RobinTR6 Posted April 7, 2014 Author Report Share Posted April 7, 2014 Thanks Peter, had a go at your idea which improves but unfortunately doesn't cure the problem. So you both believe turning the dizzy drive shaft clockwise one tooth will re establish correct dizzy cap rotor arm relationship. It will mean re timing the mu as well. Quote Link to post Share on other sites
Guest ntc Posted April 7, 2014 Report Share Posted April 7, 2014 It will make not one jot of difference, who's cap and rotor have you got? Quote Link to post Share on other sites
RobinTR6 Posted April 7, 2014 Author Report Share Posted April 7, 2014 Rotor is Dizzy doctor, cap from TRGB. Tried two other caps and two other non dizzy doctor rotor, all the same. Quote Link to post Share on other sites
Guest ntc Posted April 7, 2014 Report Share Posted April 7, 2014 Did you check the port spacing ? Quote Link to post Share on other sites
Peter Cobbold Posted April 7, 2014 Report Share Posted April 7, 2014 (edited) Thanks Peter, had a go at your idea which improves but unfortunately doesn't cure the problem. So you both believe turning the dizzy drive shaft clockwise one tooth will re establish correct dizzy cap rotor arm relationship. It will mean re timing the mu as well.Timing the MU is a red herring. Haynes printed the diagram upside down and no-one noticed! I used Haynes for years until I realised the ports were closing when they should have been just opening! Its effect is marginal at best. I reckon the Lucas timing instructions were aimed at trying to minimise the pinking upon sudden throttle openings. Wont cure the misfire. So my idea helped a bit- whioh suggests we are heading in the right direction. So,yes, one tooth clockwise and recentre the micrometer adjuster. Then turn the disy to get optimum tickover rpm, unless you are certain the timing mark on the pulley/damper is still at TDC.  I'm interested in how you found the rotor/cap-contact misalignment - did you cut open an old cap?  Peter  Peter Edited April 7, 2014 by Peter Cobbold Quote Link to post Share on other sites
bluebob Posted April 7, 2014 Report Share Posted April 7, 2014 Â Hi Robin Had a friend who had a similar problem after much sole seaching we found it to be slight blockage in fuel line between tank and filter it may help just check you have a full flow from tank and eliminate as you progress hope this may help? bluebob Quote Link to post Share on other sites
RobinTR6 Posted April 7, 2014 Author Report Share Posted April 7, 2014 Ok, first the port on no.6 just opening when engine no.1 at TDC. My TDC is at 4 degrees btdc, I checked this when I had the head off and did the cam using a DTI. Lastly all pipework is new, pump reconditioned pressure at MU is 90plus and I suspect gauge may be underreading. Spoke to Neil Raven Smith and didn't think that would be an issue. The clue is still the problem starts in earnest missing at 2500 rpm Quote Link to post Share on other sites
Guest ntc Posted April 7, 2014 Report Share Posted April 7, 2014 Inlet port spacing Robin,do you have a uk head? Quote Link to post Share on other sites
RobinTR6 Posted April 7, 2014 Author Report Share Posted April 7, 2014 Yep checked that, both number, height and valves. Pete Cox gave it a once over as well as I'm no head expert. Quote Link to post Share on other sites
Peter Cobbold Posted April 7, 2014 Report Share Posted April 7, 2014 (edited) Robin The shims between MU pedestal and block will change the relationship between the disy cam and the cap. The shim, by pulling the drive gear up or down in relation to the camshaft gear, allows the points'cam to be advanced or retarded in relation to the camshaft. Note its not the disy to MU shim. http://myweb.tiscali.co.uk/tlweb/tr6/injection/pi_cards/card_6.htm That might be where the cap/rotor mismatch comes from. Dont worry about shims changing the feul timing- you have #6 port opening when #1 is on firing stroke I hope (ie port opening when rockers 11 and 12 are rocking). Â Put it another way you want to get the points' cam further clockwise at the correct crank timing point, which the shimming will do. Then the cap should fit correctly. The giveaway for a wrong shim on the MU/block will be that eccentric dog not pointing at the correct angle -see second figure and text. You can see that by removing the disy. Â Peter Edited April 7, 2014 by Peter Cobbold Quote Link to post Share on other sites
RobinTR6 Posted April 7, 2014 Author Report Share Posted April 7, 2014 Peter, interesting thought and not difficult to try, I can just loosen bolts and lift the dizzy a bit . Sounds like its worth a go. Quote Link to post Share on other sites
Peter Cobbold Posted April 7, 2014 Report Share Posted April 7, 2014 (edited) Robin,I'm not sure I'm right - ignore the MU/block shims, 7:56pm post, for the present.  It might be a disy fault - too much cfa swing. Or wrong points, or points plate. The relationship between points-cam and cap is wrong somewhere. The total swing on the rotor arm twisted by hand should be about 12 degrees. If it moves much more than that suspect the cfa. If the points open, static, when the rotor arm has less than 12 degrees swing before it leaves contact with the cap contact suspect wrong parts. Might be worth sacrificing an old cap, cut top off, to see the relationship better. Points gap I'm sure youll have checked !  Borrow a fellow members disy then you can be sure its that!  Peter  In a nutshell there's not enough radially between the position of the points on the cam and the cap-contact to allow the rotor arm to contact it over about 12 degrees of cf advance. If someone can post a photo of a standard disy viewed from above, cap off, you might spot the difference. My guess is the points are wrong fitment - too short from post to the tip of the cam-follower. So they break when the rotor arm is well on its way over the cap contact, and leave contact completely above 2500rpm. Edited April 7, 2014 by Peter Cobbold Quote Link to post Share on other sites
