honda305 Home honda305 Auctions honda305 Gallery honda305 Forum


honda305.com Forum

Login
□ Search
□ FAQ 
□ 
Vintage Honda Owners,
Restorers, Riders and
Admirers

marking on points cam

Points Based Ignition | Electronic Ignition Upgrade
LOUD MOUSE
honda305.com Member
Posts: 7817
Joined: Mon Aug 15, 2005 8:23 am
Location: KERRVILLE, TEXAS

Re: marking on points cam

Post by LOUD MOUSE » Sun May 01, 2016 10:28 pm

My reply to DOUG6PIPES was in response to this.
<<when the rh cylinder is on F on the alternator rotor with the points just opening where should the line on the end of the points cam be>>>
To me his question brings to question what a 180 engine is set to in the ignition area of engines so I replied to that.
Now were he to ask how to set points and cams I would have told him that in the FAQ area of this forum at How I Tune My Engine he will see how to set the cams and timing and have it run well.
I responded as I saw a reply (well intended) which I thought wasn't totally correct.
Why do I usually not go TOO IN DEPTH is that What And How I know And Do Engines Would Fill This Forum.
KISS. ....................lm




Two answers and this one is correct. .................lm
LOUD MOUSE wrote:Keep in mind the engine is a 180 crank.
You install the cam chain with the "O" on the cam sprocket vertical to the center of the head casting and the line on the point cam toward the "O".
Now to set the timing/valves you must rotate the crank a cycle so the line on the points cam is down/vertical to the center of the head casting and the rotor is at "T". ....................lm
DOUG6PIPES wrote:can anybody tell me , when the rh cylinder is on F on the alternator rotor with the points just opening where should the line on the end of the points cam be
Last edited by LOUD MOUSE on Mon May 02, 2016 2:41 pm, edited 1 time in total.

User avatar
PhilD
honda305.com Member
Posts: 83
Joined: Thu Apr 03, 2014 3:53 pm
Location: Leeds,UK

Re. Marking on points cam

Post by PhilD » Mon May 02, 2016 2:00 pm

Loud Mouse is of course correct but a bit more explanation may be useful to less experienced forum users. Cam timing is set with the right side piston at top dead centre, the O on the cam sprocket vertical with respect to the mid line of the cylinders and in this position on the 180 degree CB motors the line on the points cam is also at 12 O 'clock. Timing is however set on the overlap stroke (end of exhaust beginning of intake ) with both valves open. Since the cam shaft rotates at half engine speed a further 360 degrees of crank rotation bringing the right cylinder up to the firing position on the compression stroke takes the line on the points cam through 180 degrees so that it is pointing down at 6 O'clock as Loud Mouse states. Since these are 180 degree cranks the left cylinder fires 180 degrees after the right cylinder and in this time the cam shaft has turned through a further 90 degrees such that the line on the points cam is now at the 9 O'clock position. I hope the following pictures will clarify this. First shows right sided points closed just before firing position with line on points cam almost at 6 O'clock, second shows points just opened with line on points cam at 6 O'clock as LM states,. Third picture is taken without moving the crank but ohmeter has been swapped to the left side points which are closed, final picture shows camshaft rotated a further 90 degrees ( 180 degrees crank rotation ) and left side points just opened with line on points cam at 9 O'clock. Hope this helps.
PhilD
Attachments
Left Cylinder Points Just Opened.jpg
Left Cylinder Points Just Opened.jpg (149.52 KiB) Viewed 2668 times
Left Cylinder Points Closed.jpg
Left Cylinder Points Closed.jpg (149.95 KiB) Viewed 2668 times
Right Cylinder Points Just Opened.jpg
Right Cylinder Points Just Opened.jpg (146.79 KiB) Viewed 2668 times
Right CylinderPoints Closed.jpg
Right CylinderPoints Closed.jpg (133.22 KiB) Viewed 2668 times
1964 CB72
1964 CB77

LOUD MOUSE
honda305.com Member
Posts: 7817
Joined: Mon Aug 15, 2005 8:23 am
Location: KERRVILLE, TEXAS

Re: Re. Marking on points cam

Post by LOUD MOUSE » Mon May 02, 2016 2:59 pm

My reply to DOUG6PIPES was in response to this.
<<when the rh cylinder is on F on the alternator rotor with the points just opening where should the line on the end of the points cam be>>>
To me his question brings to question what a 180 engine is set to in the ignition area of engines so I replied to that.
Now were he to ask how to set points and cams I would have told him that in the FAQ area of this forum at How I Tune My Engine he will see how to set the cams and timing and have it run well.
I responded as I saw a reply (well intended) which I thought wasn't totally correct.
Why do I usually not go TOO IN DEPTH is that What And How I know And Do Engines Would Fill This Forum.
KISS. ....................lm
PhilD wrote:Loud Mouse is of course correct but a bit more explanation may be useful to less experienced forum users. Cam timing is set with the right side piston at top dead centre,
the O on the cam sprocket vertical with respect to the mid line of the cylinders and in this position on the 180 degree CB motors the line on the points cam is also at 12 O 'clock. Timing is however set on the overlap stroke (end of exhaust beginning of intake ) with both valves open. Since the cam shaft rotates at half engine speed a further 360 degrees of crank rotation bringing the right cylinder up to the firing position on the compression stroke takes the line on the points cam through 180 degrees so that it is pointing down at 6 O'clock as Loud Mouse states. Since these are 180 degree cranks the left cylinder fires 180 degrees after the right cylinder and in this time the cam shaft has turned through a further 90 degrees such that the line on the points cam is now at the 9 O'clock position. I hope the following pictures will clarify this. First shows right sided points closed just before firing position with line on points cam almost at 6 O'clock, second shows points just opened with line on points cam at 6 O'clock as LM states,. Third picture is taken without moving the crank but ohmeter has been swapped to the left side points which are closed, final picture shows camshaft rotated a further 90 degrees ( 180 degrees crank rotation ) and left side points just opened with line on points cam at 9 O'clock. Hope this helps.
PhilD

DOUG6PIPES
honda305.com Member
Posts: 4
Joined: Fri Jan 15, 2010 2:05 pm
Location: gillingham kent

ignition timing

Post by DOUG6PIPES » Wed May 11, 2016 3:29 pm

many thanks guys i do appretiate all your comments, you have confirmed that i have assembled the engine correctly ,i have sparks and fuel but the bitch still refuses to start not even a cough or splutter, nearly suidcidal
Doug

Post Reply




 

CB-77 | CYP-77 | Road Test | Riding Log | Literature | Zen | Marketplace | VJ Survey | Links | Home