A question on ignition timing methods

terrylangley
Posts: 36
Joined: Sat Sep 30, 2017 8:15 pm
Contact:

A question on ignition timing methods

Postby terrylangley » Mon May 20, 2019 12:25 pm

I have in the past set up the points and timing in accordance with the workshop manual and all has been well. As an experiment I then adjusted the timing by rotating the points back plate with the engine running at normal operating temperature until I got the smoothest idling in the same way you adjust the tickover with the air adjusting screw. The engine ran well afterwards and still does. On my current project I have fitted Pazon ignition and timed the engine exactly in accordance with the Pazon instructions. After just 90 miles I adjusted the primary chain and on starting up to check all was well I noticed the rear wheel turning the wrong way!! The engine was running backwards!! Assuming my ignition was too advanced I retarded it a smidgen and all was well when restarted. So my question now is, is it better to fine tune the timing with the engine running for smoothness or stick to the method in the manual? I will adjust the pazon ignition with the engine running but would be very interested in the method other owners use or recommend and the results achieved.

Thanks for your interest, Terry Langley.

User avatar
grahamhibbs
Holder of a Nylon Anorak
Holder of a Nylon Anorak
Posts: 191
Joined: Fri Dec 06, 2013 3:09 pm
Location: Handcross West Sussex
Contact:

Re: A question on ignition timing methods

Postby grahamhibbs » Tue May 21, 2019 12:34 pm

I was interested in hearing the replies from those who know as I've never thought of adjusting the timing as you described, but none have been forthcoming so perhaps you are the only person to think of it.
Regards
Graham
West Sussex

1942 Ariel w'ng
1928 Ariel Model B
1960 Ariel Arrow
1960 Ariel Leader

Ivor Collins
Posts: 78
Joined: Sun Mar 30, 2014 11:04 am
Location: Leighton Buzzard ish
Contact:

Re: A question on ignition timing methods

Postby Ivor Collins » Tue May 21, 2019 5:08 pm

When I was a teenager and before we had timing discs or any idea what the timing should be, the norm was to advance the distributor to best engine speed and then retard a little.

I would hope that, for a standard engine and using timing equipment, the manufactures settings could not be bettered but it does beg the question, if the engine can run backwards, it must surely be too far advanced!

Ivor

bh.sprint
Holder of a Waxed Cotton Anorak
Holder of a Waxed Cotton Anorak
Posts: 329
Joined: Wed Oct 31, 2012 7:21 pm
Location: South Yorkshire
Contact:

Re: A question on ignition timing methods

Postby bh.sprint » Tue May 21, 2019 7:28 pm

Re the timing on the engine.

When the Standard Leader had points ignition the bike ran well and started well after spending time getting the timing exactly as the workshop manual recommended.
On the 270 Leader with Pazon I set the timing as per the instructions to get the engine going and then using a disc with the peg in the hole but check the position of the piston using a DTI in the plug hole and relate this back to the peg position. On the Arrow it is spot on 20 degrees when I winde the engine back, this engine it is a bit out and there is a difference beween the two sides of 2 degrees . So I set it to be correct on the advanced side and 2 degreees out on the other side.

Occasionally the engine will start in reverse from cold, mainly, you can hear the slightly different tone to the engine and the engine kicks back as it starts.

See picture

Brian H.
Attachments
IMG_0331.JPG
IMG_0135.JPG

Ivor Collins
Posts: 78
Joined: Sun Mar 30, 2014 11:04 am
Location: Leighton Buzzard ish
Contact:

Re: A question on ignition timing methods

Postby Ivor Collins » Wed May 22, 2019 8:18 am

Any ideas as to how an engine can run backwards if the spark is occurring at 20 degrees before TDC?
Does this only happen when retro fitted electronic ignition is used or can it happen with both?
I have only ever used points ignition on mine and never had it happen

Ivor

User avatar
Bob.Murphy
Holder of a Silver Anorak
Holder of a Silver Anorak
Posts: 825
Joined: Thu Nov 29, 2012 10:32 pm
Location: Kirkliston, on the West side of Edinburgh.
Contact:

Re: A question on ignition timing methods

Postby Bob.Murphy » Wed May 22, 2019 11:16 am

Its only 20 degrees before TDC when the engine is turning forwards.

If it kicks back a full revolution the ignition will be triggered by the other side of the cam/magnetic pick-up. Lord knows what that gives in terms of 'before TDC' in reverse but it seems to work :lol: .

Bob.
My avatar shows the late Len Rich in 1970 with the bike I now have - a 1958 Ariel VH

nevhunter
Holder of a Golden Anorak
Holder of a Golden Anorak
Posts: 3590
Joined: Tue May 10, 2011 9:42 am
Location: Victoria.. Australia.
Contact:

Re: A question on ignition timing methods

Postby nevhunter » Thu May 23, 2019 11:11 pm

I've had a few 2 strokes that will easily run backwards. It can be pretty disconcerting. The timing it has going forwards has minimum effect on what it will have in the other direction. The difference is dependent on the cam shape in the magneto. It can be altered to make sure it won't fire when turning backwards, and most don't fire when turning backwards. Kicking back when starting is responding to the "normal" firing spark. Nev


Return to “Two stroke”

Who is online

Users browsing this forum: No registered users and 1 guest