Any advice on this big bore (180cc! ha!) kit?

[photobiker]

Hey ladies and gents,

Thought I would utilize the interwebs, gtam, and it's intelligent users for some advice.

I gots a kymco 150 bike, not scooter (think cbr125, but not compatible) and came across this ad for a little oomph.
http://www.ebay.com/itm/180cc-kit-Ky...item4cfde0d4b2

So...
I know I could save the $ for a bigger bike,
There is absolutely NO info or any reviews (that I can translate) on this so sorry for having nothing more for info other than this photo,
I only know that the stock bike is a 125cc that was bored out for NA markets,
I know I'd have to rejet the carbs (no experience, but willing to go for it),
I know that insurance don't likey the upgrades.

So here's things I know that I don't know (+ things that I don't know that I don't know but I can't list them cuz I don't know them...now I'm just confusing myself .. sorry)
Questions..

1. How high of a chance that the piston will explode out of this "inexpensive" upgrade and smash my danglies into bits?

2. In your opinion, do you suppose I'd get some reasonable power out of it? Highway riding is what I'm thinking... just a few more hps would be nice to not stay in the slow lane ALL the time.

3. Scale of 1-10, 10 being jetfighter tech, 1 being "make a coffee with coffee beans and a mallet", how hard of a project is this?

4. Likelyhood of needing an aftermarket exhaust? Reading another post about a cbr125 seems that stock is ok...

5. How high of a chance this "inexpensive" upgrade goes boom and I need to stop drop and roll?

6. I guess any advice is welcome...other than "buy a new bike". I get it, I should get a new bike. But this is a fun bike too.

Thanks in advance if you have any advice. Also thanks if you make good comments. Like "that's what she/he said". It's always a winner these days.

[Brian P]

1. Depends entirely on the quality of the parts (complete unknown) and the knowledge and care of whoever puts it together (probably you - but it's a single cylinder air cooled engine, pretty simple, just don't do anything stupid like mix up the piston rings or install them upside down or get the cam timing wrong).

2. It should help a little.

3. What's your level of experience with engines? Can you read and follow instructions in the shop manual? Do you know to recognize something going wrong and STOP rather than forging ahead and breaking something? As engines go, yours is pretty close to as simple as they get. Trickiest bit for people who haven't worked on engines before is compressing the piston rings - it's not hard but you have to be CAREFUL. And you have to not do stupid things. Piston installed backwards is another good thing to not do. Still, systematic approach, check everything as you go, check check check and check again, and it's not that hard.

4. Shouldn't matter.

5. See answer to question #1.

Hope this helps ...

[TheDirty]

As mentioned in the ad, there's no fueling modification supplied with the kit. You can't just put it in and run as is.

[Brian P]

IIRC this is a carb engine. The carb will kinda-sorta respond to more airflow through it by drawing more fuel through the same jet. As a first guess and in the absence of any real-world experience, put in a main jet a couple sizes bigger and see what happens. Get it checked on a dyno with exhaust-gas analysis pronto, though. On that hard-working air-cooled engine, you do not want a lean condition under heavy load, but too rich is no good, either.

edit: On poking around, it appears that Kymco uses Keihin CVK carbs, which plenty of Honda and Kawasaki bikes also used before switching to fuel-injection. Haven't found what that specific bike uses but other similar models seem to use those. You can get Keihin carb parts anywhere. Maybe ask the vendor if he has any jetting suggestions. Jets are a few bucks each, here.

[JohnnyP636]

Description says 100% made in Taiwan, in my experience that means %100 POS!

[crankcall]

I'd be on side with that upgrade, who cares if its totally made in Taiwan, its a bolt on part for a Kymco.

On the Web Page for the parts they state ," increase size of main jet" .
This is a pretty simple fix. Count the number of full turns when you unscrew the old main jet and thread new one in same number of turns, this will get you close as a start point.

[JohnnyP636]

I'd be on side with that upgrade, who cares if its totally made in Taiwan, its a bolt on part for a Kymco.

On the Web Page for the parts they state ," increase size of main jet" .
This is a pretty simple fix. Count the number of full turns when you unscrew the old main jet and thread new one in same number of turns, this will get you close as a start point.

