Now harder to kick start

[Greybeard]

As you may recall, I recently did some work on my A10 semi-unit Plunger engine. The camshaft was changed from standard to the Road Rocket 357? cam. I still have flat topped low comp pistons. Apart from the camshaft and followers, the engine has new little end bushes, new piston rings, new big end shells. The ignition timing was set as per Road Rocket, 9/32"? BTDC. Since the rebuild the engine now requires a fairly heavy kick to start it. After the previous rebuild, six years ago the engine was pretty easy to kick over to start. If I didn't know better, I'd say the engine had higher compression pistons. It's strange! Is this phenomenon caused by the new camshaft, or the more advanced ignition timing? I don't believe the engine is still stiff; I've done a few hundred miles since the rebuild.

[JulianS]

Timing could be out - Road and Super Rocket given as 3/8 BTDC until 1960 when it changed to 13/32.

[Triton Thrasher]

Sounds like your new rings have bedded in properly.

[Greybeard]

Sounds like your new rings have bedded in properly.

Yes, but six years ago I put new rings on these pistons and the bike started easier, as you can see in this video, taken soon after the rebuild: https://youtu.be/GL0wT8kriTA

[Triton Thrasher]

Maybe six years ago the rings did not bed in so well and the engine had poor compression.

[muskrat]

G'day GB.
The 357 will only make a tiny difference to the kickstart pressure. My A7 plunger with a 357 and 7.5:1 pistons is a no effort starter. TT may be right.
Cheers

[stanwhite]

New rods?  A bit longer?  (apparently, there are some out there).  Slightly higher compression as a result?

Thinner head gasket, or you forgot to fit it? 

Or...  This time, you lapped the valves in properly

Cheers,

 Stan.

[berger]

I have not been to the pub, I think your leg needs some of popeyes spinache

[chaterlea25]

Hi GB,

The camshaft was changed from standard to the Road Rocket 357? cam.

I'm pretty sure I remember the new cam is a 356 

Anyway that should not make a difference to starting
As the so called petrol available now is crap retarding the ignition a tad  helps
As the pistons are low comp there's no point in setting to the RR or SR  figures (that are not applicable to today's fuel anyway)
I seem to remember Orabanda's best dyno figures were with using 32 degrees BTDC 

John

[worntorn]

A hot cam with more overlap should reduce kickover compression a little.
This is partially offset by the extra force needed to compress the valve springs more, if lift is greater.
All in all it should still be a bit easier to kick thru than with lower performance, lesser overlap style of cam.

[Greybeard]

Thanks for all those comments chaps. I reckon the timing may have moved a bit and it is now a bit too advanced. As I'm not home I may have to close the points a bit to retard timing. I have that right, don't I?

[Triton Thrasher]

If it’s not kicking back, I don’t see how ignition timing can make the engine harder to turn over.

[Greybeard]

If it’s not kicking back, I don’t see how ignition timing can make the engine harder to turn over.

She was fighting me yesterday with some kickbacks. Mind you, I'm not used to putting a lot of force into the kick so I was being less than persuasive about it! I'll see how things go this morning.

[duTch]

 With my 357 & flat-tops, as long as I'm assertive, I don't generally have trouble, except when I get complacent as I did one day leaving the Bottl-oh with a box on the tank....

[bsa-bill]

Got it - GB bet you keep your wallet in your right hand trouser pocket, recent events have lightened it considerably therefore requiring more effort on your part to get that KS lever down - do you have an odd R/H clog lying around