Topic: coils Spark when the ignition switch is turned on!

[mystic_1]

heh yeah reading back I see that you'd already figured that out.  Carry on!

mystic_1

[dave500]

hey terry,i thought the seats were of a hardened steel,unleaded shouldnt hurt them?mine are good 3 years on 98,maybe the ones you fixed had another problem,carbon fouled letting fire through?

[Terry in Australia]

hey terry,i thought the seats were of a hardened steel,unleaded shouldnt hurt them?mine are good 3 years on 98,maybe the ones you fixed had another problem,carbon fouled letting fire through?

G'Day Dave, I don't know if they're "hardened" per se, when the CB750 came out, I think just about every country in the world was still putting lead in their fuel, so considering that Honda were so cheap they didn't use primer on their candy tanks, I'd doubt it?

Having said that, after so many years, the seats and valves are probably "work hardened" anyway, and it did take a bit of work to clean up a couple when I lapped them in yesterday, but I'm sure they'll be fine for a few more years. Cheers, Terry.

[TwoTired]

It's old cast iron heads with the valve seats ground into the base metal that need the lead in the fuel.  Aluminum heads have steel seat inserts, and unleaded is not required to keep them lubricated.  So, wear from unleaded fuel is not an issue if you have aluminum heads/steel seats.
I think just about any steel is harder than cast iron, AFAIK.

Cheers,

[dave500]

i was talking to a triumph bloke a while ago on the same subject and early pommie stuff had cast iron inserts into alloy heads.,im sure the jap stuff is hard steel.

[Terry in Australia]

It's old cast iron heads with the valve seats ground into the base metal that need the lead in the fuel.  Aluminum heads have steel seat inserts, and unleaded is not required to keep them lubricated.  So, wear from unleaded fuel is not an issue if you have aluminum heads/steel seats.
I think just about any steel is harder than cast iron, AFAIK.

Cheers,

Yes and no Lloyd, Aussie Ford 6 cylinder cars built from the late 1970's to mid 1980's had aluminum heads with steel inserts, but when unleaded gas was officially introduced in 1986, the valve seat material was changed to a harder material again (stellite?) to cope with unleaded gas. Cheers, Terry.     

[Deltarider]

It's a bit strange this leaded/unleaded business. I remember back then the official advise from Honda Holland was to tank leaded every fourth time. What I've never understood was the 'memory effect' as BMW named it. They (BMW) said that their models with no hardened seats after some tenthousands km's on leaded could safely switch to unleaded. Anyone?

[IHWillys]

As I understand it, it is a cushion affect of the lead deposits on the seat and valve faces.  The "memory" affect is really just that a layer of lead deposits was built up and would continue doing its thing for a long while.   However, I know this "theory" or concept of what the lead was doing for valves and seats is disputed. 

Also as I understand it, the tetraethyl lead was not in the fuel for the purpose of allowing seats to survive, that was merely a resulting side affect.  The lead was used as a very effective and stable additive to increase the octane rating of the base gasoline fuel.

I used to purchase TEL in gallon containers mixed with kerosene for mixing into premium fuel for my '55 Pontiac as the engine needed higher octane than premium fuel.  Stone Oil Company out of Georgia was the distributor of the product I used, Lead Supreme 130.  It worked great as an octane booster.  I have no idea if it helped the valve seats or not.

Ken