72 CL350 uneven exhaust pressure

Yep. I plan on soaking everything and try syncing them xb's way. And yeah, the dirtier side does seem to have a small crack. I'm trying to track down some choke plates in the meantime. It's looking like I may have to buy some junk carbs and cannibalize them unless someone else has an idea?
 
Good news for once!! Talked to a local shop owner who said he'd hook me up with some choke plates and new screws to install them too!
He had a pretty good idea where he suggested installing a 8mm screw and then after tightening them down, crush the exposed threads so they don't vibrate themselves loose. Said replacing the screws, should you need to take them out is a lot cheaper than if they decide to come out on their own.
 
Im a little confused did you check compression at the plugs? Low compression in one cylinder usually indicates a bad exhaust valve. Low compression in two adjacent cylinders typically means you have a bad head gasket. Low compression in all cylinders would tell you the rings and cylinders are worn and the engine needs to be overhauled. Guessing it's not the rings and cylinders as you just had them done, unless the shop went over. Could be your vakves are not seating correctly.
 
FINALLY got a chance to try xb33bsa's throttle plate/carb sync after cleaning the carbs and changing the choke plates.

I'm now sure that my carbs are synced (thanks for the method) and still have uneven pressure. I read a post a while back about pulling one of the spark plug wires and tuning a cylinder at a time but I can't find it anywhere now. Anyways, I tried pulling the wire and no matter which one I pulled, I had stronger exhaust pressure in the same pipe.

Any ideas on what I may be missing?
 
Sounds like you need a manual, and a local friend.
Can't tune via the web.
The factory manual will walk you though all of this.
But really it is a huge up hill battle with pods.

Also this "exhaust pressure" how exactly is that being quantified again?
 
Suffly, I'm with you on the local friend bit. I for sure need someone who's been there before. As for the manual, I have the clymer book AND a shop manual as well.

As for exhaust pressure, that's what the manual says you're supposed to do by feel. Literally hand behind the pipe and adjust until they become even. Only problem is, they never become close. One hits what feels like solid pressure, the other is like half that strength.

Maybe I'll record some audio or something.

In the meantime, if anyone following this thread lives in Indy and likes beer let me know!
 
It was such awesome weather so I didn't wait for the new k&n pods that should be here tomorrow. But here are two videos. I've tried adjusting the idle screws as well as the pilot screw. Maybe there is a leak somewhere in the exhaust? Maybe someone has an idea?

https://vimeo.com/122387705
Left side - tried to show the difference in exhaust pressure. Pulled the plug and still have more pressure on the bottom (left side of the engine) pipe.

https://vimeo.com/122388366
Right side - pulled the plug and the engine dies. If I roll the throttle, I can keep it running, I just didn't shoot that. Same thing though, more pressure on the bottom pipe.
 
Yep. Both pipes are hot. I get a spark from both plugs when I pull them and plug them in and lean it against the engine. Can't tell you the exact compression cause I didn't have a gauge with me. Next time I'll be sure to check though.

How can you tell it's not firing? Is it because basically nothing happens when I pull the spark plug wire? Can you explain why would that pipe be putting out more pressure without a spark than the firing side?
 
If you are getting good spark at both cylinders, then the dead cylinder is probably because of lack of fuel. If you increase RPMs, does the cylinder begin to fire?
Did you clean both carbs?
I noticed that you mentioned the good cylinder was correlated to the dirtier carb. Maybe the clean carb was put back together incorrectly.

Just throwing some questions out there, I don't mean to infer you did something wrong.
 
Don't worry alzcbz, if anything is wrong, it's probably my fault. I don't take offense, I'm still learning. It could be something stupid like I need to adjust my idle screw up more. And YES, when I rev it, it will run. There could be something together wrong, but I was pretty careful when assembling.

I did clean both carbs by soaking and then blowing them out with my compressor. I always do one at a time to make sure that I have a reference when putting them back together.
 
Oh and last time I checked compression, both cylinders were right at 120, which is low. I'm hoping that's due to the Pistons and rings not seating quite right just yet.
 
You need to start actually solving problems and getting a good base line.

-I still struggle to see how a hand over the exhaust is a tuning strategy but hey....
-You said there is a hole in one muffler? That will be an issue.
-Pods suck
-If you have cracked choke plates I would assume other things are broken.
-How are you getting your 120psi reading? Using what tool?
-Do a leak down test, more info to be found.
-Have you used a vacuum set of gauges to sync the carbs?
 
surffly said:
You need to start actually solving problems and getting a good base line.

-I still struggle to see how a hand over the exhaust is a tuning strategy but hey....
-You said there is a hole in one muffler? That will be an issue.
-Pods suck
-If you have cracked choke plates I would assume other things are broken.
-How are you getting your 120psi reading? Using what tool?
-Do a leak down test, more info to be found.
-Have you used a vacuum set of gauges to sync the carbs?
Click to expand...


I'll take a picture of the page in the manual. It's kind of funny, they have a ping pong paddle as a reference to the sort of vibration. As in, when you have a ball bouncing under a paddle and it starts speeding up as you lower the paddle. There are no vacuum ports, so using vacuum gauges to sync is out.

I rebuilt the carbs, new seals and jets and replaced the choke plates. I checked the compression with a compression tester gauge http://www.autozone.com/loan-a-tools/compression-tester-gauge/oem-compression-tester-gauge-set/424906_0_0/.


As far as leak down test, what do you think of the one toward the bottom http://www.dansmc.com/leakdown.htm?
 
dont worryu about a leak down test you already confirmed that you have decent compresion and it is even on both cylinders
i am going to suggest that it is fuel delivery issue ,at laeast at idle on the left
the hand pressure(feeling exhaust pulse) test is a very viable method but you gotta have that left cylinder firing first !
you could try swapping the points wires and swapping sparkplug leads in order to confirm the ignition is not causing the issue
 
How far into the carbs did you get? Did you remove the emulsion tubes?
These were mine before cleaning.
 
i strip them down almost completely and soak everything that isn't rubber. including the pin that holds the float on. I replaced those tubes when i did a rebuild and rejet, maybe a year or so ago? First time i pushed those tubes out, they were STUUUCK tight. So tight that i thought they weren't supposed to come out. I also blow the tubes out, to make sure anything that might be in them, rattling around comes out.

Just put the K & N pods on, i think Thursday, i'll get a chance to try to tune again. The pods came with re-jetting suggestions, so i may go back and check my jets against what they said.
 
there are some tiny holes(maybe just one per carb) that feed fuel from small throttle openings.these holes should be just below the bottom edge of the throttle plate and need to be clear flowing(not plugged or fowled)
 
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