Tach and Carbs

NerdyNerd

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Two questions!
First off what does it mean if when I give the bike gas it revs but takes a while to rev down. I heard that it could be a lean mixture
Second, I'm working on installing a digital speedometer/tachometer. I have most of it working at this point but it states that you need to connect yellow black to the positive of the ignition to trigger the signal. Does this mean you wrap it around the spark plug wire or something else?
Here's the link to the gauge.
https://www.amazon.com/DKMOTORK-Mot...3e-92a8-c11e5d52aa41&pd_rd_i=B07WW3L3Y8&psc=1
 

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what does it mean if when I give the bike gas it revs but takes a while to rev down.

Check carb synch and ignition advance.
connect yellow black to the positive of the ignition to trigger the signal.
My chinglish thinks that may be PULSING position
1676581834066.png

ie the coil terminal that's not the +12 side, the wire from the points, pamco, TCI ignition module.
 
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I would try wrapping the wire around the plug lead, if it works great if it doesn't it wont hurt anything.
With regard to the hanging idle first does the throttle snap back when released.
I will shoot that a try and yes it does. I even tried throttling it by hand with no cable attached. It idles well but just takes for ever to rev down.
 
Two questions!
First off what does it mean if when I give the bike gas it revs but takes a while to rev down. I heard that it could be a lean mixture
Second, I'm working on installing a digital speedometer/tachometer. I have most of it working at this point but it states that you need to connect yellow black to the positive of the ignition to trigger the signal. Does this mean you wrap it around the spark plug wire or something else?
Here's the link to the gauge.
https://www.amazon.com/DKMOTORK-Mot...3e-92a8-c11e5d52aa41&pd_rd_i=B07WW3L3Y8&psc=1
This is a freshly rebuilt engine with new valves and valve seats, it also doesn't have points under the covers so it's weird.
 
To check for an air leak with the engine idling spray some engine start or similar around the carb couplings to the head and filter. if the engine speed alters you have a leak.
 
To check for an air leak with the engine idling spray some engine start or similar around the carb couplings to the head and filter. if the engine speed alters you have a leak.
That is a fantastic idea. I will give that a try this evening. Thank you!
 
when I give the bike gas it revs but takes a while to rev down.
and......if an air leak @ intake isn't the issue, the carbs not being in "synch" will also cause hanging rpms that are slow to return to idle. There's an adjustment screw for that in between the carbs.
 
and......if an air leak @ intake isn't the issue, the carbs not being in "synch" will also cause hanging rpms that are slow to return to idle. There's an adjustment screw for that in between the carbs.
I'm going to build a carb sync bench with a couple vac gauges this evening and get these synced up and see if that does the trick. I'm in high altitude so I ordered a jet kit since the main jet needs to be dropped down
 
Are you sure about that? Since you have the TCI ignition, I'm going to assume you also have the BS34 carbs that came on the later TCI bikes. They were set up pretty lean from the factory and many of us jet them up a bit even on a totally stock bike. Your carbs running richer because of your altitude may be just what they need. You also haven't mentioned whether or not you've done any modding, like changing the exhaust and/or air filters. Those changes usually require richer jetting as well. But there's more to jetting these carbs than just changing the mains. You usually need to "adjust" the pilot (low speed) circuit as well by changing the pilot jet and/or the air jet. Your hanging idle speeds can be a sign of leaness in that circuit.
 
Are you sure about that? Since you have the TCI ignition, I'm going to assume you also have the BS34 carbs that came on the later TCI bikes. They were set up pretty lean from the factory and many of us jet them up a bit even on a totally stock bike. Your carbs running richer because of your altitude may be just what they need. You also haven't mentioned whether or not you've done any modding, like changing the exhaust and/or air filters. Those changes usually require richer jetting as well. But there's more to jetting these carbs than just changing the mains. You usually need to "adjust" the pilot (low speed) circuit as well by changing the pilot jet and/or the air jet. Your hanging idle speeds can be a sign of leaness in that circuit.
All fair points. I swapped to pod filters from the previous airbox. Same exhaust for now. I will do some tinkering to try and figure the best ratio. I'm still learning the fine details of carburetors so thank you!
 
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