Cafe Racer Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
Hi...new to the forum and new to my 73 CB350. I am learning as I go...

The bike sputters a little and sometimes dies when I come to a stop. I was told the jets were probably clogged. I took the carbs apart and cleaned them although they looked pretty good. I couldn't find any clogs in the jets and was able to thread a fine wire through all the jet holes. I put it back together and it still sputters and backfires sometimes. I replaced the old fuel lines with clear hoses and I notice a lot of air in the lines and it doesn't seem like they ever fill up. Is this normal or should those fuel lines always be full of gas? I wonder if maybe there is a clog in the petcock valve or something.

My ultimate goal is to complete the transformation to cafe that the previous owner started.
 

·
Registered
Joined
·
241 Posts
Off the top of my head, here's some tips/questions:

How many jets did you remove/clean? How exactly did you clean the carbs? There are a lot of parts and a lot of passages that need to be spotless clean. You should have removed the main jets, emulsion tubes (and needle jet if separate from the emulsion tube), pilot jets and idle screws/springs/orings etc at a minimum. When you hold the pilot jets up to a bright light and look through them do you see a full round circle? Do both look the same? Have you blown carb cleaner and compressed air through <every> passage in the carbs after removing every thing that can be removed? You say you poked a wire through the jets - what kind of wire? In general that's not recommended as the jets are very soft and pilot jet holes are very small. It's difficult to not change the size of the hole and thus change the size of the jet.

Where are the idle screws set? Do they still have their o-rings?

Do you have any air leaks? How did you check? What air filters and exhaust are on the bike? Have you changed either in any way since you got the bike?

Where are the needles set?

Are the carbs reasonably close to being in sync?

Have you removed/inspected/cleaned the petcock? If there was any crud in it did you clean the tank?

What condition are the points in? What is the point gap? Where is the timing set? Do you know how to set the timing on both cylinders? (set left point gap, set timing by rotating points plate, set right timing with right points point gap).

Do you have new spark plugs?

What is the charge level in the battery?

Have you got fresh oil in the gearbox? Have you pulled the dipstick and smelled it to make sure there isn't any gas in the oil?

Have you checked and adjusted the valve clearances?

You didn't use any parts from a Keyster carb rebuild kit did you?

Michael
 

·
Registered
Joined
·
7 Posts
Discussion Starter #3
Wow! There are A LOT of things to check...

Here's what I did with the carbs.
- Removed the float bowl
- Inspected floats and they moved freely and looked to be in good condition.
- Visually I don't see any varnish deposits and everything looks pretty clean.
- I removed the two jets in the center and both look clean and I can see through them when held up to the light.
- I removed the sleeves/tubes and they look clean.
- The wire I used was very fine and required NO forcing through the holes but I won't do that again if it is not recommended.
- I removed the slow jet which sits under a rubber cap and it looked clean as well.

At this point I think I was really targeted on clogged jets since that is what I was told was probably the problem.
- I did NOT remove the idle screws
- I did NOT blow compressed air through anything
- I did NOT check for air leaks and the filters are the aftermarket pod type. I don't think they are K&N but look like them. You might be able to see them in the photo on my profile if it's not too small.
- I don't know how to check needle the needle seetings...need to read up on that.
- I think the carbs are reasonably synched??? Visually they look to pull at the same time and the same distance but that's probably not the best way to check this huh?
- I did NOT clean the petcock but will because it doesn't seem to me that gas is flowing freely from the tank. However, I don't know what normal flow looks like. The hoses from the tank to the carb are always half full of gas...never completely full. IS THAT NORMAL?
- I am NOT sure how old the plugs are but the rebuilt engine supposedly has only 100 miles on it.
- The battery is brand new and charged completely
- Don't know how to check the points but will read up on that.
- The oil is new but I have NOT tried smelling it to see if there is gas in it
- Don't know how to check the valve clearances but will do some reading on that too.
- I did not replace any parts in the carbs.

I really appreciate the feedback. Being new to this I have no idea where to start troubleshooting issues and you have given me a lot to look into. Lots to learn....Thanks.
 

·
Registered
Joined
·
4,721 Posts
how about starting with the basics

compression reading

valves properly adjusted

inspect ignition, make sure points are clean, no metal transfer or arcing, and properly adjust everything

from what you say the carbs sound like they are clean and even if not

getting the vitals inline and knowing all is well

is a great place to start regardless
 

·
Registered
Joined
·
2,740 Posts
If your looking for some really good stuff to clean your carbs, check out this product called Dragon Fire carb & chock cleaner. I just recently restore some very nasty Mic carbs and this stuff worked wonders. My technique is spray, air blow and ask questions later.

Dragon Fire is now part of my main arsenal for carb cleaning.
 

·
Registered
Joined
·
4,721 Posts
is it spray can or can it be had by the gallon?

is it caustic?
 

·
Registered
Joined
·
3,431 Posts
Dollar Bill,

Take your aircleaners off and see if that makes any difference. Had a similar problem with my cb360. Only problem now is I can't find any of the proper new aircleaners for the bike, and pods won't fit.
 

·
Registered
Joined
·
2,740 Posts
HackAsaw - it comes in a can spray, trust me you don't need a gallon of the stuff. I just buy a new can of it for 6 bucks today. (price + tax) Dragon Fire loves to eat gas varnish and old gas grim. You can enhance the cleaning action with a little steel wool or small steel bristle brush. For cleaning out jets - nothing I've used to date comes close to this product.

