ET: Engine (Twin) Still Can't Start My Twin, Replaced Mag, But Not A Pop

[greg brillus]

Hi there Carl, I'm now stating the obvious but would it be possible for some other Vincent owner who lives near you to pop in and assist you........sometimes a second pair of eyes is worth while as they may pick up on something you have missed........they also have a set of legs to help fire the bike up........If the engine fires up and quits shortly after, if your carbs have chokes, you should be able to close these as the engine struggles to run, this should draw in some fuel and keep the engine running if only a bit rough........if this happens, even if you manually put a hand over one bell mouth to choke one cylinder, this would indicate the fuel level in the bowl is too low.......rotating the carb on its manifold stub will increase the height of the float level, even if its just temporary to get the engine running........on the 276 carbs the lower main cap nut that holds the jet block into the base of the carb body, is available in 4 different heights........this effectively alters the float level.......but not something the average owner would know unless you had several of them sitting on the bench.......On my Rapide both these lower nuts were wrong, and the level was too low.......On a 289 type carb this issue would be worse as the 289 carbs are much bigger than the 276 type........Good luck.......Greg.

 

[CarlHungness]

Hi there Carl, I'm now stating the obvious but would it be possible for some other Vincent owner who lives near you to pop in and assist you........sometimes a second pair of eyes is worth while as they may pick up on something you have missed........they also have a set of legs to help fire the bike up........If the engine fires up and quits shortly after, if your carbs have chokes, you should be able to close these as the engine struggles to run, this should draw in some fuel and keep the engine running if only a bit rough........if this happens, even if you manually put a hand over one bell mouth to choke one cylinder, this would indicate the fuel level in the bowl is too low.......rotating the carb on its manifold stub will increase the height of the float level, even if its just temporary to get the engine running........on the 276 carbs the lower main cap nut that holds the jet block into the base of the carb body, is available in 4 different heights........this effectively alters the float level.......but not something the average owner would know unless you had several of them sitting on the bench.......On my Rapide both these lower nuts were wrong, and the level was too low.......On a 289 type carb this issue would be worse as the 289 carbs are much bigger than the 276 type........Good luck.......Greg.

Thanks so much for the concern..I'm makin' everyone including myself nutso...have SO many damn hours in this problem I am at wit's end and will just have to give it up. No Vincent owners nearby...ace mechanic Glen Bewley lives five hours away and even he's frustrated with me because he knows that I know what-to-do and how to do it. Bike ran great for years..then pig to start, finally got it going..and started the journey. Finally got it to run with the B-TH and sounded terrible...couldn't re-start..then re-started and still lousy. Got it to run with the Lucas..sounded OK but ran for a few seconds. Had Lucas rebuilt last week, installed, ran for a few seconds, could not re-start. I re-timed it, and having one bitch of a time doing the ATD with the timing chest on...got it going again for few seconds, and now nothing. Can't get it to run long enough to put my hand on the chokes, which I thought of, and hand over the carb..now can't get it to fire at all...has to be a fuel problem and wondering just where there could be an air leak (which must have appeared out of the blue). Am mentally worn out, so have to get on with other projects. Possibly Glen can take a look at it in September..he's worn out on it too and doesn't want to discuss anymore, he's busy. I finally get the ATD on, and then finger tighten my bolt that goes in the earth brush hole (to hold armature) and as soon as bolt touches armature, light goes BACK ON...so it's ON-OFF with the damn light..and finally I had to figure 'it has to be withing a quarter of a degree so will leave the light on"..so it has been timed OK. Then when I tighten ATD the ears on the ATD won't retract..so fiddle, fiddle..finally get the ATD where I think it is OK...and bike fires momentarily...then seems like no fuel. Have had exhausts and timing cover off 3-4 times, and on and on...wears you out mentally, especially since I've installed everything from the trans gears to pistons to dis-assembly and assembly of the whole machine 3 times in the past and have read every word ever written on the machine I believe.

 

[ACD]

Carl, with the ATD causing trouble and locking up when you tighten it, and requiring a bit of a fiddle as you say to get it to return. Could it be whatever is causing it to lock in the advance position as your installing it is catching and locking it in full retard once its on. It would allow it to start but with a dead cold engine not run because the ATD would be locked at around 4 degrees?

 

[CarlHungness]

I just thought of that too..but, first time I installed the rebuilt Lucas the ATD was installed without the timing chest
on and all went well..and the bike started, ran for a few seconds. So now, and boy do I not want to do it..I'll yank the pipes, drain the oil, remove the timing chest cover, re-time the plot and install the ATD with the cover off so I am
positive it is working as it should. It's a nightmare.

