Topic: Help! Bronco Bike is sick!!! Need your thoughts!!

[smithrelo]

Ok, put on your thinking caps:

Bronco bike ('74 550 4 K) died on me today. 

I'm driving along 35 mph, bike sputters a bit, but I give it gas and
it goes ok, sort of like its choking up?? then I get to light, pull
in clutch and bike dies.  Neutral light and oil light are lit.  I
Hit the starter, it fires up and I go another 2 blocks and it REALLY
starts to sputter, then I pull in clutch and it dies between gears,
and as I turn right, it stays dead - NO neutral light or OIL light,
no headlight, starter does not fire at all, just dead. But HOrn
works, and so does right hand turn signal.   So I check fuses - all
OK.

So I'm broke down on road, no neutral light, no oil light, starter
will not work at all (like kill switch is off, which it is not) BUT
I do have right turn light working and horn works BUT no headlight!

So "LEE" nice Harley guy helps me and we "direct connect" the
starter and it tries to start up.  But now throttle and gas seem not
to be speaking same language.  Throttle turns, but engine surges and
then dies.  So now police are stopped admiring how nice Bronco bike
looks, and they all try to help.  We direct connect it again, open
choke a bit and it acts like it might go.  I'm now just hoping to
get it home and we take off, go 4 blocks and engine dies again. 
Throttle does not operate correctly.  Engine will not run.

So I open Choke up full, get it to fire up via starter, and we go
another 2-3 blocks - whereupon it sputters and dies while I'm reving
it at 4,000 rpm. So I'm stuck in middle of 6 lane HR parkway. Really
fun ride now!!

So we push it across busy traffic while cops stop them.  We open up
choke again, and it starts with starter, revs up good and seems fine.

So I get it home and you'd think it was right off the show room
floor-idles nice a 2000 rpm, with choke closed, (this is normal,
when it is hot..perhaps I need to drop that down a bit) but anyway,
as I pull into garage, it is just fine!

So my question is:  do I have 2 problems?  or More??
one- maybe an electrical problem between starter motor and starter
button?  Or perhaps kill switch is going bad??

and second problem:

Perhaps clogged fuel lines? fuel filter needs replacing?? or carbs
(recently rebuilt - with less than 300 miles on rebuild?)

So, does anyone have any ideas? 

I'm scheduled for lasik surgery Tomorrow 4:00 and I asked dr. if I
could go for ride Sunday - they say yes! But Now Bronco Bike is
sick!!!

Open to all suggestions - my problem is tomorrow about 2 pm I won't
be able to see!!

Linda
:(who is very, very unhappy with BB right now!!)

[Terry in Australia]

Linda, for my 2 cents, I reckon it's electrics. It's very rare that you've got both fuel and electrical problems at the same time, you'll need to check all your electrical connections (maybe AFTER your lasik surgery, ha ha!) and give each one a clean, and if you can find some silicone grease put a dab in each connector to keep the moisture out. Cheers, Terry.

[douglascoolgrey]

I'm betting plugged gas line. Do you have inline fuel filters. How do they look? Dumb question, but do you still have gas in the tank? I'm thinking the electrical problems resulted from you hitting the starter and draining the battery while trying to get her started again.

[smithrelo]

Terry/Douglas-

thanks-I just check her and NOW there is a spot of gasoline on the floor about 8 inch circle. Under where the tubes run from the carbs (you know those 4 plastic tubes that dump under the back of engine).  This spot is NEW-as Before I had carbs kit put in, it dripped gas all the time (floats were 30 years old!! and were sticking) Then after carb kit, no drips at all...now I have a drip. hhhmmmmmmmmmmm
 sooooo now, looking at gas drip, wondering if I have a float sticking, which is a real possiblitiy, as the throttle acts like something is not kosher in the carborator apparatus.

I'm now trying to find where exactly that gas is coming from.  I never drained the battery-that is what was so weird-no oil light, headlight,no neutral light...but plenty of juice to horn, blinkers, etc.  And when we did that connecting with a metal piece between the start thingy's near the fuse box...fired right up.

 Very weird...

I don't know if I have fuel filters in-line...but think I might take the fuel filter off and see if it is clogged.  And Yes, I have gas in tank-my same thoughts..but now I'm wondering if there is debris in fuel tank?

