Topic: installing new motor update

[carl550k]

well, this past weekend i put my new/used motor in my 550k. son number one helped and we had it up and running in about 5  hours.the new engine sounds 100 times better than the old one.it had "runs like new" written on it.there is almost no cam chain or valvetrain noise at all. also very smooth.the new motor also came with the intake manifolds on, left them alone,used my rubbers from old motor,used rubber bands under the clamps to make a tighter seal to the carbs and manifold, there should be no leaks.the idle still wonders around 3 grand before idleing down, should be an air leak, but from where? could it be the caps on the top of the carbs?i have had them off before. the timing is right on and the advance is fine. this problem was worse with the old motor but is still there with new motor.any ideas

[TwoTired]

I don't remember what year model carbs and motor you have.

Rubber bands deteriorate pretty rapidly.

Check for air leaks by spraying wd40 at the boot interfaces.  The temporarily plugged leaks will change the idle speed for a short time.

Carb sync?  Pilot screw settings?  Timing advance?   Idle speed knob?

[carl550k]

carbs are bench synced, not too bad, pilot screws are 1/4 turn out, plugs look great,idles at 1200 all day, advance free and works as checked with a strobe timing light.

[DammitDan]

A bench sync and a live sync may provide different results... I'd invest in mercury stix or a morgan carbtune (if you can afford it).

[TwoTired]

Since I "STILL" don't know which model carbs you have.  I'll take a wild guess that your pilot screws are too far in.

But, I won't be making any more wild guesses until I know what to guess about.

Good Luck!

[eldar]

There is another thing to check. I dont know if the 500/550s had this but the later 750s had a high idle adjustment for use with choke. If this is adjusted too high, you can get the high rpm for a while before it comes down. The high idle is generally set at 2500 rpm on the 750.

[carl550k]

twotired, the carbs are factory keihin with the pilot screw on the airbox side, factory airbox with a uni filter, mac 4/1 exhaust.

[eldar]

Unis flow better than stock filters and 4-1 usually require rejetting UNLESS it was factory. You have macs and likely need to rejet for more fuel hard to say for sure though and jets can be expensive.

[TwoTired]

The 77-78 carbs (also Keihin) are quite different than the earlier models.  And, the pilot screws work opposite the earlier models.
If you have the earlier carbs, start the pilot screws at 1 1/2 turns plus or minus 2/3 turn.  That's the setting for the stock pipes and filter.
Your 4 into 1 may need other tuning/ jetting for the carbs including a different pilot screw setting.

There is also a separate choke setup for 77-78 carbs.

Set up data for all the Cb500/550 carbs are in the FAQ and the shop manual.

Good luck!

[carl550k]

 twotired, the bike is a 1976. from what i have read on many of these threads, the pilot screw on the airbox side controls the amount of air to the carbs.have tried many different settings from the stock 1 1/2 out from fully seated to where they are now at just 1/4 turn out from fully seated. this setup makes the plugs grayish to a light brown.the main jets are stock 100's. the local honda dealer can get me 105's for less than 15 bucks.the only reason i didn't rejet is because of the motor swap. was hoping the new motor may eliminate the idle problem, guess not.still there but not nearly as bad.