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Discussion Starter · #1 ·
I have been trying to get my 1969 cb175 K3 running and finally made it happen, but I can't get it to idle right.
It will start up and then when I give it gas it will stay reved up and slowly come back down and then stall. I have cleaned the carbs twice and set the valves and timing and point gap.
Any ideas/Help??

Also I put in a new clutch cable and it now seems to be slipping but wasnt before.
Sorry for the amateur questions.
Thanks
 

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I'm dealing with the same issue on my 73 CB350G. Best of luck, if you find a solution, let us know!
 

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Sensei
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...... The symptoms you discribe indicate that your carbs are "out of sync".....
Assuming your point timing is "spot-on" and the carbs are clean, their floats are set (adjusted) correctly to 21mm, and the shut-off needles are working, Start by setting both "mixture screws" to one turn out from "gently bottomed"... You will have a 1/8 turn plus or minus range from this setting once you get to the fine tuning stage.....
Take off the air cleaners so you can see the carb slides, and adjust the idle screws out untill both slides close as much as possible....Then adjust each carbs cable until the slide just starts to lift, and back it off untill the slides fully close again... Lock the carb top cable adjusters there.
Fire up the bike opening/closing the hand throttle slowly until it idles at the desired speed...Hold throttle there, and Adjust each idle screw in until it just starts to "pick-up" and then back it off to the desired idle again.....
Fine tune using the mixture screws one at a time until the maximum revs occur, and leave them there.... Lower the idle screws back to the desired idle.... Check to make sure BOTH carb slides start to lift simultaneously, and the same amount....(touch one slide with a fingertip while watching the other).... Re-install air cleaners..... If necessary, adjust the excess slack out of the cable by using the adjuster at the throttle end....
PITA, but worth it..... Steve
 

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Not trying to horn in, but he may have to slightly readjust those mixture screws after putting the air filters back on - I always have to on the CB200.......
 

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No problem Bill, and of course, you're correct...... Depending on the air cleaners you are using, some "tweaking" is often necessary... Adjust mixture screws slowly to max revs again, reset idles if/as needed, turning each side's idle the same amount.....Sync should be preserved....
 

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Discussion Starter · #6 ·
Great thanks alot, I'll give it a try as soon as I get a minute.
 

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Discussion Starter · #7 ·
I tried all that and even adjusted the point gap ,re timed my bike and adjusted valves again.
I can't figure it out. :(
 

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Sensei
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So...The symptoms remain the same...overrevs and then slowly falls off and stalls? We'll need to narrow down the other possible causes.... These bikes will try to run on one cylinder and show symptoms similar to yours, so the first thing we have to know is more specifics...

Were you able to get a steady idle to adjust the carbs by holding the throttle slightly open?

When you "timed" it, did you use a strobe to check the advance units correct operation? (it could be sticking, then falling off)

What are the compression readings?

Are you getting good spark on both plugs (one coil wire could be compromised, swap sides and see... or better yet, "borrow" the CB200 coil temporarily)

Are both pipes equally hot? , equal pressure while revved/running?

Did you disassemble and actually clean/inspect the carbs components (jets, holders, etc), or just spray cleaner until it went through?

Is the battery known to be good?
 

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Discussion Starter · #9 ·
Aright I am at work so I'll tell you what I know as of now.
The bike would actually idle sometimes but then start reving really really high on its own.
Then sometimes I couldn't even get it to stay running.

-The bike has a new battery
-I did completely disassemble the carbs and put them in a carb dip and made sure all the jets and everything was clean
and clear. Also adjusted the float heights.
-I haven't taken compression readings (What is the process for this) I do have a tool for it ,but its been a while
-It seems like I am getting good spark on both plugs( Whats the best way to check?) I just take them out and put them against the engine..
- The pipes seem to be equally as hot maybe slightly different.
-Not sure if they have equal pressure or how I would be able to know.
Thats what I know now ,but I will be going to the garage tonite hopefully.
Thanks
 

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Sensei
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Compression test:
Run bike enough to get it to normal operating temperature......(hot)
Shut off fuel at petcock....
After removing both plugs, Install compression test meter into one spark plug hole
Holding throttle WIDE open with choke also open (lever down), Kick it through 5 or 6 times...Or e-start/roll over for 5 or 6 seconds.....Record PSI reading
Repeat on other side....
PSI readings should be about 165 to 170 PSI OR better on BOTH cylinders.... An 8 PSI difference between cylinders, or any reading lower than 150 is an indication of imminent tear down/re-ringing being due.....These bikes WILL still try to run with 120 or more PSI, but produce negligable usable power below 140/145 or so......