Thanks again.  I'm just real puzzled.

Linda

[TwoTired]

Check your points to see if the point gap is correct or if water got in there and shorted things out temporarily.

Similar symptoms occur with fuel starvation though.   Um, er, you did try reserve setting didn't you? Also check that the tank's cap vent are clear.  The tank's fuel must be replaced with air as it is used or it gradually builds up a vaccum and then fuel won't drain out.  Fuel starvation causes low fuel in the float bowls and as the level goes down the idle jet starve first before the mains.  You can then get high RPMs, but not idle RPMs, until the carb bowls get so low as to starve the mains, too.  Also, fuel contamination can cause a myriad of strange issues.  Ah, I just read that your carbs are over flowing.  Contamination can cause this too. Your fuel strainer in built into the petcock of the tank.  Have you check teh gas tank for rust and or other crud?  Rebuilt carbs will clog up just as fast as old ones with garbage in the fuel supply.

Did you mean to say that during this time the starter would crank, but the engine wouldn't fire.  Or, was the battery too low to fire the spark plugs anymore.  Did turning off the headlight improve things any?
You might check your battery and the connections to it.

If it happens again you'll need to isolate the problem to fuel or spark.  Opening a carb bowl drain screw should tell you if gas supply is an issue.  Remember, on the the 74 CB550 only two carbs starve when the tank level gets low, 1&2 or 3&4 depending on which fuel line is connected to which petcock nipple, reserve setting should then restore full supply to the starved carbs.

The electrical strangeness clouds the issue a great deal.  So many unkowns.  But, there are hundreds of connectors that can corrode and get dodgy.  So, too, can an ignition switch that is 30 years old.  Issues like that must be handled with methodical testing or wholesale cleaning of all the contacts in the electrical system.

I think we need more data.  Just too many variables at this point.

Good luck,

[chippyfive50]

My hunch is with Terry in the land "framunda". It is easy enough to check the fuel problem, but Given your symptoms, I think you may  have a fatigued / loose  power wire in the harness between the frame and headlight bucket. See if you can get BB to run with the bars turned hard one way or the other. I just hand built a replacement harness for my 71' , and there are several points where the +12 is tapped for different elements of the system on the original harness. It may just be a loose connector in the headlight bucket, you can take the light out and check very easily: only 3 #2 philips head screws. The black wires are +  and the black/white stripe goes to the coils. http://oldmanhonda.com/MC/WiringDiagrams/MCwiring.php#class  has a  good simple diagram. With the bucket off you can test the wiring with a multimeter to confirm if you have power to all components. (make sure the key and on/off  switch are on)
You do have a lot of variables, check the easy stuff first...

Lasik is a miracle, and you get some hip riding goggles too!! ,  just passed a year on mine, it is truly amazing.....
good luck.....

[smithrelo]

Chippy, thanks for the info.  I'm just puzzled over fuel leak.  Strange to have zero problems for 10 months and then boom...leaks today.  Even stranger, it is still dripping out about one tablespoon ever 4-5 minutes - and has been doing this for over an hour!

At this rate I will definitely be out of gas soon!!!

I will get this lasik thing behind me and then hopefully be able to check for debris in gas filter next week.  I'm just bummed because I wanted to ride Sunday with "Denver Rusted Nuts"  and I asked them to meet in the south...and now I'm the one with no bike    (feeling real bad about that right now)

Linda
who welcomes any further suggestions and will start checking bike when I can see!

[oldbiker]

Hey Linda, what is Lasik surgery??

[Jonesy]

...it stays dead - NO neutral light or OIL light,
no headlight, starter does not fire at all, just dead. But HOrn
works, and so does right hand turn signal. So I check fuses - all
OK.

So I'm broke down on road, no neutral light, no oil light, starter
will not work at all (like kill switch is off, which it is not) BUT
I do have right turn light working and horn works BUT no headlight!

Linda, sorry to hear about your bike. From what you describe, is sounds like the issue is in the wiring between the main fuse and the fuses going to the head/tail lights. I don't know how much help this will be, but it might help you narrow down where the trouble is occuring (see picture).  Good luck!

