Fuel

heya pesqueezo,

firstly, fuel... iv read the posts on here too... and it seems most people agreed 95ron fuel was best. What i was told when i got my carbs balanced, was to put the best petrol you can find in the tank. I dont know what you local area is like but it's damn hard to find a good drop, they put some real crap in fuel. I'v found BP ultimate (98 ron) to be the best... if ur super keen sniff the petrol <!-- s:-? --><img src="{SMILIES_PATH}/icon_Eyecrazy.gif" alt=":-?" title="Eye Crazy" /><!-- s:-? --> and alot of the time ul smell kero an other yuk yuk

Test whether or not the hoses are the wrong way around on ur bike... at the reserve switch... i know i found out the hard way myn was on reserve all along. Try to avoid using reserve, poke a torch in the tank and you see why...

I had a similar problem on my fizzer, where on hot days the bike would flood if the engine was stop/started a few times within a short period. I had to turn the tap to off... hold down full throttle, and it would jsut idle, until the floats emptied a bit, then the revs would go through the roof, and away id go. Oh also if it floods, u can jump start the bike... with some throttle and it sorta 'pumps' the excess fuel outta the engine... helps if ur on a hill tho..

those are my experiences, hope it helps.

love larry

 

Most FZR250's run above 12:1 compression which warrants the highest oct fuel you can find but what most people dont realize is that the higher the octane the denser the fuel is. This then effects fuel/air mix from the carb's because of the position of the jets. This is how it can seem that high octane increases performance, though, in fact it's just a better air fuel mix.
If your bike has been tuned to ULP, Premium or Super (98oct) changing to the other will effect your combustion because of the change in fuel density.

Some of the early model FZR250's were gravity feed fuel systems and for this reason some people have removed/disconnected the pump. The pump does not make much difference until you are on reserve tank supply as fuel starts to fight gravity into the carbi.

A lack of power at the low end of rev's could be the exup. There is a valve in your exhaust that reduces the amount of exhaust that escapes. It progressively opens as the bike reaches higher revs and helps create back pressure in the cylinder at low revs to increase power output.
Check that the cables are moving when you rev the bike up to confirm they are operating.

leaving the fuel on:
will it flood...yes! its gravity feed fuel line for about the first half of the tank. This means if you have a full tank of fuel, turn it off, if its half or less, up to you. Its really if your not riding for a week not 2 days.

 

That sound is your fuel pump, so it seems at least it is operating.
I do recommend experiementing with different oct fuel, you can even buy octane boost additives if high grades are unavailable to you.

I also recommend running "injector cleaner" even though your bike is carbi.
The reason is that the injector cleaners will not disolve your rubber seals like carbi cleaners can. But remember your bike is only a few liters. most bottles treat 60L so I've only added about a 3rd at a time. makes a massive difference to idle and take off.

also remember different fuels only improve detonation timing (tho the higher the oct the cleaner it burns with less polutants) and effects your fuel/air mixture.

keeping that in mind while you ride you will hear what your engine is doing.

 

just keep in mind, dont put all the injector cleaner in, use about 1/3rd of a bottle and while its running through you will lose alot of performance (at lease i did) until your next refuel. Its then that it feels much more responsive and free flowing.

lets us know your progress.

 

I only ran normal unleaded in mine (91 octane) and never had any problems. It just went cheaper for the same distance... Shell optimax has been known to cause problems in FZR's, fouled plugs, etc..

Pull the hose off the tank and see if petrol actually comes out when on reserve, there have been instances of the reserve port being blocked..

 

Hi all,
There is only one difference between fuels and that is the price of it. If you think octane makes a difference you are kidding yourself (it is all in your mind). Higher octane fuel burns slower (anti-knocking particals in the fuel) than lower octane fuel. In fast revving engines such as the fzr you want the fuel to burn as quick as it can, so that the spark plug has a chance to burn all the fuel. I am with Dave on the fuel put 91 BP fuel in it and forget about what fuel you will ever put in it again. Also if you use the same fuel you can keep one aspect of your bike the same until you figure out what the other problems are. If your bikes have a fuel pump they will not flood themselves over night because fuel would have to pass through the fuel pump. Even bikes without fuel pumps will not flood because the valve in the float bowl chamber stops fuel from getting through.

