Author Topic: ROOKIE Question (Read 21697 times)

kightboy · « **on:** February 15, 2013, 02:43:48 PM »

hi
please pardon me for a rookie question
i had a k75 20 years ago and then a series of R1100 and R1150RTs and always used premium fuel.
now, back to the Kbike and it's amazing smoothness.
for this 1994 k75 - what fuel grade?
i assume the highest octane possible but, then, assuming anything frequently gets me in trouble (with my redheaded wife) !
Chris

frankenduck · « **Reply #1 on:** February 15, 2013, 04:06:46 PM »

K75 rider manual says: "... middle or premium grade."

TimTyler · « **Reply #2 on:** February 15, 2013, 05:13:02 PM »

The recommendations from Germany say 91 octane RON which translates to 86 octane here in the States. That's Regular grade; usually the least expensive at your local pump. Lift up your seat and read the black label there for your bike's fuel recommendation.

I did 7000 miles coast-to-coast and back last summer in a short period of time and I kept a mental log of the mpg and performance of my K75 during the trip using all different grades, brands, and ethanol content. The only gains I recognized were experienced using ethanol-free fuel. Octane didn't seem to matter at all.

My local pump offers 89 octane ethanol-free so that's what I usually use.

motodude · « **Reply #3 on:** February 15, 2013, 06:48:56 PM »

I have about 122,000 miles on K75's and have always used, "Regular". Which around here is 87 octane as measured the way they measure it here. Or something.

Tom

argent brick · « **Reply #4 on:** February 15, 2013, 07:13:36 PM »

It does not seem to make any difference what I burn here around San Fran and the Bay Area counties. The State of California its own idea about what it calls fuel. 91 or 87 octane, I can't tell a big difference. It's all junk.

Chaos · « **Reply #5 on:** February 15, 2013, 07:21:49 PM »

Mine's always had regular, 185k. I'd stay away from any ethanol blends though, or burn it out as soon as passible.

argent brick · « **Reply #6 on:** February 16, 2013, 12:53:07 AM »

I would too, if I could. I would love to find real gasoline around here somewhere.

Qdude · « **Reply #7 on:** February 16, 2013, 05:14:45 AM »

between the Ethanol and regular blends, I have found no taste difference at all.

motodude · « **Reply #8 on:** February 16, 2013, 10:36:40 AM »

Let me amend my previous statement.

I have run what was called super when it was, "e0" (no alcohol). But that is a recent development. You'll notice your gas mileage increase with "e0" but that is a function of the missing alcohol not so much the octane rating.

Tom

Niemand · « **Reply #9 on:** February 17, 2013, 11:18:23 PM »

In case anyone is not familiar with this website to help find ethanol free gas... (Sorry, Lynn, only northern Cali apparently.)

http://pure-gas.org/extensions/map.html

argent brick · « **Reply #10 on:** February 17, 2013, 11:38:06 PM »

Yeah, I just can't win. I have to drive about 4 hours to get some real fuel.

Lawrence · « **Reply #11 on:** February 18, 2013, 12:18:56 AM »

This thread is basically addressing fuel requirements for K75s. Can I assume the K100 bikes need the same standard of fuel?

TimTyler · « **Reply #12 on:** February 18, 2013, 01:51:49 AM »

Quote from: Lawrence on February 18, 2013, 12:18:56 AM

Can I assume the K100 bikes need the same standard of fuel?

Yes. They just need 33% more :)

argent brick · « **Reply #13 on:** February 18, 2013, 03:35:08 AM »

I would have guessed 25% more.

2000rsv · « **Reply #14 on:** February 18, 2013, 07:06:43 AM »

Quote from: argent brick on February 18, 2013, 03:35:08 AM

I would have guessed 25% more.

Nope, the K75 would use 25% less than the K100, but the K100 would use 33% more than the K75. :hmm:

Percentages are like that.

Where's the 'Hot for Teacher' emicon?

argent brick · « **Reply #15 on:** February 18, 2013, 02:21:19 PM »

It all depends upon how you crunch the numbers. It is amazing how you can get numbers to say anything you want. The politicians do it all the time.

My 25% comment was based upon the the idea that you have a four piston motor in the K100. Take one away and you now have a K75. Twenty-five percent less motor = 25% less fuel used.

frankenduck · « **Reply #16 on:** February 18, 2013, 02:51:24 PM »

Factory specs are 47 MPG for a K100 and 56 MPG for a K75 at 90 KPH.

Though very similar they are also very different - compression ratio, weight, gearing, etc...

Lawrence · « **Reply #17 on:** March 11, 2013, 04:11:31 PM »

Okay Dr. Duck, I'll bite. Which has the higher compression ration, K75 or K100 series?
As an aside, the mileage returned by my 1985 K100RS seems to coincide perfectly with the figure you stated. I'm a happy rider! Doubly so due to the fact I have access to E-0 fuel in both regular and super blends. Life is good!

wmax351 · « **Reply #18 on:** March 12, 2013, 11:46:10 AM »

K75 has higher compression.

But that's at 90kph. When do you actually ride at that speed? :dunno

Will get about 27mpg, WFO at 120 mph. Actually pretty impressive.

Lawrence · « **Reply #19 on:** March 12, 2013, 02:55:48 PM »

"K75 has higher compression.

But that's at 90kph. When do you actually ride at that speed? :dunno "

90 kph would work out to about 50 mph. I reckon we do a fair bit of riding at that speed. Second, you believe the compression ration changes according to engine speed? Just how does that work???

wmax351 · « **Reply #20 on:** March 12, 2013, 03:46:02 PM »

Quote from: Lawrence on March 12, 2013, 02:55:48 PM

"K75 has higher compression.

But that's at 90kph. When do you actually ride at that speed? :dunno "

90 kph would work out to about 50 mph. I reckon we do a fair bit of riding at that speed. Second, you believe the compression ration changes according to engine speed? Just how does that work???

The compression is a fixed quantity. The Cam profile has an effect on the effective compression ratio.

pdg · « **Reply #21 on:** March 12, 2013, 05:16:04 PM »

90kph = 55.92mph (might as well be pedantic about it :neener: ) Given the spread of speed limits in Europe, 90kph is a convenient middle ground for manufacturers to aim for maximum MPG.

As said, the published compression ratio is a fixed quantity, simply calculated with the combustion chamber size at TDC compared to BDC. That's the static compression ratio.

Dynamic compression ratios are where the cam profiles come into play (amongst a few other things) - the less valve overlap there is the higher the dynamic compression (etc.)

I think wmax351's comment was split - stating that the K75 engine has a higher static compression ratio, then going on to say that the factory MPG figures are calculated at an average 90kph.

latunabernie · « **Reply #22 on:** March 12, 2013, 05:33:08 PM »

Hi Chris,

I have a 1987 K-75 C
I use regular gas 87 octane.
Calif. has been getting screwed with gas prices.
Regular is 20 cents a gallon cheaper than Super.
Regular cost $4.29 in the L. A. area.
Came down frpm $4.31 last week.

Bernie in So. Cal.

pdg · « **Reply #23 on:** March 12, 2013, 06:24:04 PM »

I so WISH we got screwed that badly with fuel prices here...

Regular unleaded is currently about £1.40/litre. That works out to about $7.90/US gallon. Super unleaded is usually £0.10p more per litre (about 56 cents/US gallon). Apparently, the price is due to go up again soon too.

frogy · « **Reply #24 on:** March 12, 2013, 07:46:19 PM »

I have always told my friends when they complain about fuel prices,"get on the internet and check the rest of the world".It didnt work ,they still bitch. :loco:

News:

Author Topic: ROOKIE Question (Read 21697 times)