Author Topic: My M21 is trying to kill me!  (Read 719 times)

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PIT-STOP

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My M21 is trying to kill me!
« on: 02 May, 2024, 19:18:15 »
Hello,
I wonder if anyone can advise me plesae? I have an M21 that I have broght out of 'retirement', and so it has needed a full refresh. I have done all the ingition timing to 'the book', , along with fitting a new carb. All is set up and has been checked and double checked for accuracy, and yet when trying to start it, all it ever wants to do  is kick-back and throw me though the garage roof. On the odd occasion I'm brave enough (frustrated and angry enough) and it starts, it runs just great. I just darn't even think about starting it once it is hot, as that is the worst!

 So I'm thinking this must be technique, or fuel,  or something. Any thoughs help or advice would be much apprecaited. I don't want to have to resprt to push starts everywhere I go if I can help it.

Thank you.

Bigsingle

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Re: My M21 is trying to kill me!
« Reply #1 on: 02 May, 2024, 19:51:45 »
Is your magneto ok , maybe it needs to be rewound and magnetized,  or check it for spark when hot .cheers.

PIT-STOP

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Re: My M21 is trying to kill me!
« Reply #2 on: 02 May, 2024, 20:44:47 »
Hi, someone has been in touch to say that I need to check the magneto design against my setting up, as the location the cable comes in makes a difference (from the contact breaker end, if the cable enters to the right it is fully advanced when the cable is pulled tight. If it is to the left, it is fully advanced when slack apprently). I have a feeling this feels to be the problem as the more retarded I put it, the worse it feels.  I will be checking- but thought I'd post this here now in the hope it helps someone else.....or someone has had the same experience.

Mike40M

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Re: My M21 is trying to kill me!
« Reply #3 on: 02 May, 2024, 21:24:23 »
After my WD16H had slept for a couple of years, I decided to start it. First kick, it kicked back, then remembered to retard ignition. Second kick it started. Guess you have the same issue.
By the way, when starting my Manx after renovation, I could not adjust timing properly until it was able to run at high revs. Found it could start with anything between 40 degrees BTDC and 12 ATDC. Though no kick lever, only run and bump.

neil1964

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Re: My M21 is trying to kill me!
« Reply #4 on: 02 May, 2024, 21:43:35 »
How did you set the ignition?
The M21 usually has tight advance (the advance/retard cable is on the right (rear facing when looking at points from drive side)
So when you set the ignition timing to 7/16" with the ignition lever tight.
When you start this you slacken the cable by backing the lever off approx 2/3 and fully tighten when up to speed

Of course there is a risk that someone has replaced the mag with a loose when fully advance type (cable enters left side nearest the cylinder barrel) so you set ignition to the same 7/16" but with cable slack.
To start these you tighten the cable typically 2/3  and then slacken fully up to speed.
Hope that makes sense?

PIT-STOP

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Re: My M21 is trying to kill me!
« Reply #5 on: 03 May, 2024, 07:27:07 »
Thanks all. I have sorted it I think, and some of the detail given is spot on I think. The haynes manual says very clearly to set it when slack, but it should be set when tight. I was starting on full advance whilst thinking I was on retard. Thank you all. I am now looking forwards to some happy steady motoring this summer. Thank goodness for the forum.

maddogmargetts@yahoo.co.u

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Re: My M21 is trying to kill me!
« Reply #6 on: 04 May, 2024, 16:49:16 »
interesting. So in the end it was a timing issue? I found with my M21 that using the timing hole in the top of the cylinder head with an old wheel spoke with TDC marked along with a mark just before to set the contact breaker to just opening worked well. It used to need retard to start but for the last year or so this wasn't necessary. Not sure why it would change unless the timing had slipped. On checking it was perfectly set. I did, however, put on a new carb which was the 276 with separate float. Now it suffers from fuel starvation!! When it's runing it is fine and dandy. I had the magneto rewound and set up but still find hot starting a problem. Wait 10 minutes and it's fine. I am interested to know how you set the timing?
john

maddogmargetts@yahoo.co.u

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Re: My M21 is trying to kill me!
« Reply #7 on: 04 May, 2024, 16:50:34 »
oh yes and my M21 kicks back sometimes and once it caught my leg. My goodness the bruise!! Black and blue from knee to ankle. They really can kick back at you...
john