Low performance and weird noise after new CDI installation? By worzx (Read 488 times)

[worzx]

Hello everyone!

I would like to get some help with my 50cc 139qmb engine powered scooter. Today, bought a new CDI, the common blue racing one for the scooter. That was the only one the store had available which known it has no rev limiting. So I installed it, started up the engine, everything went fine, actually the engine started easier than with the stock one.

I took the scooter on a drive, it had better acceleration, top speed, so overally better performance. However after about 2-3 kilometers when I accelerated from a stop, a strange sound appeared. It appears when the engine is revving higher than with the stock CDI, this is about 50-55 km/h. The performance also got overally bad after this, basically about the one I get with the stock CDI.

I let the engine cool for 10-15 minutes, gave it another go, but the sound appeared at the same speed and it actually gets weirder in higher RPMs. When I got back, I installed the stock CDI and gave it a try. The scooter goes well with it, I mean it has about the same performance as it was before the new CDI, however the noise also appears here at high RPMs, when the CDI is limiting, but it is not that loud. Also it can be heard when the scooter is on the stander with both the old and the new CDI.

Description of noise: It is some kind of a high, sharpy sound, getting louder as the RPM goes up. It also kind of "vibrates", so it is not continous, it starts, gets loud in about 1-1.5 seconds then it disappears slowly, and it starts again. When I ride the scooter It is more louder and looks comes from the left-side, but if the scooter is on the stander it's hard to find it's source.

The scooter ran about 1000 km, bought it newly from a dealership.

Anyone can help me find the source of this sound and bottleneck?

[Alleyoop]

Running at high rpms it could be a fuel delivery problem or a CVT problem or bad bearing somewhere.
Get a Video of the sound it is making on the center stand that may help in pinpointing what is making the sound.
Alleyoop

[worzx]

Thanks for the reply. I'll make a video if I can, until then, I'll try to get some more informations on it. Remembering back at first I thought something stuck in somewhere, I mean it felt like I'm braking the rear wheel (where a drum break is applied). However since the performance bottleneck applies at every rev, the sound is only at high rpms.

Since I was hearing on the left side when driving, I assumed something is wrong in the variator. Can something cause this in the variator? A washer maybe?

[Alleyoop]

If on the left side I would suspect the Weights they are probably worn down and rattling or the plastic guides are chewed up and effecting the variator how it moves in and out and would make some metalic sounds. So first check your CVT take the cover off and start it up and rev it and see how the belt and variator are working as well as the clutch pulley . Something worn in the Variator will cause some lost performance also a worn belt will cause high rpms and lost of top end so the CVT is something to suspect.
Alleyoop
Here is how it should work:

[worzx]

Thank's for the reply, I'll check the CVT. However, I would like to ask if something like that is caused by the CDI, so because of the higher rpm, and if so, what should I do to prevent it?

[worzx]

So I made a video about the noise, here it is: 1drv.ms/1Ji5wl2

[Alleyoop]

Sounds like the tranny gears. Get a Funnel or make one up or just a Screwdriver and hold the end of it on the tranny case and see if the noise is coming from there. Try and pinpoint using a funnel or a screwdriver exactly the are the noise is coming from. But to me sounds like the rear by the Tranny.

If it is by the tranny check the oil and or change the oil and fill it up again. It may be on gear oil.

Now the CDI may cause Higher or lower rpms but not that sound.
Alleyoop

[worzx]

Okay, thanks, I'll check it out probably during the weekend. Also, I did not really found the source of the sound, I can only predict that it's more likely coming from the back end, somewhere near the wheel, or the back of the CVT. However, I'll check it out as I said.

Some more information about the noise, maybe it would help to determine the source: The whole chassy is vibrating as the sound "pulses". I can feel it on every part of it, including on the throttle lever.

About the CDI, I was asking if the high rpm can cause malfunctions like this. I mean, if I find the problem, fix it and replace something if I need to, is it possible that the high rpm will kill it again in that short time?

[Alleyoop]

I do not understand why you think its the CDI? Let me ask this the CDI that you put in is it REVVING HIGH all by itself? Or is the motor making more RPMS at WIDE OPEN THROTTLE? High RPMS can be caused by the Variator weights being to light and or hanging up and not allowing the Variator to Close and push the belt up which in turn would cause lower mph to end speeds.
A Performance CDI what they do is ADVANCE the timing for a little more power. But TO advanced or to retarded you would have problems starting the motor.
Alleyoop

[Alleyoop]

Jul 15, 2015 12:06:18 GMT -6 worzx said:

Okay, thanks, I'll check it out probably during the weekend. Also, I did not really found the source of the sound, I can only predict that it's more likely coming from the back end, somewhere near the wheel, or the back of the CVT. However, I'll check it out as I said.

Some more information about the noise, maybe it would help to determine the source: The whole chassy is vibrating as the sound "pulses". I can feel it on every part of it, including on the throttle lever.

About the CDI, I was asking if the high rpm can cause malfunctions like this. I mean, if I find the problem, fix it and replace something if I need to, is it possible that the high rpm will kill it again in that short time?

Yea that sure sounds like something in the rear is the problem and it could be the Clutch, Bearings, the Gears low on oil but THAT IS EASY to pinpoint. Like I mentioned just get a screw driver and touch and around the back tranny case and you will feel the noise as they say. Or just make a FUNNEL out of a newspaper and go around the case and by the clutch area and put your ear to the wide part of the newspaper funnel you will know where the noise is coming from. It may be a broken spring or clutch pad if your lucky and not in the tranny and or bearings. So check the CLUTCH with the funnel and or screwdriver.
Alleyoop

[worzx]

Looks like you did not get my point, sorry, I'll try to explain it better. I don't blame the CDI because of the sound. I just want to know if higher rpms (which the new CDI allows) can cause problems like this in the future, because it revs more, and I assume the engine gets warmer and the materials are affected better. So basicly my point is that this problem is caused by the higher RPMs, or it would appear with the stock CDI, which won't even let the engine to that RPM where this appears if I don't drive it for a long time.

[Alleyoop]

Well here is the take on high rpms, these motors the red line is 8000 rpms so if your going 8K+ your motor is not going to last long and crap will happen. Now this is a 50cc and it should not be doing over 7K rpms they make their max hp at around 6500 rpms so if your going well into the 7K with the 50 then you are asking for problems.

I would get a tach and find out what rpms the CDI is allowing you crank the motor to. But from the VIDEO it appears the noise is happening WAY BEFORE WIDE OPEN THROTTLE so my take is something is not right in the rear and it could of been caused by to high of RPMS and something gave.
Get this tach it is a very nice and good tach and you can go from scoot to scoot with it. It installs in 5 minutes. I always tell folks A tach is like a fortune teller it will tell you the past present and future. With a tach you can tune your Carb and Cvt to get the best from your ride. And Once you have it tuned the tach will let you know when things are going south so you can jump on the problem before it gets really bad.
Alleyoop

www.trailtech.net/digital-gauges/tto?cat=117

[worzx]

Yes, I've been thinking about getting one, especially for temperature, but I think I'll go with an all-in-one if that's exist and I can get my hands on it.

The sound apears at the RPM which is right the maximum for the stock CDI. At the first run today, I did not event got it with the stock, but I immediately got it with the new one, and after that with the stock too.

Anyway, thanks for the help. I'll look into the CVT and the gears, and I'll write if I have progress.

Thanks for the help again!