[js360T]

new guy to the forum. I have a 1975 CB360 that is getting under my skin because I can't figure the thing out. The bike starts up first kick, idles, then when I drive it I usually only make it about 2 blocks before it's dead with fouled plugs. The plugs are dry, black, and sooty.
I have been through the carbs because I read that meant it was too rich. (?) The carbs were pretty clean, but the floats were a little high so I lowered them to 18.5mm. Carbs back on.. same thing. fouled plugs. I adjusted the air/fuel mixture screw in, same thing, starts great, idles, then fouled plugs.
I then replaced the coils and condenser with a used set off ebay. same old story, starts, idles, fouled plugs. Battery has been checked and is fine, fuses, fine. Fuel filter is clean, petcock is running fine, air filters seem ok. I even ran it once with no air filters on and got the same end result of fouled plugs. Can you guys solve this riddle for me because i'm about to lose it! For some reason it can't handle the load of riding and fouls the plugs and there I am again, doing the push of shame back home. Thanks in advance.

here's a pic

 

[jayel]

first get the compression checked, low compression will run but not right, choke working properly? then find out what size jets are in it,

 

[js360T]

i always read check the compression. i have not done that because i dont have a way to do it. if it has low compression, what can be done about it?

 

[tbpmusic]

i always read check the compression. i have not done that because i dont have a way to do it. if it has low compression, what can be done about it?

It (low compression) can be dealt with, just costs money and time.......

Try going to an auto part store or local car shop. Sweet talk/bribe (beer works) them a little, most folks will be curious enough about the bike to check it (the compression) for you.
Remember, warm engine, throttle wide open, NO CHOKE.

Costs very little, and it's basic diagnostic info you should get FIRST..........

 

[gs1327]

Maybe a stupid question but you do have the choke in the right position, no?

 

[js360T]

Choke is off. A few weekends ago I had just started it and flipped on the choke and it died instantly. I wanted to try to choke it to see if it would run better. Eh, not so much.

 

[66Sprint]

The reason we ask is because someone here was trying to ride with the choke on (lever up)..... He thought that lever down was choked.... easy mistake, but many fouled plugs later......

 

[js360T]

If It were only that easy. I'm jealous of that guy.

 

[66Sprint]

Normally, flipping the choke OFF immediately or too soon after starting will stall the bike....starting with it off and flipping it ON will richen the mix and keep the bike running....You flipped and stalled...Sounds like it WAS already on....You see why we ask.....

 

[js360T]

Got a grip on the choke operation. I had a 72 cb350, a 79 cb750k. I'm so frustrated with this 360 right now! Anyone have any other ideas?

 

[js360T]

If it helps, the previous owner told me he did not turn the gas off. Ever. Idiot. Yes I changed the oil. Also, I've noticed black smoke coming from the wrong end of the exhaust, like a leak. Can the exhaust get clogged or no? If so how is it unclogged?

 

[66Sprint]

Sorry, didn't mean to frustrate you further.... The best other reasons would be overjetted, or weak spark, and/or low compression......What size mains are in it?

Smoke at head or header muffler joint?

 

[js360T]

it's hard to tell where the smoke is coming from, but i think it's near the header/muffler joint.

i am working on getting a compression tester. hopefully i'll be able to check it tonight/tomorrow.

i need to check the main jet size. i have no clue what size they are. i think the carbs have been rebuilt. maybe someone changed them out.

 

[66Sprint]

The rebuild kits often come with the wrong size jetting....

 

[js360T]

The attached image is from a honda shop manual "Honda Cb250.360.CL360.CJ250T.Cj360T"

if that sounds like the original honda jet size seems like a good place to start. I gotta say tho, I dont know how to tell what size is in it. Is it big enough to have a number printed on it or is this something i have to try to measure?

thanks for all your help. i'm really hoping maybe this jet thing will work out! i've struck out everywhere else.

 

[Bird76Mojo]

There are numbers stamped into the jets.

GB :mrgreen:

 

[js360T]

haa.. sweet! i'll check em out asap.

 

[js360T]

i checked the main jet and it is a 68. the thing that threw me off was the other one was a 110. shouldnt it be a #35? any ideas?

 

[66Sprint]

Yes, the slow (pilot) jet should be a #35,.... #68 is correct for the mains (primary and secondary circuits).... Are you saying you have a 110 PILOT jet?.....

 

[js360T]

I'm embarrassed to ask this, but i'll go ahead since i am consumed with fixing this bike for some reason. go ahead and laugh if i am confused. ha.
does the Secondary main jet sit in the end of the needle jet holder? i'll draw a pic since my brain works like a 2nd grader. sorry for the bad cell phone pic.