Topic: From never riding to cross country bike tech in 2 months, or 'god im a noob'.

[narcoticrex]

Hello all!  Great forum you have here!  I spent last night browsing topics, up to like page 25 

This might be a long post, as I am going to explain what I am trying to accomplish, and explain what I have done in detail so as to pre-emptively answer questions.

Allright, I am leaving the country for a while in a couple weeks, so I decided to buy a bike, ride it back to NY (Im in VA now), then perhaps start riding west, depending on how much time i have/condition of the bike.  Why?  Well to do something I have never done, and to see things I have never seen!  It is about 550 miles from here to NY.  Not wanting to spend a ton of cash, I went out looking for a bike that I could do a minor rebuild on and be ridden at least 1000 miles. 

I went out and bought a 76 CB 750, and overpaid for it.  It is in sort of rough shape, but I figured "Hey a little work, and she will be like new!" Now, this is before I started checking out SOHC forums and the like - I just got a copy of the garage manual and figured "No sweat!  I brought my Tempo back from the brink, a motorcycle should be cake!"
I took my new prize to a friend who is supposedly a motorhead.  This guy tells me I bought a piece of junk, I would be better off selling it, etc.  Cant even tell me what is wrong with it, just that "its f*cked".  Ill come back to this later.

So I spent the next couple days reading all I could about bikes, understanding how fire, gas, air and lubrication will propel me at high speeds down asphalt. I basically crammed about motorcycles.  From "neophyte" to "know enough to BS and be dangerous to the health of the motorcycle" in 48 hours.  Armed with my new knowledge, I went out and bought a 77 CB 550 that needed some minor work.  I still dont know that much about bikes, but I know that I got a great deal - this thing has 10K miles, looks beautiful, the only thing wrong was a busted throttle cable, bad battery, and frozen caliper, also some blown fuses.  When I got to the guys house, the tank was off, some fuses blown, and no battery in sight.  Was under a tarp, looks like it had been sitting awhile - but we got it to fire up and idle fine - even turned it off and started it back up several times.  My friend said to me "When that thing fired right up, I was flabbergasted.  You know that was sitting there untouched for months." I will post pics soon. 

So right now, I am in the process of fixing up the 550.  I might use some of the 750 parts that seem to fit - for example, the frozen caliper, I am going to remove and switch with the 750.  The 550, as far as it stands right now, is in good running shape - but when I got it home on Fri night, wouldnt start back up, we flooded the plugs trying to get her to kick on.  Bought new plugs on Sat, fired right up with no tank on it, but was running 3k rpms, which I am pretty sure was the gas in the carbs burning up.  Turned it off and havent restarted it since, as I am waiting for the throttle cable to come and put everything back together. 

So now on to the meat of my post - getting the 750 to run, because I think there is a good bike hidden in there somewhere, I just gotta coax her out.  When I first bought the 750, I went to the guys house, he fired it up and we stood then and BSed for a while, it ran a little rough, but not too bad.  I paid him on the condition that he deliver it to my house the next day.  The next day when he came, the bike was backfiring, smoking white smoke and stalling out.  The guy says "I dont know what different from yesterday!  Im not selling you a lemon, this is a good bike!"   He tells me it is bad gas - I empty the gas out (no rust in tank), replace it with regular 87 from Sheetz, and it fires right up from a kickstart.  Relieved, I call it a night.  The next day, it fires up and runs for a little while. I shut it off, wont restart.

So after doing a (very little) bit of work and cursory inspection on the 750, I noticed that if you put new plugs in, it fires right up.  You can then ride it for about 20-30 minutes, and then it starts idling rough and running like crap - at which point if you check the plugs, they are sooty and wont fire anymore, without a cleaning.  Now, after reading alot of posts on here, it seems that this is a carb issue - it is running rich, and excess gas is being burned and fouling the plugs.  Also, this engine stalls out if the idle isnt set at a pretty high rate (sorry no tach, cant say how much, but I would guess at least 1700).  I did take the carb bowls off the bottom to check out, they looked clean, but I didnt take the carbs apart.
The shop manual says the causes of sooty plugs are 1) Too rich a fuel, 2) excessive idling 3) poor quality gas 4)clogged air cleaner 5) wrong heat range plug.  I dont think it is 3, 4 or 5. 

