Funkmethod
CB750 Member
1980 Cb750C
Coming on here because I'm just about out of options on what else to try.
My bike runs totally fine once its up to operating temp. The thing screams. No backfiring it's perfect really. Just can't seem to get it to start without full throttle and holding it there for a few minutes before she gets to temp. I have to crank up the fast idle to max. And as the bike warms up the idle rises as the temp goes up as well. So i need to turn it down while I'm riding. It does not like the choke what so ever! Cold starts, while its warming up nothing, it's just wants to shut it down. Which i think may is a solid clue to why it's problematic.
Here's what ive done...
Rebuilt entire top end:
1.Like new cylinder jugs, came off a running 750 because my were scored to badly from seized pistons in cyl 1 and 2.
New rings, pistons etc... that all went well.
2. Have rebuilt the carbs completely.
New o rings throughout synchronized all the carbs perfectly.
Tried bypassing the air cuts because i thought it was possibly those running to rich but that made things worse so i went back to the original o rings.
That's really it i havnt messed with the ignition system because like i said the bike runs mint once up to op temp so i feel like messing with the points wouldnt do anything but i know those are fragile so i leave them alone but idk maybe that could effect idle.
Kinda at a loss here because ive definetely improved the bikes performance by quite a bit but i just keep having this same problem of having to start with the throttle full and fast idle max then slowly adjusting my fast idle as it warms up. Not sure if it's my carburetors or what else cause everything seems okay except these dang cold starts.
Anyone have any thoughts on this? Or ideas of what the hell is going on with this? I feel like im so close .
Coming on here because I'm just about out of options on what else to try.
My bike runs totally fine once its up to operating temp. The thing screams. No backfiring it's perfect really. Just can't seem to get it to start without full throttle and holding it there for a few minutes before she gets to temp. I have to crank up the fast idle to max. And as the bike warms up the idle rises as the temp goes up as well. So i need to turn it down while I'm riding. It does not like the choke what so ever! Cold starts, while its warming up nothing, it's just wants to shut it down. Which i think may is a solid clue to why it's problematic.
Here's what ive done...
Rebuilt entire top end:
1.Like new cylinder jugs, came off a running 750 because my were scored to badly from seized pistons in cyl 1 and 2.
New rings, pistons etc... that all went well.
2. Have rebuilt the carbs completely.
New o rings throughout synchronized all the carbs perfectly.
Tried bypassing the air cuts because i thought it was possibly those running to rich but that made things worse so i went back to the original o rings.
That's really it i havnt messed with the ignition system because like i said the bike runs mint once up to op temp so i feel like messing with the points wouldnt do anything but i know those are fragile so i leave them alone but idk maybe that could effect idle.
Kinda at a loss here because ive definetely improved the bikes performance by quite a bit but i just keep having this same problem of having to start with the throttle full and fast idle max then slowly adjusting my fast idle as it warms up. Not sure if it's my carburetors or what else cause everything seems okay except these dang cold starts.
Anyone have any thoughts on this? Or ideas of what the hell is going on with this? I feel like im so close .
