Kymco People 50cc 4T impossible to derestrict?

[redguard]

Hello guys,

For 3 weeks now I'm a proud owner of a 2nd hand Kymco People S 50 scooter. I like it a lot except the engine power that could be better. So I brought it to my dealer and told them to boost up the perfomance. I discussed possible modifications combined with my prior research and we agree that they will install an unrestricted CDI and exchange the variator rollers. They tried everything but said in the end that it didn't make any difference so they put the original parts back in. They told me it's just the engine and the scooters weight which doesn't allow more performance.

I'm sure there must be a way to get more power out of that engine. They said the only way now is to replace 50cc with 80cc. Is it recommended or should I keep trying other ways? I'm not sure with what kind of "unrestricted" CDI they replaced the original CDI, but shouldn't it make at least a small difference if you put a proper derestricted CDI in there? As I read most restrictions on these Kymco scooter are on the CDI. And are there any other ways to boost the engine power?
At the moment I'm reaching a top speed of about 35mph and the acceleration could be better.

I'm pretty new to all this so I'm sorry if I'm maybe using improper terminology.

Thanks a lot!
Redguard

[chaz35]

Hello Redguard, welcome to the forum.  I can't help you with 4T, all the mods I know about are for 2T engine, which are pretty easy to mod. 

I think you can get big bore kits for 4T engines, but sorry don't know details.  I suspect 4T will be pretty expensive to mod.  Do some research and compare cost to mod your 4T to buying a 125 or 150cc scooter.  You will probably find cheaper to forget the mods and just get a larger scooter.  My 2T mods have cost more than to trade up to larger scooter, but I am OK with that.  Good luck

[redguard]

Thanks for your answer chaz35. Since I need to get another drivers licence and the insurance and everything will be more expensive here in the Netherlands, I want to stay with my 50cc and just try to get the best out of it.

I found the following unrestricted CDI which seems pretty good. What do you guys think about that piece?

http://www.scooterdynasty.com/cdinarakuracingfor50cc-125cc4-strokekymcoscooters.aspx

Furthermore I read that the new Kymco 50cc 4T models (I have a 2009 one) are pretty much only (or mainly) restricted by CDI, so getting a good unrestricted one will do the job. Any experiences with that?
As I checked (in the service manual and when the mechanic opened the motor) it seems there is no restriction on the driver boss in the variator of my scooter. It's a smooth pipe with a constant diameter which means no restriction. Am I right?

Thanks for your help guys!
Redguard

(Kymco People S 50 4T 2009)

[chaz35]

if you haven't already done so, try looking at some of the other 50cc forums for scooters that have 4T engines.  For example Agility, Vitality have 4T engines.  Good luck.

[Abner_Bjorn]

I don't know about this specific engine, but I have tuned a lot of 4 stroke 50s over the last 5 years.  Once you get the CDI sorted you should look to your CVT system.

Get a performance variator and replace your rollers with Dr. Pulley sliders.  I'd go a couple of grams lighter than stock.  Next swap your 3 small clutch springs and the big contra spring.  Go up one step.   Most 50's come stock with a 750 rpm spring.  Switch up to a 1,000 rpm spring.   I normally replace the stock belt with a Gates Powerlink belt when doing the clutch springs.   I don't know what the upgrade in belt would be for your scooter.  Thought I'd throw in my two cents.  :-).

You will end up with much better acceleration and a bit more top speed. 

[redguard]

I don't know about this specific engine, but I have tuned a lot of 4 stroke 50s over the last 5 years.  Once you get the CDI sorted you should look to your CVT system.

Get a performance variator and replace your rollers with Dr. Pulley sliders.  I'd go a couple of grams lighter than stock.  Next swap your 3 small clutch springs and the big contra spring.  Go up one step.   Most 50's come stock with a 750 rpm spring.  Switch up to a 1,000 rpm spring.   I normally replace the stock belt with a Gates Powerlink belt when doing the clutch springs.   I don't know what the upgrade in belt would be for your scooter.  Thought I'd throw in my two cents.  :-).

You will end up with much better acceleration and a bit more top speed.

Thanks a lot Abner_Bjorn!

I have a couple more questions about your way of modifiying the scooter.
What weight should I choose the sliders to be exactly? Does 5.5g sound like a good choice?
And do I have to replace the clutch springs and contra spring with +1000 rpm ones? I'm not sure what the + means.
I don't have to the tools and experience to do that myself, so I thought about buying the parts myself and bring it to my scooter dealer and they can do the replacing for like $10.

Furthermore do you think it's a better idea to make all these CVT modifications instead of replacing 50cc with a 80cc cylinder?
How about the wearing of the motor, will it last shorter than with stock parts?

Redguard

[Abner_Bjorn]

You're welcome redguard.  My opinion is that most 50cc scooter, especially the 4 strokes will last you the longest and give you the best reliability if you leave the stock cylinder in place.   I do not have first hand knowledge of the People 4t 50.  I have tuned dozens of Yamaha C3s and 2012 newer Zumas over the last 5 years.   
Stock roller in the C3 is 6 grams.  I replace those with 4 gram Dr. Pulley sliders.  I like Prodigy Variators from seller autotech355 on ebay:  The NCY gold variator is supposed to be good also. 
I don't know what the stock weight currently in your scooter, but I would go 20 to 30% lighter.
Yamaha stock clutch springs are rated at 750rpm.  I replace these with 1,000 rpm.  Again I don't know what your scooter comes with stock.  Finally I replace the stock Yamaha belt with the Gates Powerlink premium belt.  The 25% stiffer contra spring will put more wear on your belt than the stock clutch set up.  The Powerlink belt goes nicely with this.   
You are trying to optimize the power going from your engine to your rear wheel.  This can be done without trading longevity and reliability.

On the People S 50, you might want to search and see what people are doing to intake, exhaust and jets.    Most of what I work on is fuel injected, so no concern for re-jetting when you open up the intake or exhaust.   Good luck.   AB

[Tseg]

I recently bought a 50cc 4T Kymco and the dealer and I had a brief discussion on de-restricting scooters (I was not particularly interested) and his comment was something like "when we do it, sometimes the owner sees performance gains, sometimes they do not... I always wonder how much is psychological?"

Per another poster, with any mod it is important to consider the entire flow of impacts... change a spring, need a stronger belt... get a stronger belt, need  stronger pulley... have a stronger pulley, etc, etc...

With my scooter (different model), there was a mod recommended about removing a washer in the air intake tube.  That was the recommendation, by several.  After further investigation I found out this ultimately will cause the scooter to run lean, which means it runs hot... answer: well yes, of course you now need a larger Main Jet... and if a larger main jet is installed, what might be that unintended consequence?  Point being is there are a lot of moving parts all engineered by Kymco to work in balance out of the factory.  Be careful and thoughtful through research to make sure the complete sequence of impacted parts, suffering points and performance is considered in advance.  Take all forum advice with a grain of salt... it is just one data point.  As a famous US president once said, "Trust but verify".