trophy160 Posted July 12, 2015 Author Share Posted July 12, 2015 Thanks for the points suggestion, Richard Farrant has also raised that as a possibility. I'll take a look at them this week. it's only going to be possible to look at them when the engine is cold, hopefully I can get an indication of how tight they are. Nic Quote Link to comment Share on other sites More sharing options...
Nick Johns Posted July 12, 2015 Share Posted July 12, 2015 (edited) it's only going to be possible to look at them when the engine is cold, hopefully I can get an indication of how tight they are.Nic Checking the points with a cold engine may not indicate a problem, lubricate the pivot pin, then another road test is required Edited July 12, 2015 by Nick Johns Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 14, 2015 Author Share Posted July 14, 2015 I wondered if it is worth pulling the points off the pivot pin so as to clean the pin or does this sound unnecessary. Hoping to have a go at it tomorrow Quote Link to comment Share on other sites More sharing options...
Tony B Posted July 14, 2015 Share Posted July 14, 2015 Can't do any harm. Good bit of basic maitainence anyway. Have a good look at the cap as well. Quote Link to comment Share on other sites More sharing options...
datadawg Posted July 15, 2015 Share Posted July 15, 2015 I wondered if it is worth pulling the points off the pivot pin so as to clean the pin or does this sound unnecessary. Hoping to have a go at it tomorrow I hope you figure out what's wrong. Any chance you can post photos of what you do from now on, so the unenlightened (me) can learn from this? Yes, I am clueless Quote Link to comment Share on other sites More sharing options...
Tony B Posted July 15, 2015 Share Posted July 15, 2015 Looking at 'Other places' you'll be pleased to know, you're not alone! A number of various MV's seem to have been suffering point and capacitor failure in hot weather. Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 15, 2015 Author Share Posted July 15, 2015 Not getting anywhere fast here, no pun intended. Combined Ops Headcorn 2015 is not looking very promising! I removed the points today, cleaned and oiled the pivot and then went for my standard road test. 1.5 miles up to my house, let it stand for 20 minutes whilst I had a cup of tea then attempt restart and if all OK back to the barn where I keep it. It restarted reasonably OK and I did manage to drive it back straight away, but it was running very badly, spluttering, the odd backfire and were it not for the fact that it was down hill it would not have made it back, so problem still there; conclusion - it's not sticking points. I'm at a total loss knowing where to go now, this is a summary of what I have observed and done during the course of my testing. I should say that I don't check all the failure modes on each journey. I have fitted an in line (with the mechanical pump) double SU fuel pump which is located under the batteries. I have not particularly noticed it clicking away rapidly when I have the power loss problem - from this I conclude there is probably not a vapour lock in the fuel line After one of my journeys (when it would not restart/run properly) I cracked open the banjo on the carb, there was an escape of fuel - conclusion fuel was getting to the carb I am now running the Saracen with one of the beehives partially propped open to improve engine cooling After another journey when it would not restart I pulled plugs 1 and 2. Both were a nice light biscuit colour, both appeared to be dry. - conclusion, The engine was not running rich and flooding, the fact that I had been cranking the engine should I thought had meant that the plugs might have been damp with petrol. The fact they seemed dry made me wonder if the carb was supplying fuel to the engine or could it have been that the enginne being pretty warm that the fuel simply evaporated from the plugs? I changed the coil, no difference - conclusion either it was not the coil or the NOS coil had the same problem I changed the condenser, no difference - conclusion either it was not the condenser or the NOS condenser had the same problem I ran the engine from fresh fuel in a Jerry can, no difference - conclusion it is not a stale fuel problem On one of my test runs (this was on a coolish day) I measured the temp of the carb and felt it just to be sure. It was only around 30 degrees - conclusion it was unlikely that fuel was boiling in the float chamber. That said, other days the engine and carb have been very hot I removed and cleaned the points pivot, no difference - conclusion it is not points seizing as they get hot. When I consider what has been tested/changed, I don't think I can convincingly say that it must be fuel or must be electrical. I tend to think that it is a fuel problem but it may be dangerous to do so. So where do I go from here? It is the case that running reversed reverse flow cooling I have a non standard configuration and that this may be the problem. Certainly one of my next options is to convert it back. My only hesitation is that I think there might be a primary and secondary problem. It clearly does get hot on a hot day and reverting to reverse flow cooling will help this. But I get the feeling that a secondary problem is occurring which is causing my problems. The reason I say that it that following some of my tests the engine bay has just not been that hot, I'm sure a reversed flow Saracen having driven 10 or 20 miles would be a lot hotter than mine having just done 1.5 miles. So I'm now at the point where I think do I change to reverse flow cooling or perhaps I should fit a new carb (I did strip the carb a couple of years back) Nic Quote Link to comment Share on other sites More sharing options...
fv1609 Posted July 15, 2015 Share Posted July 15, 2015 Nic you have pulled plugs 1 & 2 but that is only half the carb. What do the far end ones look like? Quote Link to comment Share on other sites More sharing options...