[smithrelo]

Ok-now things are really strange:

Bronco Bike is not"dripping" gas, it is 'squirting" gas out of one of the tubes that hang down from engine.  It has continued doing this for past 12 hours and now I have almost a cup of gas in a bucket under the bike.  I have checked it and and when it sqirts the gas, it is exactly like you took a syringe of gas and pushed it out all at once.  (sorry for being so technical hahaha)

so now, having had it set on "stop" on the petcock all night, I've now changed it to "reserve" to see if that stops the squirting.  I cannot work on it today, because of Lasik surgery (which is where Dr. re-shapes the cornea of your eye with a laser...very popular in US as it "usually" overcomes the issue of wearing glasses!)

But Dear Hubby says, get your eyes right,  and we'll get Bronco Bike to dealer first week of June and have them check the carbs, as they did the work and it has less than 300 miles on their work...so they should stand behind it?

Anyway- DH also asked about "gasoline" - we just changed from the "winter" gas to summer gas here in Colorado and he thinks I should drain all gas, check the fuel filter, and refill tank with "summer" gas as middle octaine rating, rather than top octaine rating winter gas which is in it now.  Sorry if I'm giving too much info, but what are your opinions on the gasoline issue??  (NOTE:   When bike was fitted with carb kit, last June, dealer told me to run "highest" octaine gas in bike.)

Jonesp-thanks for wiring diagram-Dear hubby wants to help me trace wires when I can see, as he thinks I might have a crimped wire and he has a new "ohmeter" thingy that he is dying to use!!

Linda (who is getting nervous over Lasik - and can't take a STIFF DRINK!!!)

[Dennis]

Linda,
There is obviously a fuel problem. The existance of an electrical problem seems to be undetermined at this time. I would try to solve the fuel problem first. You mention that there were carb kits installed by a dealer recently, but I do not recall any mention of the tank. I would suggest that the tank be completely emptied, and removed from the bike. Remove the petcock and dissassemble completely. Check all passages for foreign material. I have had some unseen fuel varnish become dislodged from the bottom of a tank (which appeared to be clean) and find it's way into the passages of the petcock which obviously in not a lot of fun when you are 20 miles from home and on your way outbound as I was that memorable day.  Rinse the tank with your cleaner of choice until it runs clear. Then reassemble it all and add a small amount of fresh clean fuel.
There is plenty of good advice above about what to do with the carbs. I would open the drains and allow some fuel to flow through and see what happens. If the leakage cannot be stopped then the bowls will need to be removed for further inspection. If you return to the dealer and he finds contamination in the carbs, my guess is that he will be charging you for labor to remove clean and reinstall carb set.
After the fuel issues are resolved, then it will be much easier to determine if an electrical problem exists.
Good luck with BB and
wishing you a speedy recovery from your surgery!!

[Jonesy]

Anyway- DH also asked about "gasoline" - we just changed from the "winter" gas to summer gas here in Colorado and he thinks I should drain all gas, check the fuel filter, and refill tank with "summer" gas as middle octaine rating, rather than top octaine rating winter gas which is in it now. Sorry if I'm giving too much info, but what are your opinions on the gasoline issue?? (NOTE: When bike was fitted with carb kit, last June, dealer told me to run "highest" octaine gas in bike.)

The octaine rating does not change with the seasons. The SOHC-4's were recommended by Honda to run on 91 octaine or higher (=premium fuel). What you're husband is referring to is the amount of ethanol mixed in with the gasoline at different times of the year by fuel companies to help control smog. Sometimes the ethanol plays havok with older fuel system parts that were engineered for the days of straight gasoline.

As for the diagram, my pleasure. It doesn't really do much, but may help to explain the wierd combination of what was still functioning on your bike. If the dealer did the work, I'd take it back to them and have them put it right!

Hope everything goes well with the peepers! May you (and Bronco Bike!) have a quick recovery and be back on the road.

[TwoTired]

The SOHC-4's were recommended by Honda to run on 91 octaine or higher (=premium fuel).

