Help with Backfire and is that starter noise normal? 75 cb360

keeleydavis

keeleydavis

Been Around the Block
Hello,
So I just rebuilt the carbs (used a kit with o-rings and needles) and cleaned the 30 year grime out. I also have installed a new starter motor and swapped out the starter clutch and rotor, since the original was cracked. I fired up the bike for the first time and it seemed the left side wasnt firing yet. My thought was the gas hadnt yet made its way there. I rode up the street and then the left muffler started backfiring. Got home and started it again and puffs of smoke would shoot out of the muffler end, connectors and even the carburetor. There was smoke in the airbox after a big backfire. What could be happening?

Also watch this video and listen to the starter motor once the bike dies. Is that a normal sound? Thanks so much

http://www.youtube.com/watch?v=gmXExQfkfF0
 
Starter sounds normal to me.

The weakness on the one cylinder, popping and backfiring, could all be symptoms of being too lean. Spray WD40 around the carb manifold to search for intake leaks while the engine is idling. If there is a leak, you will hear the idle change when you hit the leak. Make sure there are no cracks in the rubber. If you have not replaced the intake pipes, do so. If they are still the originals, they should be replaced, even if they look good.

Also, if you just rebuilt the carbs & replaced the float needles, it's possible that you do not have the float level set properly. Low float height will make the cylinder run lean, especially at idle. How did you go about setting the float height? It takes a little bit of subtle knack to adjust floats.
 
AlphaDogChoppers said:
Also, if you just rebuilt the carbs & replaced the float needles, it's possible that you do not have the float level set properly. Low float height will make the cylinder run lean, especially at idle. How did you go about setting the float height? It takes a little bit of subtle knack to adjust floats.
Click to expand...

Why should I replace the intake pipes? Are you talking about the Carb Insulator like this http://www.ebay.com/itm/Honda-CB360-CL360-CJ360-Carb-Insulator-16211-369-000-/380398372039?_trksid=p4340.l2557&forcev4exp=true&item=380398372039&nma=true&orig_cvip=true&rt=nc&si=e3PGHb8BqM3B8vy4S390zvMtccs=&vxp=mtr

I bet your totally correct about the float. I replaced the float needle and the part that the needle rests in. Any advice on how to adjust the float?

Also something I forgot to mention about the starter, it made that wind down sound for quite a while one time after the engine stopped.
 
The starter clutch is a one way clutch. When the engine stops, if it turns backwards due to compression, it will spin the starter. Normal.

ADC is right. the backfiring is usually a lean condition. This is often caused by out of balance/sync of the the throttle. At idle, one carb is carrying all the load, the other is shut so far that the cylinder leans outs....spits and pops out the intake.

Before tearing anything apart, synchronize the carbs and adjust the idle mixture.

You can usually tell which cylinder is the culprit by pulling the spark plug wire off one cylinder. the engine will keep running on the more open carb, and stall on the less open carb. When right, it either stalls on both, or keeps running on both, depending on idle speed.

ALSO, I had a problem with an idle miss, single cylinder not firing (The left is the most common) when the points cover intermittenly shorts to the terminal fitting on the left side points. I carefully bent the area of the points where the screw is slightly upward to clear the housing. An thinner than stock, or no gasket, on the point cover can cause this.
 
OK, so you didn't set your float heights at all. You probably didn't synchronize your carburetors or any of that other stuff that is part of rebuilding carburetors. Taking carbs apart, cleaning them, replacing a few parts, and slapping them back together will not be a successful "rebuild" unless you do the necessary adjustments. For me, I almost never replace any parts when I do a carburetor rebuild. Usually cleaning and adjustment is all that is needed.

A seminar on how to adjust carbs is a little beyond the scope of a forum post. Time for you to get busy and do a little research, look at some YouTube videos, study the service manual, and systematically approach properly setting up your carbs. If you don't have a service manual, (not hard to find a good PDF will a little googling,) then you are just screwing around instead of fixing.

Here is a thumbnail version of what you need to do:

Take carbs back apart, and set the float heights.

Replace the intake pipes if there is any deterioration to the rubber. These get old and hard with age and develop cracks. Make sure they are sealed well to the head.

Install the carbs and balance them. If there are vacuum ports for synchronization, that is the best way, but it is possible to get it pretty close by grounding one spark plug at a time and set for the same idle on both sides with one cylinder at a time.

Adjust the idle air mixture screw. If you synchronize your carbs by ear, this has to be done on each carb first.

You got a pretty good tip about the possibility of one of the points grounding out on the inside of the points cover. Make sure you don't have a problem there. As far as setting your points and timing, there is a pretty good YouTube video on the procedure. I'll leave it to you to do your research and find it.
 
Help with Backfire and is that starter noise normal? 75 cb360

Okay so I got some new carb intakes but I just realized I need a little advice as to how to get those screws loose. Should I remove the battery to get a better angle?
 
