Help/ideas needed to get my stupid brain working. EDIT: It's running!

[John Orchard]

So,
. Yam DT1.
. PVL ignition 1.8mm advance, great spark.
. Radically ported cylinder, intake port lowered 4mm.
. GYT high comp head.
. Mikuni VM36
. Expansion chamber.

She no starting, not even a kick when spraying aerostart down the plug hole.

I'm thinking maybe the radical porting is not condusive to kickstarting speeds? With such delayed intake closing, maybe any fuel charge is being pushed back out?

Can PVL ignitions have good spark out of the cylinder but not under compression?

I would appreciate any ideas, (my brain hurts) thanks :-)

Never before have l been stumped like this.

John.

[ralph311]

Well I'll take a punt. :-)

I haven't used that aerostart stuff but I'm assuming that if there's a spark at the right time then it's at least going to make a pop?? So there's either no spark or its sparking at the wrong time (eg 180 degrees out).

If you take the plug out, put a timing light on it and spin the engine with an electric drill you should be able to see when its firing. If that's correct it only leaves no spark under pressure.

There are those cheap ignition testers on ebay that let you set/adjust a very large gap, to simulate ignition under pressure, but I haven't tried one.

[John Orchard]

Well I'll take a punt. :-)

I haven't used that aerostart stuff but I'm assuming that if there's a spark at the right time then it's at least going to make a pop?? So there's either no spark or its sparking at the wrong time (eg 180 degrees out).

If you take the plug out, put a timing light on it and spin the engine with an electric drill you should be able to see when its firing. If that's correct it only leaves no spark under pressure.

There are those cheap ignition testers on ebay that let you set/adjust a very large gap, to simulate ignition under pressure, but I haven't tried one.

Hmm good ideas, l've set the timing as per PVL instructions but l'll try a 180 degree swap tomorrow.  Then if l don't get any pop l might look towards ignition power. Thanks.

[sleepy]

I have seen a PVL on a 490 Maico that would show spark with the plug out but with the plug in the kick speed wasn't fast enough to make it spark. Would push start ok but no kick start. This was confirmed with a timing light not flashing with plug in but would flash with plug out and a good kick.
Could be 180 out as the timing marks are a bit strange on PVL's. Timing light will confirm.
Don't think the porting would be the cause. 
If all else fails put the stock points ignition back on for a test.

[geoff]

I have had the same problem with an Electrex World fitted to a Mk V11 Bultaco. You could not kick it fast enough to get it to fire, push it and off you would go. Turns out that the later ignition kits are supplied with two stators to solve the problem!

[Momus]

John, the various PVL's are not all suitable for relatively slow rpm kick starting. I was forced to investigate after a seller knowingly sold one to me for my B50/Clews that was incorrect. There are various PVL's out there selling cheap with low winding numbers that are apparently redundant homologated units made for 15000 rpm Karts .  There are also various mismatched combinations of stator and coil. PVL list about 70 different stator P/N's.

[John Orchard]

Thanks Guy's, Marcus these low winding stators that don't produce enough power at kickstart speeds, will still spark at kickstart speeds out of the cylinder?

[John Orchard]

I once was working on an Suz RGV250 that had a bad misfire, the sparkplugs were fouling, I'd heard that lifting the plug caps about 10mm off the plugs can cause an increase in voltage to the plug, allowing a fouled plug to fire. Having to jump the large gap allowed the system to build-up a higher voltage to make the jump? Sure thing, the RGV would run fine with the caps lifted off the sparkplugs!

Is there another way to increase the voltage to the sparkplug in this instance ?

[John Orchard]

Thanks Gentlemen, got it running ...... farking PVL ignition!  Just had to put me workboots on and kick like fark!

My first experience with PVL, I'll be looking for a YZ ignition I think, anyone want a cheap PVL?  :-)

[ralph311]

Nice one John :-)

Personally I don't trust replacement ignitions as far as I can throw them, and not just pvl. As far as I'm concerned putting a timing light on them is an essential part of the installation process. Getting it started is one thing, the next is checking the damn thing is doing what you want it to. Sometimes the timing marks seem to be completely random. :-)

[Nebo]

   Yes John.      Momus is correct.  Your Stator does not have another windings to Generate enough voltage on kickstarting.

   This is a common mistake when buying any after market System.  OK  for Electric Start or Push Start and or Rollers . Examlpe Go Kart .

    Stator must have between 4000 and 5000 windings. What Number is on the Stator?.    Example 1086.

    Tell me the Number and I will tell what Stator you have.

     PVL is one of the best Systems made if you have correct the one.

     Advantages are Less Kick back, Less Plug fouling, Better Thottle reponse. Better Advance Curve , Less chance of Detonation.
  .
     Have PVL on two of my brothers Maico,s.  They start very easy.    The bikes have won may Events.
     
   
   

[Momus]

John, same issue as yours: sparked out but hard to start in and a dodgy advance curve.
Nebo is onto it. There will be a stator on their list that works very well.

I am using the very similar Sellettra CDI that is matched for rpm and advance on a couple of high winding little Hondas and they are very good.

[shoom]

Yeah, I don't trust the PVL units, seen too many motors burnt up from them.
The ones to go for are the electrexworld, ricks place and this one : https://www.regulatorrectifier.com/catalog/1972-1977-honda-xl250-xl-250-lighting-stator-cdi-coil-ignition?fbclid=IwAR1DBB3x7Il1Mna66eECs8ecPoXisXzCduft1a7qEE679_tXgEd_jec0JZI

not only do you get CDI ignition, you can convert to 12volt at the same time.

The Selletra units are good, as they make pretty much all the inner rotor units in the first place for a myriad of bikes, they are more up to date with making sure their units are fit for purpose.