Mileage

Hey all,

What is the standard gas mileage that I should be expecting out of my 1983 XJ650 Maxim? I just got it as a starter bike and am curious what it will be needing for gas come this summer.

 

You should get ~45 mpg, if the bike is running right. It's mostly a function of how much you twist the throttle.

Use regular gas, not premium, regardeless of what the Hog-nobs tell you.

 

Bosozoku - can you shed some light on your regular vs premium preference? I always thought the premium was better for performance, mileage and engine life.

 

There is no more energy in higher octane pump fuel than there is in 87 octane regular. Period.

The only way to exploit the higher octane is to have enough compression, or boost, that you need to use the spendier gas. Otherwise you're paying for a fuel quality that your engine can not take advantage of.

It's not strictly a matter of compression- my 900 has 11:1, my FZR600 has ~12:1, and both are happy with regular gas. A large combustion pocket with an older design, like the last centurys' HDs, will detonate at 9:1 c/r on regular fuel when under a sustained load.

I've got a link that explains it in better detail...Let me see where it is.

edit: bikes obey the same rules as car engines- http://www.freerepublic.com/focus/f-news/1770628/posts

Take a look at ch 6.13 on the third page of this article- http://www.cs.uu.nl/wais/html/na-dir/autos/gasoline-faq/.html

Your engine will make the best power on fuel that has just enough octane so it does not detonate- anything more goes to waste.

 

I knew cheaping out on the regular was going to pay off! As much as I thought premium was better - I never actually ran it in any of my vehicles.

Thanks for the info.

 

Serious ly think on that one
Yama specifies Premium.. There are not joking with comp ratios usually above 10:1 on these things .. the risk of detonation is real and Holed pistons can really mess yr day. Those couple of dollars "saved' may not feel so good in yr pocket when that happens.
My experiences are that even 91 is iffy.. producing significant ping and a v noticeably reduced 'snap' in throttle response. In order to adequately run low test either the comp has to be lowered and/or the ignition timings significantly retarded.. Simple Physics ..no amount of 'Belief' is going to change reality.
IF yr Yama runs OK on 'Regular' then it's in real need of Work.

 

Alright, I'll think on it.

 

I run premium on real hot days because it runs cooler. But regular is good enough for everyday riding.

 

No, the Yamaha shop manual specifies regular gasoline, and makes no mention whatsoever about premium.

The same manual lists my 650 as having a CR of 9.2:1

Haven't got the 750 manual handy, but the big ones' is-
The 900 is 9.6:1, with the same fuel requirement. Regular

Would you please break out the manual and take a look at reality before you spit numbers out?.

But, if putting premium in the tank makes you happy, by all means do so.

 

I tend to run regular on the most part.
On occasion when I know I'm going to twist it I use Premium.

 

This helps alot, I was told by the PO of my bike that i should only run the prem gas. so i have, i think now im going to take Hvnbnd advice and only put that in when im going to twist. Thanks

 

Well...if yr happy then Enjoy Yr saving a huge Dollar on a fill-up
All I can say is mine is at 10:1 comp (Owner's manual) and it without doubt 'pings' like crazy and runs poorly on Regular.. but then so does my '71 Beetle with it's 7:1 compression aircooled engine.

 

Danilo, what model bike do you have?
My Yamaha service manual shows the XJ750 and the XJ650 both have 9.2:1 compression ratio. My XJ750RH owners manual says to use regular gas.
I plan on trying both grades of fuel and see what my bike tells me.

 

Actually, I have read that running premium when not needed actually reduces the performance of an engine, as the higher octane is achieved via chemicals that slow down the burn rate of the fuel, leading to lower combustion pressures, etc.

http://www.factorypro.com/tech_tuning_p ... power.html

BTW, homemade octane boost is much cheaper than premium, if you are so inclined:

http://www.elektro.com/~audi/audi/toluene.html

 

I have been using premium in my bike for a year now. not much more go then regular but i heard that the premium gas does not leave as much carbon buildup as regular. i could be wrong. can any one shed light on this.

 

first a question then some BS
is octane rated the same way now as it was back in 81, 82 ?
i give Mr Ed the expensive stuff 'cause it gives me that warm fuzzy feeling
it's a karma thing

 

Premium will burn cleaner but not give you any more bang for your buck unless you have turbo or supercharger, If you get a ping then I would check your timing, If that's right then run the higher octange, It's hard to find higher octange around here without ethonol, But since bikes don't have converters to worry about like cars then don't see a problem, The ethonol makes the fuel burn cleaner but you lose some of the punch. Certain cars too much ethonal will mess up o2 sensers and converters.

Thanks my take on it anyway.

 

Pinging is usually caused by one of two things. Generally, as Gearhead has stated, ignition timing is the main cause. But a lot of Yammies are fixed ignition and can't be adjusted. Other timing issues can occur of course. Definately worth looking at in case a PO has "modded" the timing plate. A mate bought a brand new XJ900 Diversion in the early nineties and it pinged out of the box. Dealer fix was to elongate the non adustable timing plate holes. 8O

The other choice is mixture. If it's running too lean then light pinging can occur. Particularly once the engine temp gets up a bit. Try a quarter turn richer and see if it makes a difference.

I can't think of any manufacturer of any vehicle prior to 95 recommending use of anything other than regular.

 

octain ratings in different parts of the country are different. Primeum here in colorado springs is 89 octain. Good luck finding 91. The cheep stuff is 85 octain and mid is 87. And we pay just as much for the 89 crap out here as you pay for the 91 elsewhere in the country. I run the 87 and dont have a problem. Keep in mind I am at 6000 feet. So as to theoretically need lower octain. Beats me how it all works.

 

The specifications on the inside of my 85 xj700 actually call for 91 premium. It also states that I should be using regular not unleaded. It is the original cover. I have even gone so far as to use a lead substitue in mine for this reason. I am concerned that the valve seats are not hardened and might recess into the head witout it.Since there is no catalitic converter on my bike, I would believe the extra lead will help the longivity of the engine and the valve seats. I also usually run the high test 93-94 octane due to the amount of stop and go traffic I encounter which keeps my engine extremely hot in my daily driving. 45,000 miles and still runs strong.