Topic: grrr bog down then dies on highway SOLVED!

[Ayrity]

Hey guys, I know this topic has been talked about to death, and I did a TON of searching just now but was hoping for some active help as I go through this.

So the bike was running beautifully. I cleaned the pod filters really well and oiled them, not too much, re-installed. I also just got my side covers from maier, put those on. That is all that has changed since it was running well. Before I did those things, I could ride for hours easily. Now I run for about 20 mins or so and it bogs down at highway speed and gurgles slower and slower then dies if the clutch is put in.

Suspected fuel not flowing well to the carbs. Took off a drain screw from a bowl (one from each side of the set of carbs) and drained the fuel in there, then turned on the petcock, looks like great fuel flow to the carbs. Tried driving home with the gas cap cracked, no difference. I am letting it cool, and am gonna check the spark plugs and post pics. If I waited even a few seconds after it died, it would start back up again and sometimes die if revved, but sometimes would drive a block, sometimes would drive for miles. Seemed to lose power for a split second sometimes then "catch" again, but would have steady power if kept above about 7k rpm.

I dont see how it could be the jets or anything being clogged since it runs for at least 20 mins well from cold. And I am 90% sure with that test I did that I have good fuel flow to the carbs. Also even if the spark plugs are crapped up, I dont see how that could be the problem, again because I can run for a while before the problem happens. Ill check my charging system when I go out there soon too, but again, starts up, lights are bright, and I always seem to have good power to start it up again. Any ideas? Thanks for dealing with another "bog and die" thread. Post again with battery and plug info soon. By the way 1976 cb550 in case you dont see my sig

[OldSchool_IsCool]

I'm leaning towards fuel starvation.  Have you checked the in-tank filter?  Do you have an in-line filter?  Any kinks or high spots in the fuel line?  When was the fuel line last replaced?

[manjisann]

Check and be sure that fuel will flow freely through all 4 carbs, I'd imagine it's possible to have it flow great to two and poorly to two as well. Check float height (doubtful that's it, but an easy check). If nothing else has changed since it was running great, as far as the carbs go, and the above checks out (along with what OldSchool suggested) then start suspecting electrical.

I'm having a similar problem with my bike and I'm suspecting one of my coils is crapping out after it gets warm and some decent use. Once this happens the bike begins to bog down and the exhaust note becomes much deeper and more pulseing. I got home and checked the pipes and the inner 2 were only warm, not toasty hot like the outer two. Once the bike sits and cools for a while the bike will fire on all 4 cylinders again. The caveat to the above info is I have not definitively tested my coils yet, and I have not had the bike running correctly since it was finished. However, that doesn't necissarily mean I'm wrong about the coils 

HTH

Brandon

[bucky katt]

check the fuel tank vent in the cap too.

[Ayrity]

thats for all the answers. check the plugs, could only check the outer two, damn fat walled socket. but i check all 4 caps and they all sparked well. and the plugs looked nut brown. Sorry, but I did say that I rode with the gas cap cracked so it is not the cap! do you really think it could be the coils, ugh I know nothing about that. how do you test those? I dont wanna ride till it dies and then try to hold a volt meter while revving on the side of the highway! Battery was in good 12-13 volts.

[Ayrity]

uh also just checked the oil level on a hunch, wiped the dipstick, checked oil level (and yes I did level the bike out, it was not on the kickstand haha) and the stick came out as dry as I put it in! obviously not a good thing, but could this be the problem I was describing?

[OldSchool_IsCool]

I'm still thinking fuel, but I've heard that overheated coils can be an issue.  I'm not sure how to test them unless you have a spare set hanging around.  If you suspect only one coil, like Manjisann's problem coil, you could swap the yellow and blue wires at the points, then swap wires 1&2 and 3&4 to see if the fault changes to the other 2 cylinders.

Maybe a heat shield could be fab'd and used to test??

[OldSchool_IsCool]

uh also just checked the oil level on a hunch, wiped the dipstick, checked oil level (and yes I did level the bike out, it was not on the kickstand haha) and the stick came out as dry as I put it in! obviously not a good thing, but could this be the problem I was describing?

Low oil would lead to overheating.  Overheating can lead to engine lockup (non-terminal, but not healthy!).  I suppose the early stages of heat lockup could cause 'er to slow down the way you describe.

At any rate, get some oil in there!

[eurban]

Certainly having the correct oil level is a good thing but I doubt it is causing your bogging.  I would tend to go back to what has changed since the problem occurred.  Did you mess with your fuel line routing in the recent pod cleaning/side cover event?  Assuming you did not, I would say that your cleaning and oiling of the pods is the most likely culprit.  Perhaps your idea of "not too much oil" is in fact too much oil.  It is pretty easy to over oil pods. Try cleaning them again, letting them fully dry and then run briefly with no oil (on the pods ).  Is the problem now gone?  If not then onto other things . . . .

