I have received a lot of help from this site, so I thought maybe I could post something that might help others. These are mostly troubleshooting hints.
My '76 550F has run rich ever since I've had it; 1 yr. Spark plugs are black, dry, sooty.
I have an original set up except for the exhaust which is, I believe, is a rusty old Mac 4-1.
069A Carbs
098 Main Jets
038 Slow Jets
Original Air Box
Needle is set at the 2nd from top slot
All the parts are original Keihn parts
I haven't accomplished any carb synching because for what I use the bike for; cruising around the neighborhood in the evening with a 4 mile highway run at the end, the bike has operated fine. And, I don't have a carb synch tool...yet.
Over the winter I took the carbs apart, cleaned and put in new O-rings from an aftermarket kit and checked the float height (good). My thought here was that the old O-rings, dry and brittle, were letting additional fuel into the engine.
And here is the crux of this post:
I noticed that the new O-rings didn't really fit very tight around the main jets, and the float valve O-rings were very inconsistent in their fit. Some tight, some not so tight. A red flag went up, but I went ahead with the assembly.
So my bike was still running rich this year and when my exhaust collector rusted through, I decided to take another look at the carbs while I wait on a new Mac 4-1 exhaust.
This time, I ordered the O-rings as an OEM kit from Bike Bandit. The main jet and float vale rings were MUCH better fits. (The bowl o-ring was the wrong size, but I was able to re-use the aftermarket rings on those.)
So, lesson 1: Be careful what you order. The o-rings in the original Honda packaging were far superior to the aftermarket o-rings.
Now, I put the bike back together yesterday minus the exhaust, which hasn't arrived yet. Basically, the exhaust ports were exposed.
So I started it up and to make sure everything was firing, I put my finger in front of each exhaust port. Cylinders 1, 3, and 4 were all firing as expected: HOT. On #2 cylinder I could literally put my finger into the exhaust port hole. No fire.
So, lesson 2: To check if #2 has spark, I hooked up the timing light knowing that no spark = no timing light; the spark and timing were fine. So I knew I was getting spark.
So, lesson 3: How do I know if there is any 'suck' coming from the cylinder? I took out the carb synch screw at the inlet manifold and felt the suction. I also compared it to #1 and they were similar with my calibrated finger tip. So I knew the cylinder at least had the ability to suck fuel if it was available.
So, lesson 4: How could I prove that everything will work if the cylinder was getting fuel? So I took the overflow tube from the #2 carb and blew into it to pressurize the bowl a little and force fuel into the cylinder while I kept my calibrated finger in the #2 exhaust port. Wahlah. HOT!
So now I have to take the carbs back out and see what I did wrong on #2.
Which brings me to lesson 5: This winter when I took the carbs out and put them back in it took me about an hour to get them out and 2 hours to get them back in; and a lot of cuts and bruises in the process. I wanted to try and figure out a better way since I will no doubt be doing this more as I try to tune the bike with the new exhaust.
I read here in the forum that some people remove the inlet manifolds from the engine along with the carbs. I decided to try this and I highly recommend it. I put new O-rings on the inlet manifolds and assembled the manifolds to the carb isolators without the clamps in place so the assembly had a little give to it. At the back end, I left the air box in and the inlet boots in the air box remained installed.
I tilted the entire assembly and slid it in from the left side until the assembly was lined up front and aft but still tilted.
Then, I used a long cheater bar to gently compress the assembly into the air box area until I could clear the studs for the inlet manifolds.
Then, I worked the inlet boots over the carb inlets at the aft end.
With everything hooked up, it took me less than 30 minutes.
So, I hope these little hints help someone else. Thanks for all the great info.
