HELP !!! Tachometer trouble... By dimplepwr (Read 9,953 times)

[dimplepwr]

So, I purchase a new 150cc GY6 (SSR Rowdy) as a project bike and I everything has been good up till I changed out my coil. I upgraded to a "performance" coil from the stock one and since then my tachometer has been going crazy when the bike is running. To put it simply, it dances all the way from 1,000rpm to 12,000rpm at random no matter how much gas I give it.

My stock coil was had only one prong to at the top. There is also a ground wire but that was attached to the frame. The new performance coil has two prongs, one of black connection and another green ground connection.

I tried two different things:
1) I left the original ground connection from my old coil on the frame and connected a second grounded wire from the green prong on the new coil to frame. My thinking was the original ground wire was for the tachometer... but that didn’t work...

2) I also tried plugging the original ground wire that was attached to the frame into the ground connection on the new coil thinking it needed the reading from the coil, that did not work as well.

I am at a loss The bike runs great with the new coil I just want the tach working. Any suggestions other than going with a new tachometer?

[Bashan]

I don't think your tach is reading off of the coil, that's a lot of juice for an instrument. It is probably reading off of the CDI or by induction off of the plug wire. Can you get a pic or accurately describe the appearance of your CDI and plug wire. Tachs are a newish addition to the murky land of Sino-scooters so this is a bit of undiscovered territory. Rich

[bcgreatness]

you can move your tach wire to run from your cdi, just follow the wire that goes from the cdi harness that runs to the positive on the coil, ive done so already and its pretty spot on.

[Bashan]

I was just doing some work on my wife's Puma. It has a tachometer and I noticed a couple odd things. The CDI is DC powered with only a black wire into the two prong. There's a black/white wire in the pulse coil slot so I doubt it's the kill. It doesn't split off from the CDI but I can't see what it does deep in the harness. I bet the pulse wire triggers the tach on this thing. I can't see anything on the CDI or coil that would handle it. Rich

[sprocket]

Weird and wonderful world of Chinese scooters...

[dimplepwr]

Apr 7, 2012 3:13:57 GMT -6 bcgreatness said:

you can move your tach wire to run from your cdi, just follow the wire that goes from the cdi harness that runs to the positive on the coil, ive done so already and its pretty spot on.

I have seen from other tachometers a black wire that comes off the tach, wraps around the coil wire and senses the pulses from the coil but I can't see an additional wire. Like this. I agree with the scooter doc, I think the tach might be getting its pulse readings from the CDI. I was going to upgrade it the CDI to a performance one, I wonder if that would help or if its just the way the Chinese wired it.

I'll try and take a picture of my coil and CDI for everyone.

[sprocket]

If you have a wire wrap on the high tension lead to the plug.. that is the tach pick-up...there is no other...very common on inexpensive tachs...

[dimplepwr]

Apr 7, 2012 15:55:37 GMT -6 Bashan said:

I was just doing some work on my wife's Puma. It has a tachometer and I noticed a couple odd things. The CDI is DC powered with only a black wire into the two prong. There's a black/white wire in the pulse coil slot so I doubt it's the kill. It doesn't split off from the CDI but I can't see what it does deep in the harness. I bet the pulse wire triggers the tach on this thing. I can't see anything on the CDI or coil that would handle it. Rich

So here are some pictures of the set up... Right now I have it set so both the new coil and the CDI are grounded separately with green wire as you can see on the frame.

Through research I have found that only some tach’s have a sensor wire the warps around the base of the coil wire but mine does not have one of those wires. I think it getting its reading from the coil through the CDI. I have found through the manufacture that my system is DC. I was also thinking of just replacing the stock CDI with a 9000RPM performance CDI to see if the stock one is not capable of understanding the coil. Remember that my stock coil only have one connection on top of it and this new performance coil has two connections.

[dimplepwr]

my stock CDI

Attachments:

[dimplepwr]

New performance coil. Stock coil only had one connection on the top where this one has two.

[dimplepwr]

Whole set up with grounds.

[sprocket]

You want to get some clear silicone on those coil connections ... moisture can get in there and cause a short.. the stock coils have a rubber boot over them for this reason...

[Bashan]

Apr 9, 2012 12:11:36 GMT -6 dimplepwr said:

I think (the tach) is getting its reading from the coil through the CDI.

I have a question on that, how is the signal getting from the CDI to the tach? Rich

[dimplepwr]

Apr 10, 2012 14:43:38 GMT -6 Bashan said:

Apr 9, 2012 12:11:36 GMT -6 dimplepwr said:

I think (the tach) is getting its reading from the coil through the CDI.

I have a question on that, how is the signal getting from the CDI to the tach? Rich

I called the company that distributes this scooter to see if they have a wiring diagram and they don’t. The on site mechanic was nice enough to invite me down so he can take a look at it next week. Ill keep you guys posted. There was a little bit of an English barrier but he said the black wire on the CDI goes to the tack. He kept saying connect the black wire with the black and yellow wire and see what happens. That is all I could understand. Got any ideas on what he was talking about prior to making the long trek to the distributor? Do you think he means disconnect the black wire them from the CDI and wrap it around the yellow wire going to the coil? I have seen that with in other tachometers.

[dimplepwr]

Hey Bashan, I saw the generic 150cc DC CDI wiring diagrams you posted, thanks for that. Its sad that the distributor of my scooter doesnt even have them...

scooterdoc.proboards.com/index.cgi?action=display&board=wiringdiagrams&thread=6179&page=1