Would anyone be willing to hazard a guess, give diagnoses on the 750? Thank you for reading my saga, and I will be posting pictures not only of the repair/rebuild process on the 750, but also of my cruises around Virginia and then hopefully of the 2 day cruise to NY in May!
Any words you have are welcome, even if you just tell me im nuts

[mlinder]

What plugs do you have in there? d8ea? d7ea?
Have the choke off? Leaving the choke on will cause, obviously, plug fouling. check the float heights. Incorrect float heights can cause bad AF mixture.
Clean the air filter.
Barring anything really wrong, those should fix your richness problem, assuming jets are correct.

[moham]

I offer no diagnosis, but for the 750, I would bet that there are at least two questions that will be put to you by others:

1) are you using the stock air cleaner, etc.?
2) what kind of spark plugs are you using?

And from my own (quite limited) experience, any of these older bikes that have sat unattended for any length of time need MUCH attention paid to carburetors...

[moham]

and thus...(I'm not quick enough)

[mystic_1]

I'd be looking at the slow jets, if the bike sat they're likely to be dirty and would lead to some of the symptoms you describe.

mystic_1

[Aaron J Williams]

Barring anything really wrong, those should fix your richness problem, assuming jets are correct.

and assuming that the floats aren't full of gas and sunk
If you have the old style carbs then the float bowls are held on by a wire clip. Unclip the float bowls with the fuel valve shut off and see if there is any junk in the bottom of the bowls. With the bowls off, open the fuel valve and let gas run out of the carbs. This will flush out any junk in the needle and seat and also tell you if all 4 are getting gas. One by one push up on the floats to see if the gas shuts off. That tells you if your needle and seat are working correctly. Finally, put the bowls back on and start the bike up. If it doesn't run right then you might have to take the floats out and check to see if they are full of gas. On brass floats you can shake them and hear gas sloshing around inside. On foam floats you have to weigh them wet and then re-weigh them after they have dried out overnight to see how much of a weight difference there is.

[Geeto67]

ditch your "motorhead" friend. He obviously doesn't know about old hondas and seems to be getting in your way.

Honestly, if the clock is ticking fix the 550 as best you can and sell the 750. Ditch it and get traveling since the more time you waste before you leave boils down to sights unseen.

How about some pics of both these bikes...might help to know what you are dealing with.

[narcoticrex]

Thanks for the ideas and replies guys!  The bikes are actually at a different location (in my cousins garage), so when i go to do some work tomorrow I will test stuff out and get some pics up for you guys.

I am planning on keeping the 550 and probably selling the 750, but since the engines are similar, i was sorta thinking of using the 750 as a guinea pig, to learn and test on - it wil also obviously be worth more when i sell it if it is running.

the 750 looks like a pig, but like I said, I know there is a good bike in there, and I want to find her. 

updates soon...

PS forgot to add that i have NGK d8 plugs in there, and instead of an airbox are some new air filters the previous owner bought (1 on each carb).

[78CB750CAFE]

where in VA are you?
I am in Centreville, I have tools, manuals, some spare 750 bits and just enough knowledge to be dangerous as well. LMK if ya need a hand, I can use another strong back to help get my engine back in the frame as well.

Drew

[hapsh]

I would stop working on the 750 and focus on the 550, as it was said before, the clock is ticking.  That said I would just say you need to be prepared for an "adventure" if you decide to go 500-1000 miles on a classic bike that is not thoroughly gone through.  Any number of things could go wrong if you don't make sure they are all in working order.  It also helps if you have lots of experience with older bikes so you will be more likely to be able to diagnose a problem and fix it on the roadside.  I would go through the entire tune up procedure that is outlined in the Shop Manual to give yourself peace of mind before you start your trek.
Cam Chain adjustment, Valve adjustment, set point gap and timing, and clean the Carbs, adjust airscrews, and vacuum balance the carbs at the minimum.  Then after you have it running decent I would go for some short rides down the interstate at 65-75 mph to see how it is purring.  During one of the rides shut the engine off and pull to the side and check all your plugs.  Those will show you if your mixture is good, or if you have any issues that might cause failure along the way; sooty -too rich, will lead to fouling, light tan to white -on the leaner side, may lead to detonation and holing your piston.  I tell you all this because I took two of my bikes in the 80s for some long rides before I thoroughly went through them and got stranded twice.  One from a holed piston due to a bad condenser that caused arcing of the points to the point that timing was jumping high and low advance at higher RPM.  The other had slightly lean mixture in mid throttle on one cylinder causing it to seize.  Both problems could have been caught if I had just checked a little closer.