125cc stroker project :D

[Koert]

Hello,
my name is Koert and I live in the Netherlands!
I'm building a 125cc stroker at the moment
Only the engine will be placed under a Kymco DJ50
Thats because Dio's and Spree and such are extremely hard to find in my country
So I had to go with the kymco witch has the same engine
What makes my project special is that I'm the only one in my country who has ever build a kymco engine bigger then 80cc.
They never even heard about cilinderkits that are bigger then 80cc!!

So, my project started a while back when I saw an aircooled bigborekit on E-bay.
I bought the kit, bought a scooter for Ôé¼50
And I asked a friend to cut the casses to size.
It didn't take long before we realized that the crank wouldn't go in without cutting the threaded holes in the cases.
So we glued pieces of alluminium in the cases and cut the cases to the correct size.
Now the only thing we have to do is redrill the holes!
The holes won't be in the same place as before because that won't work.
They will be shifted by about 1mm
We did this because I don't want to use all kinds of sealant to try making the cases leakfree...

The to do list:
-some work on the cilinder (remove the sharp edges from the ports and piston)
-Weld some extra material around the intake on the cases (so they can be made alot bigger)
-Make a membrane housing for a Honda Cr85 membrane
-Weld an exhaust
-Make/buy a manifold to fit my 26mm Dell'ortho

I hope my Englisch isn't to bad

Koert

[Trafficjamz]

Is this the 52.6mm crank?

[Wheelman-111]

Greetings:

And Welcome, Koert. It sounds like you have a very special project going. I think I speak for all of us when I ask...

Where are the pictures?!

There is a wealth of knowledge here on the Forum. Mini-strokers and big-bores and even some big strokers and Liquid-Cooled kits have all been done. Feel free to share and to ask questions. Your English is just fine.

[Koert]

@Trafficjamz
It is a 52.6mm crank

@Wheelman-111
I have only 2 pictures so far

The holes in the cases will be drilled tomorrow!
I'll take some pictures and post them here

Koert

[Wheelman-111]

Greetings:

Mmmm, scooter innards! We like looking at the Machinery.

So those cases are not yet modified? The boost port looks like standard-size AF16E at the moment.

May I suggest you get your machinist friend to plane the cylinder and intake mating surfaces. There appears (Maybe it's the pics...) to be a good amount of pitting, which isn't conducive to a good gasket seal. You probably want to avoid a case leak on a build with this much output.

[Spreetard]

Welcome to the forum! I'm exited to see your countries first Full Stroker DIO!

I think that a 26mm carb may be a bit on the small side for the full stroker setup (though it's a very nice carb for a 72cc).

The 30mm OKO can be had through online resources in a kit with a ct chrome intake manifold and reeds, along with an adjustable throttle cable. I paid 150, but i think scooterassasins has the kit for cheaper. Try to get the six-petal reeds also, the added flow will help your stroker reach it's full potential.

Of course, being I've not built a full stroker, this information is just what I've gathered from the forum resaerching for when I build one

[bakaracer]

Wheel the top of the case looks like it has been already opened up to fit the 55mm bore kit. The sleaves on the 55mm kit is 58.5mm.he just needs to cut the boost port to match. Getting the 6 petal reed won't gain any power. The opening is the same diameter as the 4 petal reed cage.the 6 is used more for circuit race to better the on/off throttle repsonse. He needs the over sized reed cage that uses a yamaha blaster reed cage.those manifolds are the krs large or the taiwan big black manifold.Those manifolds can hold up to a 33mm keihin in the spigot.major inlet case porting and welding like he is going to do to enlarge the carters and inlet to make the engine flow better to use the full 125cc's

[Spreetard]

...good to know. But baka, do you think the 26mm is going to be big enough for 125cc?

[bakaracer]

No its to small. The exhaust port on the 55mm is about 30mm. The smallest I would use is a 28mm carb. If he is going to weld extra material on the block to open the ports up then he is going to increase flow and that 26mm carb won't supply enough air and fuel. That will be his restriction.they have stroker exhaust pipes with 33 to 35mm inlets to the j pipe so the exhaust port can be opened to match that size.most guys I know that run a pipe with that large of an inlet and ported the exhaust port to match run a 30mm or larger carb.

[Koert]

okai... the 26mm might be a bit small...
But thats a carb that I have
Compared to a 2005 Honda cr125 38mm carb my 26mm is verry small I agree
But I don't really see why it is too small, because a Aprillia rs125 has a 28mm as standard..
And thats an engine that is designed for 125cc use...
For as far as I can see the flow on the honda verticall engine is far from ideal.
Compared to a 2005 Honda cr125 38mm carb my 26mm is verry small I agree
But doesn't a smaller carb give a better throttle response?
I can allways upgrade to a bigger carb.
BUT I could be all wrong..
In our national scootersprint racing championship we have 50cc racers with 30mm carbs!
All information is welcome

Koert

[bakaracer]

Are you going to use the engine for sprint drag racing or circuit roadracing?

[Koert]

Well I will use it mainly for cruising round my town...
But I need some full throttle madness for taking on all the Yogrr's round here...
Round here, the Kymco is like the ultimate sleeper.

Koert

[bakaracer]

Depends how much case porting you do ,the minimum size carb I would use is a 28mm and go with a flat slide carb.the throttle response is much more crisp than a round slide carb.run a boost bottle to increase that on/off/on throttle response that town riding needs.if you are welding extra material to make the block transfers and intake larger than 30mm would be the smallest I would run.

[z50r-ghost]

Welcome to the forums, Koert!

Wow dude, the first 125cc in the Netherlands... (applause!)

Lookin good so far! Keep us posted with your project & you speak better English than many people here in the USA.

j

[Koert]

The holes in the carters are drilled!
It is looking nice!
But I have to go to work now, so can't take pictures now.

Koert