I have recently bought a Starfire which has been standing unused for about 4 months that I know of could be more. I put fresh petrol in started no problem ticks over well but after about a minute or so it just stops no missing or spluttering just stops, couple of kicks and it starts up again then once again after about a minute or so it stops. I have done this about 4 times before I decided to put it back in the garage and find out what the cause is. have checked the points they are ok as is the plug so am wondering if this could be carb issue it has the concentric carb fitted but this is the first bike that I have owned that has a concentric carb fitted all my previous bikes had monoblocs. Am looking for advice thanks.
doing what your bike is doing is usually indicative of a dodgy electrical component.
they are cold when when you turn the bike on and warm up electrically after a while - generally failing when hot.
the 1st and cheapest place to start is the condenser which is across the points
replace that 1st and clean/rest the points while your'e there
Might also be the fuel tank breather or float bowl breather is blocked.
Thanks for those replies. Not at the moment convinced it is a petrol problem as bike starts and ticks over OK and when it stops you can start it up straight away either first or second kick. Have been looking on line about testing the condenser with a multimeter. you discharge the condenser first then set the multimeter to ohms but online they do say at what setting to set on the scale mine has setting from 200 2000 20k 200k 2000k which none do I use. Then you set the meter to DC volts but once again do not know which setting to use my meter says 200m 2000m 20 200 600 which setting do I use when testing the battery for volts I use the 20 setting
For what the condenser costs, I never bother testing them.
Just stick a new 1 on
If your condenser is external to the points, you can use a car condenser mounted conveniently near the coil, usually cheaper components
Testing with a multimeter is quick and easy. I've just fitted a new one on my B40 as the test results were hit and miss. The original spec is unavailable, so I've fitted one from an early mini (half the price) under the seat next to the coil. If you do this make sure it has a good earth.
Thanks for that on my Starfie the condenser is under the seat bolted to the rear of the toolbox like you say I think I will just buy a new one and go on from there.
The new one goes across the contact breaker wire on the coil to earth.
Check polarity of coil whilst your there.
If bike is neg earth, then points wire will go to neg on the coil along with condenser wire.
Condensers tend to fail when the engine is being stressed at high RPM manifest by a misfire.
Points failing tend to give you a slow speed, just pulling away misfire. I totally agree that a component getting warm can fail but surprises me that it could get hot that quickly and fail that way.
I've had issues with modern fuels deteriorating causing rust in the tanks, grit and rust in the fuels.
I suggest removing the tank and washing it out thoroughly.
Strip the carb (taking care to note the pilot setting and needle setting as you go. Blast the small passage ways with carb cleaner and then compressed air (particularly the tiny compensating hole just inside the main choke - usual caveats re no wire or drills down jets).
Check the fuel filter inside the tank on the tap is intact and not clogged.
Reassemble with new gaskets and washers (o-rings rarely fail) and take care not to overtighten flange nuts (lock washers, self locking nuts preferred) and fresh low ethanol high octane fuel (premium) eg Esso Synergy Supreme this is ethanol fee at moment but will go E5 soon.
Also if laying it up might be best to slosh some 2stroke mix around the tank to add a little oil to the surface and then wash/dilute out before using again.
Thanks for those replies I will work through the suggestions,however I am not convinced at this stage it is a petrol problem I am 81 years old have been riding bikes since I was 16 not continuosly but continuos since 1995 I have restored an A10 a C12 A65 A7 so I have had numerous problems both fuel and electrical which at times have caused a few headaches. In my experience if it is fuel related then you normally get some warning missing spluttering that kind of thing. In all those years I cannot ever remember having a blocked main jet but have had a number of pilot jet blockages plus other carb problems you usually get some symptoms like with a blocked pilot jet normally the bike will try to start but will not and if it does start then it will be missing and spluttering. Now electrical that is my weak point they have always caused me the most headaches like now trying to test the condenser have watched videos on line the first one I watched a guy set the ohms on the multimeter to 20k then putting one lead on the connecter the other on the body if you get a high reading of 18-19 then condenser is OK if you get a low reading 1-2 then condenser is faulty. Using that test on my condenser I get no reading at all. The only thing with Starfire is this is the first time I have ever had a bike with a concentric carb all my other bikes have had Amal Monoblocs maybe concentrics react differently,the main reason that I suspect an electrical problem is the sudden stop of the engine no prior warning it is like switching your light off at home it is that sudden but you can start the bike up again with just a couple kicks and the whole saga starts again runs perfect for about a minute then suddenly stops. I do appreciate the help that I am getting Thanks.
