Zs172fmm 4 valve head

[Okierider]

https://m.made-in-china.com/product/...091462475.html

Found this in a Facebook group advertised with a 75mm big bore kit (around 271cc, but called a 300).
I’ve asked the guy selling them on Facebook if the 4v head adds to the height or width of the motor but got no useable answer. The 75mm kit with 4v head is advertised for $450, the 75mm kit for $100 shipped.

Anyone know anything about these?

Edit: looks like the whole kit here-75mm and 4v head. Some are claiming it was all installed and dynod at 28 crank horsepower but I haven’t seen any proof of it.

https://m.made-in-china.com/product/...112478765.html

[Thumper]

The hardware on the cam gear inside there looks like a centrifugal advance for variable valve timing. I can't think of any other reason for a weighted elbow with the weight off-center to use centrifugal force to advance the valve timing as you increase rpm. Pretty cool.

edit: WRONG! see the next post below.......

I like the kit. But I already have a brand new 2 valve head that I am going to work on porting, and an OTOM overbore cylinder/piston kit. I won't be the one to test this new 4 valve head, but I can't wait to see it installed on your bike!

[superjocko]

Originally Posted by Thumper

The hardware on the cam gear inside there looks like a centrifugal advance for variable valve timing. I can't think of any other reason for a weighted elbow with the weight off-center to use centrifugal force to advance the valve timing as you increase rpm. Pretty cool.

I like the kit. But I already have a brand new 2 valve head that I am going to work on porting, and an OTOM overbore cylinder/piston kit. I won't be the one to test this new 4 valve head, but I can't wait to see it installed on your bike!

It's a compression release that makes the bike easier to start.

[Thumper]

Originally Posted by superjocko

It's a compression release that makes the bike easier to start.

So the weighted arm releases the device when it starts. Well that makes sense, but where did you read/find that out?

Before I ordered my Templar, I assumed that the teeny choke lever was a compression release lever.

But it doesn't need one to let the starter crank it up. I should try using the kickstart. I have to do that EVERY time on the KTM 250 2stroke. Fortunately, it pops right to life

[Okierider]

Originally Posted by Thumper

So the weighted arm releases the device when it starts. Well that makes sense, but where did you read/find that out?

Before I ordered my Templar, I assumed that the teeny choke lever was a compression release lever.

But it doesn't need one to let the starter crank it up. I should try using the kickstart. I have to do that EVERY time on the KTM 250 2stroke. Fortunately, it pops right to life

I only ever kickstart mine. It’s faster than the starter lol

[superjocko]

Originally Posted by Thumper

So the weighted arm releases the device when it starts. Well that makes sense, but where did you read/find that out?

It's a common feature on many small engines.

[Okierider]

What sort of carb would be appropriate for a 4v head 271cc motor?
The stock 172 comes with a 28, would a 30mm be enough to feed it?