PVL IGNITION SYSTEM

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PVL IGNITION SYSTEM

Postby ian jamieson » Thu Aug 30, 2007 5:33 pm

I have a problem with my 1974 CCM. Runs sweet with plenty power for couple of laps than 8 strokes on anything more than half throttle. I am using a PVL system and have set up the timing using strobe plus replaced both the coil and the magic box at various stages but after nearly a year its driving me crazy. I know that Mark will say throw it off and get an Interspan but as that would set me back another £600+ I want to have a final attempt to get it running. Anyone have any experience with the Rex Caunt/PVL system or any other (sensible) advice?
Regards

Ian :( :(
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Postby minetymenace » Thu Aug 30, 2007 8:02 pm

Hi Ian, only got general advice...
The fact that it runs sweet for a while and then starts to play up would indicate to me that it is set up properly and the fault is a thermal one that occurs after an initial "warm up" period.

Finding a fault by swapping out components is not a very satisfying way of diagnosing the probelm. If you use this method, swap one item at a time, and if the problem is not rectified, reinstate the origonal item.

As the sub-assemblies of any electronic ignition system tend not to have any "user servicable parts" (unlike points nishers) it should not be too hard to isolate the probelm. You only have a power supply (battery/alternator/wiring etc), magic box, coil(s), LT and HT leads and spark plug(s), so isolating the fault should be straight forward.....as long as the fault is repeatable.

I would start by finding a fool proof way of making the problem repeatable, but keep in the back of my mind that if I spend too long looking for a fault in one part of the system (ie the ignition system), perhaps I should look at something else (eg the fuel system).
Last edited by minetymenace on Thu Aug 30, 2007 8:05 pm, edited 1 time in total.
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Postby beat » Thu Aug 30, 2007 8:03 pm

is it not posible, your spark plug is overheated and is creating this problem? it sounds a bit for this for me. have you tried a higher ( heat resistante ) value already ?
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Postby JB » Thu Aug 30, 2007 9:28 pm

I had a Triumph Trident with Lucas Rita than ran well for a short while then would misfire to a halt. The problem was poor earthing of the amplifier box that caused it to overheat and not work properly. Might be worth checking every joint for a dry/loose connection.

John
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Postby HPbyStan » Fri Aug 31, 2007 2:46 am

JB, I had a Lucas Rita on the B50 flattracker for one weekend in 1999. The thing got hot and shot the timing so far ahead that it blew the whole left side of the head gasket right out of the engine. The ole BSA is sounding like diesel but Gilkey kept going and won the heat race anyway. When he pulled in the pits, the engine wouldn't shut off. It was a "total loss" ign with no charging system but when we unpluged the battery it kept on running. We could have killed it with the gearbox BUT, we wondered where all the extra ign energy would go then so we kept running it and gunning the engine until it finally stopped. Never figured out why all that happened and now I wonder about the ground setup on that bike. I went back to my 305 H*nda points system and had no more problems... HP
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Postby TomH » Fri Aug 31, 2007 7:37 am

One thing to check with the Analogue PVL is that you are not using Resistor Plugs or a Resistor Plug cap.
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Postby TomH » Fri Aug 31, 2007 8:19 am

Another thing to perhaps consider is where the CDI Unit and Coil are located. Have you mounted them directly above the engine / beneath the tank?
Sounds like they could be getting too hot if the problem goes away when the bike has cooled down. Perhaps you could try a temporary mounting elseware and see if the problem persists, although I realise you haven't many alternative locations.
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Postby Mark Cook » Fri Aug 31, 2007 10:22 am

Try a smaller main jet Ian, sounds more like fuel to me?

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Postby Andy Chaos » Fri Aug 31, 2007 1:05 pm

I had a missfire with a pvl when the engine got hot ,a new coil solved the problem,but you say have replaced yours, You can use a strobe or somthing like a skitsu rev counter to see if when the engine starts to missfire the counter drops off or the strobe goes intermitant. That way you know it is the ignition and not mixture etc.
Hope this helps

Or you could do what i did and go to Mark for an Interspan you wont regret it.

