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Discussion Starter · #1 · (Edited)
This is my first bike (1974 Cb360) and it was time to clean the carbs. I took out all the jets and cleaned them and left the carbs soak in a dip bucket. I placed the carbs back together. And did the whole guitar string Synchronization. I also added a new petcock valve because my old one was acting up. I went to turn on the bike and when i did its as if i pulled the throttle all the way back and it just continued to accelerate. The rpms needle was HIGH. The first thing i decided to check was the throttle cable and see if it was snagged or caught on something. But it didnt look like it. It actually sat on the lever mechanism kinda loose. I think i didnt synchronize the carbs right maybe thats whats cause alot of air to go in the engine. If it is that how do i go about synchronizing them them if i have to have the motorcycle on and it just revs up like crazy. Or if it might be another issue please let me know. Ill open up the carbs again this weekend and 20180226_180339.jpg 20180226_180304.jpg 20180226_180519.jpg 20180226_180318.jpg 20180226_180534.jpg 20180226_180330.jpg see if theres any damage or maybe i misplaced a jet. I would rather not buy a synchronization kit yet if i dont have to. Thanks in advance for your response.

*Update so i went and took it apart from the engine and took a few photos. Also do yall think maybe my intake manifolds wherent tight or maybe there is a breach that would cause it to rev like that?
 

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It's not a misplaced jet. To get that type of response something has to be preventing your throttle plates from closing completely. When the engine is running with no load it takes very little throttle opening to accelerate it to red line.

A bit of searching will give you some ideas on how your could make your own manometer (synchronization kit) with very little expense. The job can be done with 2 vacuum gauges which you might be able to borrow from your local auto parts store.
 

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I didn't see it mentioned - is your idle screw set correctly?
 

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Discussion Starter · #4 ·
The idle mix needle on the side? I did take them out and added a new o ring on one of them ( which was a pain in the ass)
i put them back with the spring. is there a proper way as to placing them back. As in not to tight? download.jpg
 

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No - the thumb screw that adjusts your idle speed. It's a knurled-knob.

The mix screws should be approx. 1.5 turns out. tighten them until you JUST feel it tighten, then back those out.
 

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Ben, although I owned a '75 CB360 new back in the day, I will defer to those who know more. With that being said there are some basics at play here. From the pictures it looks like the bench sync (guitar string) and the idle screw setting shold be OK. Just make sure the butterflys are closed. The engine must be getting air from some where. I suspect the carb boots are leaking. The bolts and clamp look wrong. The bolts look like countersink heads. I think there should be JIS hex bolt. The countersunk head would not spread the clamp load as intended. The clamps look like hose clamps. The stock clamps provide a more even squeeze around the boot tube circumference. I would also check the condition of the gasket. If it was my bike, I would replace these parts with new from Honda. The condition of the boot is important. They should be soft rubber. Keep at it.
BTW- add you location and bike model to your avatar.
 

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Discussion Starter · #9 ·
James may be right. There is two things i wasn't sure about and that was the idle mix needle and the boots. When i placed the carbs on the boots they just didnt feel like they fit well. They are not soft at all as well, and one of them looks a little rough. Ill probably just end up buy new boots i need to replace the anyway. Thanks for your response it was helpful.
 

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Discussion Starter · #10 ·
Gene, Oh ok yeah I thought that was used to synch up one of the carbs and then you attach the other carb and synch it with the #6 screw. Is there a proper way to have the thumb screw set? Thanks.
 

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Sorry for the delay - got distracted. Your carb Sync screw - again, IIRC (you should get a manual, invaluable) is approached via a hole in the frame under the seat. You'll need a special tool or a super long harbor freight screw driver.

The idle adjustment should be set at it's loosest point, then adjusted when warm so the bike idles between 1000 and 2000 rpm. What that is doing is pulling the carbs open to a degree (forgive my terminology, I'm a hack) so, when warm, idle is held where you want it.
 

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Am I correct in reading that the throttle cable is sitting loose? I’ve had an issue before with my 360 where the cutout in the throttle wheel that sits between the carbs was misaligned and catching on the idle set screw you guys have been discussing. I’d look to make sure that there’s nothing obstructing the full rotation of that throttle wheel on the carbs.

EDIT: Asleep at the wheel, apparently. Looks like you've checked for that.
 

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Discussion Starter · #13 · (Edited)
Ok sorry it took awhile to respond i was a bit busy. Thanks everyone for your tips and help, it helped me solve the issue.

Sorry im on my phone typing this.

Ok so this is for anyone in the future who has the same issue. First my idle needles wherent set right. Make sure when you screw them in to screw to it barley firm. Where it wont screw in unless you use force. Then counter screw 2 rotations. Second, one of my idle needles o ring was a bit rough so i change it. The new o ring was a bit to thick so it didnt fit to well and was a pain to remove from the carb. So i just reorder a brand new needle and did the same thing as above. Thirdly, i was still getting air somewhere after the above procedures so i sprayed some carb cleaner around my carbs until the engine reved up. And the culprit was the left carb boot, intake manifold, or whatever you call it. It was in bad shape and mustve had a crack. Also, the boots did not have gaskets from the previous owner. So also added those. So i changed that bad boy with a new one. Fourthly my rpms where still pretty high at neutral so as the above user said i fiddle with the thumb nobe on the side of the carb till my rpms are where i needed them. If you have questions id be happy to answer. Good luck!
 
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