John L Posted April 8, 2014 Report Share Posted April 8, 2014 (edited) I have been following this with interest, as I have always noticed that the rotor arm is sparking/blackened on the curved heel part, but I don't have any misfiring. Distributor is at TDC on #1 Edited April 8, 2014 by John L Quote Link to post Share on other sites
RobinTR6 Posted April 8, 2014 Author Report Share Posted April 8, 2014 TRGB suggested shortening the spring that controls the base plate movement, improvement but still missing after 2500rpm.......At least Ive now fitted Pinky's hood, very nice and my interior has affived from John Skinners. Just need the car to drive proper....trying to get a mates mate who runs a rolling road (was at Malvern so knows his Triumphs) to investigate as I'v run out of ideas Quote Link to post Share on other sites
Peter Cobbold Posted April 8, 2014 Report Share Posted April 8, 2014 TRGB suggested shortening the spring that controls the base plate movement, improvement but still missing after 2500rpm.......At least Ive now fitted Pinky's hood, very nice and my interior has affived from John Skinners. Just need the car to drive proper....trying to get a mates mate who runs a rolling road (was at Malvern so knows his Triumphs) to investigate as I'v run out of ideas Post a photo of the disy from above, and inside of cap. Quote Link to post Share on other sites
Peter Cobbold Posted April 8, 2014 Report Share Posted April 8, 2014 I have been following this with interest, as I have always noticed that the rotor arm is sparking/blackened on the curved heel part, but I don't have any misfiring. Distributor is at TDC on #1 It looks like the spark is occurring on almost the last possible bit of the rotor arm, since it rotates anti-clockwise with the pointy end leading. What do the contacts inside the cap look like? My guess is they'll be blackened on one side, the anticlockwise-most side. Why? It may be the pick-up design is meant to cover Triumphs that have vacuum advance fitted and run at cruise with much more advance, maybe 45 BTDC .In them the spark will occur earlier and so be positioned nearer the midddle of the rotor contact. But it works so you can leave well alone. ( But to bring it nearer the centre you need to move that pickup a bit clockwise in relation to the cap so the spark occurs sooner - then reset the timing by turning the disy.) Â Peter Quote Link to post Share on other sites
John L Posted April 8, 2014 Report Share Posted April 8, 2014 Peter Could I be in fact one tooth out on distributor drive? Â Robin TR6 You say you have a dwell of 31 degrees, the book mentions 35 +- 3 degrees, could you try opening up the points a bit more? Â John Quote Link to post Share on other sites
RobinTR6 Posted April 8, 2014 Author Report Share Posted April 8, 2014 Cap is unmarked (its a new dixxy doctor one) and lets face it done but 3 miles with me testing driving 100yds up the road and back, anyways herewith picsand yep its a Lucas 41219 recon'd by a well known tr specialists..    this one a bit out of focus shows the relationship between the rotor at rest with no.1 cylinder at TDC (leftmost white tippex) and a few cms to the right of it the position of the rotor arm fully advanced  Quote Link to post Share on other sites
graeme Posted April 8, 2014 Report Share Posted April 8, 2014 Robin, Â Have you changed the plugs yet? Â Graeme Quote Link to post Share on other sites
Guest ntc Posted April 8, 2014 Report Share Posted April 8, 2014 (edited) the rotor at number 1 should face where the vacume unit would be so looks right.dizzy clamp is not flat you maybe loosing ground with that Edited April 8, 2014 by ntc Quote Link to post Share on other sites
Peter Cobbold Posted April 8, 2014 Report Share Posted April 8, 2014 Try screwing the micrometer so that the points are as far anti-clockwise as they will go*. Then reset 10BTDC static by turning the disy not on the micrometer. Retest. I cant see why a rebuilt disy supplied with a cap should not be a pair, but we'll see. Clutching at straws I fear. Â * because cf advance pulls the rotor arms's firing position clockwise, maybe enough for the rotor tip to not be close enough to the cap contact it is approaching. But the cap would have to be really very badly mismatched. Quote Link to post Share on other sites
RobinTR6 Posted April 9, 2014 Author Report Share Posted April 9, 2014 Haven't changed plugs as they are new. Did try swapping with some used good ones, no difference. Will have another go with Peters suggestion today......Grrrrr  Don't suppose anyone had a cp dizzy I can borrow for a day to prove that's where the issue is ? Quote Link to post Share on other sites
stuart Posted April 9, 2014 Report Share Posted April 9, 2014 Don't suppose anyone had a cp dizzy I can borrow for a day to prove that's where the issue is ? That will definitely tell you if its a problem with the dizzy itself, What advance weights are fitted and is there any sign that they have been altered? Stuart. Quote Link to post Share on other sites
TR NIALL Posted April 9, 2014 Report Share Posted April 9, 2014 Maybe one of those cheap Dizzys off of Ebay then Sell it on afterwards. Quote Link to post Share on other sites
oldtuckunder Posted April 9, 2014 Report Share Posted April 9, 2014 Haven't changed plugs as they are new. Did try swapping with some used good ones, no difference. Will have another go with Peters suggestion today......Grrrrr  Don't suppose anyone had a cp dizzy I can borrow for a day to prove that's where the issue is ? Hi I have a brand new Powerspark dizzy with cap and rotor in the workshop, unused but with electronic trigger instead of points that you are welcome to borrow for the price of the postage that may help isolate the problem. Quote Link to post Share on other sites
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