I am surprised that no one has mentioned ignition, back fire through the carb, suggests too advanced timing! You mention switching the ignition on, this suggests electronic ignition, many of these are set at maximum advance and have a limited advance curve, therefore at start their is too much advance. This is the case with my Comet, so I am altering a ATD to only advance 6 degree at 700revs then the electronic device takes over. This should give an ideal start timing and idling timing.
Starting Vincent Life with a Backfire!
- Thread starter KennyNUT
- Start date
See post 10.
First things first.
Thanks to a local VOC member (Rob) calling me yesterday it spurred me onto today's activity together with davidd's words ringing my ears of "don't go throwing lots of new things at the Comet just yet! So I dismantled the float bowl and checked the float and needle on the Amal 289. Float was fine but the cone of the brass needle at the base was not mating with the brass inlet for the fuel were the double banjo bolt fits and so was not cutting off the fuel once the chamber was full. I cleaned it out and lapped it in with a bit of Brasso until the surfaces had gone from dull to shiny. Fitted it back together and no sloshing of fuel down the crankcases. So a better result.
However, the truly embarrassing part.............I cannot start the bike at all, now. Fuel is fine, the spark plugs are sparking. I even changed the plugs as 4 came with the bike. It so nearly catches but fails to. I have started supermoto singles before, so am completely flummoxed!
Before anyone thinks I have done anything else to the carb, I have not. Yesterday I also spent some considerable time pummelling my foot with the kick start. The bike would not start then either and that was before looking at the float bowl today.
I phoned the vendor today and went through the start procedure again.
1. Turn on left fuel tap.
2. Tickle the carb (2-3 seconds).
3. Choke 1/4 to1/2 on (same position when it started before (when it backfired back through the carb!).
4. Push on the kick start gently until TDC and use the valve lifter to ease that through and complete the kick start stroke gently. Return the kick start to its normal position.
5. Switch ignition on.
6. One good gentlemanly swing with the valve lifter raised until releasing it on the down stroke of the kick and...........................nothing. Occasionally, a dull burble, very occasionally a backfire (I put that down to too much choke or fuel between the cylinder and in the inlet tract. There is certainly not the same amount of fuel around when I first posted this thread, so I am a bit happier with that.
Repeat until exasperated!
Now all his time I have to thank my wife for not saying anything, even although she knows what I paid for this piece of motorcycling history. I also pulled back from asking her to push the bike to allow me to try and bump start it!
To the timing - There is a black box plastic tied into place between the two front prop stands. I have not attempted to remove that, though I presume it takes away the need for contact points. Are the settings on it adjustable?
I am determined not to give up this Beast, that clearly I do not yet know! But it is testing my patience somewhat!
Any other advice, truly welcome.
In fact you have all been so supportive, I joined up to the VOC.
Thanks to a local VOC member (Rob) calling me yesterday it spurred me onto today's activity together with davidd's words ringing my ears of "don't go throwing lots of new things at the Comet just yet! So I dismantled the float bowl and checked the float and needle on the Amal 289. Float was fine but the cone of the brass needle at the base was not mating with the brass inlet for the fuel were the double banjo bolt fits and so was not cutting off the fuel once the chamber was full. I cleaned it out and lapped it in with a bit of Brasso until the surfaces had gone from dull to shiny. Fitted it back together and no sloshing of fuel down the crankcases. So a better result.
However, the truly embarrassing part.............I cannot start the bike at all, now. Fuel is fine, the spark plugs are sparking. I even changed the plugs as 4 came with the bike. It so nearly catches but fails to. I have started supermoto singles before, so am completely flummoxed!
Before anyone thinks I have done anything else to the carb, I have not. Yesterday I also spent some considerable time pummelling my foot with the kick start. The bike would not start then either and that was before looking at the float bowl today.
I phoned the vendor today and went through the start procedure again.
1. Turn on left fuel tap.
2. Tickle the carb (2-3 seconds).
3. Choke 1/4 to1/2 on (same position when it started before (when it backfired back through the carb!).
4. Push on the kick start gently until TDC and use the valve lifter to ease that through and complete the kick start stroke gently. Return the kick start to its normal position.
5. Switch ignition on.
6. One good gentlemanly swing with the valve lifter raised until releasing it on the down stroke of the kick and...........................nothing. Occasionally, a dull burble, very occasionally a backfire (I put that down to too much choke or fuel between the cylinder and in the inlet tract. There is certainly not the same amount of fuel around when I first posted this thread, so I am a bit happier with that.
Repeat until exasperated!
