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Discussion Starter · #1 ·
I would want get out more power from my yzf. I have 2010 yzf with 25k km on clock. I'm looking at naraku cyclinder kit with head. Naraku have 180cc and 200cc kits and they cost about the same.
And I have some questions about engine.
What would be better 180cc or 200cc?
What happens with fuel injection does stock fuel pump and injector is OK? Will malossi force master 2 do the job?
Stock crankshaft with bearings will hold that power in long term like 2 years?

Naraku 180cc kit : Zylinderkit Naraku 177ccm 62mm Keramik für Yamaha YZF-R WR, Xmax 125 kaufen | SCOOTER-ATTACK and head Zylinderkopf Naraku 21/23, 62mm für Yamaha Xmax, YZF, WR 125 kaufen | SCOOTER-ATTACK
Naraku 200cc kit : Zylinderkit Naraku 200cc 66mm Keramik Yamaha YZF-R WR / Xmax 125 kaufen | SCOOTER-ATTACK and head Zylinderkopf Naraku 22/25, 66mm Yamaha Xmax / YZF / WR 125 kaufen | SCOOTER-ATTACK
malossi force master 2 fits on yzf? : Ungedrosselte CDI Ungedrosselte Zündeinheit Malossi Force Master 2 Yamaha X-Max / X-City 125cc ie Euro 3 kaufen | SCOOTER-ATTACK
 

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2008 YZF-R125 (180cc)
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I would want get out more power from my yzf. I have 2010 yzf with 25k km on clock. I'm looking at naraku cyclinder kit with head. Naraku have 180cc and 200cc kits and they cost about the same.
And I have some questions about engine.
What would be better 180cc or 200cc?
I looked at the 200cc kits and beyond 180cc I felt like there wasn't really much cylinder sleeve left (looks very thin), and afaik that's all quite important for cooling, not melting etc. The 180 seems to be a fairly tried and tested formula, and better documented so I went with that.

> What happens with fuel injection does stock fuel pump and injector is OK?
fuel pump should be fine. Stock injector runs out of duration on a 180cc so you need bigger. 160cc/min injector seems to work well but it will need mapping for the new injector..

> Will malossi force master 2 do the job?
The FM2 should do the job more or less. It has no wideband input or autotune option so will need a dyno tune though which is $$$ (and another each time you change something). Downloaded maps are an ok start but will never really let you get the best performance and that's a lot of money to spend to only then get half a result by not bothering to actually get it mapped properly. PCV + Autotune is a very nice and flexible setup which means you can skip the dyno but it's $$$

> Stock crankshaft with bearings will hold that power in long term like 2 years?
I've got about 6k miles from my 180 cylinder (started off similar mileage to yours) over about 2 years and crank was fine but the bigger cylinder changes the balance factor of the crank which means your bearings will probably fail sooner. Cylinder/compression is still fine but the bearings are shot now. I started off with a working 125cc with about 23k on it, blew the cylinder and replaced with a 180 and it was fine for about 6k more miles (2+ years) and by the time I took it out a few months ago it was a chorus of top and bottom end rattles. I've done a whole video which explains this in detail here:

That being said, even as 180cc (without balance factor adjustment) it was never particularly happy at high rpm either and was much more responsive down low/mid which was a bit disappointing since I was interested in improving the top end a bit. It would do high rpm it but it didn't like it and that showed in the bearing wear. My newly built engine (also 180cc, identical to the previous) but which has the balance factor issue corrected seems much happier at high RPM and responds much more like the original 125cc cylinder used to (likes to scream) but quicker.

I think the balance factor issue is something people overlook when considering a 180cc and that can lead to disappointment...and nobody seems to talk about it or understand why it's a potential issue. I couldn't really find any info about it when I did mine at first so just kinda did it and figured it lasts as long as it lasts...seeing how it eventually failed confirmed what I had suspected.

I certainly won't be building any 180cc (or bigger) engines without some sort of crank balance adjustment in future. The difference with how it runs now vs as an "unbalanced" 180 is quite stark.,the old unbalanced 180 engine was reluctant, this new one it just like LETS GOOOO!

I think the problem to some extent is that people think you can just put a new cylinder on an old tired engine and squeze twice the power out of it and everything will be fine. And it probably will...for a bit....but then it won't.
 

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Discussion Starter · #3 ·
Thanks for your answers! They helped me a lot! ;)

fuel pump should be fine. Stock injector runs out of duration on a 180cc so you need bigger. 160cc/min injector seems to work well but it will need mapping for the new injector..

How big is original injector is? Can you show me some website where I can buy 160cc/min injector?



The FM2 should do the job more or less. It has no wideband input or autotune option so will need a dyno tune though which is $$$ (and another each time you change something). Downloaded maps are an ok start but will never really let you get the best performance and that's a lot of money to spend to only then get half a result by not bothering to actually get it mapped properly. PCV + Autotune is a very nice and flexible setup which means you can skip the dyno but it's $$$

This would be the nicest and the most flexible solution? Yea it cost a lot but in the end it would be worth.
 

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2008 YZF-R125 (180cc)
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you can get a 160cc/min injector here: 14.99US $ |New Fuel Injector Motorcycle 160cc/min 10 Holes Replacement Motor Nozzle Injection Fuel Engine Injectors for R125 Motorbike Blue|Fuel Injector| - AliExpress
The original listing for the one I got has disappeared but that looks just like the one I got.

As far as I understand it the stock injector is 100cc/min. As your injector flow goes up you lose some precision for smaller amounts..so don't go bigger than you need to or the bike will run worse where it needs less fuel (low/mid) because it just can't make small enough increments accurately. I have a 160ccinjector for most of the last 6000 miles and it seems to be a pretty good fit.It's not quite as smooth low/mid but can handle high rpm much better than stock.

This would be the nicest and the most flexible solution? Yea it cost a lot but in the end it would be worth.
yeah the PCV + Autotune is a great solution. You need to get an o2 sensor bung (hole) welded into your exhaust and that can be tricky/expensive because exhaust is stainless and thing so needs very delicately TIG welding, but then you have a wideband sensor and it just tunes as you ride based on AFR targets you set. That's the setup I have and I love it. And whilst you can run 180cc cylinder just fine on the stock I did a video on making a map using this setup:

Once you have that setup in place it also makes switching from stock injector to 160cc super simple (just go ride and let it tune), rather than having to get it dynod or whatever to even run ($$$). The fuel numbers for a 160cc/min map are VERY different from the numbers for a stock injector map.

Similarly if you then wanted to put a different sized cylinder on (e.g. 200cc) you could just fit it and let it figure out the map itself.

There's times when you can 'help' the autotune and you can also apply it selectively (e.g. if you only want to tune your top end but the rest of the map is fine). This guy did a great video on that side of it:
 

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Discussion Starter · #5 ·
I looked at scooter attack there are some aftermarket heads. There are naraku head 21/23mm valves and for 62mm bore (177cc) Also there are naraku head 66mm (200cc) with 22/25mm valves. And now I have question about stock head, how big valves stock have? There are needs to change head?
 
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