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Discussion Starter · #1 ·
i have a 63 T120C Bonnie with the 11:1 pistons in it.
i have to replace the valve guides, the guides themselves are the same sizes as the 6T and TR6 but the springs are a bit longer (white dot) outer (2 1/32") and inner (1 3/8")

i have a set of the 6T TR6 springs (red dot)that measure outer(1 3/8") and inner (1 17/32").

everything else seems to be the same, the valves and guides.

can this be used in place of the longer springs with no damaging effects or is this not interchangeable?
hoping somebody has come across this and has some input, thanks, mike.
 

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Discussion Starter · #2 · (Edited)
upon decarbonising the piston heads i found that the pistons are not the 11:1 that are supposed to be there but are 9:1 that i matched to a 72 650 parts book.

what i could read on the dome was ID.15 and then E9488.

hope this helps.

edit: while cross referencing part numbers i guess i have answered my question, i can use the 6T, TR6 springs i have. but i wonder why i have the longer springs in it now? what would be the gain? or perhaps if whenever the pistons were changed they kept the TT special head configuration.

oh well, now i can fix it and get back on the road.

if anybody has any remarks about this i would still appreciate them. thanks, mike
 

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Discussion Starter · #3 ·
well i found out why the guide broke.......
the hole in the head is worn so a new guide just slides in full seat. not good.
i'm at a loss of what can be done at this point.
i didn't find an over sized guide for sale anywhere.
how about using the heavest duty locktite? or yamabond?

any help please, this old girl can't be finished yet!

mike.
 

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They make ovesized guides but you need to have the bore checked to find out what size it is before ordering. They need to be an interference fit. I think you might have some luck with the Kibblewhite web site.
 

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Overlength springs may have been used to co-exist with lumpy cams; you might want to check the spec.

Jimmy hit it concerning the guide bores; they need to be looked at and possibly re-bored, then appropriate oversize guides fitted. (they are available up to .008 over, I believe)
 

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Discussion Starter · #6 ·
thanks, i'll have to take this to the local shop i guess, machining is out of my scope.
 
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