CB360 grinding on startup

hillset · Jul 28, 2018

Hi Everyone,

I have a 1974 CB360 that I'm having problems getting started up. The bike previously ran fine, but about 6 months ago I decided to install a pamco ignition and pull the points. During the process of installing the pamco, I broke the camshaft pin and had to replace the camshaft. With school and work getting in the way, the bike sat for about 6 months until I was able to get the new camshaft in this week.

I installed the cam and the cam chain per instructions I read in the manual / online (lines on the cam sprocket level with the cylinder head, cam chain tight on the front before installing the back cam chain tensioner in the back). Now when I go to start the bike, I can hear the starter motor engage but after a second or two of running the starter motor, there is a loud banging / grinding noise from the engine. It doesn't sound like a backfire, it sounds like metal-on-metal which makes me worried.

I verified compression before I pulled the original camshaft and I've verified spark on both cylinders since getting the pamco installed. I'm thinking I should pull the top end cover again and just make sure nothing is wrong with the chain / sprocket / cam but I'm not really sure what to look for. I've posted a video of the sound on start up.

Someone on hondatwins mentioned that it could be the starter clutch that has gone bad, but I've been reading that a failed starter clutch should cause the starter to run without catching. Can a failed starter clutch cause the noise I'm hearing? Is there a way to check my starter clutch before I invest $50 on new parts and a rotor removal tool? Is there anything else I can check before replacing the starter clutch? Thanks for your help.

https://youtu.be/eVpaNaazcqs

themotoworks · Jul 30, 2018

does it do the same thing if you kickstart it? what I'd do is try narrowing down your variables before you start pulling things apart again, one of the things that you can look at on those engines is whether or not the cam chain tensioner bottom actually seated properly in it's seat, it's very hard to see and I've dealt with a similar noise because someone did a rebuild and had the tensioner bottom jammed behind the seat, made an awful racket. I'd also consider pulling the stator cover off and possibly removing the starter and chain to isolate the starter clutch, then try kick starting it, it should be easier than removing the cam cover again.

kagraves · Aug 25, 2018

I can't quite remember but I believe the cam could be rotated 180 so the valves are opening and hitting the piston as it comes up to tdc. Also check the tensioner and cam chain while you are at it. I might back off all your tablets and try to crank it over so the valves do not open but the engine will turn over.

MiniatureNinja · Aug 25, 2018

sounds to me like you have timing incorrect or coils backwards

hillset · Oct 6, 2018

Ok I wanted to update the thread because I've tried the things you guys recommended last time but I'm still having the same issues. Here's what I've done so far:

- I replaced the alternator and starter clutch (the old one did have a bulge in the outer casing and one of the pins was jammed into the slot).

- I verified the alignment of the cam chain on the cam sprocket. The attached pictures show that the cam sprocket aligns with the top of the cylinder head while the rotor has LT aligned with the mark on the stator. I also verified the front of the cam chain is tight and not kinked.

- I've verified the pamco unit timing as best as I can. The unit is aligned exactly how it's shown in the pamco manual and I've gone over the wiring several times. I'm still having problems using my timing light to verify timing since I can't get the bike to start, but based on what I've read I don't think I can be far enough off on timing to prevent the bike from at least firing.

- Also, from what I've read I don't think the cam can be rotated 180 degrees off. Based on posts I've seen on here and the manual, as long as LT on the alternator is aligned with the mark on the stator and the lines of the cam sprocket are aligned with the top of the cylinder head, the timing is correct.

Bike is still making the same noise as in the video and is not starting. Is there anything else I can check? Should I just totally scrap the pamco and go back to points? I can't think of anything else to check so I'm open to any suggestions. Thanks for everyone's help.

Pete12 · Oct 7, 2018

The cam turns at half engine speed, so it can be 180 degrees out.

furu14 · Oct 7, 2018

To me it seems that the camshaft is 180 degrees off...
the lobes are on top. if the picture is on cyl 1?

hillset · Oct 7, 2018

Ok I got the cam turned 180 degrees and reinstalled. Just to verify, with the left cylinder at TDC on compression stroke the cam lobes are pointing down, the alternator is at LF, and the lines on the sprocket align with the top of the head. I double checked the wiring and verified spark on both sides. The timing light is more consistent now and I’m sure it’s firing when LF on the alternator is aligned with the firing mark on the stator (with the timing light hooked up to the left spark plug wire). It’s still making that grinding/wheezing noise and not starting. Anything else I can check?

hillset · Oct 10, 2018

Ok a small update:

I pulled the cylinder head cover again to verify everything, here's what I see:

Rotor is aligned with LT mark and timing mark on the stator

Left piston is at TDC on compression stroke

Cam sprocket lines are aligned with the top of the cylinder head and left cam journals are pointing down

As far as I can tell, this is the proper alignment for the cam.

I sprayed some starter fluid into the left cylinder and got a small backfire with a puff of black smoke out the left exhaust but still no sustained fire. My thinking now is that assuming cam / spark timing is correct, the problem could only be:

1. Fuel delivery - I'll pull the carbs and make sure sitting fuel hasn't gummed up the jets

2. Wiring - less likely since I can see a spark on both sides with the plug resting on the cylinder, but its possible I could have something wired backwards. I've tried switching the blue / yellow wires but it's worth trying again.

After that I'm pretty much out of ideas. If anyone has any other ideas I'm definitely open, thank you guys so much for your help.

hillset · Oct 10, 2018

Just verified the wiring, the diagram from pamco shows pamco white to blue wire from left coil + pamco green to yellow wire from right coil. I've verified that's what I have in the pictures below.

Still getting the same wheezing sound on startup. Is it possible I've blown a second starter clutch? I really don't want to have to take off the left side crankcase again unless I absolutely have to. Thanks to everyone for your help.