Cb360 starting/running issues. Fresh 378 rebuild

Thanks for the advice. Do you have any methods you use to find a leak?


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The more I think about it, a vacuum leak sounds like a very likely cause. That's probably why it wasn't starting before. Then I raised the floats, letting more fuel in, which could now be compensating for the leak.


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Using carb. cleaner or WD40 as the bike idles, spray around intakes, it the idle rises or dies completely, you look closely at the intakes to see where they might be leaking. Like I say, they could be perfectly fine, but if gaskets or O rings have shifted or not seated, this could be the problem. Once the intakes are confirmed seated, the make sure the carbs are seated properly in the intakes. Once this is confirmed, start the bike, find an idle and use the wd40 again, if the idle rises, try to direct the spray directly into the linkage going into the sides of the carbs. if the idle rises again, then you might have found the culprit.

I use WD40 and only because some people have told me the carb cleaner can actually dry out seals. There are probably several people on here that can give you better info than me, but I'm trying to give as much help as my experience will let. In between the carbs where the linkages are it is very common for those gaskets to tear, or the plastic washer (if your carbs have these) to dry out and get brittle. You can find good usable stuff at ACE hardware to replace these if you can't find a carb kit that includes them.

I loved Yamaha triples, and was always able to buy then cheap, because the p.o. couldn't get them to run right. Joined an XS site and found these little tricks that made them quite the beasts when sorted. I had Leno ride my 850 and coming from a guy who rides a jet bike, he was amazed how the bike ran.

Again, I'm no expert and I don't even know if the 360 is similar to the 850 carb wise, but there are some basics that transfer to almost anything. It sounds like you are close and getting closer and sometimes the little things can frustrate the hell out of you. As others have said, your carbs are sensitive and they'll get you where you need to be. I just want to keep you from the mistakes I've made and spending way too much time or worse $ chasing this issue.

Got her idling today! Turns out I did have the throttle stop screw set wrong. That was my bad. I was messing with it and never put it back. I connected the vacuum gauges to see how the sync is and they're a good bit off. Left at 5 and right at 10. They're both low so I'm going to check timing really good. I Noticed the right header pipe isn't getting hot either. Hoping that will clear up after syncing. If it doesn't, I'll check for fuel and spark. For now I'm going to order a sync wrench because I don't have a screwdriver long enough to adjust them. Thank you all so much for your help! I don't know what I would do without all you amazing people here on dtt.


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If that pipe isn't heating up, check spark, you might have lost a coil or some loose wires... Usually an easy fix. Make sure the plug isn't fouled by the earlier issue. You could swap the coils and see if it happens to the other side, but initially I'd follow the wires and make sure something didn't get pinched or knocked loose....

The actual number on your sync gauges doesn't matter much as long as they're pulling the same vac pressure.


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Looks like my vac numbers are right around the factory specifications too, so I should be good. I was confusing cmhg with inches


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Ran into a speed bump. Smoke was shooting out of the head gasket when I went to sync carbs. Took the valve cover off to check torque of cylinder studs and a couple felt looser than the others so I decided to re-torque. Also found out I used anti-seize instead of oil on the threads. So I cleaned that off and used oil on the threads instead and torqued them down. The outside studs under the spark plugs didn't have any lubricant at all. So I think they might not have been tight enough. It's right by one of those where it was leaking. Hoping this fixes the leak.

While I have the valve cover off, I decided to check the cam timing. Looks a degree or so off. Looking at this picture, is there a way to fix this? Maybe loosen the bolts and try to adjust the sprocket on the cam a little?





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Did the stack height change? Did you get any metal shaved off of the head or the jugs? If so, you can either slot the cam gear, get thicker gaskets (defeats the purpose, usually), or live with it.

I've decided to live with the slight late cam timing after learning that it shouldn't affect the performance or reliability too much.

Got the bike back together today and checked compression. It's around 200 psi after a few quick bursts on the kick lever!


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