Andy 1975 CCM
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Postby ian jamieson » Fri Aug 31, 2007 5:00 pm

Thanks for all your comments and suggestions. I have tried most of them already as you would have guessed including jets. plugs, coils etc however I will persevere with this some more.
Great idea about the earth wire John will check it out and reposition. Also Andy thanks for the suggestion about using the strobe to confirm that it is in fact the electrics that is the problem.
If all else fails than it looks like some dosh will be heading to Wiltshire for an interspan system.
Thanks

ian
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Postby Ed V » Sat Sep 01, 2007 7:25 pm

Ian,

We have been using PVL ignitions now for 7 or 8 years on everything from BSA/Tri twins to BSA/CCM singles and have yet to have a failure with one so I have to go along with Mark on this one as it sounds like it is too rich after it warms up. What do your plugs look like? Black sooty? Are you using resistor plugs? Resistor wires? either of these will not work well with the PVL.

Ed
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Postby ian jamieson » Mon Sep 03, 2007 8:24 am

Ed
I am following the ignition route because the mixture is near perfect according to the plug reading. Using non resistror plugs etc. Have tried the usual trick of switching off fuel and runnning dry to see if the engine clears as the fuel drops indicating richness and also flooding with tickler to see if mixture weak but no change at all.
I am now resorting to fitting points and a total loss battery system to test and prove if it is ignition or mixture.
reagrds

ian
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Postby Ed V » Mon Sep 03, 2007 4:32 pm

Ian,
Switching to points and total loss should definitely show whether it was the ignition or not.
Best of luck
Ed
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PVL Ignition System

Postby Smartfam999 » Tue Oct 09, 2007 2:45 pm

Your symptoms sound very similar to that I experienced with my B40 Classic Scrambles. I struggled for 3 or 4 meetings this year. The motor ran well until I left the line then would choke up, eight stroke and eventually not run on much more than 1/4 throtte. Of course when I took it home it would start fine and as I don't have a practice ground and the neighbours have limited tolerance, a blast up the road is not PC nowadays was unable to reproduce the symptons. I messed around with replacement PVL, stators, coils, plugs, plug leads and plug caps but nothing made any difference. What I did notice was contact between the PVL rotor and the Stator. Looking into this further I found that the backplate was not sitting down square caused by one of the spacers being too short. Looking into why it was shorter I discovered that the spacer was yielding and collapsing. So I binned the aluminium spacers and made some steel ones being very careful to set the stator up square. Low and behold I could now ride around the track in practice but at full throttle it was still eight stroking, however if I just eased the throttle back it ran properly. I returned to the pits, removed the 230 main jet gave Terry Weedy £1 and in return he gave me a smaller 210 main jet. Next practice everything was just about fine although a slight misfire and heaviness going through the revs - but fine at full throttle. I then leaned the 106 needle by dropping it from the middle to top groove. In addition I replaced the 3 cutaway slide with a 3 1/2. ( 2 adjustments at once !). There is now absolutely no hesitation or misfire anywhere in the rev range. I plug chopped at LLantony after the finish line and the plug looks just about a perfect.


Hope this helps

Dave
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Postby CDB50MX » Wed Oct 10, 2007 5:30 am

This may be way off the mark , but I lost a race once due to lack of fuel tank venting . The symptoms sound the same , just a thought .

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Postby ian jamieson » Fri Oct 12, 2007 4:03 pm

thanks for suggestions. Tried the fuel venting as a solution however I will definitely look at the stator suggestions. The strange thing is that it runs perfectly for 2/3 laps before this develops. My engine man is away until next week but we are going to look at it then
Thanks for all your advice. I will let you know how I get on with the problem

regards

ian :grin:
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Postby beat » Fri Oct 12, 2007 6:31 pm

have a look also at the fuel piping / Tap as well. dos enough petrol running outh for say 2 ore 3 minutes continously ?
low level in the floater bowl at higher rpms cost me once a race and a complete engine as well :cry:
a other chek costs nothing and says a lot : run the bike withouth airfilter,
kink rubbers , etc. and see haw it gos by breathing free.
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