1st Performance Upgrades

Seeing as I noticed before I'm going to have to strip the bike back to get at the carb for a few things & I'm going to be tinkering within that region anyway, I've decided to get the K&N 'style' induction air filter to fit on the carburetter now. I did some asking about & some say it's a 38mm diameter connection & others say a 42mm. I do know there is a bigger carb to buy to fit these engines as an upgrade in itself so not sure whether one measurement given is in regard to one of these? They're only a few £s, which again I was surprised about, so I bought one of each size to be sure. I'm hoping it's the bigger 42mm diameter, if so I have a use for the 38mm elsewhere.
You can have a shop about for them on Ebay, they come in various sizes & fit bikes & scooters from 50cc up to 250cc & are fairly universal & in either the washable K&N style or the foamy type if you prefer.

They are meant to boost horsepower, although not sure it will be a great improvement on it's own, together with other mods it will all add up but, again it's an improvement none the less. & a better improvement over the stock filter that would've needed replacing overtime. At this low price point I'm unsure why such air filters just don't get installed at the factory to start with to be honest? But then again there would be no extra income generated from replacement parts I guess?

Performance induction air filter:

For only £11.34 there was an race performance DC CDI unit available to use with the bike on Ebay also. So far this bikes been very cheap as a project, it's been great. Changing the unit is basically a 4 stroke's equivalent of how a 2 stroke is derestricted to allow for a greater power / speeds. The unit controls & alters the power curve of the engine & removes the RPM rev limit set by the original CDI. All in all it's a better quality unit in a nice aluminium housing over the standard plastic cheap looking one, if nothing else & people have noticed how much smoother the curve & ride itself is over standard.

You need to see whether your particular bike fires with an AC or DC system before purchasing a performance CDI. In this case I've been assured it's a DC system (I guess the same for the SKYJETS etc also?), although there are ways to tell by counting the number of wires for instance. However, I haven't had the bike fully stripped back to see that for myself, so I'll just go off of the information & hope it's right, I can always pick up an AC unit if not. Just in case the plastic connectors themselves don't match up I ordered some 15 AMP terminal block connectors for a £1.00 while I was at it. You could go for bullet connectors or something similar but would have to solder them onto the wire ends. Of course you could directly solder the wires together but future swapping would be hampered by having to mess about to unsolder them to replace a future unit. That would be up to you. The CDI unit appears to be located underneath the fuel tank.

There are many units available but the one in question I picked up was a Casoli DC unit that works with Honda based 156/157fmi engines like this one & the GY6 Honda based scooter engines in DC. You should be able to pick them up on Ebay or somewhere like Ali Express for £10 - £15:

http://www.aliexpress.com/item/Racing-motor-Alloy-CDI-for-157FMI-CG125-150cc-200cc-250cc-4-stroke-Engine/1395408488.html

*If you see something for either 157fmi or 156fmi it's the same engine. The exact measurement is 156.5 and some manufacturers round it up one way or the other.

The unit is supposed to offer a boost of about 8 - 10 % in BHP. Likely around 2 BHP at the most. Doesn't seem a lot on paper but seeing as the 125cc engines put out about 11.4 BHP in total it could be a nice little boost. & still keeps it under the legal limit.

11.4 \ 100 = 0.14 (that's 1 % of 11.4 BHP)

0.14 x 8 = 0.912 BHP

0.14 x 10 = 1.4 BHP

(8- 10% improvement).

Casoli performance CDI unit:

Original CDI unit:

I think it's best to wait to do all this at once seeing as I would need to keep on removing parts of the bike to the same extent over & over again for each part & carb adjustment and I offer this advise to anyone else. I know putting bigger jets in the carbs can be a good upgrade but at this time I won't mess around too much with the fuel / air mixture. I could find myself in engine running trouble jumping in with that alongside everything else. If I need to revisit that later on I will do.


*EDIT. Read ahead, I had trouble getting a performance CDI unit to function with this engine. Don't order one unless it's at some point in the future and you know for sure it's a working model that's compatible with the engine (and if you do manage to find one drop me a comment).