I want to check for air leaks before my vacuum gauges arrive and had a bash this arvo after work. I have a butane bottle so opened it up and pointed it at injectors, upper and lower clamp areas around all 4 TBodies and saw no change in anything at all. Even with this cold I could smell the gas when I was done.

On Saturday I saw liquid running down the radiator, it was fuel squirting out a hole in the fuel line, I couldn't smell it, even when wiping it on my fingers and sniffing.

Damn that boy child for bringing this bug home. Now the wife has it, there will be hell to pay for that one.

Is there anything else I can do to look for air leaks?

Other than visual inspection of hoses and joints, the only thing I've really used is carb cleaner.

Squirting at all joins/seals etc if the engine note changes then you've found a leak.

Shug

The tin of carb cleaner I have squirts out rather that sprays out. It's great for cleaning crap off but I'd have thought a mist would be best for finding leaks?

Heavy coating is fine. I think it works by filling the gap so it's not sucking air.

Shug

I thought it sucked it in and burnt it to increase RPM.
Cheers, I'll find a fire appliance first then cover the engine intake with accelerant
Might just try this out side

I bought the carbtune guages and all new rubbers for under the throttle bodies at about the same time, I just figured that they would be aged at 22 years. The 'O' rings at the bottom were as flat as a pancake with signs that they had been leaking air on two of them.

RobinW wrote:I thought it sucked it in and burnt it to increase RPM.
Cheers, I'll find a fire appliance first then cover the engine intake with accelerant
Might just try this out side

Go to supercheap and get a can of Start Ya Bastard.

It is made to combust and not hang around as a volatile liquid all over your nice engine.

I had a major air leak under the last intake manifold, but spraying anything ( SYaB, water) on it made no discernable difference to the running of the engine.

Cheers Rossko, I got a tin and flooded everything. Didn't find any leaks at all.
I guess the gauges will tell the story when they arrive.

Soapy water in a squirt bottle.  

Get everything up and running so there is pressure inside and spray all the joins, or suspect areas.  If the water is nice and soapy, it will be pretty obvious if anything is leaking out by the amount of bubbles forming.  

Bubbles = leak

No bubbles = no leak.  

Hope this helps.

Yeah but we are looking for vacuum leaks so the bubbles will be on the inside.

RicK G wrote:Yeah but we are looking for vacuum leaks so the bubbles will be on the inside.

Ah well, cancel my previous.  NFI then.

I'm not sure that the carbi cleaner burns (some might, others may not)......but I sure wd-40 burns and quite veraciously at that. I know that spraying it around makes an oily mess but if you know where the suspect leak might be, perhaps you could get away with a tiny squirt right at it?????

I think there are 2 schools of thought here.......

#1 squirting excess volatile fuel substance in around the leak should cause that fuel to enter through the leak and add combustibles to the air flow hence picking up the idle.

#2 squirting anything in around a vacuum leak might temporarily fill the gap and shut off the leaking air hence momentarily correcting the lean condition at that point and smoothing the idle there. Problem is, a non combustible while shutting off the air leak will also contaminate the fuel load on that cylinder creating as much of a mis-fire as it fixes in lean air correction.

You can also put a rubber hose over the end of a propane torch and maybe get a couple of hose size step down adaptors so you have a small say 1/8 or 1/4" hose pouring out raw propane, then stick the end of that hose very close to where you think the leak may be. Theoretically, when you hit a leak the propane should flood in there & pick up the idle momentarily.
Don't forget to check around the bottom fuel nozzle O-rings, they can be sucking air there as well as at the intake manifold sleeves.

On 4V early bikes (or any bike with an airflow meter.......leaks anywhere between the meter and the intake plenum can also create problems.

With all the different drive ability problems being discussed at one time currently, I can't remember which members are talking metered engines and which of you are not.