Triumph Rat Motorcycle Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
Hi,

Should I be using a lead substitute in my 1947 T100 Tiger? What about marvel Mystery Oil? Both have been suggested to me.

Thanks,
Wayne
 

·
Registered
Joined
·
348 Posts
yes and no.

if the vavle seats have never been replaced than it will need lead additive. if they been changed out than normal gas is good.

as oil run whatever you like (brand wise)
 

·
Registered
Joined
·
970 Posts
If it were me I would just run it. The T100 had alloy head and Triumph always used good valve seats so they probably fine. If not and they do erode, then fit a new pair of exhaust seats and you will be 'upgraded', but I doubt you will need it.

Make sure tappet adjustmenst are correct and ignition timing about right and I would be very surprised if you ever have any problems.
 

·
Registered
Joined
·
2,934 Posts
I add lead to my gas. Even as late as '70, Triumph was saying 'recommended 97 octane, minimum 95' and that was leaded gas. Of course, I think they calculate octane differently ... anyway, I use this stuff.
Why not just run leaded Sunoco racing fuel; 110 octane, mix it down with pump premium and get the octane and the lead without hoping that the additive is compatible with the continuously varying pump gasoline formula.
Last time I bought it the cost was about $8/gallon.
Mix with 3 parts 93 premium at $2/ gallon and it's a reasonable 97 octane solution.
 

·
Registered
Joined
·
810 Posts
I have the 8 bolt 'cracked head' design on my 59. When I put the top end on, I wasn't planning on keeping it, swapping it for a 9 bolt with unleaded upgrade. I never got around to the swap! I retarded the spark about 1 degree and lowered compression; also don't demand a lot from the motor, just ride it easy. This was recommended in an article of 'classic bike' back in the 80s, because of the fuel octane was getting lower and lead removed. One thing the article mentioned was the lead helped lubricate valve guides and so SOME manufactures took advantage of that and made cheaper valve guides, some didnt, so unleaded didn't matter with the ones that used better material! Anyway, to my surprise my cracked head runs well on low octane. I had to rejet the monoblock because the plugs would foul, but once the fouling was remedied. It runs great! I can run 87 octane, sometime 92 and the kicker never kicks back, starts easy and runs smooth, dosen't ping and stays cool. It would have to idle a long time to overheat it. I rode it a lot from 2004 to Nov 2008 and never change the plugs. I didn't have this luck with 67 -69 Bonnies but it helped. I never got the 9 bolt for lack of funds, so I haven't disassembled it to see what is really happening. Maybe you might put some lead additive periotically, just for good measure. I should have done that myself and probably will this next season. But if you got the bike apart and can afford unleaded changeover, that would be the best. Just take it easy, these old bikes are up against physics like stress metal fatigue rust, funky fasteners Etc. My motto is instead of hopping up the engine for more power; de tune it. It's easier on the butt and arthritis.
 

·
Registered
Joined
·
970 Posts
Red gives a good post. AS regards octane, just afterthe war most fuel in the UK was 'pool petrol' 65 octane. The 7:1 Triumphs ran well on it. I think you can probably get away up to 9:1 certainly 8.2:1 ( with the alloy heads) Only older Thunderbirds have cast iron heads.
 
1 - 8 of 8 Posts
Top