Topic: Sat over winter, Struggle to stay running

[CbBrat550]

Hey everyone, this is the very first project I've taken on and I am hitting some roadblocks! It is a 1976 Honda CB550K, and I Tried starting it today after it had sat over winter, and I wasn't getting anything. After messing with the idle screw and giving it some gas it finally started sputtering and would struggle to stay on. It had been running better before winter, but not perfect; it would die after about 10 min of running or after getting warmed up. I am not sure if this a carb issue or fuel issue, it almost seems like it could be both. I will go over everything I have replaced on the bike just for clarification. Any ideas would be greatly appreciated!! 

.New coils/plug wires/spark plugs that all are getting spark, along with dynatek electronic ignition
.4into1 delkevic exhaust
.cleaned carbs and replaced gaskets, 110 main jets, uni pod filters
.litium Ion battery with new rectifier/regulator
.switched to blade style fuses.new starter solenoid, wiring harness
.I have adjusted valves, ignition timing, cam chain tensioner

I plan to take the petcock our of the gas tank and cleaning it, as well as take the carbs back off and replacing the intake boots because they are cracking, along with checking the floats and what not. The plan today was to set up my carb synchronizer but I couldn't get it running long enough to check them, and that's where I am at so far!

[Bankerdanny]

Was it running properly before?

Generally issues like this are from things getting gummed up. Modern gas doesn't sit well. If the boots that connect the carbs to the head aren't sealing up properly that will make things much more difficult.

Are you using the choke correctly? Lever up (parallel to the ground) is 'on' (closed). When you cleaned the carbs did you check to make sure that all the choke butterflies are completely and evenly closed when the lever is up? Once the bike fires up you will typically have to move the lever down just slightly or the bike is too choked (unable to get enough air) and won't rev or idle.

The bike does not have a fast idle cam like the 77-78 carbs, so you need to use crack the throttle a tiny bit during cold start and then to keep the RPM's up until warmed up and the choke is fully 'off' (open).

[calj737]

... I Tried starting it today after it had sat over winter, and I wasn't getting anything. After messing with the idle screw and giving it some gas it finally started sputtering and would struggle to stay on. It had been running better before winter, but not perfect; it would die after about 10 min of running or after getting warmed up.

Perfect example of poorly tuned carbs. Fuel level improperly set is likely responsible for dying after 10 minutes of running.

[sixthwisconsin]

Did you drain the bowls for storage? Bankerdanny is right, modern gas does not like to sit around and will gum up small passages quickly. I am able to get no ethanol gas and I still drain everything for storage including the tank. My tanks are lined and I store in a heated garage so no rust issues.

Calj's point is valid as well. Sounds like you need to throughly go through the carbs.

And what? You think winter is over in Ohio?

[Deltarider]

1. It's dead easy to verify if fuel reaches the floatbowls. Just remove a drain screw and then open and quickly close the petcock.
2. To check the petcock is even easier. You don't have to unscrew it from the tank.
3. The fuel that has been in the floatbowl all winter is not the best fuel for easy starting.
4. Are fuellines the correct dimensions? Your model is supposed to have 17 and 28 cm with an ideal internal ⌀ of 5,5 mm and NO 'extra' inline filters.

[CbBrat550]

Thanks guys! So I ended up doing a full carb rebuild/clean to the best of my ability, even though it had already had some new parts. I emptied the tank and checked the petcock and fuel lines to see if they were clear, and they were. The one piece that seemed to be the most gunked up was the mixture screw on each carb. Either they had gotten really dirty or had not been replaced in a while. After replacing all of this, the intake boots, and resetting the mixture screws, it started right up. It still seems to be running a little rich because the spark plugs have carbon build up, so I plan to clean my filters/plugs and try to tune my carbs better. It's been a lot of fun learning how these old machines work! I appreciate the feedback again!

[Bankerdanny]

It generally best not to use the aftermarket brass that comes in the non - Honda kits. The jet sizes are unreliable and things like the float needles are often shorter than stock,  which screws with yippy float heights.  The jets and needles almost never wear out and if you need richer jets order forum a place like jets-r-us that will sell you genuine Keihin jets ans needles.