some like it hot

M

mxb401

New Member
i have to say i love reading and researching all of the awesome bikes you all build..the level of knowledge i have gained from this forum has been huge....i gained just enough to be dangerous

so..i bought this beauty a few weeks back and have been working on it ever since.
honda.jpg

its a 72 cb 350...looks better in the photos but not a bad ride...i want to turn it into a nice brat, but its a work in progress. we've been having some great weather so all i want to do now is ride.

it was running fair when i bought it, not great, but not bad, would sputter a little bit, and the bike need a good going over.
First off the tank was nasty...looks like someone used a liner years ago, and thanks to your all i used the vinegar trick and got it looking good.
tank.jpg


the bike is stock, i assume original carbs, so far i got new plugs, new petcock, cked the points, changed the oil, cleaned out the carbs with compressed air and carb cleaner and cleaned out the jets, replaced the diaphrams...new fuel lines...removed the in line filters....

the bike runs like a champ when it is cold...and even warm.....we can tune it...idles great...choke works...BUT after about 10 minutes of riding it just dies...it wont idle unless its on choke...and just cant figure it out...its getting spark...both cylinders are free....its getting fuel...

im thinking my next step would be buying the rebuild kit and giving it a shot. i have to say, today was fun during those 10 minutes of riding...but it got super frustrating and i had thoughts about driving it into a creek. :)

i could use some help on this one, i have big expectations for this pig and right now..its just not acting right.
many thanks to all of you...
 
Hey!

Great looking CB. I had the same issue as you and was thinking carb or electrical. Eventually I checked the valves which were beyond tight (measured when cold) and readjusted to spec. Now the bike doesn't die when idling (when completely warmed up/hot). Hopefully this helps!
 
thanks man...i hope to get it looking kinda like this..
untitled.png

...but if i cant get it to run it doesn't matter what it looks like...hahahah
 
Sounds like debris from the tank is clogging jets. Carbs need another good clean. Did you check the filler cap on the tank? It has to breathe air in to compensate for fuel level dropping.

And what about that bike is appealing: The crappy tires that are not suited to going around corners or riding in the rain? or perhaps the stupid lack of mufflers to make noise unbearable and upset carburation? Maybe it's the lack of fenders so the front forks can flex at will or the low bars and stock pegs to break your wrists and back?

Not my idea of a bike I'd want to ride. I do like the low street rod look, but so few of them come close to getting it right IMHO.
 
thanks for your response...ill pull the tank and make sure its real clean...i did clean the filler cap really good...and got a new rubber gasket..

i guess i should be specific and say i like the seat...and how they left the tank and the covers original stock paint....it matters more to me that this pig will run, than how it actually looks.
 
Cleaning tanks can be a monumental PIA, but check the cap and check the fuel tap which may be full of debris too. It's a good idea to do it outside or organize good ventilation.
 
You sure the choke is OFF? My bike will run and idle fine for right around 8 minutes with the choke on and as soon as it gets warmed up it runs like crap and DIES unless I take the choke off. You also need to set all the carb settings with the bike WARM, as they will not idle correctly set cold. Mixture, idle speed, sync if you can, warm.

Other than that, it has been mentioned to check the valve clearance with the engine stone cold,

Also the coils on these bikes will get WARM and stop working if they are old or have been overheated.
 
thanks for your response frogman...im going to check the valve clearances tonight as soon as i get home and flush out the carbs again....
i am sure the choke is off (i made that mistake on an old bike i had)

on the positive side i guess after all this ill be an expert at removing and rebuilding my carbs....haha
 
Re: some like it hot - ' 72 CB 350

ok..so i checked the valves lastnight....the good news is the valves are spot on..the bad news is...the valves are spot on :)
i was hoping they would be way off and i would have something here to post...something like.
'i ripped it around lastnight and froze my knuckles off'
but i cant

when i cleaned the tank i used the old petcock....and didn't install the new one until the tank was clean...
@teazerwhat is the fuel tap?? is it inside the petcock??

i need some help...im going to try to rip apart the carbs again tonight jsut to see if theres anything there...and double check the tank...but it just seems weird that it will run real hard for about 10-15 minutes..and then die...i also checked the battery lastnight..and its good.

anyone else have similar issues?
 
