1966 Atlas Idle Problem

Rohan said:

Should be able to adjust the slide and mixture screws right down until it will no longer even idle.
.

Click to expand...

Yes, even when the timing is fixed at full advance.

If that is the case why won't mine idle down? Worn slides????
I can adjust mixture screws until it will barely idle, but that wouldn't be set right, would it?

Beach said:

If that is the case why won't mine idle down? Worn slides????

Click to expand...

I have used a product called "Lock Ease", available from NAPA. It is a silicon - graphite spray. I coated the slides with it. At the very least, it makes them slip up and down easily, and may mitigate further wear on the slides. In your case, it may fill in gaps and stop or reduce air leakage, for awhile anyway, just long enough to get a handle on whether such leakage is the cause of your problem. In lieu of this product, you might try (do not attempt to ride with this suggestion) a very light film of grease such as white lithium on the slides to fill gaps and choke off any air leakage.

Usually, worn slides cause an erratic idle ... sometimes fast, then slow, never consistent .... at least that is what I have been told .... I have not experienced it.

Are you sure your slides are bottoming on the throttle stop screws? A very small CW adjustment should result in an immediate increase in RPM. If not an increase, the engine is either not running on that carb, or the slide is not sitting on the stop screw. Repeat on other carb.

Also, try removing one high tension spark plug wire at a time, to see if you can determine which cylinder (if either) is doing more work.

Slick

Right now is idling at about 1300 rpm, which is with the throttle stop screws both not touching the slide...each cylinder is running evenly and as I adjust the stop screws in the idle increases....Just can't adjust any lower than 1300...that shouldn't be right

Beach said:

Right now is idling at about 1300 rpm, which is with the throttle stop screws both not touching the slide...each cylinder is running evenly and as I adjust the stop screws in the idle increases....Just can't adjust any lower than 1300...that shouldn't be right

Click to expand...

Do you have a set of drill bits? If so, use the bits as a gauge to determine gap under the slide (where the maximum cut-away) occurs. I will do the same, then we will compare.

Slick

Will try

Beach said:

Will try

Click to expand...

Bill:

I can get a 13/64" bit under the slides without raising them off the stops, but not a 7/32". My Atlas has not run in over 2 years, but last time it did, the idle was normal, and I have not diddled with the carbs during the time the bike has been undergoing "refreshment".

If your slides are more than the amount given above ( 1/32" more would not seem excessive, but anymore is suspect), then I would investigate whether some factor is holding your slides open too much.

Slick

The 5/32 fits tight.....Do you think weak advance springs would cause this?

You should be able to drop the slides down so far that daylight won't even go through the gap.
Work on it, something must be holding them up.

Beach said:

The 5/32 fits tight.....Do you think weak advance springs would cause this?

Click to expand...

5/32 is less than mine! That would seem OK. Are you sure it is not 5/16 which is definitely too much.

Weak advance springs might be a factor. A timing light is the only way to know, and you will have to cobble up a pointer. Perhaps it is easier to simply install a new pair of springs and see what happens. Steadfast Cycles has them ... less than $10 as I remember.

Rohan said:

You should be able to drop the slides down so far that daylight won't even go through the gap.
Work on it, something must be holding them up.

Click to expand...

I think Rohan exaggerates a bit here, but dropping the slides down to about 1/8 inch should be do-able. +1 on his last sentence.

Slick

It is 5/32...took apart timing side and put another advance in..timing was staying advanced most time..

No exaggeration, but the carb I'm working on is a pre monobloc (sidefloat) type.
The slide genuinely drops down so far, if the throttle stop is wound back, that daylight can't get through.

Can't quite recall if a monobloc is the same, but I don't remember them being any different.
They can be shut right down, if needs be.
Its only (?) the throttle stop thats stopping them.

texasSlick said:

I think Rohan exaggerates a bit here, but dropping the slides down to about 1/8 inch should be do-able. +1 on his last sentence.
Slick

Click to expand...

Rohan said:

You should be able to drop the slides down so far that daylight won't even go through the gap.
Work on it, something must be holding them up.

Click to expand...

My carbs allow the slide to seat clear against the main jet holder and there can be no space seen under front of the slide .....The slide is bottomed as far as it will go without the throtle stop screw in the carb...

texasSlick said:

Beach said:

Weak advance springs might be a factor. A timing

Rohan said:

You should be able to drop the slides down so far that daylight won't even go through the gap.
Work on it, something must be holding them up.

Click to expand...

I think Rohan exaggerates a bit here, but dropping the slides down to about 1/8 inch should be do-able. +1 on his last sentence.

Slick

Click to expand...

Click to expand...

Rohan, sensibly, is talking about the gap at the back of the slide. That's the throttle opening. Measuring at the cutaway won't tell you much.

Aha, the penny drops. That explains a lot. (Thanks !).

Yes, the cutaway will alter the gap (depending on the size of the cutaway) if only looking at the atmosphere side.

After eliminating all other things I have traced the problem to worn slides in my carbs...When the bike is idling I can push on either slide and the idle drops quite a bit...I am looking for someone to resleeve these carbs now and will know for sure when this is done...