[Ayrity]

just put new oil in, so ill let ya know if that changes anything. I will run it around and see if the problem is magically gone, if not, then ill try the pod cleaning again. maybe ill run with my side covers off again? haha. I keep crazily thinking that I am creating some kind of blockage with the side covers coving over the pods... possible?

[Ayrity]

ok just took it for a ride, oil didnt fix anything. Removing the pods now to clean again... any other ideas? pretty sure my gas lines are all clear as they flowed well to the carb bowls right?

[scottly]

Does it still run ok at 7k RPM and up? I wouldn't think that would indicate restriction from the pods, or restricted fuel flow, and you've ruled out fuel flow anyway.

[Spanner 1]

Clean your points until they shine and try again...my2c.

[scottly]

Clean your points until they shine and try again...my2c.

Hmm Good "points" there Spanner (pun intended)
Also, check the point gap; if the points are barely opening, they might be working better at high Rs

[Ayrity]

I dont have standard points, I have this... How do I check this system?

but I was wondering, I read in another post by TT that you should be able to blow through the tank vent hole? I tried to and I could, a tiny bit, how easy should it be to push air through that hole with your lungs? (pods run clean un oiled no diff)

[scottly]

I dont have standard points, I have this... How do I check this system?

but I was wondering, I read in another post by TT that you should be able to blow through the tank vent hole? I tried to and I could, a tiny bit, how easy should it be to push air through that hole with your lungs? (pods run clean un oiled no diff)

I don't know about your ignition, but I would say don't worry about the tank vent: it is a very small hole, and as long as it's not totally plugged, you can focus on other things. Also, you did run the bike with the gas cap cracked, so you have ruled this out.

[Spanner 1]

AAAAGH, the dreaded Dyna ignition..... ( I don't like 'em ).....maybe something to do with that ( the part at the 'points' cam ).? Other folks will chip in that have that type ignition....

[Ayrity]

Ya, I just dont have any clue hoe to adjust that ignition... ugh. I know I said I did run with the gas cap cracked and it didnt change a thing, but, just in case, is there any real reason why I couldnt run a small drill bit through where the vent hole is through that inner plate? just to make extra extra sure?

I also checked fuel flow directly out of the petcock, 2 steady solid streams. I also re-routed the gas lines, just in case. Someone should make Plexiglas carb bowls so we can see the fuel filling or running out of it! I know there is the clear hose trick to see the fuel level, but my drain tubes are blocked like crazy, I just pulled the screw out of the hole completely to drain during the previous post's mentioned test.

[scottly]

I know there is the clear hose trick to see the fuel level, but my drain tubes are blocked like crazy, I just pulled the screw out of the hole completely to drain during the previous post's mentioned test.

RED FLAG ALERT!!! Those drain/overflow/VENT tubes need to be open to expose the bowls to atmospheric pressure!!! Carbs can't work right without them!!!!

[Ayrity]

if they were open wouldnt fuel just flow out of them all the time? 

[scottly]

Only when you open the drain screw

[Ayrity]

sorry, let me just get this straight, the way it should work, is I should loosen but not remove the screw, and gas should flow out the tube on the bottom of the bowl? because to drain mine, I have to take the screw out, then gas comes out the threaded screw hole

[scottly]

sorry, let me just get this straight, the way it should work, is I should loosen but not remove the screw, and gas should flow out the tube on the bottom of the bowl? because to drain mine, I have to take the screw out, then gas comes out the threaded screw hole

Correct, gas should come out when you loosen the screw. You should also be able to blow air though the tube, with the drain screw closed, but only about the same amount as you got through the gas cap vent, which is not very much.

[Ayrity]

ok ill check that tomorrow. I think I am going to try 2 things. 1: run the bike on the highway with the gas cap propped open so I can see into the tank (the level is low enough that it will be ok) if that doesnt fix it, I guess I am back to 2: taking the carbs off.

some questions: Could float levels be the problem here? and if they could be, why would the bike run well one week, then the next have a problem like this? can float levels change over a week? I guess maybe if one is cracked or sinking... And finally, should I try choking it out on seafoam before taking the carbs off? couldnt hurt right?

also just a question, with my "dyna" ignition, do I still have coils that could be going bad? I am clueless as to the electrical system when diverging from stock...

[Ayrity]

ok couldnt wait till AM. took the carbs off, checked the floats, none are sloshing, all the mains are clear, and i attached a hose to the gas inlets and ran some seafoam through and it came right out into the bowls... seems like I did that for nothing, ugh. side not on top of all my other questions, do 100's seem like the right jet size for a 76 550k with pods? just wondering if I should replace them while I am in here. never gave me a problem till now.