Bike won't rev quickly

8ers

8ers

New Member
Hey all, so I've got a 74 cb360 which I have recently rebuilt the carbs on as well as add pods and a more open exhaust but now the bike is very slow to rev especially under load. Other than that it is easy to start and idles perfectly. I have tried using the choke to see if it is getting to much air but it doesnt help. Any suggestions?
 
No, but it seemed like everything I found online said that the stock 360 carbs could handle pods and an exhaust. The problem is that the bike didnt run when I bought it and I ended up tearing the whole thing apart to do a cafe project so I dont know what it was like before.
 
If the only thing you touched was the carbs and it has changed that much, then it's the carbs.


If they are the stock CV carbs then you could have a ripped diaphragm or a clogged jet or something else amiss.


However, if you've changed a lot of stuff all at once (adding pod filters and changing exhaust as you stated) and now see these problems, it is a lot harder to know where to look.


I would suggest you check the big things first by doing a compression check with the carbs off. Make sure the valves are adjusted correctly and the mechanical side of things is solid.
It's quick and easy and you can scratch those things off the list of suspects pretty quickly. (and if you do find a problem, getting the carbs right wouldn't fix it anyway)


If the compression check out right, then I'd suggest another full carb disassemble and clean. Yes, you just did it, but you have to know for certain that everything is clean and correct in there.


Another thing to double check is fuel flow. Petcock, gas cap vent, inline filters, needles and floats are all suspect until proven good.


Things that can potentially cause this symptom are many and varied, from incorrect fuel flow, to valves way out or cam out of time, carbs way out of synch, clogged jets, ripped diaphragms, float bowl vents clogged, and the list goes on.


If you can share more information we may be able to help you narrow it down some.


Best of luck!
 
8ers said:
No, but it seemed like everything I found online said that the stock 360 carbs could handle pods and an exhaust. The problem is that the bike didnt run when I bought it and I ended up tearing the whole thing apart to do a cafe project so I dont know what it was like before.
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I don't know where you were looking as majority of 360 carb information was written by members on this site.
You not only need to re-jet, you need other modifications to get stock carbs working with 'pods'
 
more info while I typed.


Compression check first, then double check carbs and fuel system.


You will likely need to re-jet at some point.
If you can find a shop that has a oxygen "sniffer" wand they can analyze your jetting quickly and it will save you a lot of time doing plug chops.
One of the few times it's worth taking an old bike to a shop, imo..
 
Have you run t with the pods removed? Could be a simple as air bleeds blocked/partially blocked by the rubber flange in the pod. Pretty common issue with a lot of the pods out there.
 
I havnt tried that. the bike does have good compression, no rips in diaphragms, newly rebuilt petcock and lines and filters.

I have tried taping up the pods/using the choke to decrease airflow. Shouldn't I have seen some slight improvement if it was just the jets?
 
8ers said:
I havnt tried that. the bike does have good compression, no rips in diaphragms, newly rebuilt petcock and lines and filters.

I have tried taping up the pods/using the choke to decrease airflow. Shouldn't I have seen some slight improvement if it was just the jets?
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It's not so much about quantity, as quality. The Keihin 3 jet CV carbs need a long intake prior to the air entering the carb because they don't do well when the air is turbulent. The stock air box helps to ensure that the air is smooth and laminar when it gets there.

Also, in reference to your exhaust, what do you mean by "open"? Are you running a performance exhaust system or did you just cut the exhaust off at the foot pegs?

Finally, double-check your timing with a strobe light. If it's running too far retarded, then you'll lose all kinds of power, especially under load.
 
And when I say slow to rev, I mean all the way from 2500 to 8000 at a pretty constant rate if that helps.
 
I'm running 2 of these shorty mufflers from dime city. http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-exhaust-parts-12-inch-shorty-muffler-80-03310.html
 
8ers said:
And when I say slow to rev, I mean all the way from 2500 to 8000 at a pretty constant rate if that helps.
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Definitely sounds like timing, though you could be combatting more than one problem.

Try turning the points plate about 5° in the clockwise direction and see if the problem gets any better. I still recommend making use of a strobe light, though.
 
OK, your going for 'the look'
I can tell you, it can look the way you want it to or you can have something that works
360's really don't like short exhaust and up-jetting will create a rich mid-range
It will need at least a 107.5 secondary main jet and may need up to a 125 secondary depending on exhaust
The bottom end should be fine on stock jetting.
You WILL need to set float level at 21mm

Lean bike to right side, remove generator cover , turn on ignition and turn crank with ratchet point should arc/click when you reach LF l or RF l timing marks.
It's a good idea to remove plugs, re-insert into plug caps then ground them to engine
That will tell you if timing is close enough.
Points gaps need to be 0.012"~0.016".
When your done, try turning the end of points cam to make sure it is free to advance, could be stuck/rusted in retard position
 
Thanks, I'm going to look at the ignition system tonight for all those things. By the way, I did my own exhaust piping between the stock headers and aftermarket mufflers so the system isnt too much shorter than stock.

P082212_1704_zps7eb5d78a.jpg
 
Exhaust will be fine at that length, should improve bottom end
Problem is going to be carbs and ignition, setting points correctly takes a bit of practice, particularly if you have to 'split the difference to get both right (may have to adjust one gap to low or high end to get timing right on the second cyl)
BTW, the points cam is not the bolt on the end, it's a 'tube' with a bump ;D
 
Another thing that is weird is that I pulled the spark plugs and they are carbon fouled, just totally black and they were new when I put the bike back together. So that should indicate that there is too rich a fuel/air mixture right?
 
Or timing is retarded. With the timing running too retarded, the mixture lights up too late and all the heat ends up going out the exhaust pipes instead of staying in the combustion chamber. This quickly leads to carbon fouling as things don't get hot enough to burn it all off.
 
Ok, so it appears that the left cylinder point would light up slightly left of the LF mark so I fixed that and now have it spot on. Im not sure about the right though. after I did the left(which was on compression stroke) I rotated the crank CC till I saw the F line line up, however there was no spark as the contacts pulled apart and I couldn't get my circuit tester to light up. And I pulled the right plug and the spark plug looks brand new. Do I have a bad point?
 
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