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Electra Tappet clearance

Submitted by nicholas_clarke on Tue, 14/11/2023
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Light Twins

Dear all, 

As I revel in the eclectic joys of Electra ownership I have just noticed a discrepency between the technical information for rocker / tappet clearance between my usually trustworthy 'Norton Twin Cylinder Rebuild Manual'  (photo attached) and my recently received original Norton Electra Owners manual and provisional parts list (second photo attached).   The rebuild manual quotes Electra clearance as 6 thou inlet and 8 thou exhaust where as the original Electra Owner's manual which would have come with the bike quotes 4 thou inlet and 6 thou exhaust - the same as the Jubilee and Navigator.   Before I adjust them can experienced owners confirm that 4 thou and 6 thou are the correct settings?

Cheers   Nick 

Attachments
Manual.JPG
Tappets.jpg

Submitted by peter_holland1 on Wed, 15/11/2023

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As a Lightweight owner in late '60s, it seemed the tappets always needed re-adjusting. 

I read somewhere that larger clearances were suggested for continuous peak power in hot countries.

I set the inlet clearance by lightly clamping a 6 thou feeler with the rocker adjuster. Use left hand. And tighten the adjuster clamp with an 11 mm open end spanner. Use right hand. Drag the 6 thou feeler out and check a 4 thou feeler sips in.

Same with exhaust using an 8 thou feeler.

On later lightweights like yours the larger adjuster clamp bolts generally keep adjusters in place. So the gap seldom gets larger. Settling head and cylinder base gaskets soon close the tappet clearances. Been discussed on your head gasket query.

There must be other ideas.

Cheers.  Peter 

Submitted by andy_sochanik on Wed, 15/11/2023

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Tappet clearances for ALL Lightweights are: Inlet = 4thou; Exhaust = 6thou

I have heard of running them tighter for racing, 2 & 4 thou, BUT I have NOT seen any other figure quoted - both the Twin Cylinder Manual & the Provisional Manual & Spares List state the above figures.

See attached (1) Extract from the Twins Manual, and (2) pages from the Electra Provisional Manual & Spares list.

Attachments
Scan_0001.jpg
Scan_0003.jpg
Scan_0004.jpg

Submitted by michael_ball on Thu, 16/11/2023

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“I have heard of running them tighter for racing​​“​​

 

The Electra race is when I go and buy a burger.

Submitted by alan_osborn on Thu, 16/11/2023

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Racing an Electra??? Sounds a bit silly. Thanks Andy.

Submitted by nicholas_clarke on Fri, 17/11/2023

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Hi Andy and Peter,

Thanks for confirming this - I was led astray by my normally reliable 'Veloce Press' reprint of the Norton 'Twin Cylinder Manual' which eroneously shows the Electra's Inlet clearance as 0.006" and the exhaust as 0.008" - the same as the Heavyweight twins.  I was in a rush when I was setting them and noticed they were different from the Jubilee and Navigator and should have looked a little further - had I done so I would have noticed that they have also miss quoted the Navigator exhaust clearance as 0.066".  Now that would be noisy!!!    Lesson learnt to always double check when you notice something out of the norm.   

I have reset them today and it is sounding better and I have re-torqued the head iaw the manual to 15 ftlbs and used double rocker box gaskets with a smear of blue Hylomar in a bid to cure the illusive oil weeping from the front of the heads.  The weather was too foul for a proper test run and although an eternal optimist I have a sneaking suspicion from all the evidence it is the head gaskets leaking round the front studs.   A job for this winter perhap......

Thanks again for all the help - the Electra is a real joy and has exceeded expectations!   But I mustn't let it distract me from starting the Navigator rebuild......that blue is absolutely stunning!

Take care out there.   Nick 

Attachments
Lightweight Tech Data page.jpg
Manual front page.jpg
Manual back page.jpg

Submitted by robert_tuck on Sun, 19/11/2023

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I am an inveterate experimenter , and have "played" with clearances on the 99  ,Atlas and  the Ducati.. I dislike clatter . I suspect your bike would run quite happilly on 3 and 5 thou providing its use is confined to pootling around on lanes and B roads . The SS and Daytona cams are very similar and the extra clearance probably just allows for more expansion when being ridden at continuos  high speed . Valve timing is very slightly altered and this effect may be used to advantage if maximum power from  optimised timing is desired  and a bit of extra clatter is accepted. I will be "experimenting" on my production racer 650 project  and will post any interesting results.

 


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