Now all his time I have to thank my wife for not saying anything, even although she knows what I paid for this piece of motorcycling history. I also pulled back from asking her to push the bike to allow me to try and bump start it!
To the timing - There is a black box plastic tied into place between the two front prop stands. I have not attempted to remove that, though I presume it takes away the need for contact points. Are the settings on it adjustable?
I am determined not to give up this Beast, that clearly I do not yet know! But it is testing my patience somewhat!
Any other advice, truly welcome.
In fact you have all been so supportive, I joined up to the VOC.
I think you have very early in ownership stumbled upon one of the most outstanding juxtapositions on the current world. That would be the massive love/hate relationship that only a Vincent owner can experience!
My first Vincent managed to make 100 miles of heaven before destroying a defective bearing on the drive side of the crank giving me the opportunity to have my very first complete dismantle on a Vincent engine.
It reminds me a bit of the classic tale of two young lovers of Victorian times -- She offered him her honour, and he honoured her offer. After that it was honour and offer and honour and offer.
I'm sure you will get it sorted.
I suspect now that the float needle has stopped leaking you may not be getting the required fuel. Tickle it until there is fuel everywhere, and then as we say, don't make love to it, Kick the f^#*&% thing!
If it doesn't start, pull the plug and see if it is wet.
Dripping wet = too much fuel
Bone dry = not enough fuel
Keep us posted
My first Vincent managed to make 100 miles of heaven before destroying a defective bearing on the drive side of the crank giving me the opportunity to have my very first complete dismantle on a Vincent engine.
It reminds me a bit of the classic tale of two young lovers of Victorian times -- She offered him her honour, and he honoured her offer. After that it was honour and offer and honour and offer.
I'm sure you will get it sorted.
I suspect now that the float needle has stopped leaking you may not be getting the required fuel. Tickle it until there is fuel everywhere, and then as we say, don't make love to it, Kick the f^#*&% thing!
If it doesn't start, pull the plug and see if it is wet.
Dripping wet = too much fuel
Bone dry = not enough fuel
Keep us posted
and adding to what Robert says..... Did the last attempt at starting end in a backfire that may have knocked the timing off? If your ignition drive is the kind that is on a taper, this is not uncommon.
Cheers, John
Cheers, John
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Old saying----"70% of carburettor problems are electrical." You seem be close to fixing the 30% that are fuel related so don't give up yet! It would be interesting to know what type of ignition you have and the foregoing suggestions re ignition timing are worth investigation. 35 degrees of advance is the maximum you should need with modern fuels and ethanol will probably snorkel your fuel hoses. Keep us informed.
You are obviously no novice but here are a few more things to throw into the mix:
Do not assume that the spare spark plugs are OK. If you remove a plug and check for a spark (away from any fuel) this will confirm some high tension output but does not necessarily mean it will fire under compression.
Try eliminating one thing at a time, e.g. use a new plug or one taken from a definitely running engine, etc.
Your mention of a "black box" suggests electronic ignition of some sort but not the make. The ignition timing is usually adjustable by moving a pick/back plate. This may be accessed through a hole in the timing cover, inside a dummy magneto or some proprietary unit housing bearings and the pick up and back plate.
Note that if you ignition is Boyer based some of these units are quite voltage critical. If the battery voltage is too low the electronics revert to full advance at kick starting speed. If your battery is not well charged you may get a spark but it will be too advanced and prone to back fire.
Good luck. I'm sure that your perseverance and tenacity will get you there.
Do not assume that the spare spark plugs are OK. If you remove a plug and check for a spark (away from any fuel) this will confirm some high tension output but does not necessarily mean it will fire under compression.
Try eliminating one thing at a time, e.g. use a new plug or one taken from a definitely running engine, etc.
Your mention of a "black box" suggests electronic ignition of some sort but not the make. The ignition timing is usually adjustable by moving a pick/back plate. This may be accessed through a hole in the timing cover, inside a dummy magneto or some proprietary unit housing bearings and the pick up and back plate.
Note that if you ignition is Boyer based some of these units are quite voltage critical. If the battery voltage is too low the electronics revert to full advance at kick starting speed. If your battery is not well charged you may get a spark but it will be too advanced and prone to back fire.
Good luck. I'm sure that your perseverance and tenacity will get you there.
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My beloved (in a very early days sense) Vincent 1950 Comet has once more offered me her honour (thanks, Robert)!
It started happily, not once, but each time I tried later today. What a great way to start a NEW year!
