Inspection 1200 TS

mcdammitt

mcdammitt

New member
Location
N.W.Lower Michigan
Hello,
I am in the middle of inspecting top end parts and all the valve springs are around 33.5 free length. My book is telling me 42mm free length. What is it?
Scott
 
is this a 1980 model bike ?
your short valve springs tell me that it is

after the cylinder head issues in 1979 the factory made a change to the valve springs and top collet plate on the 1980 bikes which proved to be not so good
they changed to shorter valve springs with a different collet plate but that meant that is a very short period of time the closed seat pressure approached zero lbs so the valves bounced on their seats and thus wore out very quickly
if your valves had deep groove marks in them that is the reason

factory changed back to the 43mm valve spring set up in 1981 so the short springs are only found on the 1980 bikes
you would be best to buy a set of 43mm springs and a set of correct collet plates and use them on any rebuild

 
they also had shorter valve buckets (correctly called tappets) and since yours will have created wear on the cylinder head bores for them, it would be best to retain them, even if they are a bit short, but better would be to accurately hone the tappet bores and fit new long type.
I have mixed feelings on this one tho'
CLEM
 

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The shorter tappets were fitted to just about all later engines.  They also have a larger ID to cater for the double valve springs, making them the lightest, and therefore the most desirable of them all...

Lots of 100000+miles 120s running fine with these buckets/tappets/whatever. :D

piet
 
Yes it is a 1980, so valve springs, collets. Also I have a picture of the exhaust valves. Would you guy comment on these? What is the length of the short and long tappets?
Thanks for the input.
Scott
 

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mcdammitt said:
Yes it is a 1980, so valve springs, collets. Also I have a picture of the exhaust valves. Would you guy comment on these? What is the length of the short and long tappets?
Thanks for the input.
Scott
Click to expand...


Curious?.........why does the middle valve look different ?.....where the stem meets the head.

Always interested,and slightly worried when i hear about the 1980 heads and their short valve springs,two of us run 1980 Jota's and I often wonder what is fitted to ours. ::)............did they create warranty issues back in the days?
 
Schurminater said:
Curious?.........why does the middle valve look different ?.....where the stem meets the head.

Always interested,and slightly worried when i hear about the 1980 heads and their short valve springs,two of us run 1980 Jota's and I often wonder what is fitted to ours. ::)............did they create warranty issues back in the days?
Click to expand...

Bike is now almost 40 years old and probably has had a valve replaced, for whatever reason.  Not every dealer/engine builder/backyard bodger used factory OE replacement parts.  Even these differed slightly over the years.

Many of these engines caused bother in one way or another, quite reasonable to assume many issues were rectified while they were relatively new.

piet
 
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