Need help, Mixture too lean. Can't figure out what it is.

[bobjohnson]

I decided to just order the gaskets for the airboxes and they came in today and it didn't help much. Still dies with choke and now won't idle, I checked the compression and it got up to 125 psi. Also it kinda has a knocking sound when I am engine braking. Ugh!

Well you already found out you have an airleak so you have to fix that. Now that you have new intake tubes, try the air leak test again. If it still revs up, youll know you havent fixed the problem. If you HAVE fixed the problem (I dont think so), you need to dial in the carbs again because youve got them (semi) set up for a really lean mix, which will be way, way too rich now that there isnt tons of extra air coming in.

The "knocking" sound is probably pre-ignition cause by a ridiculously lean mixture at high speed when you chop the throttle. Try not to do that until you get the problem fixed.

 

[pablohoney]

I did another leak test and the rpms dropped quite a bit. What else could be leaking besides the intake manifolds or airbox gaskets? Think it was near the base of the carbs.

 

[Terry]

have you replaced the gaskets between the carb boots and head? Are the carb boots new? Check and make sure you didn't tear them when installing the carbs. Are you sure the carbs are seated completely into the boots? Did your bike have the metal cages over the carb boots, my early XS does is the reason I asked? Are you using the correct clamps over the carb to boot connection, not hose clamps but the narrow metal ones from Mike's? If you've got a rebuilt motor and only 125PSI compression, that don't sound right. Check the tourqe on the head bolts, with new head gasket the large acorn nuts should be about 25/26lbs. or you could go up to 28/29lbs.

One other quick thought, have you checked the diaphrams in the carbs for pinholes or tears?

Terry
J'ville, Fl.

 

[crazypj]

sounds like cam timing is still advanced.
XS will run with timing off 2 teeth in either direction
You did have front run of chain tight when you re-set cam timing?

 

[pablohoney]

All very good suggestions, unfortunately you are wrong. No, just joking. ;D

I did replace the gaskets and soaked the boots in WD-40, they have no cracks and are very pliable. Didn't tear them. Yes, they are completely pushed on there.
Yeah, I have the cages. I have to admit, I am using hose clamps. No good?
I will retorque them down and check the valve clearances in the morning.

I checked that too, the diaphragms, are in great condition.


God, I hope it still isn't too advanced. I have taken that engine out nine times already, I don't wanna do it again. :'(

Yeah, I did, quite tight.
Thanks.

 

[bobjohnson]

Ok you still have an air leak (if it wasnt leaking, the RPMs wouldnt drop, they would stay completely constant). Spray whatever youre spraying at specific areas, not all over the entire system. When you find specifically whats leaking, thats what you need to replace/fix.

WD40 will dry out rubber, NOT make it more pliable.

 

[pablohoney]

Will do.

Really? ???
I read that WD-40 was the way to go in making rubber more pliable. Either that or transmission stop leak.

 

[pablohoney]

I replaced the manifolds and the choke gaskets, but there is NO CHANGE!! It definitely stopped the leakage but it runs no different.

What will it take to make this bike run? :'(

 

[pablohoney]

Maybe this will help, After i replaced the manifolds, it is making this sound, kinda like a squeaking, coming from the rear of the engine near the carbs.