Hi All,
I'm new to Australia and learning as I go here. I've read thru the old octane threads and have a come away with a fair bit of new knowledge -- thanks. But I'm hoping to squeeze a bit more out of your brain-bank.
I just drive my m750 600km this weekend. Before leaving I replaced my plugs and they looked much darker than usual. On the last leg of the journey she started running rough, surging a very small bit on constant throttle and feeling bogged down in the low RPMs.
I pulled the plugs again this AM and they are black and fouled, but dry.
During the trip the weather was a cool 14-16°C and I ran the best gas I could find, never less than 95 octane (Australian, RON).
Rather than mentally weigh the myriad of pros and cons to lower octane vs. greater octane and loose myself in every nuance of the threads, I drove to the BP and filled it up with 91 to see for myself.
After a few km the bucking had all but stopped. By the time I drove home, about 15km, the lugging feeling at low RPMs had all but cleared up. BUT, it does idle a tad faster and requires a throttle goose to drop the RPMs back down. We're not talking a huge RPM gain here, and I'm not concerned if this is the only symptom.
My questions stem from the (mis) information I've been living with for years, being new to Oz, and what I've read here:
Is the displayed octane in Australia RON, will 91 cause issues when the weather warms up, or did the mech miss something on my last tune up a few weeks back?
The bike is a 2000 m750 with carbs and 15,000km on it and its entire life has been fed US octane with a 93 rating.
Thanks for any advice and I hope these questions are new enough to prevent the masses from getting up in arms about "another octane thread".
http://en.wikipedia.org/wiki/Research_Octane_Number#Measurement_methods (http://en.wikipedia.org/wiki/Research_Octane_Number#Measurement_methods)
We use RON in Australia. Unless you've got high compression pistons, you should run your bike on the lowest octane you can get (except for E10, which causes problems) to avoid fouling. I generally use 91, and only use 95 when I'm unable to find 91.
Quote from: suzyj on August 08, 2010, 11:21:35 PM
http://en.wikipedia.org/wiki/Research_Octane_Number#Measurement_methods (http://en.wikipedia.org/wiki/Research_Octane_Number#Measurement_methods)
We use RON in Australia. Unless you've got high compression pistons, you should run your bike on the lowest octane you can get (except for E10, which causes problems) to avoid fouling. I generally use 91, and only use 95 when I'm unable to find 91.
Really? I have a S4R and the manual says to use premium unleaded, at least 95 RON
KPhinney, you might want to check your needle jets. Just pull the air filter, lift the slides and look at the jets. If they look oval you found your problem.
some of our 98 octane fuels are denser, and have been known to cause issues with fouling. but the fouling caused by higher octane fuels is just a symptom of the worn needle jets. with good needle jets it shouldn't foul on any fuel. it doesn't need anything higher than our 91 due to the std low compression. it may run better on some brands of 95, but i'd be surprised with a 750. a 4v motor may have different reaction.
Quote from: suzyj on August 08, 2010, 11:21:35 PM
http://en.wikipedia.org/wiki/Research_Octane_Number#Measurement_methods (http://en.wikipedia.org/wiki/Research_Octane_Number#Measurement_methods)
We use RON in Australia. Unless you've got high compression pistons, you should run your bike on the lowest octane you can get (except for E10, which causes problems) to avoid fouling. I generally use 91, and only use 95 when I'm unable to find 91.
Quote from: howie on August 09, 2010, 02:18:24 AM
KPhinney, you might want to check your needle jets. Just pull the air filter, lift the slides and look at the jets. If they look oval you found your problem.
Quote from: brad black on August 09, 2010, 03:03:14 AM
some of our 98 octane fuels are denser, and have been known to cause issues with fouling. but the fouling caused by higher octane fuels is just a symptom of the worn needle jets. with good needle jets it shouldn't foul on any fuel. it doesn't need anything higher than our 91 due to the std low compression. it may run better on some brands of 95, but i'd be surprised with a 750. a 4v motor may have different reaction.
All very good info and helpful. Thanks a bunch. I'll check out the needle jets and let y'all know what I find and probably will end up sticking with 91 despite the stated 95 RON called for in the manual.
For all of those out there who want to chime in with their opinions of the "correct" octane to run please allow me to share my own thoughts;
your bike may be different than all the rest. Try different octane ratings and see how it acts. I've always followed my manual and never thought twice about paying the extra buck for the "good" stuff. I tried and I learned, but only learned what works for me.
Indeed a correct thought, as some engines are borderline.
Update:
Well, I'm of no use to myself. Having looked at a few carbs in my day I'm out of my realm with the one on this m750. Things I've noticed: Regardless of the position of the choke control, the choke slides are staying closed whether the engine is warm or cold, running or stopped. Unless running and accelerating in which case they open slightly but of course all of this is without the engine under load.
Typically I'm used to finding the main jet between the choke valve (if equipped) and the throttle valve. I can't find it on this one. Nothing but clean, smooth metal is visible downstream of the throttle valve as well. Anyone have a diagram?
I went to our local Ducati shop looking for a Haynes manual or the like and they have none. Amazon doesn't sell to Australia, and eBay doesn't have what I need. Still looking, but in the mean time any help is appreciated.
The "choke" has no effect on the slides or throttle, it is a misnamed enrichment device. The main jet is in the float bowl, and for all practical purposes, does not wear out, the needle jet is what wears.
You can find a parts break down here:
http://www.ducati.com/services/maintenance/index.do (http://www.ducati.com/services/maintenance/index.do)
Look up 2001, the carbs are the same.
Here ya go.
http://cgi.ebay.com/ebaymotors/Haynes-Manual-Ducati-600-620-750-900-2-valve-91-05-_W0QQcmdZViewItemQQitemZ170525883478QQptZMotorsQ5fManualsQ5fLiterature (http://cgi.ebay.com/ebaymotors/Haynes-Manual-Ducati-600-620-750-900-2-valve-91-05-_W0QQcmdZViewItemQQitemZ170525883478QQptZMotorsQ5fManualsQ5fLiterature)
http://cgi.ebay.com/ebaymotors/HAYNES-REPAIR-MANUAL-DUCATI-600-620-750-900-91-05-_W0QQcmdZViewItemQQitemZ380254461511QQptZMotorsQ5fManualsQ5fLiterature (http://cgi.ebay.com/ebaymotors/HAYNES-REPAIR-MANUAL-DUCATI-600-620-750-900-91-05-_W0QQcmdZViewItemQQitemZ380254461511QQptZMotorsQ5fManualsQ5fLiterature)