Starfire Problem

[bikerbob]

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.

[KEVINBACON]

rubbish in the carb!

[bikerbob]

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.

[neil1964]

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!

[bikerbob]

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.

[Steve.S]

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.

[rhyatt]

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

[bikerbob]

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