Lead Replacement Fuel Additive

[MentalScientist]

Hi Yall,

Does anybody know if you need to use a lead replacement fuel additive on a 1986 43F?

Thanks.

[motorang]

Yeah me.
No you dont. The engine (valve seats) is fine with unleaded fuel, however there is a minimum octane rating, equals to European ROZ 91 Octane.
So you might want to carry an Octane booster if you travel abroad (some parts of the ex Sovjet Union etc only have 70-80 Octane available especially in rural areas).

Andy

[MentalScientist]

Nice one fella, thanks for the advice.

:)

[scottieh]

Regarding octane, i have an 85 43F that has consistently run 85 and worse octane for many years. I rebuilt two of my engines with a copper gasket that slightly reduced compression for touring through mexico and central america and it worked down there without a problem. No pinging, no knocking.

I once had a high comp wiseco piston fitted on a stock bore 43F and it needed damn near 100 octane to run without pinging, and man that thing ran like a bat out of hell. If i used anything below 100 it sounded like gunfire between my legs. Crazy knocking.

[MentalScientist]

The reason I was asking is because when I run the bike at around 70 on a dual carriageway, it starts knocking quite heavily when I release the throttle. Never had this on a bike before and I'm thinking this might be pinking.

Off to Portugal on Sunday so I'm hoping the bike makes it around!

Thanks for all the advice I've had in the past on the rebuild. I'll try to throw up some pics of the restoration when I get back.

[motorang]

Hi
There are different Octane ratings around.
In Europe we use RON/ROZ.
In the US the AON system is more commonly used.

AON 87 = RON/ROZ 91
AON 89 = RON/ROZ 93 (normal)
AON 91 = RON/ROZ 95 (super)
AON 93 = RON/ROZ 98 (super plus)

rule of thumb: AON + 4 = RON/ROZ

My XT600 1987 engine came with a European "Normal" fuel recommendation which was 88 ROZ for leaded or 91 ROZ for unleaded fuel then.
For the US "regular gasoline" was in the spec sheet.
I am running it with unleaded ROZ 91 or later ROZ 95 (Eurosuper) since there is no 91 around any more, or for the same price as ROZ 95.
No problems in the valve or piston department.

The later XT600E models (2000 and newer) have a requirement of RON/ROZ 91 unleaded in the manual, most likely because there was no lower Octane unleaded fuel around.

Thats all for stock piston etc. Any tuning (higher compression piston, racing camshaft, different carb ...) may require different fuel.
Heavy knocking is NOT a normal thing with those engines. You may be safer with 100 ROZ fuel as long as you do not know the reason for that.
Are you sure it can not be a loose primary drive nut? Sounds very "knocking" as well, engine case, front right side just where the oil filter sits. Easy fix, even when on the road, with engine in frame.

Andy

[MentalScientist]

Thanks Andy for your response. I guess I'll put the best fuel in that I can for this trip.

The knocking sounds like a top end thing but I'll check all the bolts and fluids etc before I head off.

Thanks again,

Simon.