Note that after the SOHC4's manuals were printed, the octane rating system was revamped and the RON system was adopted in concert with the introduction of unleaded fuels.  (you used to be able to buy 100 octane at the pumps.)  Anyway, today's 87 octane regular is equivalent to the old 91 octane regular sold back in the 70's.  Unless you've upped your compression ratio from the stock 9:1 or 9.2:1, regular gasoline will work just fine in the SOHC4s.  In fact, the extra additives in modern high octane fuels will just leave more deposits in the chambers.  Which, in time, will eventually raise your compression ratio and then create the need for high octane fuel until you de-coke or decarbonize the deposits in the combustion chambers.

Cheers,

[Gordon]

Two Tired is right about the octane rating, and up where we are at Denver elevation 85 octane is equivalent to 87 at sea level. 

[chippyfive50]

Hey TwoTired,  did you once host a performance site dedicated to the 550?

[TwoTired]

No chippyfive50, twern't me.  My first name is Lloyd.  I think the guy you want is Rob Lloyd.  I read a bunch of stuff off his site while it was still there.  Pity it's not accessible anymore.  It had some good old stuff about power upgrades for the 550.

Cheers,

[bryanj]

Linda, you should always turn the gas off every time you stop. the floats arent designed to stop the gas flow when the engine aint rumnning. Check all the connectors and please tell me you havent put a set of waterproof troousers under the seat (or anything else!) as this blanks off the air inlet.

[smithrelo]

Hi all and thanks for the advice.  As I can see better, I'll start finding the problem!

Ok-today I can see mountains beautifully, but up close....not so good yet-Dr. said give it a week and see how reading/close up work is doing then.  Amazing!!!  (I keep reaching for my glasses!!soooooo funny!)

I confess...I had the petcock set on reserve..not stop.  So that is why 1 cup of gas squirted out.  Since correcting that, no gas has leaked out.  But, I did notice the black specks in the gas that squirted out. So, when I can see better, I'll drain gas from tank and check the fuel filter.  And probably wash out the tank.

Obviously I need to drop down to 87 octaine gas, so that will happen when I'm checking the fuel filter.  It may be next weekend before I can see well enough to start working on those items.

No, I have not put anything big under the seat.  Just the regular tool kit (original) and lots of extra fuses...which thankfully I have not needed. 

Again, thanks for all the advice.  I'll check it out next week when I can see better, and if need be, and if it will run, I may be able to get it to the shop.  But I am going to check fuel filter first...those black specks indicated something was not right on fuel cleanliness...so that's where I want to start.

The electrical problem will be a good project for DH and I, as he is not a rider, but likes to play with his "toys" and has brand new ohmeter that needs to be played with!


Linda

[CB750F2]

G/Day Linda.You have mentioned that the petcock was on Reserve when you thought it was in the Normal position. There is a gasket between the Petcock and the tank connection that can crumble with age and block the reserve port. To check this you need to drain the tank and remove the petcock. If gasket is damaged blow out passages and replace gasket. This problem happened to me - the bike would run fine with the petcock in the normal position but would run out of fuel when switched to reserve. Pat in Nth Qld

[bryanj]

When you remove the petcock, if it is the one held on with two screws inside the bowl, careful with the fiber washers under the screw heads as if they are not in good condition gas will flow through no matter what position the lever is in!

[smithrelo]

Interesting!  The petcock did not have any kind of gasket...no rubber at all....hmmmm-perhaps I need to get one next week and put it in there?  and there were NO fiber washers either!  I'll definetly do that, as I was surprised not to see some type of rubber gasket...hmmmmm-

I am going to read up on the fuel system and while the tank is off, give everything a good look see.

Last night Dear Hubby and I were discussing Bronco Bikes problems, and we came to the conclusion that it is a "trophy Bike" much like I am a "trophy Wife" (inside joke here...I am MUCH older than DH...so he calls me his Trophy Wife!) anyway, we came to the realization that Bronco Bike only seems to run when Tempratures are between 60 and 85 degrees Ferenheit....so I can ride BB probably 60 days a year!! LOL

And I can see up close MUCH better today!! YEA

LASIK is fabulous!

Linda

[Gordon]

Don't worry Linda.  You'll get the kinks worked out soon enough, you haven't even had the bike for very long.  When I got my 750 it had been sitting in a garage for several years.  Now it's my main means of transportation, I ride it to work almost every day.