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Discussion Starter · #1 ·
Just got my cb360 running. Now I need to tune the carbs.

When I start the bike, it starts perfectly but idles at 4k RPM. When I turn the throttle stop screw, the idle doesn't change at all. When I turn the pilot screws, there is no change in idle at all.
I pulled the filters to see what the rest state of the carb slides were, the left is just slightly open and the right is all the way open.

Does this mean the carbs need to be synced?
How do I adjust the right carb slide to come down to match the left carb slide?

Thank you in advance
 

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Sensei
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Carbs are assembled incorrectly or missing parts or both......
How far did you disassemble them when you cleaned them?...

Time for another phone call, too much to type.....
 

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Discussion Starter · #3 ·
Carbs are assembled incorrectly or missing parts or both......
How far did you disassemble them when you cleaned them?...

Time for another phone call, too much to type.....

I will call Saturday. Actually, Crazy Pj rebuilt my carbs for me. But we will figure it out tomorrow
 

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If the slide is all the way open it is probably stuck, you can pull the cap off the top and see if you can get it to drop like it should. IF it is in backwards that will do the same. Sometimes they get stuck in shipping since carriers care little about what's inside the package.

PJ does a great job on these from what I have been told, I doubt he would have let it leave with issues.
 

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DUDE!... IF Crazy PJ rebuilt them they are 100% ... He definitely knows what he's doing.....

Franz is likely correct and something happened during shipping (or maybe installation).....
 

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Discussion Starter · #6 ·
You're right. Word on the street is Pj is the boss at these carbs, and when I got them back from him I saw why. They look amazing.

I took the top off like frogman said, slide was stuck so I pushed it back down and its now the same as left slide.
Put back together, started it, idled really good for a few seconds then jumped to 4k again. Tried messing with idle adjustment but still isn't working.
 

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If the slide is all the way open it is probably stuck, you can pull the cap off the top and see if you can get it to drop like it should. IF it is in backwards that will do the same. Sometimes they get stuck in shipping since carriers care little about what's inside the package.

PJ does a great job on these from what I have been told, I doubt he would have let it leave with issues.
Slide position is totally irrelevant on CV carbs, you can completely remove slide at idle and nothing will happen (if everything is working properly beforehand). The issue would be cable adjustment or fitting, 'closing' cable out of adjustment is common (causes opening cable to be too 'tight'') Did you remove the cable bracket from carbs before shipping them to me? (not that it really matters it's just really difficult to tighten screw when carbs are assembled) Check twist-grip has at least 3mm slack, check opening cable has slack. Slide stuck after shipping is a bit unusual but that won't cause 4K idle. Choke operating lever isn't bent and sticking on? Have you done a carb sync? I set them to open together but will need sync when you get bike running. Idle screw is the cable on left carb, pilot system is the brass screws on either carb, were set at 1 or 1.5 turns out and will probably need adjusting when engine is hot
 

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Discussion Starter · #8 ·
I did not remove the cable bracket when I shipped them to you.
Choke lever is not bent.
I have not done a carb sync yet, as I figured doing that at 4k rpm wouldn't affect anything until I have the idle speed down first.
Cable slack is good as well.
 

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Air leak.... Some possibilities;

One (or both) of the carbs is NOT fully seated in the rubber manifolds.........

Manifold to head: gasket bad, loose bolt, warped base plate......

Age cracking in manifold rubber...Not always readily apparent, often at the rubber to steel plate juncture....
 

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Discussion Starter · #10 ·
I was just looking for those issues.
The gasket seems to be ok, and the manifolds are brand new so I am assuming they are crack free. Didn't see anything noticeable by eye.
 

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Discussion Starter · #11 ·
Can't find any air leaks.

Obviously putting the choke on tames the idle because not as much air is going in. Right carb is blowing some misted fuel out when running with choke on, slight puffs of air as well.
 

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Check right intake valve clearance....

Too tight allows extra fuel/air mix in and can cause revving above normal idle, and might help explain blowback.....