Thanks for the input everyone

wondering now if it could be the Coil??

if the coil was bad, does it make sense that when the coil gets hot it wont function properly?? because the bike runs awesome for about 10-15 minutes...and then its dies it will run only w/ the choke on..and as soon as i turn off the choke it dies....
 
Re: some like it hot - 72 cb350

if its in the gas cap to let the fuel tank breathe?? then yes. i was able to remove the old nasty gasket, wire brush all the pieces..and put on a new gasket, and put the fuel cap back on.

im going to take apart the carbs again tonight...clean out the tank again...and see what i can get done...i love these bikes when they are running right
 
Not exactly. That's all important stuff too, but there is a small hole (1mm or so diameter) somewhere inside that gasket ring that allows air in through the various parts of the cap. If you cant find one, it's probably blocked.

If you have the tank drained. You can either blow into the fuel tap to see if air escapes out of the cap, or apply a partial vacuum to the tank and see if you can hear air leaking in.

Don't hook it up to a 100PSI compressed air source though. That makes for a very funny shaped tank. :-(
 
Re: some like it hot - 72 cb350

thanks teaz....yes i was able to blow air..and i could hear the air flow out of the tank cap.

i tested the compression lastnight..and that looks ok...got it started..but it didn't want to run off choke..and the left carb wasn't working consistently. i ordered 2 carb kits from the DCC guys and hope to rebuild it w/ the new guts...its clean otherwise...so i hope this solves all my issues.

i did find one interesting question. i found this over on hondatwins...something about ligning up this screw??
carb.jpg


Can anyone give me a little more details around this? i couldn't find any information on the internet box
thanks again for everyones help!!!
 
Have you tested the fuel flow rate to the carbs? Is it possible that the flow rate is low and the bowls are emptying out as you run it?

Did you try hooking both carbs up without float bowls and turning on the gas tap (with a catch tank under of course) to see that both are flowing at a reasonable rate?
 
The 'screw' you marked is where primary main jet fits. It needs to be tight in body.
There should be a 'rubber' plug over the pilot jet (9 o'clock position)
Secondary main jet is at top
Mixture screw is the one on outside left, with the spring on it
 
Re: some like it hot - '72 cb350

thanks for your help pj...

still having issues w/ the right carb firing....
i found that the float was leaking..so i got a new one.

it starts..and runs w/ the left side running fine...but the right side is donzo.
i pulled the plug on the right side and it looks like its getting spark, and is wet...the fuel lines are are clear and i can see fuel feeding the carbs.

so far i:
rebuilt the carbs w/ the stock jets
new float
new battery
new diaphrams
new plugs
ck the points
ck'ed and adjusted the valves
cleaned the tank
new petcock
clean the gas cap

i didnt really want to take it to a 'mechanic', but man this is getting frustrating....any thoughts?? My dad said something about bending out the spark plug to see if it will still be strong enough to spark (i realize that that would ruin the spark plug) i didn't get to try it, but would that test to see if the spark was strong enough??

-mike
 
You adjust the plug gap by bending side electrode, just don't lever on the center electrode.
It doesn't ruin plug
Set gap at 0.028" or 0.7mm, you need feeler gauges
 
hey pj.
thanks for the response...i gapped them @.028.

i should've explained my dads trick...it supposedly tests to see if the spark is strong enough...you straighten the electrode and then put it on the side of your block, try to crank it over..and see if the spark can still reach it...i didn't try it, and never heard of it. (It ruins a spark plug, but then again its only $2.)

but im just wondering if its my coil is too weak that its not pushing enough spark on the hand side.
 
It's easier to unscrew plug cap and jamb lead between fins.
You only get a 4~5mm gap but if it sparks that nice and blue, it will spark further (usually 8~10mm)
 
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