Kickback

[blethermaskite]

Hi, I have a Mk3 widecase 350 which I have been kick starting now for over 40 years (I am 65 with a touch of arthritus) so from cold......fuel on, full choke, ease on kickstart to compression, then just nudge it over compression with the kickstart, let the kickstart return to the top of its travel, give the throttle about 1/16" open, then a good determined kick, mine starts first or second kick every time.......my 250 desmo is far less fussy about this procedure and will normally start by just kicking it over from any point in the 4 stroke cycle. Hope that may help.
Stay well,
Cheers,
George

[ranton_rambler]

Sounds the same method as my 175. I have just serviced it and having opened up the points gap a bit (which I think slightly advances the spark) it does seem a little more prone to kicking back now.
I also found the left-side starter difficult at first. If the bike is warm I can re-start it astride the bike, but when starting from cold I keep the bike on the stand, stand on the left and use my right foot.

Nice ride to the shop today for some milk too!

[DBDBrian]

Hi Frank, as said, the crankshaft requires momentum, I don't know what the kickstart to crank ratio is without checking, but it will turn the engine more than two revolutions with one full kick.
If you attempt to start the engine with the piston just before TDC on the compression stroke, it will fire immediately thus causing the kickback, as there is insufficient inertia in the crankshaft to take it over TDC.
By moving the piston past TDC before kicking , there will be no ignition for almost two revolutions of the crank, thus creating sufficient momentum, so when the engine fires BTDC, to take it over TDC on to the power stroke and continues to run.
The cylinder pressure will not close the exhaust valve, as the lifter will be mechanically holding it off it's seat when in operation.

[frankfast]

So will the bike fire with the exhaust valve open via the compression release or do you have to close it before kickstarting? Your description of the kickstart procedure for a single is really helpful. Thanks.

[graeme]

Close it before trying to start otherwise no compression

[Ventodue]

Doesn't spark ignite BTDC which is when I'm getting kickback? I thought you want to kickstart the bike on the compression stroke.

Noooo ... and yes, Frank .

You want to START the movement of the kickstart lever when the piston is going down on the power stoke, i.e after TDC, AFTER THE SPARK. Now, because you're pushing on the kickstart lever, the piston is now moving, and it will continue to move down to complete this false 'power' stroke.

But you haven't let up pushing on the kickstart lever, so ... Back up comes the piston, this time on the exhaust stroke. And then back down it goes again, this time on the inlet stroke.

And NOW back up it comes again, this time on the compression stroke - and this, just as the kick start lever gets to the bottom of it's movement.

And this time, just before TDC ... SPARK. Fire! Vroom! Go!

[Ventodue]

So will the bike fire with the exhaust valve open via the compression release <snip>?

(Rarely on some humongous singles, but) Not on our little bikes. As per Graeme: the exhaust valve needs to be properly closed.

The valve lifter/decompressor/whatever is only then to help you ease the piston over TDC before you kick that kick start lever like you mean it ...

[frankfast]

Doesn't spark ignite BTDC which is when I'm getting kickback? I thought you want to kickstart the bike on the compression stroke.

Noooo ... and yes, Frank .

You want to START the movement of the kickstart lever when the piston is going down on the power stoke, i.e after TDC, AFTER THE SPARK. Now, because you're pushing on the kickstart lever, the piston is now moving, and it will continue to move down to complete this false 'power' stroke.

But you haven't let up pushing on the kickstart lever, so ... Back up comes the piston, this time on the exhaust stroke. And then back down it goes again, this time on the inlet stroke.

And NOW back up it comes again, this time on the compression stroke - and this, just as the kick start lever gets to the bottom of it's movement.

And this time, just before TDC ... SPARK. Fire! Vroom! Go!

That all makes sense and is very clear. Back when I had Ducati round case twins I never paid attention as to where the pistons were within the four strokes and usually had no problem starting. But singles are different and are more temperamental when kickstarting. In the past I wouldn't pay attention to the process and this single started fairly well. But that was when my knees were good. Now, I'm probably not getting the power into the process that I used to get. I'm still concerned that there maybe another problem since I've got good compression and spark but I haven't seen the plug wet with gas. Perhaps my leg is not strong enough to suck gas into the chamber from the carb. Fuel seems to be the missing ingredient.

[DBDBrian]

Try pouring a little drop petrol down the plug hole, before trying to start the engine, it may prove a point.

[frankfast]

I tried that and that's what confusing. Even with spark and compression I got nothing. Even tried spraying stater fluid into the manifold. Nothing.