Z250 to 300cc Bore up

[wayanlam]

Havent started a thread in what seems like eons, ha ha...

Been so busy with work, family (we have a son whos almost 3, and another one due in Jan 1 2018!)

I sold my red Ninja 2009 back in 2013~ and then bought the Z250 in 2014.



Due to local regulations, bikes that are over 250cc are hit with an additional 70% taxes. So here yamaha, kawasaki, etc are all boring down their 300~320cc bikes to fit into the 250cc bracket.

About a month ago i finally finished upgrading the Z250 to a Z300.

Link to original page on YouTube.

Thats the day we started to taking the bike apart for the bore up kit~

About 3~4 weeks later i was doing my 2nd hard break in session.
did an oil change 50~ km after bore up, and then drove another 200~250 km before replacing oil, oil filter, clutch plates, and clutch springs.

The added torque caused the clutch to slip, and that wasnt feeling too good, ha ha...



Before the bore up i already had the full exhaust system, porting, power commander, and tuning done. But i was never quite satisfied, since i knew there was more to be had!

Link to original page on YouTube.

Even with the slipping clutch, the bike was a blast to ride. I did 200km trip in about 3 hours going across and around the island a little.

Just ordered a Ninja 300 Throttle body in the states, which a friend will bring back to Bali in Sept. So thats something interesting to look forward to. atm i still have the stock 28mm bore throttle body that comes with the 250cc version. while the 300cc bikes in the states have a 32mm bore.

Thats about all i can report on my bike

[backinthesaddleagain]

Oh that's cool. I think we only have the Z125 in the US. Congrats on the upcoming addition to your family.

[DannoXYZ]

Very nice!

Link to original page on YouTube.

Link to original page on YouTube.

[sharky nrk]

Did you simply use a OEM Ninja 300 cylinder bank and pistons to complete the job?

[Zaph42]

If I had to guess, the compression was upped a bit. That's a nice power curve, a little more than what a stock 300 can get without engine work.

[wayanlam]

Originally Posted by sharky nrk

Did you simply use a OEM Ninja 300 cylinder bank and pistons to complete the job?

no, we went up with a larger bore, while the oem 300cc actually has a different crank shaft and piston rod if im not mistaken, allowing for a longer stroke.

OEM 250cc: Bore/stroke: 62 mm X 41,2 mm
OEM 300cc: Bore/stroke: 62 mm × 49 mm


OEM 250cc cilinder stacked under the bore up kit

and some die by side comparisons:




if you put this bad boy into a oem 300cc bike, you would end up with like 356cc~

a friend actually told me to try source an oem 300 crank and piston rods if i wanted to go up even more, but i think ill leave it at 300, ha ha...

i haven't even put in the bigger throttle body yet, which should help in the top revs where the engine needs that extra little bit to breathe.

[DannoXYZ]

Wow, that's some really thin cylinders!!! About 3,5 to 4,0mm?

[wayanlam]

Originally Posted by JacRyann

Very nice!

Link to original page on YouTube.

Link to original page on YouTube.

thanks!

i didnt realise i had to only pate the video code, and not the rest, he he

[sharky nrk]

Originally Posted by wayanlam

no, we went up with a larger bore, while the oem 300cc actually has a different crank shaft and piston rod if im not mistaken, allowing for a longer stroke.

OEM 250cc: Bore/stroke: 62 mm X 41,2 mm
OEM 300cc: Bore/stroke: 62 mm × 49 mm

Ahh yes that is correct, the OEM 300 is through stroke not bore. What brand kit did you use? I assume its something common over there that we don't have in the states?

[wayanlam]

Originally Posted by sharky nrk

Ahh yes that is correct, the OEM 300 is through stroke not bore. What brand kit did you use? I assume its something common over there that we don't have in the states?

The cylinder block is an OEM kawasaki block, bored out to the limit, and then a sleeve inserted and honed to fit a (i think OEM from some bike...) cylinder that is that correct size.

