I just got my project up and running and went out for my first ride. Problem is the bike won't go over about 50mph unless I'm going down a steep hill. Details:
1967 CB77 Eng# CB77E 1052719
Had a reputable old Honda shop in San Francisco rebuild the engine, bored out, new pistons and rings, top end, clutch, starter motor..
I removed the engine to save $ and cleaned up the carbs myself. I had moved by the time I built it back up, had to take a second pass at cleaning the carbs (the little air tunnels feeding the idle stage were obstructed) and I set up according to Ed Moore with new contact points. After doing that, I have a bike that starts reliably, idles nicely when warm, and winds out pretty well (I'm still breaking it in, it has only run about an hour on the rebuild).
I can put things together, but I'm a bit lost when it comes to fine tuning. I know this bike should make more power. Any advice? Any old Honda fans in my newly adopted town of Nashville TN?
thanks, Burvis
It has to make more power than thisI should also mention-
I bought a new front sprocket from Ohio Cycles that seemed to have a different mounting setup, so I ended up going back to the one that came with the bike. That one has 16 teeth as opposed to 13 teeth on the one Ohio Cycle sold me. And the bike feels very highly geared, in other words, barely gets off the line. I bought NOS stock airfilters. One of the mufflers is dented pretty good, looks like maybe as much as 15-20% diminished capacity. I was told that would have a performance effect.
Hi,
not living in Nashville, but I'll try. standard sprockets should be 15 teeth (front) and 30 teeth (rear) for a CB77. it doesn't matter what sprockets you use, as long as the ratio is about the same. I don't think that the muffler is the issue here. a few questions to get an idea : what is the compression ?, same on both cylinders ? are there any engine sounds that you don't recognize ? if you pull out the spark plugs (no compression) does everything run smooth (pushing the bike in first gear) ? what color have the spark plugs ? is the battery full ? is the advance unit working properly ? are you sure that the carbs are rebuild-ed ok ? are the main jets clean , right size ? float hight ok ? are the cut outs in the carb slides pointing backwards ? is the petrol line not obstructed ? answering above questions can help me or other forum members to pin-point a direction. jensen assembly of Japanese motorcycles requires great peace of mind (Pirsig)
Great, thanks for trying to help. I probably just need to keep messing with it, something I'll do more of this weekend. I can eliminate a few from your list:
...what is the compression ?, same on both cylinders ? I haven't been able to test, but it was just rebuilt, bored out, new pistons and rings. The shop has a great rep in San francisco- Charlies Place. Seems to know his stuff. I'd be quite surprised if it's a bad build, but I will check it if I can't get it to run better. ...are there any engine sounds that you don't recognize ? It sounds really good! normal amount of valve train noise for a parallel twin in my experience. Nothing else amiss, doesn't pop or ping. Sometimes the motor kicks back against the electric start which sounds a little nasty. >>>if you pull out the spark plugs (no compression) does everything run smooth (pushing the bike in first gear) ? what color have the spark plugs ? will perform this test this weekend. ..is the battery full ? is the advance unit working properly ? battery is new, full. Is there a good test of the advance? I assume it would run really poorly at low or high rev range if the advance wasnt working, and it runs great throughout, just doesn't pull strongly enough under load at higher revs. >>>are you sure that the carbs are rebuild-ed ok ? are the main jets clean , right size ? float hight ok ? Two rounds of cleaning on the carbs, and rebuild kits installed with new main and idle jets, float pins, etc. I am pretty confident they are ok, just maybe not set up well enough. Not sure about float bowl height. Performance issues tied to this? I would have thought just might cause gas to leak out the overflow tubes. >>>are the cut outs in the carb slides pointing backwards ? I will check this weekend. They should be backwards? Or forwards? I suppose I could have gotten the two slides reversed when the engine was out. Just realized the channel in the side of the slide is no guarantee if you've reversed the slides... >>>is the petrol line not obstructed ? no, getting plenty of gas. As above, the best way to describe this problem is a lack of power at higher revs. It will rev out all the way oto redline out of gear. But pretty weak under load. thanks for the help. Are you not expecting a little too much if the motor has just been rebuilt? Revving to the redline 'out of gear' isn't going to do it a lot of good at any time. A rebuilt motor will be tight until it's run-in.
Say 500 miles at slowly increasing workloads, with a little spur up the rev-range to vary the duty occasionally. Trying to get max power so soon after a rebuild is asking to reduce the life of the motor. Take it easy and you will be rewarded with more power and reliability later. The slide cutaways should affect the motor at the top end of the range. G '60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F Haha, I realize I made it sound like I was riding WFO out of the gate. No, apart from winding it up once by accident due to turning the forks before my throttle cables were sorted out, I've been taking it easy, I know that much. I also know to change the 'break in oil' after the first few hours of operation.
But we may be onto something with the throttle slider cutaways. Rookie question. Should the cutaways be toward the back (air filters) or the front (intake ports)?
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