I still suspect that one of your carbs is flooding, causing the rev rise....Since the air supply to that cylinder is still restricted (idle position on the carb slide), the plug eventually gets "wet" and the bike tries to run on the remaining cylinder ...unsuccessfully.... So it stalls out....Then BOTH plugs probably show wet or carboned up....

DID you replace the shut-off needles and seats, or at least make sure they DO completely shut off fuel flow when the floats rise?
 

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Discussion Starter · #11 ·
I'll try the compression test when asap.
I didn't check if the shut off needles work (how would I check that?)
I also did not replace them.
I will also check my plugs and see what there status is.
I really appreciate all the help
 

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Sensei
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Take bowl off. turn on fuel...should flow out until the float is lifted (by you) to 21mm ..then it should shut off completely (Warning...messy and dangerous...do this outside...lol)
 

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Sensei
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Supposedly it would, but pinched or kinked hoses or blocked overflow passage (tube) can cause excess fuel to fill up main jet tube and trickle into cylinder.... can you "blow" through the overflow passage in the bowl?....Doesn't take much to clog them.....a smidge of "varnish" or a small particulate object....It only takes a small amount of fuel to rev the engine ...Two drops from an eyedropper into the back of the carb (air side) will do it....


I have experienced a tiny bit of grit (undesolvable) get into the idle passage, rendering the carb useless..... That's why I have several spare sets of 175 carbs....If I get one that just refuses to function properly, I just replace it.... (I have five 175's, one a "sloper", and four Verts... One is actually becoming a "sloper-vert" half-breed)
 

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Discussion Starter · #15 ·
Wanna sell a set of carbs :D :D :D

I can't figure them out . I didn't do the compression test yet because I couldn't get the bike warmed up.
:?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?: :?:


The bikes getting the best of me..........I not giving up though
The plugs are slightly wet
 

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Discussion Starter · #16 ·
What year cb175 carbs will fit or are the same as my 69 cb175k3?
Thanks
 

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ALL the 175 vert carbs are interchangable (bolt-on), but AS pairs....Both the early CB and CL's used 20mm carbs...The K4 and later CL 175's had 22mm carbs....
....Interestingly, the CB/CL 200 only uses 18mm carbs, the same size as the early 125 twins ( Not 100% certain they would bolt on, but can't see why they wouldnt work)....... Jetting is sometimes slightly different from model to model as well...
Any pair that fits should be "tuneable" or at most require some parts swapping (possibly jets, slides, needles, etc)
 

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Lets assume your carbs are flooding. That means if you've had the fuel cock open, the carbs are full of fuel. Start the bike with the cock in the off position. it will run on the amount of fuel in the float bowls for a minute or two. When it stalls, open the cock for a slow count of three, close it, and start up again. Not as good as after a ride, but that should get you warm enough to get a reasonable compression test, maybe not peak pressure but enough to gauge the condition of your motor. It should also tell you if float bowl flooding is the cause of your problem. Assuming, of course, the fuel cock does indeed shut off the fuel.
 

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Why couldn't you get it warmed up?..... Won't start with wet plugs, right?......
EMPTY the carb bowls (pop the bails and leave bowls off).....Install NEW plugs...(see if they spark when hooked to your coils, then install)......Tank off and/or disconnected......Key on, Roll engine through as if trying to start... (did it "burp" and try to fire or just spin over?)..... If it "tried to run", put one TEASPOON of fuel in each bowl and put back on carbs.....Try to start.......If it now runs even briefly, you definately have a flooding problem,.....(This is what I suspect)....Repeat several times until engine is warm.... Run comp test....
If it just rolled (no fires at all), put a FEW drops of fuel in the bell of the carbs/choke on, (fuel bowl still off).... See if it "burps over" ... If it runs/burps, when trying to start..add the teaspoon in the bowls....try again....
If it hasn't started/tried to start at all, run compression check COLD....Results will be somewhat below what it will read hot, but at least we'll have a relative reading .....
 

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Discussion Starter · #20 ·
well figured out the problem.........!!!!
The slides were in the wrong carbs, left slide in right carb....ect!!!
Don't know if when I got the bike it was like that or I made that mistake,usually I make sure things go back where they belong but I could've F***ed up.
Anyways the bike is running good now except the clutch is slipping ,I replaced the cable .
Does this mean I am gonna need new clutch plates? What do you guys think
or what should be my next step?
Thanks again for all the help.
 
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