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Old 06-29-2006, 06:08 PM   #1
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One VERY good discussion on motorcycle oil

Ok I hit up the Suzuki Burgman discussion forums to look up info on a 650 I was eyeballing. I happened across this thread about one owner who, when measuring the fluids drained from his transmision. Found he was getting TWICE back what it was supposed to hold. Turns out a bearing went out on a shaft in the tranny and allowed engine oil in. Others checked and were finding some similar things happening in there bikes. So the discussion came up wether a diffrent oil would help and this guy spoke up.

/ all - thanks for bringing this issue to the forum & discussing.

I'd like to weigh in with what I think is happening. Before I do though, I want to set the criterias for comments so that we don't get into the weeds over issues such as whether Castrol Synthetic is a true synthetic vs Mobil 1 or AMSOIL, etc etc and lose sight of the bigger picture. My comments are made both as a Mech E (Masters) who has taught Systems Engineering at the university senior year level for over 7 years and as a fleet engineer (qualified to operate steam, diesel & gas turbine ships, was the Engineer for a squadron of ships under harsh operationg conditions and was the Q/A Officer on a nuke carrier.) As such I did a lot of troubleshooting and material failure investigations / analyses. So the following comments are made from that perspective.

Proposed diagnosis: As alluded to already, I concur that the likely culprit is one of inadequate lubrication - specifically viscosity break down / thinning and use of oil not meant specifically for motorcycles. This is not a slam on anyone here, so please read on before launching. Keys to that diagnosis are scoring / wear on shaft & seals and "oil transfer" during hard runs from the engine sump to the transmission sump via the clutch shaft seal.

Proposed solution: use synthetic oil in both engine & CVT sumps, change frequently and use oil that specifically meets as many of the specifications in the owners and tech manual as possible: 10w-40, SF/SG, SH/SJ/JASO MA. The latter - JASO MA - ensures that it is specifically designed for motorcycles' high revving engines with wet clutches, such as the Burgman 650 series, and is more resistant to thermal / shear breakdown. Both JASO MA and SF/SG/SH should ensure enough Zinc content to protect against metal to metal wear. And go synthetic.

Discussion: The above recommendation has already been basically discussed as a solution. What I want to do here is try to add some more value by discussing why.

Oil does 4 things, or should: clean, cool, lubricate & seal. But which to choose from? The choices and specs are far more complicated than they were even 10 years ago.

To begin with - I think that Suzuki should do a better job of clarifying what oil specs must be adhered to when servicing the Burgman. For example, the Owners Manual for the '06 Burgman 650 on page 2-4 has a table that recommends SAE 10W-40 API SF/SG on the 1st line, or SAE 10W-40 API SH/SJ with JASO MA beside it on the 2nd line. Then it has a column describing JASO T-903 MA standards. But does not specifically make any recommendations about using JASO MA oil. For the transmission, on page 2-5 of the Owners manual, it recommends using "...a good quality SAE 10W-40 multi-grade motor oil" with no API classification recommendations. Yet the most current 2006 Factory Service Manual on page 1-5 recommends using SAE 10W-40 API SF or SG oil for BOTH engine & transmission. Hmmm. That is helpful. If there is concurrence on this - we/I / moderator can put in a posting to Suzuki on this issue of clrification. But, bet it won't get far since the lawyers will delay everything. Yeah - I am a cynic.

To further the confusion, most motor oil bottles currently on the shelf are stating that they meet API SM specs and imply or out right state that SM specs supercede all previous specs. In addition, some conventional oils like Havoline state that the oil meets JASO "valve train wear" standards. But JASO MA is not mentionned. ( ) Note - I used Halvoline as an example since it was stated that it was used in the transmission in one of the cases above.

But is this really true? That SM rated oils meet all previous requirements and truly supercede earlier API classifications? And are all 10w-40 oils equal? Well not really. Lets look at SAE 10w-40 oils to start with.