I was worried about the battery condition, however, I only had a 12V Optimate for my MV and this bike is running a 6 volt system, so I ordered a 6v Sakura charger online on Sunday which arrived yesterday. I removed the battery from the Comet which turned out to be a tiny little 4Ah affair, charged it overnight and put it back in the Comet later today.
Oh my Lord - its started 3rd kick with no backfire, and with a hell of a lot less effort than when it exasperated me earlier on Sunday and Monday!
Thanks to everyone who has contributed (you are all on this thread) with a reply which took me down a different avenue of thinking with each passing day. To Rob who phoned me, sensing my absolute despair and to those who gave me the confidence to start taking apart the fuel system of this antiquated motorcycle so that I may enjoy it once more without excessive fuel leakage and backfiring. To Chankly Bore who said "70% of Carb problems are electrical" - this made me smile today! To davidd who stopped me from spending money on another carb which I thought was the quick answer (I looked at a few suppliers). To Big Ed who recognised that I am NOT a complete novice and gave me back some dignity!
The lesson, here is to think through what you know and to listen to those with more experience on a strange bike and to work stepwise though it all. To those who added humour, I thank you. I needed that when I did spend some time thinking about the two lovely bikes I turned down to buy this Comet.
A very happy NEW year to all VOC members and especially to those who helped me out over the last week or so.
I will have some questions along the way during my ownership, I am sure, so I look forward to continued support to ensure on-going enjoyment with this motorcycle.
Finally, I can now smile at my wife, knowing that I don't need her today to push me down the hill to try and start this bike in the rain! Or indeed to explain why I have paid so much for a piece o transport that won't transport me!
A couple of quick questions from me.
Is a 4Ah battery sufficient?
I will looked at the black box in more detail later and determine its make etc.
So what is best? The little black box or a decent magneto system? Should I make a project of going back to a magneto in the future?
I have a 1924 pre-vintage beauty that starts perfectly from a magneto system, though admittedly she is a 335cc motor with fewer HP!
So many questions in my head right now!
Once again, "Thanks all".
I will try to enjoy this motorcycle into 2014.
HAPPY NEW YEAR
It started happily, not once, but each time I tried later today. What a great way to start a NEW year!
I was worried about the battery condition, however, I only had a 12V Optimate for my MV and this bike is running a 6 volt system, so I ordered a 6v Sakura charger online on Sunday which arrived yesterday. I removed the battery from the Comet which turned out to be a tiny little 4Ah affair, charged it overnight and put it back in the Comet later today.
Oh my Lord - its started 3rd kick with no backfire, and with a hell of a lot less effort than when it exasperated me earlier on Sunday and Monday!
Thanks to everyone who has contributed (you are all on this thread) with a reply which took me down a different avenue of thinking with each passing day. To Rob who phoned me, sensing my absolute despair and to those who gave me the confidence to start taking apart the fuel system of this antiquated motorcycle so that I may enjoy it once more without excessive fuel leakage and backfiring. To Chankly Bore who said "70% of Carb problems are electrical" - this made me smile today! To davidd who stopped me from spending money on another carb which I thought was the quick answer (I looked at a few suppliers). To Big Ed who recognised that I am NOT a complete novice and gave me back some dignity!
The lesson, here is to think through what you know and to listen to those with more experience on a strange bike and to work stepwise though it all. To those who added humour, I thank you. I needed that when I did spend some time thinking about the two lovely bikes I turned down to buy this Comet.
A very happy NEW year to all VOC members and especially to those who helped me out over the last week or so.
I will have some questions along the way during my ownership, I am sure, so I look forward to continued support to ensure on-going enjoyment with this motorcycle.
Finally, I can now smile at my wife, knowing that I don't need her today to push me down the hill to try and start this bike in the rain! Or indeed to explain why I have paid so much for a piece o transport that won't transport me!
A couple of quick questions from me.
Is a 4Ah battery sufficient?
I will looked at the black box in more detail later and determine its make etc.
So what is best? The little black box or a decent magneto system? Should I make a project of going back to a magneto in the future?
I have a 1924 pre-vintage beauty that starts perfectly from a magneto system, though admittedly she is a 335cc motor with fewer HP!
So many questions in my head right now!
Once again, "Thanks all".
I will try to enjoy this motorcycle into 2014.
HAPPY NEW YEAR
I have a magneto and an Alton on my twin...if you ask 30 people you will get 40 answers as to what is best. Luckily we now enjoy some really good options for all of the various electronics and as members we now have the accumulated knowledge of the past 60 years upon which we can rely. These forums, the VOC facebook page are but 2 online resources..Good Luck!