Hey y'all,

I have been having a real hard time adjusting idle on my CT3. I have been trying to tune it for about a month now on and off, but have not gotten to a place that feels good yet - actually haven't gotten any idle at all. No matter how many times I clean the carb (using the methods found here) adjust the needle height, carb screws, check float height, replace and adjust throttle cable, etc. nothing seems to work. There are no real issues aside from the idle. Everything seems to run well throughout the rest of the power band, but when I let go of the throttle completely it stalls out almost immediately.

I bought my carburetor from ebay because of a stripped jet in the carb body that bricked the old one. The new carb was claimed to be the same part number (316-14101-01-00). When I got the new one, I realized the stamped numbers on the mounting flange were different than the stock one I had. Stock was 316 E3 and new one was 316 E2. Could this be affecting things?

Some notes that I'm not sure could affect things but want to mention:
- All intake gaskets are new
- Added an in-line fuel filter
- Spark plug seems to show I'm running rich (see picture here ), but none of my adjustments have seemed to make this any better
- Have not adjusted oil injection, but did verify that it works. Can this have an affect?
- I have not changed out the original reed valves. I can see light shining in from one side of them when holding it up to light though, which I know is not ideal. If anyone can point me to the part number for just the reeds that would help, but I can only find the whole assembly in parts diagrams.
- Bike starts on first or second kick almost every time when cold without choke on, but I have to give it on the throttle.

The throttle response seems decent to me, but I don't really know what to look for. Here is a video showing neutral rev response and letting go of the throttle stalling out. This was done while the bike was warm:  youtube.com/shorts/iAb1NnZ-554?feature=share

If anyone has any ideas on troubleshooting that I missed I appreciate the help. Not really sure where to go from here so I was hoping someone who has probably forgotten more info about these bikes than I can ever hope to know might have some answers.


 

Did you super clean your pilot jet I would turn the idle screw in some maybe 2 turns start it and then back the idle screw down and see what Rpm it will stay idling at. These 50 yr old tach are not always accurate 

Pilot jet was super cleaned 3 times, once ultrasonically and twice by hand. The idle screw has little effect on anything, I've tried almost every combination of positions at this point and have not even had an idle that dies slowly yet. It immediately stalls out if I let go of the throttle.

Is it possible your idle stop screw is the wrong one and/or not lifting the slide? 

(E2 vs E3 is the jetting spec, E3 should have had different "latest revision" jets.  Someplace I have the chart.)

Also it sounds a bit on the "lean" ringy-dingy side...  not rich.  You can't use a plug reading to check jetting at idle or no load. 

Here's the chart

I just noticed you said 316 carbs? Those are 125 AT1numbers. There was no CT3 E3 revision in my book.

Anyway, those are the stock CT3 jet specs... I doubt that's your problem though.

125 and 175 carbs in those years are identical except for jetting.

If you have a 4L6 slide needle, that's what I'd use.

Thanks Mark.
I've got the 4J13 in there right now set to the leanest level to try to get a start out of her. Maybe I will try swapping the idle screw over to the one that came with the bike and see if that changes anything. I can see wear indicators on the slide where the idle speed screw contacts it, so I know it is at least touching it.

4J13 needle clip should be set with clip second groove from the top.

Slight gap under original reeds isn't unusual & are blown shut on the down stroke to send fuel up the transfers, sort of.
Wouldn't be starting as easily as it does if reeds were bent 'way' up, which i've had with old style fiber reeds.
First thought is the left side crank seal behind the mag, blown partly out rather than just worn.
Not sure if the stator plate stops it getting out but thinking partly out at an angle & letting 'some' air in.
That's providing all carb airways & jets are clean.
Just unusual the way it cuts off & drops down then catches again, if that's what i heard.
Does sound 'lean' when you bring the revs up.
Has it sucked in a base gasket?.
Piston in the right way around.