Returning member - apparent fuel issue

[Guest]

Good evening everyone!

I say returning member because I had an account about 3 years ago that must have been removed due to inactivity (not sure the protocol about that). In any event, about 3 years ago, I bought my first bike, it was a '77 GS550. I bought it in the spring, worked on it a bit, and by August had a bike I was pleased with.

I then got ran into while sitting at a stop light, totaling the bike. The bike was great and I had grown to like it, so about a month later, I bought a '78. The kid who sold it to me was kind of clueless. For one, he told me the kick starter was broken...it was not. Anyways, the thing needed some work but I rode it until the snow came and stored it "correctly".

Last spring (2014) came along and we bought a house, got engaged and life generally took over. I rode the bike twice (once was from the apartment to the new house). When fall came I (stupidly) filled the rest of the tank with new gas and Sta-Bil and stuck it in the back of the garage. That's where I am now.

When I brought the thing out for the first time about a month ago, I gave it some starting fluid and it, much to my disbelief, it started right up. I took it for a little ride around the neighborhood feeling great. I then went to ride it a few days later and it would not start. I gave it some fluid and it would run on that but not any longer. A week or so later, I drained the tank (the fuel was disgusting) and whatever was in the carbs, filled up with new gas and it started right up. I took it for a nice long ride this time and everything was wonderful.

Next time I went to start it (2 days later, no beans). Again it would run on starting fluid but couldn't keep itself running. This lead me to believe the carbs had sucked in some gross stuff and I should give them a cleaning. Today, I took a few hours and gave them a basic cleaning. I did not dip them but I cleaned them out best I could, made sure the jets we're clogged (which a few were) and got them to a point where they have no real visible varnish or deposits, but certainly not the "right way" if you will. (I know, I know).

I got them back on, pulled the choke, and it kicked right to life. When it started to rev up, I decreased the choke a bit and continued to do so until it would usually just idle by itself. It would not. The only way I can get it to run is with the choke fully on and it still will die after about a minute. This leads me to believe I've still got a fuel starvation issue.

Here are my thoughts, I'd love to hear some input.

1. Inline fuel filter between petcock and and carb inlet nastied up. It doesn't "look" too bad but who knows, really. I'm planning to rig up a gravity flow gas reservoir to test this theory and the one below.

2. Petcock - In the short time that the bike is running, the clear filter will be most of the way full but honestly, I'm not used to motorcycle fuel systems. So, it doesn't look like what a clear filter would look like on a carbureted car, but I don't think it would as it's not under the same pressure? Maybe the petcock has some varnish in it not allowing the fuel to flow well?

3. Maybe there is some varnish in the carb inlet / distribution tube(s) that I didn't get that needs to be freed up?

4. Mixture - Would someone mind sharing the general tuning rules for the mixture screws? (both the ones on each carb and the big idle screw between carbs 3 and 4)

Anyways, any help you all would be willing to share would be greatly appreciated.

[chuck hahn]

Check the petcock flow by running a line off the fuel tube and use a short piece of vac line to suck on the vacuum nipple. Should be a good solid stream and not be sort of trickling. If it flows well then thats not the problem. To check the petcock for leaks, I run a line off the vacuum and the fuel nipples to individual pop bottles with the petcock in the ON position. Check bottlles next morning to see if they have any gas in them. If not good. If so, the petcock is failing. And it doesnt hurt to pull the petcock and see that the in tank filter is clean. As far as the inline filter..if the tank filter is in place and not torn there is no need for that filter.

Be sure the fuel line and vacuum line to the petcock are new will be of help also. Old fuel line can release particles from the inside as they get old..which in turn can clog jets.

By "basic cleaning" please elaborate on what you did. Full disclosure. But i suspect the carbs are maybe half clean after all that setting around.

Go here and scroll down the links on the right side to find the rebuild tutorials and clean the carbs would be my advice. Just some carb spray and air doesnt get the passages perfectly clean and delivering the proper fuel supply.

http://members.dslextreme.com/users/bikecliff/

And are we to assume this 78 is also a 550CC bike ???

[awGS550]

Chuck,

Thanks for the response and petcock test(s). I will be sure to try sometime tomorrow or this coming week. Check on the fuel and vacuum lines.

Yes, it is a 550, sorry that wasn't clear.

I think you're probably right about the carbs being half clean. I removed the float bowls, pilot and main jets, float, cap and float valve.. Soaked everything (not the floats) and blew them out. Also sprayed into all the areas I could and let sit. I have full intentions of dipping them and doing the whole shebang as I should re-jet for the 4 into 1 exhaust as the PO never did (currently running 85). I was hoping I could get away with this for a while to get some riding in. I think compared to the rebuilds on bikecliff's site, the biggest difference is the 24 hour dip.


Thanks again!

[chuck hahn]

Well its only 3 days down time. Get with Robert ( cycleorings.com ) and order up the VM oring kit and measure the ID of the orings in the intakes and order them as well from him. Turn around is usually 4 or 4 days for the kit to arrive, so thats the tear down and dipping window for you Take the basket out of the Berrymans can and you can do 2 bodies at the same time...so thats just 48 hrs of dipping and youre ready to go.

Youll be done with the bodies and jets before the kit gets there. And yes on the 24 hrs dipping time. Be well sure the internal passages are scale free!! Go to the Dollar General and look for the 3 piece tooth brushes that have the wire bristles. One brass, one steel, and one nylon. These brushes work well for scrubbing and cleaning the nooks and crannies on the outside of the bodies. I use some carb spray and the brushes when they come out of the dip and the gunk is nice and soft.

And wear some rubber gloves..that carb dip leaching thru the skin is very toxic. I got real sick once from just reaching in and grabbing the carbs out and handling as i ran them under hot water to rinse the dip off. Bad headcahe and upset stomach!!

Grab the bodies out of the can with some pliers and hold them with the pliers as you rinse them off.

[awGS550]

Thanks again, Chuck.

Yesterday while throwing on some new mirrors to brighten my mood, I squeezed the clutch lever after adjusting the grips and, wouldn't you guess it, the cable broke! Really glad this didn't happen while I was riding and it was on my list anyways (even after adjustment it never really felt "right") but I never would have guessed it was ready to break.

I've got a busy week ahead but hope to vacuum test the petcock at some point per your method but probably won't have an opportunity to tear the carbs back off until the weekend. I was just reading through your original post and forgot to mention that when I drained the tank, I did pull the petcock and the filter looked clean and not torn. I'm going to replace the current line -> filter -> line setup from the petcock to the carbs with one solid piece of hose.

[chuck hahn]

Yeah..those inline filters CAN act like a dam and slow delivery to the carbs. And I have seen little specs of black stuff wedged in jets and laying in the bottom of the bowls. Only thing I can imagine was debris sluffing off the inside of the old fuel, lines.

May as well get a valve cover gasket and do the adjustments if they havent been done already.

[awGS550]

Yeah. My big project of the moment is my father's Austin Healey. It had been stored (relatively well) for 15 years when I started working on it back in high school and more than varnish, there was what appeared to be either broken down filter material, old fuel line or just dirt/grime from old gas. Maybe it was lead! I kid.

[awGS550]

Small update - I was able to vacuum test the petcock and I found a couple things.

1. With the inline filter off, there was a nice steady flow -> Good!
2. With the inline filter attached, it was very much restricted -> Bad!

I've got to get work done on the Healey this morning but hope to get to the parts store for a nice section of fuel line to see how (if) that changes the running situation.