Topic: cold idle issue

[Scrubs]

Got a 1974 750.

that runs great when warm but when I try to start her in the morning - I  have to put the choke fully open
and give her a little gas until she fires then close the choke half way straight away while blipping the throttle
if I leave the throttle alone for a moment - to put on my gloves -fasten helmet etc - it will stall, no matter the choke posistion - until she warms up a bit (about 4 mins) it's almost like the idle needs increasing a bit, but the trouble
is if I do that, It's gonna idle too fast when warmed up? any suggestions.

I should mention I only bought this bike a couple of weeks ago and standard jetting was increased (main and pilot)to accomodate an after market muffler - not sure what sizes but has apparently been jetted by a "pro" so I think it's right - in that it feels OK when riding, maybe a little rich if anything.

I'm hoping I can make some carb adjustments to sort out the problem?

[Scrubs]

sorry just did siome searching - probably should have done that first - and it seems it's just one of those 'live with it' issues

[hapsh]

This is really a non-issue.  On the 74 550's there is no fast idle adjust, I am pretty sure there isn't on the 750 either.  That means that when you choke the engine you have to manually hold the throttle a bit to keep the idle up until warm.  All modern bikes have a fast idle cam that increases throttle when choked so it is much easier to let idle when cold.  I used to give my idle speed screw a quarter turn on cold starts so it would idle while I put on my gear, but then I would have to constantly tweak the idle speed to bring it back down when it was fully warm.  From some tips on this forum I stopped doing this and opted to get all my gear on first, start the bike and ride away.  Under load the engine warms up considerably faster and saves on gas.  I usually Choke the engine, start her up, back the choke off 1/8 while holding the throttle so I keep the engine about 1500 rpm.  After a short time the engine speed will pick up to about 2500 and then I back the choke off to half and drive off.  About 3 blocks later I shut the choke off.  Depending on how cold it is outside I may still have to hold a bit of throttle on at stop lights until it idles normally.  I set my idle at 1000 rpm when hot, so when cold it tends to idle down towards 700-800 or dies without some manual throttle.  In the winter when it was 15F outside I had to leave the choke on 1/2 for a bit longer, then down to 1/4 choke for another 5 mins.  The more you do it the better feel you will get for your particular bike.

[TwoTired]

that runs great when warm but when I try to start her in the morning - I  have to put the choke fully open

Terminology:  Applying choke for start is closing the ckoke as it operates butterflies in the carb throat to block the air inlet.

and give her a little gas until she fires then close the choke half way straight away while blipping the throttle
if I leave the throttle alone for a moment - to put on my gloves -fasten helmet etc - it will stall, no matter the choke posistion - until she warms up a bit (about 4 mins) it's almost like the idle needs increasing a bit, but the trouble
is if I do that, It's gonna idle too fast when warmed up? any suggestions.

If you feel you can't drive until the bike is fully warmed up, the early SOHC4s had a friction adjust on the throttle under the bars.  Crank the knob until the throttle stays where you put it.  Honda discontinued this feature, but I don't know what year.  My 74 CB550 has this feature.  But, I rarely use it.  Gear up, get on, and go, with the choke on, and my hand on the throttle.  Take choke off while driving the first few blocks.
There are throttle lock devices you can add to a bike not factory equipped with one.

The 750 uses colder plugs (D8 rather than the 550s hotter D7).  This extends the warm up period as well as the increased metal mass of the 750 being slow to attain operating temp.  In cooler weather you could use D7, too.  But, I'd use the hotter plug for summer months for certain.

Even "pro" engine tuners give a rats butt about cold engine run finesse, partially because the time window to tune for that operating mode is so short.  And, I don't know of ANY tuners that have an environmental chamber (excluding factory engineers).  Mods are made to be acceptable to owners during street runs.  Further, the stock exhaust is generally more restrictive than an after-market offering.  The stock restriction retains heat for faster warm up, and it tends to diminish oxygen replacement in the cylinder, which in turn, requires less fuel in the mixture delivery.

Cheers,