and put cleaning carbs in the search field at the top right . These bikes don't have magnetos and need some charge in the battery to make ignition work . Slow turning alternator is not enough . The smoke could be a fuel problem and untill you get the carbs sorted I wouldn't worry about it .
Hope this helps
Mike

[MAGOH]

Thank you so much for the advice.  Do you think I could get by with cleaning the carbs without buying the rebuild kits for now?

[wrenchmuch]

If the carbs haven't been rebuilt yet the rubber bits inside are toast . Look for just a seal kit ( no jets just the rubber bits ) and buy the float valves later if you need them . Bike Bandit shows both the gasket kit $15.16 ea.  and valve kit $28.83 ea. available . You might find them both cheaper elsewhere . Are you sure its a 73 ? The only one I can find on BB is a 350 G and its a twin . I found those parts searching for a 72 F .

[MAGOH]

Yeah, I'm sure its a 73.  The owner still had all the original papers with it.  Even still has the tool kit!  The PO said that he did rebuild the carbs a year or so ago.  I told me it was running rich.  I honestly don't know what that means exactly.  I think it means its getting too much fuel to air?  I plan on doing the deep stuff during the winter/early spring, but I really want to get riding right now.  I saw a couple other posts where people bought different carb cleaner fuel additives that they just put in the tank with the fuel.  Could that work in this case until I can get the carbs redone?

[P_Camps]

Magoh I just got my 550 July 1st and have learned a massive amount just frequenting this site.

+1 on cleaning the carbs. 

As far as replacing the float bowl gaskets I would first try to reuse them.  If they end up leaking fuel then replace them.  I've successfully re-used mine but then again there is a chance that they were previously changed.  Also, check your plugs, I've noticed that made a huge difference in how much smoke my bike emitted.

P

[flybox1]

determine what you need AFTER you tear into them.  

download the service manual. and get a clymer book for your 350F
assume the PO didnt know anything about bikes.
take a day. run your bike for 5 min. get it hot and drain the oil, install a new oil filter.
3.2 quarts of 10-40w.
set your valve gaps, do your timing, install a new battery and an air filter.
tear apart your carbs and clean their gutz. bench synch them.  get new D8EA plugs.
set your air screws to 1 turn out.
take your tank and a 5 gal bucket to the gas station. slosh your fuel tank around with whatever gas is left over, and pour it out to see what comes out.  
fill immediately with fresh gas. use the old gas in other power tools.
the search function can get you instrucitons from posts already here.
if you get stuck, let us know.
start her up.

then, if she still wont purr....let us know whats going on. we'll be here.  

nice bike BTW! we need some pics in this post.

[wrenchmuch]

Chemicals mixed with the fuel may break up some of the gunk in the carbs but will not touch hard deposits . The gunk that they might free up can easily get stuck in the jets , especially the slow jet . Its orifice size is tiny and a grain of sand can plug it . Some of these chemicals don't like rubber too much either . I think the slow jets on these carbs are held in place by a flat spring that the float bowl holds in place . The jets have a o-ring to seal them to the carb body . All these internal rubber bits are removed before cleaning with solvent as a general rule because they often swell and deteriorate in solvent . I my experience you will need to disassemble if they are dirty and you will probably break some rubber bit in the process if the bits are old . If its an o-ring you break you might be able to source these locally at a seal / o-ring supplier . Get a good battery in there and see if anything improves first . Bad spark can cause a lot of trouble . If your ignition is good then its time for some carb cleaning .

Flybox posted while I was writing . All his points are good especially the one about the PO .

[TwoTired]

I don't know the 350 as well as the Cb550.  But, they are very similar in construction/design.

Tuning carbs without completing the 3000 mile tune up check list is just plain stupid.

 You can take off the carb float bowls to access the jets.  The leaf spring jet at the bottom is the main jet.  The smaller tube next to the  big center post is the screw in idle jet.  They can both be cleaned without removing the carbs from the bike.  It helps if you have a nice variety of tools in different lengths and have double jointed wrists.  A small inspection mirror.

When you remove the bowls look in them for bits other than gas.  Gummy stuff can be cleaned off and there is hope that liquid cleaners in the gas will soften those and get them flowing through the carbs.  Gumm can also be  removed in the passages you can't get to but simply dropping the carb bowls.  However, if any bits are larger than the smallest orifice, flow ceases along with any cleaning action.

If you find sediment or rust particles in the bowls, then you have a gas tank cleaning issue to address.  You can clean carbs until you are blue in the face, if you feed them with a dirty gas tank, you will just end up with another carb cleaning task.

Dirt or other particles in the carb bowls can also block the float valves from closing, which results in fuel dumping on the ground.

The alternator operates via an electromagnet powered from the battery.  The ignition also is powered by the battery.  There has to be enough juice in the battery to excite both these devices for the bike to run.  The kick start comes in handy when the battery is low enough so that the starter motor doesn't function due to a run down battery.  If the battery is faulty or dead flat, expect to push the bike, rather than have it move under its own power.

Make sure you are operating the choke lever properly, and that what you think is the on position is not actually the off position.

Cheers,

[flybox1]

lever up = choke on
lever down = choke off.

[MAGOH]

So if I am riding and the bike is warm, i want the choke down?  It says on the choke that down is open. 

[MAGOH]

OK, turns out I was runing the choke backwards.  It just started raining so after it stops, I'll try again.  Thanks everyone and please accept my apologies for my ignorance.

[Logan80]

Asking questions is the best way to learn. No need to apologize.

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