Vintage Dirt Bike Q & A
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Dual Plugs
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Author:  newfie [ Fri Jun 10, 2005 8:50 am ]
Post subject:  Dual Plugs

Hi everyone,
I have a '74 MT250 and it has to spark plugs with only 1 plug wire. What is the reason for this?
Newfie

Author:  ricortes [ Fri Jun 10, 2005 9:16 am ]
Post subject: 

They come from the factory with a bolt/plug in one of the holes. This gives you the option of
1) Do nothing and just leave it like it is with one plug
2) Add a compression release valve, only necessary if you bump compression up IMO
3) Put two plugs in and if one fouls you can just switch the plug wire over to the second plug to get going again.

I like the #1 option myself but no harm with #3.

Author:  newfie [ Sat Jun 11, 2005 8:43 am ]
Post subject: 

Is there any difference in performance in either the angled plug or the straight-up plug?
Thanks,
Andrew

Author:  ricortes [ Sat Jun 11, 2005 9:43 am ]
Post subject: 

Not that I can feel. There's probably someone with a dyno test that will say one position gives an extra 1/2 hp over the other.

IMO: Just use the plug that goes on top. If you don't have a problem and want to restore it to factory original, buy a fitting for the second hole.

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