 

[CarlHungness]

Finally got it started and she sounded just great...for about a minute, which is longer than
any other time in the last few weeks. I removed timing chest cover so I could
be positively certain my Lucas mag installation was spot on, and after a dozen kicks the bike fired to life. It
ran fine for about 30 seconds, faltered a bit as though it was running out of fuel, I revved it, it kept on going. I
held it at exceedingly fast idle, very fast, and thought I detected a bit of falter as though it wanted more fuel,
then once more, it faltered and while I tried to keep it going, she died. And refused to re-start. I gave up, went
to lunch, came back and tried it again, and it sure wanted to start, popped, then fired for about two seconds,
then nothing. Thus, I am as certain as I've ever been the mag is fine, timing is at 35 degrees, and my problem
seems to be fuel. Overall, I think fuel delivery has been the problem all along. When I did get it running on the
B-TH this year, it sounded horrible, wouldn't re-start. Then installed the Lucas, sounded great for 30 seconds, died,
and I sent the mag out for rebuild. Now to find the fuel problem. I've had the carbs off 3-4 times, replaced the
jets, cleaned all orfices and once again flummoxed as what to do next. The lines seem to flow fuel just fine,
the carbs don't have adjustable floats. Wondering if possibly a float has a pinhole in it? The rear cylinder is
running very rich, blackish plug, and for 20 odd years it has been tan. I have a 'new' top end and pistons about 5,000 miles ago by Glen Bewley, which seemed perfect. What would cause the rear cylinder to run so rich..that I'm missing.
She sure didn't start easily. I've been experimenting with finding the short stroke, going just over and kicking with
no decomp. Also experimenting with finding a compression event, kicking and letting decomp off at bottom of
stroke or as near to that as I can. I'm getting some good full swings in and the engine is coming ever-so-close to
starting, and overall it seems as though it is flooded. My procedure has been, open petcocks, let it sit for a couple of minutes, tickle both carbs, pull decomp and run through three times...let it sit for 15 seconds or so hoping fuel will
atomize, then kick. No matter what my procedure, once started it ought to run, and has to be starving for fuel
as it revs great, then dies. At least I DID get it to run for a minute and that's a milestone

 

[greg brillus]

Carl, When you striped the carbys did you replace all the sealing washers including the one inside the large base nut that holds the jet block in........?.....Cheers........Greg.

 

[CarlHungness]

Carl, When you striped the carbys did you replace all the sealing washers including the one inside the large base nut that holds the jet block in........?.....Cheers........Greg.

Yes..but, I see it is difficult for me to get the rear carb, especially, sealed. I've had the jet block out 3-4 times and believe I've seen some seepage around the threads so wondering if I'm sucking air. I've previously read on a Vincent site that Hylomar is pretty great stuff for sealing. Thus I have smeared it on all of the smaller washers, but not the large one. I plan on more dis-assembly of the carbs again tomorrow and while I'm not in love with the idea I am going to try glopping some more Hylomar on the washers throughout. I'm hoping my problem all along has been air seepage so I'll see if I can remedy the problem, if that's what it is. It is an iffy job to tighten all the bolts on the carbs, especially the one under the jet block as I fear stripping something so I'm ever so cautious. That being said I'm in between tightening enough to prevent seepage and stripping. The rear carb especially has drips. I noticed same today before firing it up and did go back and re-tighten, but I sure didn't want to. I feel as though I'm on the cusp of disaster if I tighten a 32nd more and it's a lousy feeling. Now I'm thinking about putting the Hylomar on and waiting for a few hours before screwing anything together. That's a good suggestion Greg and I just wish I could 'send the carbs off' , get them back with a note that says, 'ready to go'. The expense of replacing the parts is one thing, but the feeling of being ham-fisted is something I have tried to avoid at all costs. I've stripped a few threads in my time and there isn't a worse feeling. I also have some cork and may make a few new washers, which I'm fairly experienced at. Some of the new washers are extremely hard and I've seen materials for the carb washers vary from medium to pretty hard. You have no idea how much I appreciate your (experienced) input. The rear cylinder's plug is sure a lot darker than it's ever been, but I haven't been able to do a clean shut off either. The great news, I think, is I'm down to considering just one problem now rather than both electric and fuel. When this thing fired today it was like hearing Vivaldi's Storm (I'm a violin player) and my head went back in Thanks.

