classic motorcycle forum
The VintageBike Message Board => The Classic Biker Bar => Topic started by: alfamisco on September 27, 2015, 05:32:29 PM
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Hi Has anyone had this problem! I have a 1959 triumph thunderbird on which I do the ignition timing manually,if set it on the right hand side at 32'' as recommended, I find that if I then check the left hand side it's 70'' advanced. I'm assuming the cams are worn unevenly as when I turn the cam half a turn the problem switches sides but I'm getting the same situation with a reconditioned cam from Distributor doctor, does anyone know of any other reason for this.Thanks John
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dizi shaft bent or needs rebushing
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Hi MARK2 If the shaft was worn or bent, would'nt the advance settings remain.the same whichever way I fitted the cam.John
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have you a pair of centres and a dti , try also using a strobe and note the difference , I have one here so will take a better look but I have been told that there can be some accuracy issues with this setup , how are you measuring the ignition ? the cap is another area for a in balance
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Hi Mark2 I tried another test, I fitted a couple of fiber washers behind the points to move them out to a different contact area on the cam, this did even things up a bit so I contacted Distributor Doctor and he says he has several spare cams but could'nt guarantee how accurate they are, so the only way to check them is to send him my distributor and he'll experiment,so that's what I'm going to do. Thanks for your help and suggestions, very much appreciated. John
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reconditioned cam from Distributor doctor ,? did you not get the cam from him in the first place
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Yes I did get the cam from him! He should'nt really sell them if he does'nt know if they are accurate, they have been machined and have a nice finish so if anyone does what the workshop manual says and timed there engine just on the right hand side, they would never know. Coarse he may have bought them in believing them to have been machined to the correct contour, he seems pleasant enough and helpful.
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let us know how you get on , I have never used him myself but see he does state on his web site his dizis are better than new (lucas) I find that part a bit hard to swallow
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Which is why people buy electronic replacement ignitions,instead of wasting money on the worn out original.Regards John.
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electronic replacement would be the way to go , and a few to choice from
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I expect it could be set up better than a mass produced original, with time, patience and lots of springs etc to get the advance curve spot on but perhaps people are just saying it looks good. I do have a Bouyer points assisted electronic system fitted, i was'nt aware I could buy an electronic system to replace the distributor.
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I think it replaces the points assembly so it keeps the original look , the machine for cam grinding blanks is some kit (martin russel has one) I would be interested to know if the dizi doctor has this machine also or is the buying reground cams from china , he may bend the points post (some say set) and send it you back with the bill , how did you measure the figures you quote
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Hi I doubt he has a grinding machine or he would know the accuracy of his cams, I think bending the points post probably would'nt help because whichever way it was bent the two cams would still be different distances from it. I set my ignition timing using a dial gauge screwed into the plug hole right hand side, engage top gear, find tdc turn the engine back about 150" to take up any free play in the gears then turn it forward and set the distributor with the points just opening at 32" before tdc, if I then check the left hand side I find the points open at 60" before tdc using my cam and 70" with his. I did have a 3,100 S Ford Capri fitted with a Lumenition electronic system which replaced the points but It was surprising how not having the resistance of opening the points upset the advance curve and of coarse I still would have the worn distributor.i think most must get them repaired as he's very busy and quotes a six week waiting time. John
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I would not worry about the advance curve , by 2000 rpm its fully advanced ,but its nice to get the balance as close as poss and think that's where the electronic would work best , I use the piston stop with a disk and split the result to find tdc
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When I was gainfully employed,we went well into distributor problems on a fleet of forklifts.One dizzy sent in to a well known and recommended repairer came back seemingly tight and ok,within a few days of 20hr/day running it was just as bad as before.I pulled it down and found they had bodged it with plastic filler and washers.From then on ,only new electronic replacement distributors from a Belgian crowd called TVH,costing less than the recon bill.A Lucas dizzy has a lot more bearing surfaces than just the shaft.They all wear and add to the looseness.Regards John.
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it never did catch on ,triumph ariel all had a go as well as others im sure , I like the dizi as its very easy to alter the timing but accuracy is not its strong point
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With the reputation for inaccuracy which I’ve been told the Lucas dizzy has (and the problem here) I thought I would take a closer look , without spending too much time I set this up , from one side to the other on the cam its ground to a difference of one degree , one degree ! if only triumph could have ground there engine cams to the same tolerance , I will not be so quick in the future to remove these units in favour of magnetos , in fact I may try this setup on my own triumph if the mag ever plays up .\
(http://i61.tinypic.com/2w1tcgg.jpg)\
(http://i59.tinypic.com/2s9508k.jpg)
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I have never suggested that Lucas equipment was inaccurate when new,in fact I am a big fan of Lucas stuff.Many of my old machines have still got the Lucas electrics they were made with,but I'm talking trucks, tractors and cranes,not bikes.Lucas fuel injection equipment[Lucas owned CAV from late 20s on.Which is where the money came from to subsidise Nortons racing effort as long as C.A Vandervell was alive.]is world class,and in fact better in some cases than Bosch.Regards John.
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Why did this setup get such a reputation for being inaccurate , I understand that triumph tried this because Lucas where to stop making mags also im sure cost came into it , am I missing something for so long as the charging is all in order I can see/find no problem
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They were probably fine when new, although I never had the luxury of experiencing that. By the time they got to people like me, the bushes had worn, the springs stretched and the bobweight pivots worn and/or seized.
I overhauled an 18DX(?) for a unit Triumph twin a year or so ago and managed to get it working well after suffering most of the above.
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Hi forgot to say I've had my distributor back from distributor doctor and fitted to my bike, it has been repaired well, looks like new and my Thunderbird runs really well, thing that's really noticeable is when I Rev the engine with bike on centre stand it used to move backwards but now it's remains stationary however hard I Rev it
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that's a rare bird you have there , they are a very nice bike I need to look at mine as its not that smooth as it does move on the cent stand