Deceleration Issue

[kelharmassi]

Hi gentlemen

I took my 1992 XII B for a long ride and went a little too fast here and there. The next morning, it started to take a second or 2 for the decelerator to close completely. I then have to decelerate, wait a little while before shifting.
Not sure if the throttle cables need lubing, adjustment or if it is another issue. Just to make sure it is not a cable routing issue, I already took the air intake box and tested but the throttle still takes a little while before completely closing.

Your help is much appreciated as usual.

Many thanks.

Khalid

[triton28]

It is difficult to reveal that "smoking gun", which is causing the problem, by digital conversation alone but here goes.
That spring on the carburetor operating mechanism is normally more than enough to snap the cables to an at rest position and I want to say if you do not see that almost instant operation when you remove the upper air box and observe the cable function then likely it is a cable problem, either routing but more often than not it is a lack of lubricant between the outer and inner cable.
However, that having been said several things come to mind:
1) after your long ride and before the startup the next morning when the problem appeared, had you moved or jostled the cables or any other procedure which may have affected the cable operation? If yes then review what you did;
2) if no and this situation appeared then possibly it may be a fuel ratio issue. How clean is the system, hoses filters etc? A lean condition, caused by a partial blockage of any part of the system, can sometimes cause rpm hang. Perhaps your long ride stirred up some grit/debris and the filter may be getting clogged.
3) you may have developed a vacuum leak possibly at one of the 4 rubber holders located between the carbs and the head; check the clamp screws for being snug.
4) since I suspect your bike is a USA model and has all the plumbing for the clean air system check along the length of the hoses at the rear of #s 1 and 4 carburetors. Those are the carburetors which provide the vacuum for the clean air system. #2 and 3 should have a short rubber plug on the brass nipples unless it is a California model which uses these 2 nipples for the emission control system hoses on the California models.
Other than that I am out of suggestions, with the exception of the most obvious item; that being check your hand position on the throttle when this occurs, sometimes we don't fully close the twist grip, no disrespect intended but I have done this from time to time myself.
Dave

[GrandpaDenny]

Is it the throttle closing slowly, or is it snapping closed and the engine is slow to respond? If the throttle is closing slowly, that's an easy fix - lube the cables with WD-40 Silicone or something similar; pull the throttle grip off and apply a THIN layer of waterproof grease to the handlebar. Then when you have everything back together, check the adjustment of the throttle cables. The deceleration cable should be just taut, and the acceleration cable should be adjusted to give 2-3mm of play in the throttle grip.

[kelharmassi]

Thank you Dave and Denny,

It looks more and more like a cable issue to me, as when I took the air box of and checked, here what I saw:
1-The carburators' operating mechanism works fine. I pushed it with a screw driver, and it snapped back normally.
2-When I use the throttle with the bike turned off, it will close normally but slow down at the end before going all the way back.
3- I put the air box back and unsure there was no air leak at that level but I still experienced the throttle slowing down toward the end of its closing.
4-If I close the throttle all the way and wait a second or 2 before pulling the clutch then it works fine and I don't experience high RPM.

I will check the air filter and lube the cables and let you know how it went.

Thank you very much for all the clarifications.

Khalid

[Nails]

The manual has detailed instructions about adjusting the cable tensions; and stuffing everything back together might change some tensions. In particular, you should have some play in the throttle between accelerate and decelerate -- about 1/8" IIRC. If there's any question, you might try backing off the tensioner near the throttle grip to see if that helps.

[kelharmassi]

Hi

I wanted to lube the cables and found the deceleration cable broken. I replaced it, adjusted the cables and I'm back on the road again, running like a charm!

Thank you for your help. Much appreciated

Khalid