Tony B Posted July 15, 2015 Share Posted July 15, 2015 Tried a new Dizzy cap? They can do some bizzare things and look OK. Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 15, 2015 Author Share Posted July 15, 2015 Nic you have pulled plugs 1 & 2 but that is only half the carb. What do the far end ones look like? Hi Clive, so implicit in your question is that the carb is split in (two?) parts feeding 1-4 and 5-6 is that correct? I'm not that familiar with the layout of the carb. Since I assumed 1 & 2 would be representative of all 8, I did not look at the others (and they are less easy to get at at the side of the road when the engine is hot. Nic Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 15, 2015 Author Share Posted July 15, 2015 Tried a new Dizzy cap? They can do some bizzare things and look OK. No, not replaced that yet, sort of assumed (bad idea!) that a hot cap must be better than a cold and possible damp one. But you're right it has to be a suspect Quote Link to comment Share on other sites More sharing options...
fv1609 Posted July 15, 2015 Share Posted July 15, 2015 Hi Clive, so implicit in your question is that the carb is split in (two?) parts feeding 1-4 and 5-6 is that correct? I'm not that familiar with the layout of the carb. Since I assumed 1 & 2 would be representative of all 8, I did not look at the others (and they are less easy to get at at the side of the road when the engine is hot. Nic Nic yes 1-4 & 5-8 each have their own half of the carb. Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 15, 2015 Author Share Posted July 15, 2015 Thanks Clive, can you think of a failure mode that would only effect half the carb when hot? It's got to be an unusual one Nic Quote Link to comment Share on other sites More sharing options...
fv1609 Posted July 15, 2015 Share Posted July 15, 2015 It would be worth trying to judge the state of as many of the plugs 5-8 as possible to see if they all share a carb problem. If they do might consider whether an accelerator pump diaphragm is ageing & when it gets warm it might allow more leakage. If the mixture in that half is incorrect then as the coil heats up, as it is bound to, there will be more internal leakage & that might cause a small drop to a critical level of voltage on the non optimum half. Are you sure the ballast resistors are left in circuit when it is running? Any coil will fail with overheat. The ballast resistors (in the junction box) should of course only be shorted out on start up. Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 15, 2015 Author Share Posted July 15, 2015 I'll pull the plugs as it was running pretty roughly when I garaged it tonight. With regard the ballast resistors I think they are OK, I measured 11.7 volts at the coil (sw) when the ignition was on & engine not running Quote Link to comment Share on other sites More sharing options...
fv1609 Posted July 15, 2015 Share Posted July 15, 2015 Yup ok fair enough obviously that is with the points closed. When they are open it will be 24v or so. Sometimes people mistakenly measure the voltage there when it is running & surprised when they get 18v or so. This is just the average between 12v & 24v as the meter needle can't respond fast enough. (A digital meter goes haywire, I have enough difficulty getting a steady reading on a constant voltage!) Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted July 16, 2015 Share Posted July 16, 2015 Nic, The only thing that does not seem to have been mentioned is that the inlet manifold is heated by coolant until the thermostat opens, if the thermostat was to stick the manifold would be too hot and fuel could start to vapourise which will give you the symptoms that you are getting. Worth investigating. regards, Richard Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 16, 2015 Author Share Posted July 16, 2015 Hi Richard, yes I had thought about simply removing the thermostat for test purposes......where do I find it? Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted July 16, 2015 Share Posted July 16, 2015 Hi Richard, yes I had thought about simply removing the thermostat for test purposes......where do I find it? Hi Nic, Here it is, on front of head just close to front engine lift loop. The puller may be necessary, Richard B may be able to help you on this. Quote Link to comment Share on other sites More sharing options...
trophy160 Posted July 16, 2015 Author Share Posted July 16, 2015 Thanks Richard Quote Link to comment Share on other sites More sharing options...
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