Topic: 76 CB750F first ride and idle/carb question

[cobra2411]

I picked up a project bike that's changed hands a few times and no one really doing much so I have no idea how long it's been since it's run. Anyway I've been working on brake issues as everything is seized. I rebuilt the master for the front brake but am waiting on seals for the caliper. Got a new braided line for the rear, new pads, seals, etc.

Anyway I decided to take it for a quick spin despite not having a front brake and it wouldn't run off the choke. The batt is fairly new but dead from sitting. It was pretty easy to kick the bike over, 3-4 kicks and it was running. After a minute or so it stalled. I started to ride it and it accelerated ok but as soon as I stopped it would stall if I didn't give it gas. If I took the choke off it would bog and stall. Also it wouldn't run over 4k, it just went flat.

I haven't looked at the plugs and I have no idea how good the gas is... The air filter is a K&N in the factory box. Does anyone have any idea of where to start and what to look at? I'm going to try and spend some time this weekend on it. The brake parts I need won't be in till Tuesday... So I guess I'll work on a tuneup to try and get it running right.

All in all though I'm amped! It was so fun to ride. I was so excited I even forgot put the tag on it...

[Spanner 1]

Good stuff!... I'm glad your 'amped' as taking the carbs off/ taking apart/ cleaning them will use-up all your 'amp'.... but gotta be done as your slow jets are blocked fer sure; " Won't run off choke, dies etc.Not that difficult, lots of help here, live and archive, welcome to 750 heaven

[cobra2411]

Just an update, cleaned up the carbs and sure enough the low speed circuit was all buggered up. I also took the opportunity to add pod filters and rejet. Bike starts on the first kick even when cold.

I've also got the winkers working and next on the list is some electrical cleanup and to get the starter to work.

Next question: Why does the idle rise as the bike warms up? If I set the idle at 1k or so when cold, once the bike is ridden for a bit it will be like 1,500...

[Cuts Crooked]

Next question: Why does the idle rise as the bike warms up? If I set the idle at 1k or so when cold, once the bike is ridden for a bit it will be like 1,500...

My 78K does that too. I don' mind it though.

[cobra2411]

My buddies 81 does it too... Just wanted to know if it's sort of normal. He fiddles with his, raising it when it's cold and lowering it once the bike heats up. I've decided to try and find a happy medium and just live with it for now... I'll fix it if I can, if not I live with it.

[TwoTired]

Next question: Why does the idle rise as the bike warms up? If I set the idle at 1k or so when cold, once the bike is ridden for a bit it will be like 1,500...

There is no computer to adjust mixture during warm up.
It is the physics of fuel atomization, that it occurs more rapidly at warmer temperatures.  This makes the fuel burn more efficient as the engine warms.