I posted this over in my project thread but I haven't gotten a response. I keep searching and I don't think I am using the right words to find what I am looking for. Keep in mind I am a motorcycle and carb engine novice.
I have a 1977 CB750K with Mikuni 29mm Smoothbore carbs that were recently rebuilt. There is also a 4 into 1 exhaust on the bike. The engine is unmodified otherwise.
Series of Events:
1) Carbs get put on the bike after rebuild and after second kick starts up. Idles a little wonky but eventually settles down and hits a nice ~1400 RPM idle.
2) I fiddle with the idle adjuster and it works appropriately.
3) I walk away from the bike.
4) Next morning I go to change the spark plugs. I get them all out but one (this is another issue I am having... I can't fit the socket over the stupid plug... I must need a thinner wall socket ?? idk). I attach the pod filters so I can start tuning to those or at least see if there is any change to how the bike runs.
**(As I am typing this I just realized I might know what the problem is. I am going to continue)**
5) I kick start the bike and the RPMS shoot straight for 4k and there is some popping (assuming this is back firing of the engine). I freak out and flip the kill switch.
6) I try a couple more times and the same thing occurs. I stopped knowing that its not a good thing to rev the engine cold like that.
7) I yank the pod filters off to make sure the slides are just barely cracked and nothing is stuck open. Everything looks great.
I take the idle adjuster and back it all the way out, so the slides are as closed as they will ever be.
9) I back the choke off and try to start the bike, no go.
10) Go back to full choke, start bike and it again it runs away from me shooting straight for 4k RPM. I kill the engine.
I am at the point where I am flat out afraid to start the bike up again. So after being clueless, I think I might know whats wrong... funny how talking something out can help your brain work.
I was going to buy the $150 perfect fit rubbers from Sudco that are designed to fit the 29 mm smoothies to a 750k. I already had these hacked up rubber heat resistant engine hose things that were on the bike before and worked. There was no problem other than looking a little junky. I figured I would save the money and get the sudco "intake manifolds" another time. So I go to fit the carbs onto the engine and its a real pain in the ass to get it back on. I double checked and they seemed to fit all the way around the inlets... I am starting to wonder if one of them slipped off and there is an air leak somewhere. Does anyone know if that would result in the issues that I am having? I am going to stop by the garage tomorrow to look at it and see if that is what happened.
Any help, insight, knowledge, experience... anything would be very much appreciated. I am trying to trouble shoot this on my own, but like I said before I am not very smart about these bikes or carb motorcycle engines at all for that matter.
Attached is a picture of the carbs and you can see the blue rubbers I am using to mate the carbs to the engine.
Thank you!