Did the carbs "snap" into the pockets before you tightened clamps?
 

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Discussion Starter · #13 ·
Let it be known, I fully trust PJ'S Carb abilities and fully assumed it was something I had messed up lol.

Went to adjust the valves yesterday, and found what couldv'e been a horrible thing. The exhaust valve adjustment screw and nut was missing on the right side. I was sad. Took the night to think it over, and pulled the top end off today. Thankfully, under the valve cover was the screw and nut sitting pretty. I pulled the head to check and make sure nothing was ruined anyway. Everything was still tip top. Unfortunately, the screws threads are marred up a little, and I don't have the correct die for it. So I am just going to order another from CMC. I am not sure if this was the cause of high idle or not, but, I am so thankful I found it before I started the bike again. I will post back in this once I get everything put back together, timed and running again.
Thanks for the help so far everybody
 

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You may want to extend pipes plus fit some sort of silencer, too loud gets really wearing after 10~15 miles
 

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Discussion Starter · #15 ·
Got the valve adjuster screw in on Friday, put it on this weekend then put the top end back together. Timed the bike then test fired after I adjusted valves, ran for 1.5 seconds then died, and won't start back. No backfires, makes me wonder if it isn't getting fuel. But, I haven't touched carbs so doesn't quite seem possible it isnt getting fuel. I suppose I could've pulled the plugs to see if there was fuel on them. Is there a definitive best method for cleaning soot offspark plugs? Left one is turning a bit black. Is this indicative of anything?

Checked timing last night, it is still tip top. It is definitely getting spark. Going to readjust valves again this afternoon or tomorrow, just to make sure that isn't the cause.
 

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Do check for a dirty fuel tank and supply chain to carbs. Todays fuel sucks bad, I don't care what anybody says!. Open the bowl drains and see if it continually drains fuel. If it drains the bowls dry and stops, need to figure out why.
 

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Thank you for this thread. I’m slowly going through the same things with my 76 CB360 as well.

I’m not really brave enough to post many questions, so I’m glad there are people like you to ask.


Sent from my iPhone using Tapatalk
 

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Do check for a dirty fuel tank and supply chain to carbs. Todays fuel sucks bad, I don't care what anybody says!. Open the bowl drains and see if it continually drains fuel. If it drains the bowls dry and stops, need to figure out why.
Got to agree todays fuel is crap, blame the farm lobby for forcing severely overpriced ethanol on everyone. Ethanol is nasty stuff, absorbs water out of thin air, causes corrosion and doesn't 'play nice' with carburettors. (I've had to invent some extra mods since Florida went 'E10' a few years ago)Fuel injection systems can compensate but you lose power and get lower mpg Make sure fuel is off for initial draining
Drain into a clean container or bowl so you can see if any dirt comes out. The vacuum adapters fit drain screw holes so you can check fuel flow without wasting gas.by fitting tube and draining into gas can for at least 5 mins then measure how much came out. you can check flow individually to make sure both shut off valves flow the same
 

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Discussion Starter · #19 ·
I will try draining the fuel tonight to check flow. Let it be known I ALWAYS run non- ethanol fuel in anything I own that has carbs. Where I live is very rural, the three closest gas stations always have non-ethanol, and off-road diesel.

Last night I was trying to see why the bike wasn't firing up, I pressed the starter button and nothing happened. So I thought it was weird the battery would be dead, but I hooked up to a charger anyway... tried again, and still nothing. Flipped the kill switch a couple times, then it fired up for a few seconds then died again. So I took the switch controls off just to see if one of the switch contacts was messed up or something, I didn't see anything but I am going to check all wiring tomorrow just to ensure.

I felt the exhaust pipes to see if both cylinders were firing, only the left was. I looked inside the right carb and the slide is stuck up again. So I will be fixing that as well.
 

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The spring in the kill switch can fail, I always used to spray 'Duck Oil' in them when servicing 'way back when' (mid 70's) WD40 also works. At least kill switch is easy to get apart
 
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