Conventional 10w-40 oil has a viscosity range of 30 (40-10). Same as 20w-50. But to get the 10w-40 viscosity requires adding more viscosity improver (VI) polymers than for 20w-50 oil. So what? It means that 10w-40 conventional oil has less oil in a liter than does 20w-50. Less oil to lubricate. Which is why GM stopped recommending 10w-40 oil after finding a lot of engine problems with it. the following are a start on the topic:
A full synthetic oil is a different case, since the base oil stock is so much "purer" in terms of carbon chain lenght variance so that one can get a true 10w-40 multi viscosity oil with far less use of VIs.

The 2nd thing to look at is do current off the shelf SM oils really meet SF/SG/SH requirements? By my reading - the answer is no - both by experience and reading the literature. In the late 90s a new oil spec came out and I saw a marked difference in the oil that I was using at the time (Castrol Syntec) - it went from clear to light brown, and dropped its diesel classifciation (Cx series) which meant to me that it had lost its ability to protect against metal to metal wear when under high pressure (diesels typically operate at 18-22:1 compressions, while cars operate at some thing like 8+-11:1). And reading various forums on the web (see above 3 examples) , I saw that the Zinc levels were dropped to meet EPA emission standards. So clearly something happened when oil manufacturers switched somewhere around the SJ period.

Now the Burgman 650 is rated at a compression ratio of 11.2:1 which is high if it were a car, and operates at high RPMs (red lines at 8500) compared to a car. In addition, I would bet that as the CVT pulley halves "squeeze" together, that they cause a linear thrust to be placed on the shaft (see TechMan page 5-5 CVT exploded diagram) especially if driven hard. The latter is just a guess but a pretty fair bet at that. And the engine oil also serves double duty lubricating the wet clutch - which has to be an added source of shear & thermal stress on the oil molecules.

To address problems with car motor oils in motorcycles, the Japanese manufacturers created the JASO motorcycle standards starting in 1994. The following link does a better job explaining the JASO standards in plain English - so I will leave it to you to read and save space here:

Bottom line is that an oil in a motorcycle that meets SG, SH & JASO MA requirements should be better at preventing shear breakdown of the oil (thinning) under hard use, and in the event of thinning, have enough Zn to protect against metal to metal wear in the event of oil break down. Because of the issue with 10w-40 conventional oil needing more VI polymers added - with resulting loss of lubricating oil on a volume for volume basis - a synthetic 10w-40 oil is the better choice.

Based on the above analysis, I personally use Mobil 1 MX4T 10W-40 synthetic oil. There are others out there like AMSOIL, etc; but, I can get the Mobil 1 at Auto Zone for a good price and it is availbale locally with out having to pay for shipping. See link

My guess is that if other owners do the same that they will minimize the occurence of the problem that reported and Jim confirmed. Maybe even help to minimize / mitigate the problkem even if it has already started but not progreessed to the point where there is excessive shaft / seal wear in the CVT.

My .02 and hope that it helps.

More info for gear oil.

Good question on gear oil. Since the specs call for a GL-5 hypoid gear oil that is either SAE 80 for under 32 degrees F or SAE 90 for greater than 32 degrees F, I looked for a straight SAE 90 wt GL-5 gear oil and could not find one readily.

I opted for the closest match while getting as much synthetic as possible. So, am using Valvoline Dura Blend (Semi Synthetic mixture) in SAE 80W-90 GL-5 hypoid gear oil. Easy to find in all Pep Boys, Auto Zone, etc and inexpensive. I change it every time I change the engine oil & filter, along with the transmission. See

I looked around at Red Line ( ) which I really like in heavy duty trannys like my Jeep 4 wheel drive limited slip. But it comes in 75w-90. Same goes for my favorite off the shelf full synthetic gear oil, Mobil 1, which is also 75w-90. And ditto for Valvoline full synthetic gear oil. I am reasonably confident that the full synthetic 75W-90 would be fine, but just being super cautious, so did not want go above or below the viscosity specs since not all that familiar with this type of gear drive and still on warranty. And have had good luck with Valvoline Semi Synth gear oil before.
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