rebuilt carbs running lean,carb sync is good, need advce?

[Todd Richards]

All

I just completed a full rebuild, clean and complete seal & air tee's replacement on a set of 4 VB44C CV carburetors. I did a bench sync to get them close, then set the pilot screws to the factory default of 2 1/4 turns out from lightly seated.

Upon assembly to bike, it fired right up, idled smooth and after a brief warm up, was off the choke & reved up quickly & decellerated smoothly-with no pop-pop-pop's.

I decided to go for a short test drive of about 30 miles to get an idea of how the plugs would look (perhaps indicate a lean or rich condition).

Upon return & cool down, the plugs were pulled, they all were very uniform in appearance, all had a lightly frosty white on the electrode... all the previous soot from when i was troubeshooting (prior to rebuild) is gone. I hope to get pictures of them tomorrow & will post for your review.

The plugs are new & are factory specified NGK DR8ES-L, gapped to 0.6mm

I went ahead and connected my synch gages (Carbtune Pro) to the carbs to dial them in. Suprisingly, they were within the Honda spec's, from the bench sync done at reassembly. They are now within 2cmHg.

I would like your thoughts regarding the pilot screw adjustment procedure (idle drop procedure) for the condition described? If the procedure is required, I will do a final sync afterwards.

A picture of the readings i obtained is attached. from this, i would assume there are no leaks in the intake system?

Given the bike is running lean... can you all please advise how i would go about troubleshooting (step by step, ignition timing perhaps?) to diagnose?

[klougnot]

Need a little more detail. How fast were you going for those 30 miles? What throttle position did you spend most of your time. Does your bike have a stock airbox and filter? You could still have leaks. I usually spray the intake rubbers with short burst of starting fluid to see if the idle picks up. You could also have bad exhaust gaskets too, but this is not as likely.

I would do one more quick ride at 65 MPH kill the engine and pull over and check your plugs. Do this after checking for leaks. If it's white and your have passed the spray test then you might want to thing about getting some needle shims to raise the needle a position or two.

[Todd Richards]

mostly around 55mph, i'd say at least 20 of the 30 miles were at 55mph. throttle steady.. Stock airbox, new filter.

I will try the leakcheck tomorrow, then the test drive @ 55mph as any faster & i may get a ticket . I would need to travel ~25 miles to get to highway where 65mph is ok. Would this be ok to drive the bike this far for 65mph test if there is a lean condition?

Also, as seen by the sychronization photo, if leaks were present on the intake, wouldn't it be nearly impossible to synchronize to this degree of accuracy?

Thank you for taking the time to help me out, greatly appreciated.

[klougnot]

55 is fine. Don't need to go that far either just a few miles. Check for leaks as there is a chance you have one. What kind of air filter are you using?

[Todd Richards]

new honda OEM air filter

[Volker_P]

A picture of the readings i obtained is attached. from this, i would assume there are no leaks in the intake system?

Sorry, wrong approach.
Vacuum synchronization needs to have everything else (valves, ignition timing, idle) set all right before.
Withan air leak, you may be able to get identical readings, however without having a good synchronization.
However as you usually get crazy doing vaccum syncronization with an air leak because readings will change arbitrarily, it seems that it is all right for you.
Nevertheless air leak verification is a "before" issue, not a result of synchronization.

A bit of white is all right for the plugs, but really snow white means too lean.
It's already good news that they all look equal.

[Todd Richards]

OK, the plan is to check for leaks.. is it possible that the vapors from starting fluid could make there way into the airbox via the normal inlet & provide false information?

If no leaks, then, in order:

Ignition Timing
Spark Advancer
Valve Clearance
Cam Chain Tension
Pilot Screw Adjustment
Set Engine Idle
Carburetor Synchronization
Compression Test

I have already done some of the above checks & services, but will recheck them when they come up, in above order

Regarding Spark Advancer Unit.. Assuming it operates correctly? How would one know when to service this component? is it an assembly that requires any type of cleaning/lubrication?

Regards

[Volker_P]

I would recommend some changes of the order:

- spark advancer: removal, cleaning and lubrication.
remove and disassemble for lubrication, especially if there is brown dust around. You'll see why as soon as you have it out. Tip has to point to rear/left/pulser with blue cables at F1.4 (180° is possible not on mounting the complete advancer but during reassemble of the advancer moving parts) If never lubricated, it may even squeek a bit when turned by hand.

-ignition timing: besides turning the complete advancer plate, the play in the holes of the pulser coils may be used to shift 1-4 vs. 2-3 for fine tuning. Pulser gap say 0.3-0.4mm

- cam chain tension. Just to be sure, set it before valve clearance. May be verified directly at the cam chain sprocket with a screwdriver. If all right, continue with ...

- valve clearance

and the rest of your list.

[Todd Richards]

All

Here is an update to what I believe was a lean condition with the engine.

Carburetor synchronization was done yesterday evening.

Today I rode the bike for ~20 miles at highway speed then went home to check the spark plug appearance. The attached pictures of the plugs reflect a somewhat uniform appearance.. I tried to get a different angle to show different shades. From my examination, it appears that plug #3 &4 have a little bit of red shade to the tip/bar? Otherwise, I can’t tell them apart. I’d like to know what youall think about the appearance of the plugs?

I checked the ignition timing and spark advancer, both was spot on! The plan for this weekend is to remove, & clean the spark advancer. Can someone recommend a grease/lubricant that would be best suited for this environment/task? It is worth mentioning that I couldn’t see any brown dust deposits inside the covered area. After wiping my finger on the engine casing the dust became visible….

I had previously checked the cam chain tension and valve adjustments, just a week or two ago, and really haven’t put considerable miles on since then….

Regarding the leak check: I would like to know if anyone has used a fine mist of water to check for intake leaks? (Hopefully, I am not showing my ignorance here?) I just cannot get myself to spray starter fluid anywhere near the engine, knowing how volatile it is.

Thanks again for your time & assistance

This weekend, time permitting I plan to go down the maintenance list in the order set by Volker.

[Todd Richards]

here are the other two plugs...

[Volker_P]

Red color is interesting. But nothing wrong with these plugs or the mixture.

[Todd Richards]

Volker

Thanks for your continued support. What are your thoughts regarding checking for air leaks around intake boots using water as a fine spray mist, & a suitable lubricant for spark advancer mechanism?

Given what you see with the plugs, would it be of any advantage to do the pilot screw adjustment, or are the carburetors tuned good enough as is?

Thanks Again, Have a Great Day!!!

[Volker_P]

For the air leak check, one may use aerosol start aid or something like that and listens for rpm changes.

For the advancer I would first use grease and then add a few drops of engine oil.

Pilot screws are just fine tunig for idle. Nothing to decide from plugs after a ride but just to get a smooth and stable idle.
Especially the pilot screws do have no impact on mixture at load! Eexcept maybe they have fallen out completely.

[MiGhost]

For doing the air leak testing you can use an unlit propane torch. Not as volitile as starting fluid.

[Todd Richards]

i like the propane idea better! thanks