Topic: CB750 K5 won't keep an idle *all ok now

[Kinch]

Ok, let me ramble a bit if you will to give some background info. I picked up a 1975 CB750 K5 in very good condition a while back and the thing drove beautifully on the way home (about 15 miles). I drove it around town for a couple of days on little 5-mile jaunts but then on my way back from about a 30-mile ride the engine started sputtering and stalled.

I had a friend pick it up and when I got home I checked the bike and noticed that there were rust flakes in the tank and that the petcock filter had broken off inside (missed that on the initial inspection  ). There were rust flakes clogging the petcock so I drained the carbs, got a new petcock filter, cleaned out the petcock, sealed the inside of the tank and put a filter in between the petcock and the carbs.

Started the bike up and it ran perfectly again for a couple of weeks. Then one day when I went to ride the bike it started a bit rough and then died. I checked the filter to make sure that there was nothing clogging it, disconnected and drained the fuel lines and drained the carbs, made sure the petcock was clean and that gas was flowing through it and everything looks fine but it still won't hold an idle. That's where I am at the moment.

I can usually keep it idling (a bit roughly) if I keep the choke on but when I take the choke out it seems to smooth out the idle a bit but then it dies. With the previous problem I can imagine something may be clogged but I'm so green at all of this I'm not sure where to start.

I plan on starting to troubleshoot from the manual but any advice before I start from you fine people would be greatly appreciated.

[neil10]

looks like you cleaned tank  and petcock but perhaps the problem lies in the carbs with dirt. which is no big problem

[Kinch]

Cool, I'll search for carb disassembly/cleaning instructions. Thanks.

[Kinch]

I'm such an idiot.

So I took apart the carbs and went through painstaking measures to make sure that each little part stayed with it's corresponding carb throughout the whole process (I'm talking photographs and notes). I cleaned and reassembled everything, put the carbs and airbox back on and when I went to make sure that the drain screws were tight I saw that they went like this

/ \   / \

instead of this

//   \\


If you know what I'm talking about right now you're probably giving yourself a good forhead slap like I am. I took every measure to avoid something like this but my unique ability to screw things up seems to have surpassed all my efforts.

Anyway, I plan on switching out the 2 inner carbs so that at least all of the screws are pointing the right way but if I do end up trying to run it and the carbs are in the wrong order is it just a matter of me having to re-sync or could I cause other problems?

Any response would be appreciated, in the meantime I'll be pushing myself down a flight of stairs.

[fuzzybutt]

just change the bowls out, they can go from carb to carb

[Kinch]

Thanks, I just realized that when I took a look at them. Did that and hopefully that's all that was mis-matched.

[Kinch]

Changed the float bowls, started it up and it's running great. Whew! Panic over.

[neil10]

clean carbs go along way

[Kinch]

Yes sir, thanks for the advice.