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KVF Replacement...

Bazlerker

Well Known and Active Forum Website User
VOC Member
I have a KVF on my Rapide which functions perfectly...except I find it difficult to set the timing accurately..Is a BTH easier?
 

BigEd

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VOC Member
VOC Forum Website Moderator
Dear Bob,
The simple answer is yes.:) The return question is if your KVF is functioning perfectly why change it? Setting the timing accurately may be more difficult but once set satisfactorily how often do you need to change it?
I have a KVF on my Rapide which functions perfectly...except I find it difficult to set the timing accurately..Is a BTH easier?
 

greg brillus

Well Known and Active Forum Website User
VOC Member
To be honest Bob, I have fitted quite a few of these mags (new BT-H) Even to my own bike, and as good as they are, I can say with some qualification that to set them accurately is a bit of a myth. As even though the alignment pin used to lock the shaft for timing works ok, you can usually move the shaft a good couple of degrees either way. A strobe light would be nice, but not normally dooable on a standard engine, and who knows what the retarded possition is......?? At least with a set of points, you can obtain accurate timing when they open, with fairly simple test equipment...........Cheers......Greg.
 

vibrac

Well Known and Active Forum Website User
VOC Member
a 6mm rod is used to set the B-th a 1/4" rod is too big thats 13 thou and is an indication of the clearances involved so we are talking very small movements well inside the sort of discrepancies one has to allow for in the 3 drive faces of the cogs twixt crank and mag pinion. Simply put the minute movement of the rod must be teated as another 'cog' interface and loaded in the direction of the drive in the same way.
Also do not forget I have always thought that the final adjustment on a BT-H is via the slotted fixing bolts, something not on Lucas mags. I always mark the boss/crankcase joint and find that final adjustment invaluable when testing our racers on the rolling road to see if movement while running gives us more or less power over the range- always worthwhile after a carb change or exhaust modification.
 

bmetcalf

Well Known and Active Forum Website User
VOC Member
Bob, does the timing change when you tighten the nut? When mine did that, I had the armature and ATD out and lapped them together with fine valve grinding paste. When the points are where you want them, carefully hand tighten the nut to where the taper is barely starting to engage, then tap it home with a socket over the nut's head. At that point, final tightening of the nut shouldn't alter the timing.
 

greg brillus

Well Known and Active Forum Website User
VOC Member
Too true, what Tim (vibrac) said.....benefit of most racers (and soon to be racing one myself) is they generally run a belt drive primary.....so setting the ignition timing with a strobe whilst running is easy. What Bruce has pointed out makes perfect sense.
 

Bazlerker

Well Known and Active Forum Website User
VOC Member
The best performance I have ever felt was after Phil Mahood set the timing for me sometime in the late '80's....Nothing since has been as good, and I listened very carefully to the instructions that Phil gave me..My impressions are all "seat of the pants", and are clouded by the fact that my valve springs are the originals, so they have probably gotten a tad tired and are thus partially responsible for the poor performance - the Beast will simply no longer pull past 100 in 3rd...Nonetheless I find setting the timing frustrating and I do not have the patience required.
 

Chris Launders

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VOC Member
What I have is a small "T" bar the same thread as the earthing brush holder with a gently rounded end, remove the earth brush set the points and LIGHTLY nip the shaft with the "T" bar and then fit the atd,this saves having to be at both sides of the machine at once. In fact the points can be set off the bike and then the mag fitted. DON'T A) Tighten it too much. B) forget to remove it and refit earthing brush unit.
It may be possible to do something along the lines of the BTH mag but I think it would have to be done to each mag individually.
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Hello Bob, I don't think the petrol is as good as it was the 80s, and I wonder if you have changed the silencer since then. Be careful lapping the ATD onto the shaft, If you do it too much, the shaft will show through the centre of the ATD, And stop the nut from tightning, The cure is to drill up into the nut a very small amount. Cheers, Bill.
 
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