You have a long experience with old machines.
When you restart do you tickle the carb again?
I've had exactly the same issue with 1036 Mk1 concentric on a Goldie.
Start up with tickler, run for 20 seconds or so then dies, phut!
I cleaned the carb thoroughly and found blocked compensator jet with rust bits (my main tap filter was ok but my reserve tap filter had a small hole in the fine mesh hence the grit).
I have the electronic test gear so cap testing is easy just with Fluke Multimeter and they are a bit of kit well worth having (so no need for me to use either Tel-Ohmike or the Hunts CRB!!
But of course for a few pennies by all means buy another cap but a lot of car caps and points available now coming from the far east are total rubbish and I'd go electronic at drop of a hat if I planned using it regularly.
No Idid not tickle the carb just kicked it over and couple kicks bike restarted. Have got the tank off and have done multimeter test on the coil using the ohms setting at 200 I get a reading 0f 5.2 changing the ohms setting to 20k and taking a reading from either connector to the plug lead hole I am getting a reading of 8.76. From what I have checked on line the reading across the connectors should be .4 to 2 and from the connectors to the plug hole 6k to 20k. Is the coil OK or do I need a new one. Thanks. I will be next taking the carb off and checking that over but because of other things may not get around to that till the weekend. Thanks
When testing, the component to be tested must be discon totally from everything else.
Primary , across the 2 lite terminals should be around 4 ish ohms.
Secondary , 1 little terminal and the other probe down inside the ht tower, about 12k ohms ish.
I say ish but these are ball park.
The ht lead should be pure copper therefore 0 ohms and the suppressed plug cap around 10k.
Just try the condenser 1st, easy and potentially quick solution
Thanks for that the coil was still attached to the bike when I did the tests will take it off tomorrow and try again. While waiting for the condenser to come I thought I might as well take the carb off check it out, the inside was spotless no signs of any dirt blew compressed air through all holes all OK. The airscrew position has got me thinking, now with a mono bloc carb the starting point for tuning is one and a half turns out, on this concentric carb the screw was not quite a half turn out are concentric carbs different. Also the needle position the Amal catalogue says posotion 2 but in the library I checked the instruction book for my model and it says position one, now I don't think this would contribute to my problem but I would like to get it correct when I put it back together not sure what position was before I stripped it as when trying to compress the spring to release the throttle cable somehow disturbed the needle clip and the needle fell out getting a bit clumsy in my old age.
The 1.5 turns out is a starting point for concentrics as well.
Needle position as you say, won't affect this problem, but put it in whichever clip your bsa manual says or failing that ring Burlen in Salisbury , they took over all things Amal and are a mine of information.
Check the ht cap resistance as age can make these caps difficult for the spark to penetrate.
Your coil readings weren't far off fine anyway.
Amongst all thearticles that I have collected over years I found this paragraph in an article Tuning your carb.
" Pressed in pilot jet
Ama; 4 stroke carburetors have .016diameterpilot jet (622/107) pressed into the body. It can be cleaned using a 78 drill....016" diameter drill. After cleaning, blow compressed air through the pilot passge.
If the pilot air screw has to be screwed in past 1 i/2 turns in to richen the mixture the standard jet can be enlarged to the next size with a 77 drill (.018") 0r with a 76 drill (.020") as necessary. If you go too far, for the majority ofbikes, a smaller removeable pilot jet (124/026) can be screwed into the tapped hole in the body."
This course of action would have to be a last resort thing, at the moment I would like to get the bike at least running consistently so I can have a go at tuning the carb properly Having checked the plug I can see that it is running quite rich. Unfortunately I am going to have leave off working on the bike for few days because of ohther commitments. I will come back and let you no how I get on. Thanks to all who have gave info.
rubbish in the carb!
