Tomos nitro 50 (2010) help with throtle problem

[jcola474]

Guys, so I am desperate for your help. My tomos nitro 50 is having problems lately... i have no problems with this moped since I got it from a deal couple months ago.

The problem is, everytime I throttle, it will not go above 4,000RPM, and it kinda bumps everytime I do a full throttle on a down slope. I don't have problems with it going up a hill. Also, everytime I stop at a traffic light, when I pull the accelerator, the engine sounds like its struggling for some reason. Please help me guys.. thank you very much.

Attachments:

[OverReved]

Hi!
Does your bike have a tachometer installed? I'm wondering where you are getting this 4000 RPM number from. What RPM did it reach before you noticed the 4000 RPM number?
What is your top speed you are able to reach on level ground?

You said "it kind of bumps...on a down slope" that could be you hitting the Rev limiter!
I've not heard of people having rev limiters at 4k on a 50cc since they are bearly off idle at that speed. Perhaps something else is going on.

[millsc]

my chinatach is wrong im sure of it says 7500 rpms max when driving but after about ten minutes of driving wont go past 6000 can half throttle at 6000rpm then full throttle can hear rpms rise tach stays at 6000

[OverReved]

6000 sounds like a reasonable rev limiter for a 125cc. Unless you have some road speeds to go with these RPM ranges and your anecdotal "hearing rpms rise" I'd say everything is working as expected.

Just because a piece of equipment has a tach that can read to 15K RPM doesn't mean it's designed to actually do 15K

[jcola474]

yes, my tac meter is installed and it reads fine. So you think there's a limiter installed to keep my moped from stopping the engine when its on idle? Sounds good to me. I just want to know if there's anyway I can improve my acceleration, from a full stop to a full throtle, my moped sounds like it's been struggling. Then on a flat road, It can't even stay on 20mph and it bumps again every now and then.

[OverReved]

You seem like a nice guy and I'd really like to help you, but your sentence structure and description is so rushed and poorly thought out that I can't figure out what you want.

If you can describe a problem if you have one I can work from there. If you want information on modifications for speed and power I can help with that. If you feel your moped is restricted in some way I can help you determine the cause and offer advice : in that instance I would need some RPM and correlating road speeds.

Good luck!

[jcola474]

I'm sorry, I'm at work earlier and can't concentrate on what I wanted to say. OK, here's my problem;

My moped start fine. My engine doesn't die when it's on idle, the engine sounds fine... However, when I start running in the streets on a flat road, my rpm would go 4,000rpm at 20MPH, after that, my moped would start getting bumby and the engine would sound like it's struggling. On a downhill, the same thing, I can run the moped up to 25MPH then after that it will start doing it again. On an uphill though, it runs absolutely fine on 25mph but a slight sound of struggling can be heard from the engine.

I tried to explain it the way I experienced it while I'm driving. I'm sorry about what I posted earlier, you see I am not a very mechanical guy when it comes to moped pls helo me...

[earlwb]

Well if the engine doesn't have a limiter built in or installed...
then one problem is if the air cleaner box comes loose so that the engine goes extra lean, then it won't rev up. Check the air intake, aircleaner and rubber boot going to the carb, and also the intake manifold on the other side of the carb going to the engine. These rubber intake manifolds tend to crack or deteriorate pretty fast in some locales too. It isn't uncommon for the intake manifold to leak. A vacuum line coming loose and being open will do it too.

Next is the spark plug wire and plug going to the spark plug, if it had come loose and allowed extra long sparks to occur, then the ignition coil could have been damaged and is on the verge of failing. The symptoms can look like what you are experiencing.

Another thing that can do it, is the valve gaps have closed up or opened too much, this can affect performance a lot too. But usually after the engine warms up it doesn't want to idle correctly and people adjust the idle speed more to compensate for it, instead of checking the valve gaps.

[OverReved]

The fact that is only goes to the 4000 RPM and the 25 MPH mark leads me to suspect that your scooter is limited to 4000 RPM and 25 MPH. You may want to look for threads on derestricting your bike.
I would suggest you check your throttle linkage to be sure it's actuating the Carb butterfly fully, but I doubt that's your problem since the engine is having it's spark cut at 4K rpm.

[mainepeace]

Has it EVER gone faster than 25 or 4k? If so, it's not a limiter. It could be an issue with the CDI or coil where its shorting out. It could also be a fuel delivery issue, or as Earl mentions, a vacuum leak. Hard to say without a bit more info.

Greg

[jcola474]

Nice, thanks everyone for all the info. I checked it yesterday and looks like OverReved was right on the dot. No leaks were found, all wires for the both inlet and outlet are still good. And also me and my buddy spent 2 days cleaning the carb and replacing the old spark plug so I guess I just need to check if the limiter can be adjusted.

It's been a while since I have used this again and I decided to do a test run last week and this is what I have experienced. It's a good thing you guy here at SCOOTDAWG are willing to help and give information, you guys are also great figuring out the problems by just reading it from a blog! That's awesome, hopefully I can get it adjusted so I can run it at least 35MPH.

If you guys want to add something up, please let me know, as I am going to be a regular scootdawg member from now on.

[jcola474]

Guys, do you think this is the same way on how to derestrict my tomos nitro moped?

www.youtube.com/watch?v=Mm56sSwQa5Y