carbs backfiring,like a dog sneezing
 

my awful 1vj ten will not start from cold.i think i may have several minor problems causeing a big one.when i do get it running and warmed up its much better at starting (when warm) but my question is,while running at idle or fast idle it will squeak intermittantly, very much like a dog sneezing, thru the carbs.i think this is happening thru the secondary barrel of the carb but cant be totally sure.its just for a second and only makes the engine skip a beat momentarilly and then its fine.
any ideas of a cause?
(ps i dont own a dog nor was one in my garageat the time!)

Sounds absolutely terrible.

I'll take it off your hands for £500 and give it a good home. Else you might have to do the whole service thing, clean the carbs, have it tuned and godknows what other things required by such an old awful bike.

If it is a detonation squeak (short sharp and high pitched)your intake valves are most likely not seating properly for whatever reason. Worn or badly adjusted.

Only other reason for it could be timing that is hopeless advanced, ignition and or cam. (but this is unlikely without human intervention) Have you taken her apart recently?

Sounds like an air leak or a carburation problem.

Check all the rubbers are tight from the engine to the carb and the carb to the airbox... If thats not the issue, I would remove the carb and check the vacuum rubber and that the slider moves up and down smoothly.

sounds lean. if you are hearing a sneeze

sneezing labrador
 

yes my 92 xt does the same, but when its warm its 100%. and it sometimes sneezes (when cranking)
Bruken is on to something i think with the valves, first thing id do is compression tests.....
1st test cold.
2nd test after shutdown.
if that comes up with poor results in any test then your valves might be migrating. engines are generally hard to start if (especially exhaust) valves aren't set correctly, so your motor heats up and the heat has the positive effect of proper running,
now, there's another thing that caught me by surprise and that was the pilot air valve....
and last, have a look at the quality of spark, ,(Bright Fat Blue Arc) not a light ciggy lighter spark, (although some are quite good haha)
Does it get floodod easily? or at all?
it'll run lean by nature because of the ignition setup.
hope this helps. ken

Had similar problem on removing inlet rubbers from carb to head found they were split from metal despite looking new on replacement starting was easy about 4th kick!