Back working on the bike, things are getting worse have had the carb off and dismantled 3 times cleaned out all passageways did not have a number 78 drill to clear the pilot jet but did have set of welding nozzle cleaners the smallest of which is0.0155 dia half a thou smaller than the pilot jet but is longer than a 78 drill so can get it right to the bottom through the jet have done this 3 times blown compressed air through all openings blocking them off with my finger so making the air blow different ways can feel air coming through all openings. Have refitted the carb but bike will not even try to start have a good spark at the plug but here is the thing after numerous kicks took the plug out and it is dry so looks as though petrol not getting to the plug although carb flooding OK and when I took it off there was plenty of petrol in the float bowl. Where do I go from here Thanks. All new gaskets and seals.
It is odd that no petrol is getting through at all.
We can assume that:
- the petrol tank is vented (no air lock)
- petrol is truly fresh and new
- petrol tap filters are clean and the taps run clear
- you are testing for moment with air cleaner off (so not clogged)
- the carb is correct 4-stroke type (not a repurposed 2-stroke one)
- carb is fitted to manifold with o-ring (not overtightened)
- throttle slide moves freely and not jamming and goes up and down in the body, and it's clicking top and bottom of travel
-choke slide is or isn't in place/being controlled with fully operational cable
- you've confirmed that the jets are clear, float chamber fills
- float moves freely on the pivot
- ideally it has a black stay up float with adjustable tangs and Viton tipped aluminium float needle
- are starting at basic setting (stock slide, needle and needle position)
- your engine has good compression (tappets correct etc)
-if you swing it over freely you get inlet manifold suction (hand over inlet to feel suction)
- the ignition is set up at correct point of cycle (ie not sparking on the exhaust stroke
- you are using a non-resistor plug, non-suppressed cap and solid copper HT lead
If you have done all of the above I cannot think of anything else.
I would give it a shot with a squirt of easy start down the inlet tract and pray!
Thanks Neil. What is strange is when I got the bike with fresh petro lin I tried to start it but it would not start so after few kicks I took the plug out and it was wet heated it up with blowtorch fitted back in bike started first kick ran OK ticking over perfectly reving with no missing but after about minute it suddenly stopped no warning just like switching a light switch off. Bike started again after a couple okicks same again ran for about a minute then suddenl stopped did this 4 times in a row decided to try to find the fault. Was advised that this is a blocked or partially blocked pilot jet. Have had the carb off 3 times cleared all openings with compressed air also as I have explained cleared the pilot jet and can feel air blowing through it The only thing that I have done extra to the carb is fit viton float needle as I ordered it along with new gaskets. Now I have a good spark but it will not start. It was starting OK before I took the carb off just would not keep running.
Bob,
If you do a search on the internet for Bushman's Carb Tuning Secrets, you may find it quite interesting.
My own thoughts are that you still have a blockage in the pilot passageways.
Unfortunately, the only way to verify this is to remove the alloy blanking plug opposite the pilot air screw. You will probably destroy it getting it out. I don't know if new ones are available. You will then be able to see that your nozzle cleaner is going all the way through the jet. At the moment, I don't think it is. Maybe you could try an ultrasonic cleaner?
I think I would drip or preferably spray a little petrol into the intake, while trying to start it, or perhaps a little petrol through the spark plug hole. It should then at least start.
If you still think it's an ignition problem, you could invest in a Spark Gap tester. This will tell you if it's sparking under compression.
Good luck, and keep at it. You will get there in the end.
Treat yourself to an HT tester.
Little plastic neon thing that goes between the plug and its plug cap.
Very useful to let you see if sparking under compression.
Failing that, as others have suggested try squirt of brake cleaner into carb air filter and see if it fires
I posted this problem on another forum and a guy said check that the float bowl is level because it can suck in and affect starting. So I took the carb off and checked and sure enough the bowl was bowed using wet and dry on a flat surface I got the bowl perfectly flat and while I was on had another go a clearing the passageways put everything back together and hey presto bike started first kick ticking over perfectly left it running for about 4 minutes then decided to call it a day, My thanks to all who tried to help me with this problem