 

[greg brillus]

I've seen the large base cap washer made so the ID was too small.........this effectively blocks off the pilot circuit all together thus it runs briefly on the rich mixture due to tickling the bowl, then it quits due to fuel starvation shortly afterwards........this sounds like your symptom.......the black rear plug could be due to the rear bowl level being too high.......perhaps rotate the carb on its spigot clockwise a little to lower said level.........worth a try if it helps........cheers.......Greg.

 

[CarlHungness]

I've seen the large base cap washer made so the ID was too small.........this effectively blocks off the pilot circuit all together thus it runs briefly on the rich mixture due to tickling the bowl, then it quits due to fuel starvation shortly afterwards........this sounds like your symptom.......the black rear plug could be due to the rear bowl level being too high.......perhaps rotate the carb on its spigot clockwise a little to lower said level.........worth a try if it helps........cheers.......Greg.

The Amal parts illustration I have does not show what I'll call 'the bolt that holds the float bowl on'..I tried to start
the bike, no luck, so removed the rear float bowl, took off the top and no fuel in it and I KNOW I had just tickled it
minutes before. I looked at the arm that is attached to the float bowl and sure enough there was a knackered washer
flattened out in the bottom boss, where the aforementioned bolt goes through. This bolt has two holes in it that
are parallel to the ground, and the center of the bolt is hollow. It appears as though one of the two bolt holes is
supposed to line up with the smallish hole that is in the arm, to allow fuel to run through it. The arm has a very
small bolt in it on the outside I'd never removed, and wondered why it was there. I scrapped the old washer off,
and it was definitely covering up SOME of the hole in the arm. Thus I wonder: How was I able to tickle the carb
and get fuel to spill out. Then again the feed hose is at the top, so fuel could enter the float bowl, possibly fill
and spill out as it is supposed to. Then too, the rear carb was still leaking at the bottom bolt. I was just too
knackered to put it back together tonight and try to re-start. But, I think (we) have found the problem. I found
the flattened washer this afternoon and then came home and read your response, so I sure hope you (and I) are
spot on. My question is: Do I remove the tiny bolt from the outside, line up the hole(s) in the bolt so they are
in line with the hole in the float's arm? That seems to be the reasonable solution, however since there are only
two holes in the bolt hole (not four) it seems as though my tightening process will have to line up the holes
when the bolt is tight, and/or one may need an extra washer on the bottom of the bolt in order to tighten
it sufficiently so it doesn't leak. At any rate, seeing the flattened washer was phenomenal. I have cleaned the float
bowl time and again and paid little or no attention to the round boss on the arm that holds said bolt. Your explanation sure sounds as reasonable as any I've ever heard. Will bolt the plot together tomorrow and see how it goes. Lord-love-a-duck, if this is the problem I'm blessed. You're just right..she ran beautifully momentarily and now I think I can see why she ran out of fuel. Thanks so much. It was just my luck to see the flattened washer, but you would have saved my bacon with your diagnosis. You've sure been there and done it. Here's a pic of the bolt, the bad washer and the tiny bolt that goes in the end of the arm. The washer was completely inside of the boss and at least half-covering the feed hole to the float bow. I was SO surprised the float bowl was empty. For years I have always shut the taps off and run the carbs totally out of fuel when parking the bike for a few days, and it takes a few minutes for the machine to use up all the fuel in the float bowl, so I knew something was awry in the feed and found the flattened washer.

 

[oexing]

Carl, the knackered washer is only part of your problem, but you do replace it anyway. You don´t have to align the two holes in the hollow bolt as it is waisted around the holes. The small hole and short bolt are just for plugging the drilling that goes into the float chamber so no other purpose and not your problem. At same time go through that drilling into the chamber for cleaning it safely. I was thinking about a check of both float chambers after you have got several seconds of a running engine: As soon as the engine has died like it does for weeks , close the fuel tap and feel for the ticklers. When fuel level is still as required you should feel the ticklers hitting the floats inside, both ticklers checked like this. So you know fuel has filled the chamber correctly. If this is not so, the chamber with low level does not get fuel , so something to investigate.
The fibre washer Greg mentioned is the large type pressing on the jet block onto the body. In case the i.d. of that washer is too small it will block the drilling for the pilot jet and starting the beast will be a pain.
These fibre washers will not seal this place easily when faces may not be extremely smooth. So I´d go for a small cross section o-ring a tad thicker than the fibre washer which will then be just a spacer, no seal. See photo, the washer o.d. reduced for the o-ring around it.

Vic