The owner might care if that piston comes apart and takes out the valves and damages the cylinder head....That wouldn't be the first time Ive seen cheap bore kits self destruct causing major engine damage

[kneedragger88]

Being that Kymco is made in Tiawan why would the BB kit be any worse? Hell the CBR125 is made in Thailand? Just follow BrianP you will be fine. I have done a bunch of scooter BB that arent a whole lot different and most kits are asian (various places) and although not Rolls Royce they seem ok for the small bore stuff. My CT70 has had Chinese 110 engine in it for years now and runs like a champ. That said I dont know how much a 30cc bump will mean in way of performance.

[photobiker]

1. Depends entirely on the quality of the parts (complete unknown) and the knowledge and care of whoever puts it together (probably you - but it's a single cylinder air cooled engine, pretty simple, just don't do anything stupid like mix up the piston rings or install them upside down or get the cam timing wrong).

2. It should help a little.

3. What's your level of experience with engines? Can you read and follow instructions in the shop manual? Do you know to recognize something going wrong and STOP rather than forging ahead and breaking something? As engines go, yours is pretty close to as simple as they get. Trickiest bit for people who haven't worked on engines before is compressing the piston rings - it's not hard but you have to be CAREFUL. And you have to not do stupid things. Piston installed backwards is another good thing to not do. Still, systematic approach, check everything as you go, check check check and check again, and it's not that hard.

4. Shouldn't matter.

5. See answer to question #1.

Hope this helps ...

Thank you, yes this helps. It also helps to let me know "holy crap there is a lot I gotta learn still" I figured installing it would be a pain, but "cam timing" sounds like "Rolex repair" to me as of this posting... I have almost zero experience. If something breaks down on a vehicle, I can fix it pretty easily, but as for having a foundation of mechanical skills...it's pretty much learn as I go.
As for the "depends on the part quality" before it blows up... is this something you could tell once one has the part in hand? Or is it more like...maybe the metal will fail, maybe not...

As mentioned in the ad, there's no fueling modification supplied with the kit. You can't just put it in and run as is.

That's the jetting fix, yes/no?

IIRC this is a carb engine. The carb will kinda-sorta respond to more airflow through it by drawing more fuel through the same jet. As a first guess and in the absence of any real-world experience, put in a main jet a couple sizes bigger and see what happens. Get it checked on a dyno with exhaust-gas analysis pronto, though. On that hard-working air-cooled engine, you do not want a lean condition under heavy load, but too rich is no good, either.

edit: On poking around, it appears that Kymco uses Keihin CVK carbs, which plenty of Honda and Kawasaki bikes also used before switching to fuel-injection. Haven't found what that specific bike uses but other similar models seem to use those. You can get Keihin carb parts anywhere. Maybe ask the vendor if he has any jetting suggestions. Jets are a few bucks each, here.

You say jets are a few bucks "here" as in a link you may have not linked or as in "here" like as in Canada?
As for carb.. yah it is a Keihin CVK 25mm

The owner might care if that piston comes apart and takes out the valves and damages the cylinder head....That wouldn't be the first time Ive seen cheap bore kits self destruct causing major engine damage

Yes. I would care. A lot. But also kinda sorta hoping it might be worth a calculated risk..

Being that Kymco is made in Tiawan why would the BB kit be any worse? Hell the CBR125 is made in Thailand? Just follow BrianP you will be fine. I have done a bunch of scooter BB that arent a whole lot different and most kits are asian (various places) and although not Rolls Royce they seem ok for the small bore stuff. My CT70 has had Chinese 110 engine in it for years now and runs like a champ. That said I dont know how much a 30cc bump will mean in way of performance.

Sounds promising...in your experience, what would you predict a 30cc increase would do? Maybe 1-2 horseys? It would be great to not slow down on hills lol.


Thanks for the advice so far guys. Hope everyone's weekend was good... one more month of winter almost over .

[Brian P]

The 180cc is 20% more displacement. With all else being equal, that means 20% more torque but not necessarily 20% more power - i.e. it'll make more torque but tend to do it at lower revs and tail off at higher revs. With a 25mm carb for that engine displacement, it's probably under-carbureted - it'll run OK, it'll just tail off in power at higher revs. It'll probably make more power than stock everywhere, but it won't be 20% more everywhere.

More torque at lower revs isn't necessarily a bad thing - the bike will be easier to get up hills and you won't have to gear down as much, it just won't necessarily have more top-end speed.

[photobiker]

Thanks B-P for the explanation. Either i do this this season, or I gets a new ride. Just a question of financials. I sourced out an exhaust and a rear shock for this thing too...and local guys to do the springs... so either I get a new old-to-me ride or a new new-to-me ride.

[holotape]

Did you end up getting the kit?