Oh - I forgot to add, it will more than likely kill you if you breath too much of it - certainly if you drink it, so don't forget to mask up and wear gloves when using this product.
 

·
Registered
Joined
·
4,721 Posts
what else have you used?

of course I need at least a gallon to make my little ultrasonic happy and five to make the big one percolate

either will bust the seam of a coke can standing in them with nothing but water, and to date, nothing else I have used cleans carbs better

but I'll certainly check out this dragonfire stuff
 

·
Registered
Joined
·
2,740 Posts
Well ofcourse an ultrasonic is going to work better!!!! You clean your carbs in pee with an ultrasonic cleaner. The chemical content is not needed with an ultrasonic cleaner. For those of us that don't have a cleaner - the spray works just fine.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #11
JackC,

Is it that the after market pod filters are not letting enough air in or too much. When I rode it yesterday there was no more backfiring but it still had trouble in first gear taking off. When I take off it sputters and then will suddenly take off...almost like it is stuck and suddenly works itself loose. When I come to a stop if I don't keep the engine revved it dies. Sometimes it will idle okay and when it does it stays between 1000 - 1200 rpms.

I haven't had a chance yet to check the petcock and the other suggestions HackAsaw gave me are beyond my knowledge right now. I will do some research on it and try to work on it Sunday. I don't have any time this week to tinker with it because I am working on a pinata and playhouse for my daughter's 4th birthday this Saturday...gotta take care of the important stuff first! Still appreciate the feedback and hope I can get to a point where I can help someone down the road too.

Bateman, racing those vintage bikes looks like a lot of fun!
 

·
Registered
Joined
·
4,721 Posts
yes the ultrasonic is the best but

if used with the proper chemicals that do indeed clean viciously and then actually seal the pores of the base metal

they do indeed work much better and wickedly fast

the problem with the proper chemicals commercially available today is that they are extremely user and epa friendly

the stuff you could readily buy 20 years ago would remove 2 or 3 layers of skin if you soaked you hand in it for just a minute or so

if you left a carb in it overnight, it would ruin the casting opening every single pore leaving it blistered and useless

today's stuff isn't in the same league until you add some of your own oleic acid, acetone, and lye making the solution much "hotter"

once you do that you end up with surgically clean carb bodies and parts after a good 30 minute bath

otherwise the new stuff can take even 24 hours to render just decent results

so yes, I'll check this stuff out since to date, I've yet to see anything carb cleaner related that I thought was anything but near useless for actually cleaning carbs that actually needed cleaning

thanks for the info and I always enjoy such useful exchanges
 

·
Registered
Joined
·
7 Posts
Discussion Starter #13
I went over the carbs again and this time shot carb cleaner down all the little holes too. I checked the float level (set to 26mm) and set the air screws to 3/4 turns out per the manual. The bike started and sounded good for a minute and then started backfiring and gas started pouring out of the overflow hose on the left carb. I take that as meaning the float is either stuck, not really at 26mm, or the fuel mixture needs to be leaned out more by adjusting the air screw.

I went to check the timing and about a quart of oil poured out when I removed the rotor cover. Is that normal?

The points looked clean. Other than that I don't quite know what to look for when inspecting them. Should you see a spark on each one when the engine turns?

Also, the plugs are now very black and sooty. I think that also is a sign that the bike is running rich. Are they toast now when they get that way or can they be cleaned?

I did read somewhere on the Internet that the carb rebuild kits come with 115 main jets and they are really supposed to be 105. Can anyone confirm that for the 1973 CB350? If it's true that could be one of my problems because when I checked my jets I noticed they were 115s.

I don't have a strobometer to check the timing or any other instruments to measure compression so until I scrape up the dough for those or find someone that will let me borrow theirs I am flying by my eyes, a dirty old manual that doesn't really answer my questions but is helpful for knowing where everything goes when I take it apart, and a regular old toolbox.

Dang, I can't wait to get this thing running right so I can start trying to make a cafe seat for it. I wonder if expanding insulation foam would work for forming a seat mold????

Thanks for the pointers!
 

·
Registered
Joined
·
7 Posts
Discussion Starter #14
Oh yeah...the timing method I tried to use was turning a flashlight on and off quickly. Didn't quite work but I just had and idea and wonder if anyone else has tried it. What about holding a flashlight behind a little fan? Would the blades turning in front of the light simulate a strobe??? I'll have to try it and see...
 

·
Registered
Joined
·
43 Posts
No a flashlight used in any type of arrangement will most defiantly not work. The pulse of the light on a timing light has to run in sequence with the spark plug pulse. You will never be able to accomplish this with a "flashlight" and "little fan."
 

·
Registered
Joined
·
166 Posts
Before I had money to buy nice timing lights and whatnot, I made my own timing device as the manual showed. Just a small bulb with a couple wires soddered to the positive and negative, connect to the right spots on your points and walla. You can't have the motor running of course, just turn it over by hand. It got it close, not close enough to run it to redline but close enough to get it fire and idle properly. I still have the damn thing and I used it to get the timing close before I fired the motor after a rebuild.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #18
That sounds like a solution I can handle Mc69!

I bought new plugs after testing the left plug to find it had no spark and my bike fired right up. It sounds smooth now and idles without stalling but there is still one issue and that is that it losses power at wide open throttle. I remember seeing something about that on another post here so I'll see if I can find that.
 
1 - 18 of 18 Posts
Top