Pesqueezo, this is what you need to do to your bike to get it running sweet, and yes most of us have had this hot start problem. With my method the problem has gone.
1. New spark plugs, NGK CR8E.
2. New fuel filter, and lines to solve any fuel problems.
3. Check float levels (10.5-11mm flat).
4. Pilot screw to 2 7/8 turns out.
5. This is where it gets fuzzy and this relates to fuel economy, carby needle on setting 3 or 2 from the top (about ~20-25 km's a tank difference)
6. Let it breath and drill several 10mm holes in the air box above the filter (dirt bike riders have been doing this for years, I currently have 9 holes).
7. Clean renew the air filter (hot soapy water).
8. Have that well earned beer ( beers) and hope that your days work was worth it.
Hope this helps a bit and keeps the bike running sweet.

 

Some fun information there, I might try the air box thing...

This will help you understand the difference between fuels for motorbikes
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Density is going to effect air/fuel mix and therefore carbi settings.

This will help you understand that engines with high compression ratios need high oct fuels.
Obviously, if the fuel is compressed more agressively you need to prevent knocking and
ULP can handle the least amount of compression before igniting. If the fuel ignites before the piston has reached the top of its stroke it will not produce much power and will distroy your engine.
<!-- m --><a class="postlink" href="http://auto.howstuffworks.com/question90.htm">http://auto.howstuffworks.com/question90.htm</a><!-- m -->

In regards to flooding, there is an off position for many reasons. in my experience the bike floods if left will a full tank over a week.

You could tune your bike to run ULP but I would think at 15k rmp you are running a risk of turning the engine into a bomb as the heat would contribute to the compression to possibly ignite early.
Both of the links are publications, not a persons opinion. But If my bike has explained anything to me its that each bike is different. Find what works for you.

 

Give the air box the treatment, you also get a great sound when the air box starts sucking more air in. Back to fuels and the information provided was excellent. Although I can't help but think that temperature would have more of a bearing on fuel density rather than its octane rating. The temperature variable would have quite a significant range depending on different times of the day or night and bike temperature at any given time. What type of fuel do you run if you don't run ULP, this only leaves diesel and Lead replacement fuel.

 

I'm gonna give the airbox the biz next week hopefully and will let you know how it goes.

Locally we have ULP 93oct Premium 95oct ultra 98oct. I use premium most of the time and
occasionally add octane booster if I notice poor smoothness in the double digits of rpm.

I wonder though, the people who are using ULP and say that high octane fuels dont work for them have rooted engines?
for example the compression ratio should be 12:1 (or there abouts) which is way suffice for Ultra 98 oct.
However, if you have an engine that has lost some of its compression it would in theory not be able to compress high octane's enough.
Therefore using ULP which will ignite in an engine thats lost its maximum compression would seem as though its performing better???
I get 140kmph out of about 2/3rds of 4th gear...
what are the ULP riders getting?? maybe their engine compression is rooted and is why they dont have enough torque to pull those types of figers.

Heat is a massive factor, on that point drilling holes into the airbox means it will probably be sucking warmer air then usual
which again comes down to density if air and fuel mix. Again, in theory the engine has a optimal operating temp.
At high rev's the temp may increase above the optimal and at high compressions there is a great chance of
detonation before the piston has reached its full stroke. (again requiring high octane fuels to prevent).
But this happening in a engine that lost compression will further damage compression with knocking.
The effects of which will get harder to notice as the bike progressively loses power and compression over time until it needs a rebuild.

Our bikes can and will burn high octane fuels unless they have been tuned with less air mixture to make it less ignitable or the engine has lost compression.

reference : <!-- m --><a class="postlink" href="http://www.faqs.org/faqs/autos/gasoline-faq/part3/section-1.html">http://www.faqs.org/faqs/autos/gasoline ... ion-1.html</a><!-- m -->



People who say they are running ULP 93oct or under have either air fuel mix set up to NOT effectively burn the petrol or they have lost up to 50% of the original compression.

To answer the question if temp has a bearing on fuel density rather then octane. High octane fuels are more tolerable to engine temp
probably partly to density, they dont ignite of hotspots in the cylinder and so this prevents knocking.
It burns cleaner for the environment with less emmisions. Temperature therefore has a greater bearing on low octane fuels rather then high ones.

