Topic: 1978 cb750 w/dual front disc - keep it or let it go.

[turin39789]

I picked this bike up from a seller on this forum, and it turned out to have problems I wasn't prepared to deal with.  Right now I'm too swamped to take on another project.  I've tried to make room but it's not there.  I might be able to do it next month but I'm just not sure where to start.

I rode the bike home from the sale on neighborhood roads.  I took it on the highway for the first time and didn't have the power it should, topping out at around 65-70.  I also noticed some oil leaking and pooling outside the #1 spark plug wire.

I had hoped it was a bad tach cable seal, so I parked it and waited for one in the mail.  Got it and installed it, took her out onto the highway and still no power and the oil soaked through my jeans on my left leg and coated my boot. 

Took it home mad and sad.  Sprayed some foot powder on it per a suggestion from here and let it idle, took it around the block. looked like most of the oil was on the left, near where the head mated but it still seemed like some was coming out below that, but it was real hard to tell.

It's sat since then.  If it's something as simple as a head gasket, I can have a friend help me pull the engine(I've never done this before) and get a new one on.  I think it might explain the oil but the loss of power still rubs me bad.  99% of the time I don't let myself take anything to a shop and force myself to learn it myself, but right now I work/school from 7am-8:30pm and have to read the rest of the time.   If this might be something I could pay for(sigh) and not be too outrageous I'm willing to, but I'm starting to think it might be better to just pass it along, with full disclosure of course, to someone better suited to fix it.  It's just hard as the bike seems in such good shape otherwise.

It's gotten so that I've stopped coming to the forums, ashamed of my inaction and inability.  I just haven't wanted to think SOHC and my 550 has been my joy for the last year and a half.

Giving it one more shot, let me know your thoughts, if you want pictures or want me to run a test say so and I'll try to get to it, might take a few days though.

[medic09]

I was recently back in school for a year and a half.  No time for anything except the long ride back and forth, reading and writing.  I only had time to work on my bike during the long winter break. What's worse, I was using it for intercity transportation while it ran terribly.  If that is your situation, and assuming that school is a priority, you won't have a lot of time for this.

So, how long till you finish school? Letting it sit won't cost you more money.  The K8 is a nice bike if you want the size.  Once it is sorted, it could be a good solid bike.  You already own it, so there's no need for rash decisions fueled by initial disappointment.

BTW, many of us can tell you stories of 'it seemed great when I bought it, till I got it home...'.  It is part of the challenge of riding old (and sometimes new!) bikes.  You probably haven't done any worse than many, many of us.

Let it go for at least a week.  Then think about your options slowly, with an open mind.  If you are just despondent over it then, send it to me and I promise never to bring it up in conversation. 

Hang in there!  And welcome to the club...

[bistromath]

Hey, sort out what the problem is before you get ticked off about it! Might be as easy as a bad rocker arm cover seal and poor tune. First things first, get a compression tester and test all four cylinders. That'll tell you right away if you need to tear it down or not. If compression is good, give the bike a thorough tuneup (there are hojillions of threads on this site relating to how to do a full tuneup, the gist is valves, camchain tension, timing, and carbs, in that order). If compression is bad, THEN start kicking the sand and looking sad about things. And then get over it and tear it down and rebuild it! I know you're discouraged now, but the good news is these bikes are as easy to work on as anything ever built, and most parts to get them running are cheap enough. Hang in there!

[turin39789]

Hey, sort out what the problem is before you get ticked off about it! Might be as easy as a bad rocker arm cover seal and poor tune. First things first, get a compression tester and test all four cylinders. That'll tell you right away if you need to tear it down or not. If compression is good, give the bike a thorough tuneup (there are hojillions of threads on this site relating to how to do a full tuneup, the gist is valves, camchain tension, timing, and carbs, in that order). If compression is bad, THEN start kicking the sand and looking sad about things. And then get over it and tear it down and rebuild it! I know you're discouraged now, but the good news is these bikes are as easy to work on as anything ever built, and most parts to get them running are cheap enough. Hang in there!

Compression is ok.  Tried it once and got 50psi,- guess my $2 yardsale gauge was bad.  Picked up a new screw on type from sears and got 100-90-95-100, not sure that I had a full seat on number 2, and this was stone cold as I already had plugs out and the bike is stuck behind my wheel-less 500 that is getting new rubber put on.

[bryanj]

That compression is WAY low you need 130+

[bistromath]

yeah but who ever heard of four low readings that are pretty even across the board? i think it has more to do with his setup than with his actual compression.

[turin39789]

I'll retest warm.

Did the test with throttle and choke open, all 4 plugs out, and a new compression tester

[bryanj]

If its an f with k pistons all 4 would be low