Big bore kits

[Kyrop90]

What’s people’s opinions on big bore kits?

Might get one might not just as a bit of fun.
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K.pickett

[stinkwheel]

That's like asking "Who's in favour of me buying bigger shoes?"

What its for and who made it?
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[RhynoCZ]

As Stinkwheel says, what is it for? If a 50cc, 125cc... ''L''oser plates bike, don't bother. It's cheaper and easier to just buy a bike with a bigger displacement engine.

If you are an bored engineer, I say do it. But it's more for the sake of the challenge, not to actually gain power/torque/speed.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[xX-Alex-Xx]

If your cylinder linings are fucked and it makes sense to bore it out rather than replace the engine, sure.

If you’re doing it for more power, don’t bother. Especially on a smaller bike.
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DILLIGAF

[Riejufixing]

[stinkwheel]

Well, the above notwithstanding, you can -for example- take a C90 out to 110 which is probably worth doing in terms of perforormance but isn't all straightforwards because the crankcases need machining out.

Many variables. I bored and stroked my 500 out to 612cc and that's like a whole different bike. Likewise if you were going to take a z650 out to 810.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[1198]

I took a Chinese 125 to 150. Decent power upgrade (from very little to a tiny bit more). However my mods were matched by a bigger carb, different (free flowing ) cone air filter and a larger front sprocket to best utilise the power ‘upgrade’. Well worth it in my view but it wasn’t expensive as I recall - total expense for it all was less than £100. It certainly made me chuckle if nothing else.
Remember the licence and insurance implication by the way...

[A100man]

I once put big pots on an aircooled VW 1600 => 1776, had to get case machined etc.
Added a hot-ish cam and twin carbs too. It did make a difference but even then not startling as I would also have had to change the gearbox to get the most out of it. Ultimately it meant I could get up steep hills in 2nd rather than 1st gear..
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[wr6133]

I big bored a vClic (Pug badged generic Chinese GY6), with the cheapest biggest kit I could find on eBay, it claimed 99CC, (was actually 88). I matched that with Big valve head, bigger carb, open air intake, freer flowing pipe, CDI, better clutch, better variator.

Made loads more power but you had to carry a spare belt everywhere because on the slightest downward incline you could run it off the clocks and shred the belt.

Cost very little to do and was worth it for the laugh. So to answer your question, it's probably worth it if the kits are cheap and you'll learn a whole load about engines doing it.

[Kyrop90]

[Kyrop90]

[Kyrop90]

[Kyrop90]

[Kyrop90]

[Kyrop90]