 

This is good we are getting somewhere in the fuel department which has not been talked about much. Higher octane fuel burns slower and therefore this may be enhancing the detonation period. Although the type of fuel will not have a bearing on when detonation occurs (CDI controlled). And to my knowledge detonation occurs just before top dead centre. Personally I have tried higher octane fuel in my bike and have found no difference. This is why I stick to low octane (cheaper fuel). Modern day bikes only recommend high octane fuel because of euro 3 standards, and as you mentioned, better for the environment. And the fact that fuel injection does not atomise the fuel well enough for good air fuel mixing (they started at 4 injector holes and have moved to 12).

I can not see the compression ratio of a bike changing all that much. It would only possible change through big end and small end wear and tear (which would cause a knock in the engine). Although compression of the engine would change through normal wear to the bore and rings. My understanding of a rooted engine would be burning oil, low compression and a knocking noise, apart from that there is not much more to go on.

Back to the air box drilling and the thought of hot air. I did think of this and realised that the holes drilled in the air box would not induct any hotter air than normal. This is because of the factory inlet position to the air box. Personally I think the factory fitting will suck more hot air than the modification because it sucks from lower in the engine (the holes are higher and therefore more air should circulate around the area).

Is your $1.40 with standard gearing? What RPM is that doing.

If you want I can take some photos of the modification. Let me know how you went.

 

The simple answer is that there are other factors that also have an effect on combustion chamber pressure and cause detonation, ignition timing and valve timing for example, and the FZR with its extreme overlaps and duration to get the revs would struggle to reach the actual 12:1.. The specs list standard compression pressure at 9.8 bar (142psi) which is only 10:1. They must have worked out the compression ratio on the cylinder volume vs the combustion chamber volume. My old V6 pajero compression tests at 140psi

Yamaha FZR250 specs also list the required fuel as "regular gasoline" and that would be mid '90s japanese regular at that.

Having said all that, at over 50,000km on the clock mine ran perfectly as good on unleaded 91 as on 96 octane, never heard pinging at any time and still had good compression.

Although you are correct when you say that there is no difference in the potential energy in the different octane fuels, only that more output can be safely obtained with a higher octane fuel if the engine is set up to run it, I.E. higher compression, turbo-charging or supercharging, and greater ignition advance.

 

Sorry - sometimes we go a bit over the top... But this forum is good and well mannered compared to some I have seen.. <!-- s:shock: --><img src="{SMILIES_PATH}/icon_eek.gif" alt=":shock:" title="Shocked" /><!-- s:shock: -->

 

When I first got my bike it did that, it felt like turbo lag hahaha.

Remember when these recommended fuels were printed there was no such thing as 98 octane. Even compression ratio's as low as 8:1 are recommended for 93 octane. Thats like saying when you purchase a new bike it recomends floba-dob-abib-bob fuel when its invented and available.
(no disrespect intended there) everyones bike is unique and if it works for you why not ay!

Everybodies bike is different but all the things previously mentioned
should be considered. Valve and ingintion timing are mechanical factors not chemical which is why I did not mention them but valves sticking is very common and a big factor in these high rev'n bikes.

short shifting isn't a problem or shouldn't be, especially with exup running.
if you leave the bike idle for 30sec and then rev it up to 12k rpm slowly, then try again but rev it up fast does it miss fire or behave differently around 8k-10k rpm or is it only in first gear?

 

Drewzor is right about short shifting, this should not be a problem. The major issue with these bikes is the lack of torque that they produce. Therefore they require some reving to get them off of the line. Having said that these bikes will also pull off the line with minimal throttle if they are running properly. Even in the latest bike reviews when they ride 600's they say that they struggle to get off of the line with anything under 6k RPM. It all depends on how fast you want to get off of the line. Clutch progression control can help with bogging off of the line.

I don't want to talk for Drewzor but I think he is getting at a floooding problem with the reving. Simple stated to much fuel can have a bogging effect on these bikes. Good fuel consumption should be something that you test as well as spark plug condition. Anything from 140-180km's would be exceptable. And remember these bikes are getting a bit long in the tooth and therefore the motors are starting to wear out and cause bogging, fuel consumption problems, small rattles and that highly important exup valve adjustment. Exup is so good that all the modern bikes (even harley's) are starting to pick up on the technology.

Best of luck and myself and Drewzor have simply been waying up the options of what is the best fuel to use related to your specific bike. You will look back at what we have said after you have a better understanding and it will all make sense.