CB360 - Help

[joegregg]

Hey guys,

I am in need of some help! I would really like to get to know motor[cycle] mechanics more by doing it myself, but I think I need help on this one.

Here's the story: (1975 Honda CB360, 10,000 miles, daily rider for the last 1,000 miles.)
One day, riding home from work my bike doesn't react to the throttle as it should. I noticed I was missing a lot of power, but I didn't feel/hear a misfire. I rode it slowly down the rode and finally pulled over. I revved it up to 5k rpm or so and it seemed a little slow, but fine, hitting on both cylinders atleast. I slowly get it home and ride it the next day. Same problem. Seemed to ride fine the first few miles then I lost power again. It idled fine at the normal level. I head home that night and it is definitely only firing on one side. I check the plugs, one is black the other is fine. I changed the plugs, start it, same issue. Clean the plug, change the oil (not filter) with a mix of Marvel Mystery oil and some good Shell Rotella. I did this in case a valve was getting stuck or it just had some old oil as I had never changed it. No luck, same problem.
I have my buddy Tony come try to help me check points and of course the soft screws on the covers were butter and I stripped them to hell. Couldn't get them off. Ordered a new bolt kit. Still could not get the covers off, so I get frustrated and take it to the only local vintage bike shop. They keep it for 11 weeks, 10 more than they said, and after harassing them enough they get it "done." They supposedly boiled my carbs, put in a new slide, a new accelerator pump, and sync it. I pick it up (in rough shape), but it rides home okay. It backfired, which it has never done before. Backfired all the way home, figured it was just some tweaking I could do to the carbs. I try to ride the next day to work, get it out, takes more kicks than normal to start, and once it does I let it warm up for a few minutes. Get on and head down the road only to find that I have the exact same power loss I did before. I'm pissed I missed the best riding season because Twin could not get to it, and then proceeded to not even fix my problem so I'd like to do it myself with some help.

Does anyone have suggestions/advice? Or other questions about something I missed, I'd be happy to answer!

Any help would be appreciated! Thanks a lot.

Joe

 

[plagrone]

The cb360 does not have an accelerator pump, so if I was you I would go down there and raise a little hell

 

[work9to5]

I've only had back fires for two reasons (1) carb was screwed up with a vacuum leak and (2) had water in my fuel system. I'm sure there are other reasons to cause them but I'd think to start with your fuel system for that. Buy a impact driver, $10 bucks. One of the best tools you'll ever own too once you figure out how to use it properly. You won't have issues with stuck screws again. You can tell if one side is not firing pretty easy. Start it, if one of the pipes doesnt get hot like the other one then your not firing on one side. Or if you can only feel output from your exhaust on one side your only firing on one side.

Generally when one plug is black it's usually a bad plug. You said you changed it though and it blackened again? Then I would check your spark plug wire on that side (look it up on google on how to test its relatively easy and doesnt require tools). If it's not that then the next place to look is if oil is getting past your rings or your valves are messed up allowing oil where it shouldn't go and not allowing your plug to spark. You really dont want it to be this btw. Is your bad plug oilly or is it dry sooty? If it is wet does it smell like gas or is it slippery and more like oil?

You don't have an accelorator pump.

I highly doubt they changed the slides, I believe your model still has a rubber diaphragm type slide. They are kinda hard to come by. I would think that they wouldve called you to tell you about the added expense to the work.

 

[irk miller]

First thing, if this story is real then we need to know who the dipshit vintage shop is. Somebody needs an ass whipping. These guys are taking you for a ride. Nothing here is more than two hours work. 11 weeks to work on parts that don't exist is effed up.

 

[trek97]

As I read this, the very first thing that came into my mind was, a torn diaphragm.

So, yes I have no doubt, they replaced one. ONE, stupid as that may be. The other is probably getting ready to let go, sooner than later. So, why not replace both.

You can simply order a new pair from your local Honda shop...takes about 2 days to get them. They arent cheapies. But, they work great. The kits (part #7 on the fiche) will include diaphragm, slide and spring.

So, first thing to do is remove the carbs and open them up and see what kind of "NEW" diaphragm they have installed. If its the cheap JBM I suggest you throw that straight into the shit can and get a new PAIR from Honda shop.

Its very easy to tell the difference, A NEW GENUINE HONDA will have a thick BRIGHT WHITE plastic ring...if its yellowing or brown then they just replaced it w another old used one, (ebay), or, better yet, superglued the hole in your torn one.

If it does not have a plastic ring and the rubber diaphragm is just stretched over the slide then its a crappy JBM.

maybe Ill get off my ass and post a pic.

New from Honda

Even though they SHOULD HAVE...
I doubt they removed the air correctors when they boiled the carbs...BUT, if they did. They may have gotten them mixed up and installed in the wrong locations. So, double check those.

Then reinstall , check sync, tune a/f needles and go from there. It will probably run great w little effort.

 

[trek97]

heres some more carb tune up info. this contains air corrector location map.

http://www.dotheton.com/forum/index.php?topic=63133.0