Cb360 starting/running issues. Fresh 378 rebuild

thrillseeker

thrillseeker

Been Around the Block
Freshly rebuilt 378cc 360 with new harness is very hard to get running. Need help!

When it does start running I have to keep the throttle fully open or it stalls. It never gets above idle rpm range. Noticed some fuel splashing out the back of the carbs when it's running as well. So I thought it was rich but when I kicked it a few times with ignition off the spark plugs seem dry. Battery is strong. Timing is good. Spark is strong. Compression good. Valves adjusted. Timing chain tight. Carbs rebuilt by pj. I also checked the temp of the headers after running for a minute and they were dead equal so it doesn't seem like a problem only on one side or the other.

I think I'm going to double check the timing and valves to make sure I didn't screw something up. I also took the carbs apart and cleaned them well since it was 9 months or so ago when pj worked on them.

Help is greatly appreciated.


Update:
Checked cam timing and ignition timing. Both set and it's still not running.

Update:
It's definitely a fueling issue. Spark plugs are dry after a few kicks. But float bowls are filling up and fuel valve seems to be working.
 
Check the sync man. I got mine back from PJ and i assumed the sync was good as well. I re benched and vac'd it and it was money.

I'm not saying PJ didn't bench them, I'm sure he did but there's no harm in double checking.

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Am I reading that right? You took them apart and put them back together because it was 9 months ago when PJ worked on them? Where's your idle mix set? Are the floats set right? Idle adjust set right?
 
Floats are set at 20mm right now. and idle mix screws are 1.5 turns out. I think my problem is on a larger scale than the idle mixture not being set right since the bike is so hard to start and it needs wot to start and stay running. Playing with the throttle while it's running has no effect on rpms. It's just not running at all or barely running on wot. Pj suggested looking at cam timing too so I'm going to look at that this evening


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Checked cam timing and it seems to be good. The pin that rotates the advancer is at 12:00 when left cylinder is at tdc. Set timing again after. Making sure it's at compression stroke by taking the plugs out and feeling compression with my finger. Still not running.


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Just went through and set cam chain, valves, and timing. Then put the tank on and opened the fuel valve and nothing flowed out. Fuel was flowing before but maybe not enough. Going to investigate that another day. Once I get that flowing I'll try to start her up again. I also made sure my ignition wiring was correct. All of that looks good.


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Make sure to have a couple gallons of fuel in the tank.
I was chasing a non-firing cylinder, ended up being the amount of fuel in the tank.
 
So I put new fuel in and got new spark plugs. No dice. The new plugs were dry after a few kicks too. Fuel is flowing to the carbs well. So I took the points and advancer off again and made a little measuring tool to make sure the pin on the cam is truly at 12:00 when rotor is at LT. I'm still not exactly sure but looks like it might be a little off to the right. My eyes are messing with me a little. My question is, does this look correct? If it's off, would it be off farther than this?

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If it was off, it would be much farther off, as long as you lined up the hash marks on the timing chain sprocket when you put the motor back together, you should be fine there.

If the plugs were dry after 2-3 kicks then you've got a fueling issue. Are the bowls filling up? Pilot holes clear?
 
Thanks. Yeah the bowls are filling up and I cleaned the carbs a few days ago. Made sure the jets were clear. Now that I think about it I didn't really check the small holes on the manifold side of the carbs


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Going to try lowering float height to 17mm to see if that helps.

First I'm going to shoot a little air into the carb to make sure the slide is functioning.

What are your thoughts on starter fluid? I'm thinking about spraying a tiny bit into the carb to see if that gets it going. Never used it before though. I did read you're only supposed to use a very small squirt and have an extinguisher on hand just in case.


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For giggles, try it all again with the jumper cables hooked up from your car but the car turned off.
 
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Sonreir said:
For giggles, try it all again with the jumper cables hooked up from your car but the car turned off.
Click to expand...
Thinking the battery isn't strong enough?


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Yeah. It's a common issue with the Honda twins and it's super easy to check before you go digging into more involved trouble shooting.
 
Cool I'll give it a try. Need to hook the points back up and time it again first. Speaking of which, how do you guys feel about the method of setting the timing in this video? He basically just centers the plate and then adjusts each point gap to open at the right time.

https://youtu.be/nDvghJiJGFc


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Not how I'd do it.

Gap the left point to spec, and then rotate the points plate to time to the left cylinder. Next, adjust gap on the right point until that cylinder is timed. If you go outside the spec for gap on the right point, it's time for new points.
 
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