b25ss not starting after rebuild

[Rookey]

any b25 aficionado out there near worcester park s.w london willing to visit and try getting my b25 going. got a spark got petrol just wont fire up. never had this trouble before. more than willing to pay for time.

[MGILBERT]

hi. had a similar  problem to my b25 starfire. make sure your contact breaker is fitted correctly, and not shorting out to the base plate.

[Rookey]

fitted electronic ignition; checked valve and ignition timing  several times; petrol getting through; good spark; will only fire up with a squirt of high octain carb cleaner; lots of kick backs; banging in exhaust indicates to far advanced but retarding  not solved problem; just will noy start on normal settings;

[idie]

Have you tried a new spark plug?

[Beesy]

I'm not local I'm afraid.

Did you use the timing tool to hold the crank in place?

Was just wondering as there are two holes the pin can drop into. One is TDC and another at 37 degrees BTDC. I wonder if the pin was in the wrong one when you set up the EI.

[Rookey]

new spark plug;new carb;used the correct timing plug;lots of bad language etc

[DAVE BRADY]

Hi,

Just a couple of random ideas that may be bit far fetched but is it timed on the exhaust stroke rather than the compression stroke and was the engine turned the right way to set the timing?  I say this because over the years I have done both of these things.

Dave.

Just another thought.  You mention a new carb.  Did you strip and clean it?  New ones can have bits of machining debris  in them as I found in a recently fitted Amal Premier Conc.

[Davidat19]

Check you have the pushrods the right way round

[Rookey]

timed on the compression stroke;cleaned carb;push rods exact length according to rupert ratio,front inlet rear exhaust

[Rookey]

engine turned the right way anticlockwise;

[DAVE BRADY]

Hi Rookey,

It looks like you have tried just about everything and you must be getting a bit frustrated.  One last last thing and shout at me if you wish.  Engine turned anticlockwise (forward) looking at the primary side I presume?
Again, I have in the past due to being in rush, timed an A10 backwards.

Dave.

[Beesy]

I sympathise with you. It is do frustrating. No-one has mentioned the coil yet, could be suspect?

I can't think of anything else that hasn't been mentioned, other than check and double check. It could be a fault in the EI system, unlikely but if your're 100% sure of everything else.Without swapping out one part for another I dont know how you would check.

Keep going you'll crack it eventually.

[LightningAndStarfire]

A good spark was mentioned, however it could be nonexistant under the higher pressure in the combustion chamber. Swapping to evidently working parts is probably the way forward.

[Colin SS90]

You said that "will only fire up with a squirt of high octain carb cleaner" could it be that you have stale petrol?

[Mike40M]

I think that your problem is carburettor related. A number of people have been complaining of problems with new carbs. Inspection and cleaning seems necessary.
Just to get a bike running, ignition timing is not that important. My Manx starts happily with any timing between 40 degrees BTDC to 12 AfterTDC.