ZS172-FMM-3A 249 to "300cc" kit

[Thumper]

I found this kit on AliExpress for $125. It is calling it a 300cc kit. The bore is increased from 72 to 74mm. I think it is probably 280cc, but I'LL TAKE IT!

This kit will probably fit the 6 speed engine (ZS172-FMM-5), but I am going to try it on the 5 speed engine. I need to find an advance key for the timing as well. I haven't been able to find a NC250 style resonator exhaust for this engine. The one made for the NC (water cooled engine) probably won't fit right.

This seems like a perfect Winter project:

[Texas Pete]

Thumper, I use this calculator for CC:

https://www.performancetrends.com/Ca...splacement.php


With the original OEM advertised "Bore x Stroke 72x61.4" figures and the above calculator I get: Engine Displacement of 249.99 CC


If I use 74mm as the Bore figure I get: Engine Displacement of 264.07 CC


Keeping the Stroke the same on the engine the Bore would have to be 79mm to get an Engine Displacement of 300.96 CC

[Thumper]

That makes sense. 72 to 74 mm is not much! Then again, the bore/stroke is already oversquare. Maybe a subtle increase in piston diameter coupled with head porting and a timing advance will bump HP to 24 or 25. I wish we could find a resonator style open flow exhaust system that fits this engine. I will keep looking.

[Thumper]

This kit got delayed in shipment. Then the order was "cancelled" but I didn't get reimbursed for the payment I made. Now there is an update that it has a new delivery date

Still waiting!

[JerryHawk250]

You can get a little more compression by only using a single layer of the head gasket. Wiseco may have a 74mm high compression piston that might work. It takes a good bit of research but might be worth the effort. I'm looking for a 72mm for the KPX.

[Thumper]

The ~10:1 OEM setup is working with regular unleaded. I am sure the 74mm piston (or whatever is in the kit) also has the same compression ratio, so will also work with regular unleaded.

I know, I know, we get 70mpg, so why not fill it with premium! But the head porting and advance key will complement the modest displacement increase.

Of course, I don't know when I will find the time to do ANY of this

[JerryHawk250]

Originally Posted by Thumper

The ~10:1 OEM setup is working with regular unleaded. I am sure the 74mm piston (or whatever is in the kit) also has the same compression ratio, so will also work with regular unleaded.

I know, I know, we get 70mpg, so why not fill it with premium! But the head porting and advance key will complement the modest displacement increase.

Of course, I don't know when I will find the time to do ANY of this

I agree. The high compression piston is not needed. Porting and the timing key will give the best results without hurting the reliability of the engine. Can't wait to see the gains you will get. I love doing this kind of stuff. The work I did on my X22R was fun and the results were crazy. I know you will post everything.

[Zapkin]

You guys are really making me want to learn!!!!

[JerryHawk250]

Originally Posted by Zapkin

You guys are really making me want to learn!!!!

All these china bikes make good projects for learning at a minimal cost. Stick around too long and you will be doing the same.

[sshoress]

I have the 22 templar x 6 speed myself modded out and I'm loving it! can hit 90mph fully pinned and head/torse tucked down. I'd still like to know if anyone has found any options for the 79mm bore/300cc kit upgrade to the 3a motor? thanks guys!

[crzyrder79]

Originally Posted by sshoress

I have the 22 templar x 6 speed myself modded out and I'm loving it! can hit 90mph fully pinned and head/torse tucked down. I'd still like to know if anyone has found any options for the 79mm bore/300cc kit upgrade to the 3a motor? thanks guys!

sshoress, can you show links on your exhaust and ignition system??

[XLsior]

Originally Posted by Thumper

This kit got delayed in shipment. Then the order was "cancelled" but I didn't get reimbursed for the payment I made. Now there is an update that it has a new delivery date

Still waiting!

If you experience any thing like this, or the seller start to make replacement sent claims, especially without tracking or will not refund...

Open a ticket with Aliexpres ASAP.

I've had sellers draw out orders long enough for customer support to expire.

Just open a ticket with Aliexpress and raise concern/doubt.

I learned the hard way.

[Thumper]

I did receive the kit. But the amount of work involved in gaining 15cc displacement is hard to justify. It is certainly not a "300" cc kit. But the quality seems high. It is an OTOM kit, 74mm.