G'day everyone, looking forward to being able to get down with other 250 fans (small capacity kings) I'm currently sprucing up my zx2r for the road, aim is to have it produce at least half its body weight in power, see how that pans out. So undoubtedly there will be many questions to follow, like why the hell can't I find a unrestricted (performance) cdi?! I've seen that issue discussed hear if someone could point me in the right direction that would be sweeet. Thanks all.
Hello, welcome and what restriction do you have now and do you know anyone who has tried the Chinese versions?
The cdi restricts the bikes rev range to 16k when it can actually rev limit at 20 (not that it's a good idea to get it there) you can actually feel that it's an electronic restriction opposed to a mechanical restriction. I've seen people discuss the Chinese cdi's but don't know anyone who has used one. Was hoping someone hear had a go with one, they should do the job, quality and reliability are obviously aquestion one asks tthemselves when it's generic Chinese parts tho.
You would want to have perfect valve springs, cam chain and tensioner blades if you hope to hit 20000 without mashing a piston into a valve. Which I am sure not many would have in their 25 year old engines. Oh my fork springs are saggy, I better replace them, but my valve springs are fine because my engine hasn't blown, yet.
Valve spring harmonics change as valve springs get older/more cycles. It is not unusual to have a slight miss at a certain revs caused by a weak spring having a harmonic 'moment' and causing a valve to float.
you are better to grab another gear at 16000, the sweet spot for power is between 12000prm and 1600prm on the zxr's
All the advise given is spot on, I have seen first hand the damage that can ensue when over revving occurs.....not pretty.
Hang on, You want it to make 70hp? Buy a 400, 70hp and a better built bike, easier parts too, Not to mention the cost, Good luck to you but set aside 5-10K If you plan to get that kinda HP. Nice bike, don't they also rev to 18k as stock?
so everyone seems to have gone a bit mental over the 20k LIMIT, I do understand how engines work hence why I put in brackets that it's not recommended to sit on the limiter, clearly, the purpose of enabenabling the bike to rev to its limitations are so I can be between 12-16k because I can't be around 16k when that's the final limit, and the amount of money involved in a project is always irrelevant because if I succeeded not only would it be hens teeth but still come in way less than just running out and buying a 10k Chinese built single cylinder. And remember there's always room for weight reduction when maximum power gain has been reached. It's a project/experiment, I have my full license and have had for many years, I ride small capacity bikes end of story. 5-10k cost for a 110kilo 60hp 4 cylinder 250, don't tell me if that was on the shelf you wouldn't want one. Ok
Simple, don't hit the limiter, pretty simple and the age of a bike gives no indication as to the ware on the components, I'd like to know the minuscule measurements for valve spring coil strength loss over the space of say even 10 years, enough to mash pistons I head you say, probably but is blowing an engine really that big a deal? Live with a two stroke for a few years and you'll get used to replacing large components like cases and valves.
The rev limiter is 19.2k rpm not sure what you mean by only revving to 16k. Pretty sure the peak is 16.5k rpm and not sure how getting the unrestricted cdi is going to change that. dont think 70hp is possible but i have heard of 50hp at the wheel on cbr250's.
