MHR bored and stroked

[LoveMyKymco]

So I burnt up my piston for my MHR race cylinder and instead of putting another MHR piston and rings in for 90 bucks, I bought the Wiseco 47.5mm piston for the yz80 off of zombie. I think the kit number is 477p2, but when I search it its hard to find anything relative. It is a little taller than the malossi, so to make up for this I plan on stroking it. Has anyone done this yet? Or at least stroked a MHR race cylinder? Its going to be interesting, I will do it on a spare block I have sitting around and try it out on a stretched and reinforced 89 honda elite. If nothing it will be fun for a few hours I guess. I need a 28mm carb.

[thebatman]

It is a little taller than the malossi,

Why not just trim the piston skirt?

I didn't stroke a MHR but i got one in tho   

[zombie]

Stroking it will make the piston taller in the jug. You will need a thicker spacer for the base. I did stroke the Malossi Sport, and was VERY happy with it. I used a cheap yz80 piston to set it up, and the plan was to replace it with the Wiseco... That plan ended when a pin clip caught the edge of a transfer, and scored the jug top to bottom. I still have a 4.5mm spacer I made if you want to try stroking. It is set for a 44mm stroker. You could also use a longer con rod, and the OEM crank to get a better rod/stroke ratio. I think you would need a 5mm longer rod to use the spacer I have, and that piston.

[zombie]

Jiangwayne.com has the best prices on the OKO28mm I have found.

[02 zx 50 s.f.]

Idk about anything bigger than a 24mm because the 30mm I just bought is becomeing a huge problem it's just toooooooo big I'm going to put a filter on to try to slow the flow down but it's huge I thought it would be good 90cc kit I just installed but we shall see oh and z how much for you to come and tune this beast hahaha if I had a boat I would have loaded that bitch up and been on my way to you you are just around the bend.

[LoveMyKymco]

30mm is close to fuel requirements for a 150cc. 17.5-19 = 49-70cc, 21mm= 65-78cc 24mm= 65-95cc 28mm = 72-130, 30mm =90-150ish

In reality you can tune any carb to work but you will sacrifice a ton of low end on a big carb and a ton of high end on a small carb. If I were you Id use a 24mm. Im guessing you have a "50mm" bore kit? it comes out to 82 I think, not 90. Not sure how they got 90 out of it.
I ran the 50mm BBK a while back and used a 24mm OKO 45 pilot jet, 140 main jet with clip in middle with a typhoon v8 pipe. Those 50mm are lower revving cylinders so a big 28 or 30mm wont really help it that much. 28-30mm is for serious stroking.

[zombie]

Yeah. 02 zx, and I have had the same conversation. He saw the big pretty dog, and it bit him.
How high does the piston sit above the jug? You need to be exact on that. I can make/send you the proper spacer. The number has to be exact.

[thebatman]

I run a OKO 24mm on mine....125mj...45pj...needle in 2nd slot
I only have something like 200-300 kms on my 50 stroker..
Mine comes to 86.4 if i am correct......50mm, 44mm, slightly ported, ex. ported-polished

I think a 30mm would be way to big... Would need hard DOWN jetting..

[02 zx 50 s.f.]

The piston is on tdc on the jug. But I am going to try to seal the manifold like you said. Idk got to make it work for now but I want to start saving for a 24mm it would be nice to have both low and top but I was looking for top when I bought the kit. As long as I am not doing a 10 mph till 20 or 30.

[thebatman]

As long as I am not doing a 10 mph till 20 or 30.


OH Hell no.... 
that won't happen   

[02 zx 50 s.f.]

But wouldn't I be Runing to lean if I do some hard down jeting?

[LoveMyKymco]

They do make a 26mm carb. Not sure if anyone has much experience with them.
You should do a couple of plug chops to determine how youre running as it is.

[zombie]

But wouldn't I be Runing to lean if I do some hard down jeting?

You have to start somewhere. You have to see what jets are in the carb to start with. You will most likely need between 40-50 pilot, and 100-150 main.