Here is something else I just noticed after adjusting the floats. The brand new o-ring gasket I installed before between the float bowl and carburator is now much bigger in length. I cant get it to fit back into the groves because of this. Did it expand from gas or something? Is there a way to shrink it again? Thanks much!
 
1. they expand
2. they may shrink if left to dry out.

At work, we buy O-Ring material in spools. We have a kit and cut to length, then glue the ends. the glue is "crazy Glue" ...

I have some very good German Crazy glue, I cut a small portion of the o-ring out with a sharp, fresh razor blade and glue the ends to make it a little smaller.

Done well, I never had one come apart or leak.

Your results may differ
 
Those screws can be a bugger to get out. You do have an impact driver, right?

Don't put the phillips head screws back in. Use either hex head bolts or socket head (allen) bolts. I like to use stainless steel socket head. Be sure to use anti-seize, especially if you replace them with stainless. Anti-seize is mandatory for stainless fasteners.

As far as those gaskets go, I don't think I have ever seen that happen. Maybe they were shitty gaskets? Anyway, they will probably shrink to fit again after being dry for a couple days.

Permatex makes a red sealer that is really good for carb gaskets. You can put it in the groove, and use it to cement the o-ring into place. That way, when you remove the carb bowl, the gaskets stays in the groove.
 
You can also put the gaskets in the freezer. That'll shrink them up a bit. As for the screws, if they are beyond buggered to where you can't even get the out with an impact screwdriver, use a small pair of vice grips. Clamp them on nice and tight and slowly start to back it out. Once you get them loosened a bit you can probably work them out with a screw driver.
 
Funny as it sounds, I use a small dab of grease in each corner of the float bowl gasket channels. Then pop the o-rings in place, they will stay put long enough to get them back on the carbs and the grease will help them slide around evenly when you tighten up the bowls.

Gas will dissolve any that gets into the bowl and you can wipe the excess of the outside.
 
AlphaDogChoppers said:
Don't put the phillips head screws back in. Use either hex head bolts or socket head (allen) bolts. I like to use stainless steel socket head.
Click to expand...

Where do you get these bolts and how do you figure the correct size? Finally got the bolt out with a screw extractor but I do need to get an impact driver for sure.
 
An impact driver is $10. Just get one, fer cripe sake! <G> You can't work on motorcycles without one.
http://www.harborfreight.com/impact-screwdriver-set-with-case-37530.html

Google is your friend. Don't expect the forum to do ALL yer fucking research. <G>

I often buy an assortment of socket head cap screws from Rusty Riders.
http://www.rustyriders.net/bolts/60pc-stainless-allen-head-bolt.html
This assortment will likely have enough bolts of various lengths to do all your outer case bolts. If not, buy two.

eBay is also an excellent source for hardware. eBay is where I originally found Rusty Riders.

Metric hardware is measured by diameter with thread pitch specified as a dimension.
Example: 6 X 1.0
This means 6 mm diameter with 1 mm thread pitch. SAE bolt thread pitch is listed as "threads per inch." Metric thread pitch is listed as the distance from one thread to the next. Therefore a 1.25 thread pitch would be a courser thread than 1.0.

You can go to your local AutoZone, Advance Auto, or Pep Boys and buy an assortment of metric bolts nuts and washers for about $25. It is an indispensable resource in the shop. With it, it is easy to identify bolt sizes and thread pitches.
http://www.pepboys.com/product/details/9276710/00014/
 
Again AlphaDogChoppers, you have given me gold!! I spend too much time on google and get caught in a rabbit hole of gear that at this point I am not too experienced with. Your info in this one thread is worth more than you know. much obliged
 
Help with Backfire and is that starter noise normal? 75 cb360

Sears Hardware stores have a large assortment of metric bolts and screws both in zinc plated and stainless. I bought my engine bolt stainless cap screws on e-bay, but all the rest of the chassis hardware at Sears.

There are stainless carb screw sets available too

If you use stainless, make sure to use anti-seize. Stainless will fall and damage aluminum threads if not treated.

I have replaced every not structural screw on the bike with stainless as I took her apart and reassembled here.

I hate rust!!!


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Re: Help with Backfire and is that starter noise normal? 75 cb360

mydlyfkryzis said:
I hate rust!!!
Click to expand...

I hate crappy fasteners, and all those bogus phillips head screws just scream, "JAP CRAP!"
 
Help with Backfire and is that starter noise normal? 75 cb360

They aren't Philips head, they are JIS .. Lol. Allen head is the way for me.


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Help with Backfire and is that starter noise normal? 75 cb360

Lolz


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static it won't matter that airboxes are off. You need to re-set tappets, adjust cam chain, and check ignition timing.
Starter sounds normal.
Carbs are out of sync
 
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