Im not sure of the Cylinder that was used because the company i bought the kit from CNC'd the info off, to keep that as propriety knowledge i guess.

i paid like $400~500 for that kit, plus labor to install, ported the intake and exhaust again, had it ported already on the stock cilinder, but it needed to go even bigger to allow for a good flow for the larger displacement. And then the whole process to tune the bike on the Dyno~

[bruce71198]

67mm or 68mm?

[wayanlam]

Originally Posted by bruce71198

67mm or 68mm?

Using a 67mm cilinder/bore

[DannoXYZ]

In U.S. you can do that easily too. Sleeves are commodity items used all the time in engine-building. You can get them from LA Sleeves or Darton or any number of suppliers in a variety of sizes. Machine-shops can also mill out block and install them easily as well. The difficult part is finding the proper pistons for the desired compression-ratio.

Wayan, do you know what the compression-ratio is after upgrade?
Have you done a compression-test?
Do you have photos of pistons?

Thanks.

[wayanlam]

Originally Posted by JacRyann

In U.S. you can do that easily too. Sleeves are commodity items used all the time in engine-building. You can get them from LA Sleeves or Darton or any number of suppliers in a variety of sizes. Machine-shops can also mill out block and install them easily as well. The difficult part is finding the proper pistons for the desired compression-ratio.

Wayan, do you know what the compression-ratio is after upgrade?
Have you done a compression-test?
Do you have photos of pistons?

Thanks.

The CR is 12.8, up from the stock 11.3 my mechanic did a displacement measurement to check that.

I neglected to take a picture of the piston cause the brand/SN was removed, and it basically looked the same as most 4 port cilinder piston, lol

[bruce71198]

Originally Posted by JacRyann

In U.S. you can do that easily too. Sleeves are commodity items used all the time in engine-building. You can get them from LA Sleeves or Darton or any number of suppliers in a variety of sizes. Machine-shops can also mill out block and install them easily as well. The difficult part is finding the proper pistons for the desired compression-ratio.

Wayan, do you know what the compression-ratio is after upgrade?
Have you done a compression-test?
Do you have photos of pistons?

Thanks.

Buy a used ZZR600 cylinder block off ebay, press the sleeves out and, with a little machining, you can press them in place of your current 250 sleeves. This will allow you to bore up to 68mm.

[bruce71198]

Originally Posted by wayanlam

no, we went up with a larger bore, while the oem 300cc actually has a different crank shaft and piston rod if im not mistaken, allowing for a longer stroke.

OEM 250cc: Bore/stroke: 62 mm X 41,2 mm
OEM 300cc: Bore/stroke: 62 mm × 49 mm


OEM 250cc cilinder stacked under the bore up kit

and some die by side comparisons:




if you put this bad boy into a oem 300cc bike, you would end up with like 356cc~

actually you'd end up with 346cc. You would need 1mm more of bore (68mm) to get 356cc

[DannoXYZ]

Originally Posted by bruce71198

Buy a used ZZR600 cylinder block off ebay, press the sleeves out and, with a little machining, you can press them in place of your current 250 sleeves. This will allow you to bore up to 68mm.

Egads that's a lot of work for some sleeves when you can get them for $20/ea! I prefer flanged tops for strength and rigidity. Also helps sealing to have them shaved not flush, but 0.002" or so above deck.

http://www.jegs.com/i/Melling/689/CSL722/10002/-1

For boosted applications, I'd go for chromoly with a wider top-flange. Best if flanges butt up against each other and at corners for support.

[bruce71198]

Originally Posted by JacRyann

Egads that's a lot of work for some sleeves when you can get them for $20/ea! I prefer flanged tops for stretch and rigidity. Also helps sealing to have them shaved to be 0.002" or so above deck.

http://www.jegs.com/i/Melling/689/CSL722/10002/-1

For boosted applications, I'd go for chromoly with a wider top-flange. Best if flanges butt up against each other and at corners for support.

Actually its no more work than installing the sleeves you mentioned. And the ZZR blocks can be had for $50 used. This nets you 4 sleeves. Not to mention the 1.5mm of solid wall thickness it leaves with 68mm bore sounds like a win win to me.