Which is best fuel?

[sanchez]

i've just changed to 91 after reading on here that it makes the bike run better. and on the ride home i noticed a random rattling noise. so its maybe from changing fuel. how damaging is this?does anybody know? Ive just filled up again so might have to just syphon it out

It is bad, very bad, does it happen mainly at low rpm if you crack the throttle open a bit?

Drain it out if it's easy to do, otherwise mabye just chuck a bottle of octane booster in and put some 98 in as soon as you get down to 1/2 a tank or so.

[peasea]

I've posted other comments about fuel on this website, under the Touring banner, HD stuff etc, but the theory is the same. If your bike rattles (pinks, knocks, farts or otherwise objects) to cheap gas, then switch asap to a higher octane. What's a few cents to give your ride the best? The knock can be damaging (rings, pistons and bearings) so don't go grabbing big handfuls of throttle under load; ease it on and use your revs, change later and run the gas out, then go for the next grade up when you refill. The best gas I've found is Gull super and BP Ultimate. If you find the knock has gone then there's your answer. If not, go up again until, if you find the machine knocks even with BP Ultimate, you have a problem. In my experience ignition timing is often overlooked. I'm happy to share my knowledge of four-stroke engines (accumulated since 1973) and what I have learnt about their needs as to octane ratings. A lot has to do with the expectations of the operator, the loads and the conditions. Nana will get by on her own with 91 when she idles to the shops in her 1300cc shopping basket cage, but Joe(sephine) Throttlebug will have a different requirement when on the back wheel of his/her tyre-fryer at 160k's while Tony the Tourer will have another story when loaded up with saddlebags and a partner. I'm happy to share knowledge and experience but I'm no petrochemical expert. Neither am I a trying to sell something; I've built a few engines though. Email; pcwordsmith@xtra.co.nz.

[imdying]

i've just changed to 91 after reading on here that it makes the bike run better. and on the ride home i noticed a random rattling noise. so its maybe from changing fuel. how damaging is this?does anybody know? Ive just filled up again so might have to just syphon it out

Well, the death rattle isn't good, but I doubt you'll cause any immediate damage. Just dilute it out with 98, every few days top it up, that'll raise your overall octane. I wouldn't go the trouble of syphoning it. It's worth trying to figure out if it is pinking, or if the noise is something else. Random rattling is a pretty good description of pinking though... when does it do it? Lightly loaded, heavily loaded?

[cbr guy]

dam that sux! i was enjoying the cheap fuel!lol. i just noticed it while cruising at 100kmh, but didnt really think much of it because it could have been a loose fairing or something, but its not.i actually weighed myself wearing my gear before the ride and i was 80kg which shouldnt be too bad of a load for my cbr250. might just syphon some of it directly into the car and fill the rest up with 95 (can't get 98 in little old inverargill) to bring the octane up a little. now i've just got the challenge of driving my bike gently for 25kms before hitting the closest petrol station, cant be good.
thanks for the help guys, you probaly just saved my engine!lol

[surfer]

91 works fine for me, seems to run better than 98 or 95. I reckon you should all change to riding an older bike

[Max Preload]

Best fuel in NZ is the cheapest one that doesn't pink. Try a tank of 91 and see if it makes the death rattle. If not (none of my bikes have), keep using it.

The problem with that being high rpm detonation is the real motor killer and you're unlikely to hear it happening until it's all over.

Octane is a measure of a fuels ability to resist detonation and in a bike engine with higher compression ratios this is important. Higher octane fuels are slower and cooler burning so without adjusting the ignition advance, using a higher octane fuel will not result noticibly in more power.

At the end of the day however, using higher octane fuel in a motor designed for lower octane fuel will not be harmful. The reverse scenario is harmful. I always use 98.

[imdying]

The ignition curve on a CBR250 would cause it to pink at load at a lower rather than high rpm, the advance is reasonably quick.