View Full Version : Vincent problems
04-20-2010, 08:10 PM
I'm working on a 54 Shadow & would like to get some feedback on a carbon fouling issue with the back head. The bike has late mark 2 amals-electronic mag-12 volt system & has been running great for 3.000mi. It started to foul the rear plug, when I checked it there was a small piece of carbon across the tip. Installed a new plug & ran it a approx 20miles, pulled it out and noticed the tip was actually pitted & rough. Still ran good until the next carbon foul.I have the heads off now & will try to post pictures latter.
04-21-2010, 03:25 PM
If you get no replies here, try the VOC which is very active with their Vincent discussions.
54 Black Shadow? You lucky B!
04-21-2010, 05:43 PM
It seems to me you get what the English call "whiskers" on the plugs. In my language the name the problem is called "pearl on the plug" and that is caused by excessive oil in the combustion chamber that is burnt and deposited on the plugs, ultimately shorting out the plug.
My B Rapide had this problem on the first ride after a long storage, oil had came down from the oil tank, past the oil pump and filled the crankcase. So when starting up the double acting oil pump needs a long ride to balance level in the crankcase and tank, if the plugs would allow.
I found plugs that kept burning clean these 10-20 miles of the intitial spring ride called "Bosch Platinum". OK, the bike smokes upon this kind of startup... I know there are ways to drain the excessive oil, but I think too much oil is better than too little.
There could of course be other reasons of oil burning in the rear cylinder too. Check the connections points of the oil return pipe and read up on the function of those "metering wires" ... -and the valve guide, and then the oil rings, and the oil ..
Ref VOC mentioned. Don't need to be a club member to use the forum for which 2 of the three categories (public, technical) are available to you merely by registering here (http://www.vincentownersclub.co.uk/register.php?).
Not to cause your email inbox to implode, there is also (extremely) chatty managed mail list on jtan you can join as well. Send an email note to firstname.lastname@example.org and in both the subject/body of the note insert the word subscribe. If not your cup of tea, same note with unsubscribe. Here amongst esoteric discussions on every topic imagineable by long time owners you will also glean a wealth of Vin info from nearly everyone of note in the hobby.
Another ready source of reference info can be found in the links top right at thevincent.com (http://www.thevincent.com/).
Regarding your machine and mention of "electronic mag" - I'm assuming that to be the excellent BTH - modern ignition systems enable these machines characteristically run rich to begin with, along with generous oil bleed down those short guides, to have even greater lattitude to burn an even less ideal mixture. Both of mine had dry fouled plugs in the past (on Lucas mags) on purely rich mixtures alone. Merely changing to a BTH cured that on the spot so a previously excellently running machine suddenly gone weak may have a developing ignition problem, especially if retrofitted with any number of well meaning alternatives to the BTH. As you don't mention smoke out the breather, or smoke in general, doesn't sound cylinder/ring related but have seen motors with misaligned top/bottom valve guides wear in short order. Might check your stems for signs of scuffing. Will mention it is not unusual for a machine sitting along time to have signs of slight oil moisture on the back of the valve heads that has drained down the guides. The manual quotes rather high consumption rates for these machines in normal operation.
If it's any comfort on diagnosing this more common affliction on Vin's, some of the more obscure causes/cures in the past were block joggle wire ports and crankcase ventilation (pressure) problems rectified by fitment of PCV valves to engines ...which then changed the problem from fouling to dry guides on machines without stem seals. With a Vin, you're never really done, and the funny thing is, most don't want to be.
04-24-2010, 09:07 AM
Alittle more information. We are going to install new joggeltubes so we were pulling the heads anyway. The rear intake rocker oil line threads were bad so i chased the threads & installed a slightly longehead bolt in the joggletube about a year ago, about the same time this appeared??? Compression is good so i have suspected the valve guides may be the problem since the carbon deposits could only be produced by burning oil. We have the new joggle tubes & will renew the valve train while its apart. Would this be better performed by a Vin specialist? We have an excellent Tri. BSA,Harley mechanic locally. I'll try to post picts.
Is there a modern upgrade to the valve guides that i should be aware of? Guide seals?
Baytown, The Shadow belongs to a friend of mine so i get to wrench on it but i do ride it some also. Lucky B-----????
Peter as you might have guessed this is Brads bike.
Figured it was, 54’s are rare birds and die cast ones like his even more so. If you’ve got your valve train down, as you’ve already had a rocker oil line thread issue, if not done already, get a set of locking rocker feed bolts from John Healey, this will ensure your rocker bearings don’t wobble in the head bores. This will require pressing the shaft out of the rocker bearing to fit the retaining nut but it’s truly worth it. I have neither joggle wires nor valve guide seals on either Vin and with a good crank case vent setup, no oiling issues - on stock cams, that is. Which I might mention now. You may have noted the lower valve guides are secured in the heads with threaded lock rings. If it appears someone has removed any remaining guide material above the lock ring that's been done to allow max lift on a sportier cam without the stem ring fouling the guide. As this guide/lock ring arrangement sits very low relative to the head surface, any oil pooling in that area will have a tendency to go down the guide. If yours have been modified thusly, if not going with guide seals, I'd cut some small shallow drains there to allow the oil to run off to the tunnel.
While having your rocker shafts pressed in/out, check to make sure these are very interference fit to the rocker and if at all suspect, get oversized ones from John. The pushrod input force to the rocker arms on these motors are slightly offset and a loose rocker shaft will cause them to bang like they have excessive valve clearance.
Speaking of valve guides/heads, as someone will be carving on these non renewable resources, I’d only entrust the heads to someone having the fixture which will align the top and bottom valve guides to each other and perfectly center them to the valve seat and in perpendicularity. That normally rules out many general Brit shops. Believe Leo Goff has a setup for this, if not then, Glenn Bewley possibly.
Regarding your joggle tubes and getting a good seal. Unlike brass/copper plumbing fittings that can be slightly compressed into conformity, the mating parts being steel here will not. As the English say, being repop’s, they will need to be very carefully fettled to ensure leak free operation and that means lining up the tube spigots perfectly within their respective fittings. If the tube is too long and your re-bending can’t achieve correct alignment, then use a very small rubber o-ring within the gland nut. As you are limited in how much torque you can apply to the copper crush washers on top by virtue of the more fragile fiber washers on the bottom side, I’d dress them as flat as possible in hopes of getting a better seal.
05-14-2010, 07:08 PM
Lucky B: Polite removal of a mild swear word, meaning you lucky person. No swearing on this list!
I was going to ask you what a Joggle Tube was.
05-18-2010, 07:16 PM
Probably means joggle wire.It is a small wire that can be used to further restricth the oil flow into a rocker feed.
Don't worry about seats.I've seen more damage done by people pulling/replacing seats than lack of lead did.Recently somebody pointed out an interesting fact.Lead wasn't introduced until the 50's in gas.
weak spark (who made your ignition?)
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