2000 GSX1200 run on 91, 95 or 98 and why?

[Banditbandit]

I had a GS1200ss - 91 or 95 was just fine - did not notice any difference between the two.

If you are popping on deceleration I'm presuming you have a aftermarket muffler on it? If so it is highly likely it is not sealed properly where the muffler joins the mid pipe. loosen the clamp here and squeeze in some high temp silicone sealant (Supercheap have small tubes http://www.supercheapauto.co.nz/onli...pid=5366#Cross).

Allow it to set overnight and reclamp the muffler in the morning.

Why ?? The aftermarket pipe on my big Bandit is not sealed - sounds great on the over-run ... between 3,500 and 2,500rpm ... crackles and pops .. I blip the throttle just to listen ...

[SMOKEU]

Why ?? The aftermarket pipe on my big Bandit is not sealed - sounds great on the over-run ... between 3,500 and 2,500rpm ... crackles and pops .. I blip the throttle just to listen ...

In my experience, if you have a leaky exhaust then the engine won't perform as well compared to an exhaust with no leaks.

[imdying]

There must be more to fuel octane requirements than just the compression ratio. My old MC19 CBR250 ran fine on either 91, 95 or 98. I didn't notice any difference in performance or fuel economy. That had a compression ratio of 11:1 IIRC. Mitsubishi GDI engines and many other direct injected car engines have a lower compression ratio than 11:1, yet they all require a bare minimum of 95 octane fuel in order to run properly, and 98 is even better.

Go and research the difference between static and dynamic compression ratios.

[imdying]

Why ?? The aftermarket pipe on my big Bandit is not sealed - sounds great on the over-run ... between 3,500 and 2,500rpm ... crackles and pops .. I blip the throttle just to listen ...

This shitty emissions system on your bike is effectively a leak, that creates that popping.

[imdying]

In my experience, if you have a leaky exhaust then the engine won't perform as well compared to an exhaust with no leaks.

It's a controlled leak into the exhaust port to promote after burning in the exhaust to help it meet emissions standards. It's not detrimental to performance, although it'll put your wideband readings out of whack when tuning (so block it up for that).

[Banditbandit]

This shitty emissions system on your bike is effectively a leak, that creates that popping.

It's a controlled leak into the exhaust port to promote after burning in the exhaust to help it meet emissions standards. It's not detrimental to performance, although it'll put your wideband readings out of whack when tuning (so block it up for that).

Naaa .. it's an after-market can I fitted myself and it does not quite seal on the engine-side ... there's a small visible gap between the pipe and the can ... It's not intentional ... except I intentionally left it that way ...

It sucks in air with oxygen which causes any unburnt fuel in the hot can to detonate ...

It doesn't seem to affect the performance .. the bike performs better with the can than with the standard pipe ... it just might be better again if I sealed it .. but hey, I never use all the performance the bike already has ...

[Tigadee]

compared to most car engines a motorbike engine is a ahighprerfromance one with high compression.You should us 95 as a mimimum.I dont have any specific knowledge to back this up

91 is apparently very dirty (was told that all the crap after flushing the pipes at the oil refinery goes into the 91 tank) and leaves more carbon residue on the insides of the engine than does 95 or 98. I don't feel too much difference in performance or economy (maybe a little), but if only for the fact that the insides of the engine will be cleaner, I use 95 or 98.

Although most if not all modern bikes run on 91, that is the minimum octane fuel recommended (as some countries have lower octance fuel).

...running it on 95 and it seemed really poppy when i was engine breaking and backfired a bit..not sure if thats good or bad although i did sound kinda cool :P

Yes it does indeed...

[imdying]

Naaa

Yeah, your bandit will have a PAIR valve.

btw, your bike is not warrantable... VIRM 11-1 item 6.

[imdying]

91 is apparently very dirty (was told that all the crap after flushing the pipes at the oil refinery goes into the 91 tank) and leaves more carbon residue on the insides of the engine than does 95 or 98. I don't feel too much difference in performance or economy (maybe a little), but if only for the fact that the insides of the engine will be cleaner, I use 95 or 98.

Although most if not all modern bikes run on 91, that is the minimum octane fuel recommended (as some countries have lower octance fuel).

Ok, so that's all wrong. Whilst there is a range of what will work in practice, there is no minimum or maximum, only correct. Putting 92 in an engine designed for 91 will offer no advantage. You underline minimum like that implies that higher is better, but it is not.

[Banditbandit]

Yeah, your bandit will have a PAIR valve.

Yeah - before the aftermarket can .. has bugger all to do with the fact that the can does not seal onto the pipe ..

btw, your bike is not warrantable... VIRM 11-1 item 6.

What ?? It's had several warrants from VTNZ since I fitted the can ...

(edit)

Naaa .. I went and looked ... it's fine ... a decibel check would show it is under - even when it is burbling on the over-run ... which it would never be checked at ...

[Tigadee]

Ok, so that's all wrong. Whilst there is a range of what will work in practice, there is no minimum or maximum, only correct. Putting 92 in an engine designed for 91 will offer no advantage. You underline minimum like that implies that higher is better, but it is not.

I emphasise minimum as in 'NOT to go below 91'. There are lower octane fuels used in other parts of the world, you see, and the motorcycle manufacturers state "use 91" so that there is no confusion as to whether or not lower octane fuels are allowed... I don't think a lot of modern engines would handle 89 or 88 octane well, for example...

You read my underlining of the word minimum to mean that there is a scale of benefits, whereas I meant differently... I said so myself that I don't feel much difference between 91 and 95 or 98, but if using the higher octane does not leave as much carbon deposits as 91, then I am willing to pay the difference in price and use 95 or 98. (Was shown the differing real-world results by a motorcycle mechanic.)

[MSTRS:Me]

It NEEDS good fuel - its a bloody sports bike!! The older bikes and cars like mine made back in the days of leaded fuel and have high compression motors especially do not take kindly to 91, leave that to the '90's economy spec sedans.

It will run lean and eventually melt pistons. That said the GSX is pretty modern, has 9:5:1 compression which isn't super high and it doesn't red line at 20,000 rpm or the sky either. So you could be safe with 91.

It may not like it though and might feel more like a slug than a sports bike. Up to you. Personally I'd use the good stuff. It is a sports bike after all.

Load of utter rubbish... (clue - there is no R in the bike designation for a start)

My GSXR 750 IS a sportsbike and runs very well on 91. Arguably it might run fractionally better on higher octane, but I reckon you'd need to put it on a dyno to really be sure.

[Paul in NZ]

There are a billion factors that determine the optimal fuel rating for an engine... Compression is one factor but combustion chamber design, emission gear, ignition advance etc etc... You name it...

Vickis wee car runs OK on 91 but lordy lordy what a difference 95 makes... The mechanic we use stressed to her DO NOT run it on anything less than 95 but its just this particular model. Another car may well be fine...

Run 95.... Pretty most owners I have talked to use it on these wonderful things

[imdying]

There are lower octane fuels used in other parts of the world

Not really, you're probably confused by RON vs MON. Not that we live anywhere but here in any case...

I don't think a lot of modern engines would handle 89 or 88 octane well, for example...

As above...

if using the higher octane does not leave as much carbon deposits as 91, then I am willing to pay the difference in price and use 95 or 98. (Was shown the differing real-world results by a motorcycle mechanic.)

It's your money...

[imdying]

Naaa .. I went and looked ... it's fine ... a decibel check would show it is under - even when it is burbling on the over-run ... which it would never be checked at ...

Item 6 is leaks, you have one.