BritBike Forum logo
BritBike Sponsor BritBike Sponsor BritBike Sponsor
BritBike Sponsor

BritBike Sponsor

BritBike Sponsor
BritBike Sponsor BritBike Sponsor BritBike Sponsor
JRC Engineering dealers
Home | Sponsors, Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons, "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Member Spotlight
Beach
Beach
West Virginia, United States
Posts: 686
Joined: August 2012
Show All Member Profiles 
Shout Box
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
Who's Online Now
27 registered members (998John), 194 guests, and 435 spiders.
Key: Admin, Global Mod, Mod
Newest Members
Gtommy, Stew Dempsey, JoeBrown, Bart223, Duckster
10175 Registered Users
Top Posters(30 Days)
Lannis 105
reverb 90
Stuart 68
koan58 68
L.A.B. 54
Popular Topics(Views)
555,042 mail-order LSR
Forum Statistics
Forums34
Topics66,612
Posts645,585
Members10,175
Most Online3,995
Feb 13th, 2017
Like BritBike.com on Facebook

Previous Thread
Next Thread
Print Thread
Rate Thread
A 65 rocker ratio #709847
09/27/17 4:33 pm
09/27/17 4:33 pm
Joined: Aug 2001
Posts: 247
Duesseldorf/Germany
Phil in Germany Offline OP
BritBike Forum member
Phil in Germany  Offline OP
BritBike Forum member
Joined: Aug 2001
Posts: 247
Duesseldorf/Germany
Hi all,

I do have a possible issue. Together with a mate I have come across a '70 A 65 Lightning puzzle. We could not resist and bought it. grin

The cylinder head has already been refurbished with new Colsibro guides and new Nucleus valves.
What makes me feel slightly uncomfortable is a measurement I have taken on the guides. The valve stem ends do protrude through the guides only 22 mm, every other head I have in reach shows a measurement of 24 mm.

10 years ago I had my own Lightning head refurbed at the shop which did the current head as well and I ended up with too long guides. The collar had hit the guides with a hot engine. Of course this went along with nasty noises. eek

If I do assemble the top collar with the collets to a naked valve I measure around 11.5 mm from stem end to the collars bottom end. This leaves me with 10,5 mm available travel for the collar when the valve is opening.

The cam is a standard 68-0437 with .306" lift resp. 7.8 mm. If the rocker Ratio was 1:1.2 I I'd end up with 9.4 mm valve lift or about 1 mm clearance.
My gut feeling is that this will not suffice due to the dynamic behaviour of the valve train and thermal expansion.

Is my assumption regarding the rocker ratio reasonable? Unfortunately I could not find a figure with the search function on the forum.

I am inclined to get the guides shortened by 2 mm.

Can you help me out with any input regarding my issue?

Thanks in advance and best regards

Phil


Best regards
Phil
Duesseldorf/Germany
'62 A 65 Star (disassembled)
'69 A 65 Lightning
'71 A 65 Firebird
'75 T 160
'84 Yamaha SR 500
Support your #1 BSA Forum and our favorite sponsors

Check out BSA on e-bay: BSA Parts in UK, BSA Motorcycles in UK, BSA Parts in North America, BSA Motorcycles in North America

 
 
Re: A 65 rocker ratio [Re: Phil in Germany] #710648
10/05/17 10:25 pm
10/05/17 10:25 pm
Joined: Aug 2001
Posts: 3,758
argyll. scotland, uk
gavin eisler Offline
BritBike Forum member
gavin eisler  Offline
BritBike Forum member
Joined: Aug 2001
Posts: 3,758
argyll. scotland, uk
Yes I had an issue, i had oversize inlet valves fitted, the new seat left the valve very proud in the combustion chamber, leading to piston clearance and valve binding issues, once the seat was cut 0.070" deeper normal service was restored, so not really a valve guide problem. Using the stock spit cam and valve springs from SRM , no issues 3K later, ( I dont push the rev ceiling very hard , its seen 6.5 k a couple of times.),
I dont know about rocker ratios, I believe Mark Parker has special rockers with offset buttons to get more travel.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A 65 rocker ratio [Re: Phil in Germany] #711244
10/11/17 9:15 pm
10/11/17 9:15 pm
Joined: Aug 2001
Posts: 247
Duesseldorf/Germany
Phil in Germany Offline OP
BritBike Forum member
Phil in Germany  Offline OP
BritBike Forum member
Joined: Aug 2001
Posts: 247
Duesseldorf/Germany
Hi there,

I have now done some measurement on the rockers. The inlet ratio seems to be 1.11, the exhaust ratio 1.16.

Anyway, I have shortened the guides to give me peace of mind. With the valves pushed to the seat the valve stems now protrude 24 mm resp. 15/16" in your money through the guides.

FWIW

Cheers!

Ph.


Best regards
Phil
Duesseldorf/Germany
'62 A 65 Star (disassembled)
'69 A 65 Lightning
'71 A 65 Firebird
'75 T 160
'84 Yamaha SR 500

Moderated by  Allan Gill, Jon W. Whitley 


Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | "OLD" BritBike Forum | DVD- Manuals & Parts books | BritBike Stickers & Decals
Upgrade to: Premium Membership | Premium Life Membership | Vendor Membership | Site Sponsor Membership
Powered by UBB.threads™ PHP Forum Software 7.6.1.1
(Release build 20180111)
Page Time: 1.846s Queries: 15 (0.004s) Memory: 0.9961 MB (Peak: 1.1208 MB) Zlib disabled. Server Time: 2018-04-27 06:45:40 UTC