Airleaks?

[Joe699]

hi all,
Ok, if you have read any of my recent posts you have probably realise I'm chasing an air leak -but for me it feels more like chasing ghosts at the moment.

I can not find it. It has also moved from the left side to the right?

I have set timing, valves, and points gap. There are new spark plugs, new carb boots, clean carbs...i'm at a loss.

I had the engine idling and reving fine but after a short ride and a 'pop' out the right carb it now has a bit of an eratic idle - it will speed up and slow down again, or take a while to come down after a quick blip of the throttle.

Are there any weird places to look for air leaks?

Or any other help is much appreciated.

It is running but just rough and I'm planning on heading away on it in two weeks - would like to try and have it running nicely before then.

No mods, 132.5 main, 45 pilot, pod filters and I just moved the needle clip down one to the 4th thinking the might richen things up a fraction - just thought it might help.

Thanks

 

[Grinder]

Did you try spraying carb cleaner around the carbs while running to try and isolate the leak?

 

[littlebill31]

Did you try spraying carb cleaner around the carbs while running to try and isolate the leak?

Best way to do it.

 

[jayel]

check the throttle plate shafts

 

[rwingsfan]

Actually the best way I have found to sniff out air leaks is with a propane bottle. Its way better at finding leaks than carb cleaner and surely much less messy!!

Best way to do it.

 

[angus67]

do you have barbed boots? If they are plugged with rubber caps, the backfire could have blown one off. Sounds like my bike until I realized it.

 

[angus67]

well? any progress?

 

[twinsarehot]

I'm assuming the carburetor boots are fine since they're new. I would suggest balancing the carbs if you haven't. Sometimes you can chase a misfire through the electrical system and carburetors only to find out that there's something wrong with the engine.

 

[Joe699]

Hi all,

thanks for the advice.

Ive tried all the above ways to find airleaks and there just seems to be none.

So I have now traced it (i think ) to either the right hand side spark plug lead, cap or spark plug. I've tried a different condenser, different coil and re set points - went to do the timing and the timing light wouldn't pick up anything of the right spark plug lead.

I pulled the cap of and if it just sat on the plug it would work the light. Took plug out to test for spark (it was a new plug too) and no go unless the cap was just resting on it, tried the other plug on that side in the cap and it produced a spark. New plugs tomorrow and I'll go from there.
Cheers.

 

[littlebill31]

I found the other day that following the carb guide really...really helps. I had a popping from my left exhaust as I had posted on other threads. I grabbed a screwdriver and, per carb guide, tightened the boot clamps until they touched each other. No more popping. The guide says to make sure you do this especially on new boots.

 

[Visegrippe]

spark plug leads have a finite life span, even wire core ones, the insulation breaks down, always, and your spark "leaks" out.

and even new plugs can be duds. couldn't start my dad's enfield for the life of us, sparked when out of the engine, but wouldn't fire. put another set of brand new plugs and it fired first kick.

the resistance in the combustion chamber is much higher than in open air, so any fault which reduces the spark enough that it won't fire in the engine might not show in the air.

 

[angus67]

my buds bike sat in his basement for 20 years. I put new plugs to replace the old, tried to start , nothing. put the old plugs in, started. the new plug's insulators were cracked around the inside midle. goood thing they didnt fall apart while in the engine.