Good morning all. I have been dealing with what I assume to be carburetor issues with my 67 Lightning for several years now. I will try to summarize the current condition of the bike as follows:
1) I purchased the bike some 20 years ago and ran it with what I assume were the original Monoblocks (they were good and worn).
2) I refreshed the top end 2 years in and included a Boyer Ign.
3) The bike never idled well and always had a tendency to race the engine at idle once it had warmed up.
4) I lived with this condition up until 2 years ago. I had a set of spare used Concentrics which I installed on the bike.
5) Same exact condition as with the Monoblocks. Engine warms up and then starts racing at idle.
6) I am starting to question everything including the Boyer Ign. Should it retard the timing when the engine is at idle?
7) I know the obvious solution is to stop being a cheap a** and buy a new set of carburetors.
8) I still would like to understand the problem better and I would appreciate any advice on the matter.
Thanks
:) :) :) :)
My instant thoughts on this one. If you are having the same problem with different carbs its quite possibly not a carb issue. Speak to boyer about it. they are very good any will usually advise or tell you where to look for the answer.
Best of.
Mike 8) 8) 8)
Hi,
I would say it is unlikely to be the Boyer but ask the question anyway.
Recheck the joint surface of head, spacer and carbs. They need to be totally flat and air tight but not over tightened.
Dave.
does sound like an air leak , the intake manifold can distort very easily , ide take them off and flatten with oiled wetndry on a piece of glass or any perfectly flat surface , same with the carb seating face. https://www.youtube.com/watch?v=L1jFtTzLh7o use this technique .
Good morning and thank you gentlemen for your input. Let me add a few more details after my attempt to ride the bike yesterday.
1. When I installed the Concentrics on the bike I did take the time to resurface the mounting flanges on both carburetors.
2. It would still be worth my while to revisit this for any possible leaks.
3. I pulled the plugs and found them very black and sooty.
4. Both carbs are set up with the needle jets clipped at the 3rd position and the idle air jets backed out 1 1/2 turns.
5. I do believe that the last time I put a timing light on the engine, I noticed a distinct advance when the RPMs were increased. I will revisit this also.
Thank you again and I shall let you know the outcome.
do the carbs have chokes?
Pockets
Good afternoon.
The Concentrics that are currently on the bike do not have chokes as I live in a fairly mild climate (western Oregon). Just one less item to muck around with.
I might have a look* later this afternoon.
(*Take every thing apart. It's not like it's the first time.)
Thanks
Hi Geeman,
As it is running rich at idle it could be that the air way to the pilot jet is partially obstructed. These small air and fuel passages seem to cause a lot issues and cleaning them is not that easy. Carb cleaner and a good blast with compressed air is a start but if these small passages are internally worn there little that can be done.
The Boyer does retard the ignition for starting with the newer Mk4 giving a bit more retard than the Mk3.
Inevitably I think that the idea in point 7 in you original post could be the answer.
Dave.
:) :) :) :)
Just a thought. Would it be possible to reset the slow running when it gets to this high reving point. The only problem I can see with this is initially after start up you will need to keep the throttle slightly open by hand for satisfactory sow running.
Not the ideal answer but I suppose it may cover the situatio n for a while. (or forever if it works)
Is it only happening on one carb or are they both doing it. Try pulling plug leads individually to check the difference.
Mike 8) 8) 8) 8)
there are various Amal concentric manual pdfs that you can download, just type into search engine click on pdf link and they should autodownload .
Thank you all for your input on this problem.
Right now I am in a bit of a crush to get some exterior painting done on my house before our fall rain is scheduled to begin on Wed. Sounds pretty exciting no?
Anyway, I feel that I need to do some serious digging (and soul searching because isn't that what owning vintage British bikes are all about? Yes, I own a few of them.) in order to determine the nature of this problem. I promise you all this: if I can't solve this problem by correcting the existing Concentrics, I'm going to buy a new set of Monoblocks. There I said it.
I'll let you know the outcome of my investigations into the Concentrics (rain is coming, it's perfect for some quality garage time).
Come Wed, in I go.
Hi Geeman, I know the US has ethanol in your fuel a good few years when stripping the concentrics did you find any evidence of corrosion caused by it on the brass jets and do you have any issues with ethanol in the fuel tank, good luck with your problem. Roy
Well I promised everyone that I would report on my latest adventure with Amal Inc. Armed with the previous suggestions of a number of members, I set out with one last attempt on the Concentrics before I finally did the right thing and bought a new set of proper Monoblocs. It went something like this:
1. First removal and check of the mounting flange surfaces. Epic warpage corrected with some serious material removal using the trusty flat file / sandpaper / glass pane technique.
2. I noticed the top of the carb bodies where the top lid mates were not flat / smooth surfaces so, more flat file / sandpaper work to correct this.
3. The carb mounting surfaces on the head were checked and lightly resurfaced as were both carb insulators.
3. The main needle position on each carb was set in the middle of the 3 positions. The plug checks had always shown a rich condition so I moved the needle clips to the top position.
4. Everything was cleaned and reassembled.
5. The first run in with the idle air screws set at 1 1/2 turns out was not so impressive. When I set the screws to 1 turn out it was if the clouds parted and angles sang. A test run found the bike with power and smoothness unlike anything before.
6. Attaining a correct (slower) tick over is still difficult but the overall performance difference was huge.
7. It would be difficult to say that it was any one thing that I changed on the carbs that produced the results (the fit of the slides in the carb bodies are still sketchy).
8. In the end I will probably by that new set of Monoblocs this winter (after convincing the CEO that I deserve them).
Thanks All