CB77 Carburetor Tuning

[e3steve]

Tough? No. New way of life? Yes!

Over-rich running (starts with no choke, from cold): first thing to check is that the slides are in the correct carbs ~ they can be reversed, leaving the cutaways facing the head ports, thus creating a thru-the-range rich mixture that's impossible to correct. It sounds as though you've cured the idle richness, though.

Your situation seems to be one of midrange lean mixture; try raising the needle a notch. If that leads to an imbalance between idle- & higher-throttle openings (i.e. slightly rich after a ride but normal after idling awhile), drop the needle back to its middle notch and try a colder plug (and re-adjust the air screw to compensate at idle). The CB was designed to run on NGK D7HA plugs, which are nla: I run D8HA in my locale, with a nominal air temp of between 26º & 40ºC during my 'riding season'. If you're using D6HA, try the colder D8HA. http://www.honda305.com/forums/viewtopic.php?t=3646

I balance my carbs using a length of small-bore (screenwash) tubing and listening to the air rush: http://www.honda305.com/forums/viewtopi ... highlight=

[nander]

Steve,

A British expat in Spain? I'm imagining Ray Winstone on a Superhawk.

This morning I pulled the bike out of the garage into the light, popped the carb tops and raised the needle a notch. Took the bike round my usual 1/2 mile tuning route through the neighborhood. Still no power over 4000k.

Pulled back into the driveway. Thought, "maybe I'm still too lean, why not try that 140 main jet?". Removed the righthand float bowl to get at the main jet. A little gas spilled on the hot engine and sizzled alarmingly. Crisis averted with a rag, I turned my attention to the float bowl in my hand...lo and behold...there was a 135 main jet sitting in the gas at the bottom of the bowl! WTF? Can't imagine how it unthreaded itself. Suffice it to say I must have screwed something up when I replaced the needle jet holder. Law of Probability? the more I mess with something, the more unique ways I will find to screw it up! Anyway, delighted at the apparent ease of the fix, I screwed the damn 135 jet back in and took her for a spin.

VICTORY!

75 degrees and sunny in Los Angeles. Borrowed a second helmet. Rode down to Little Tokyo two-up through traffic and had some celebratory shabu shabu (corny? seemed appropriate). Headed back toward home, but reconsidered.

It was so amazing to actually be riding the damn thing that I decided to get some gas and continue. Headed to Griffith park which (for the unfamiliar) is "the largest municipal park with urban wilderness area in the United States". Lots of fun roads and and pleasant scenery. I've been saying for months that "when I get this thing running I'm gonna ride it through Griffith Park". Such a beautiful day. Decided I would try to find my way to the Observatory. Didn't care if I got lost because I was pretty confident the bike was running well and not going to leave us stranded. After motoring around for awhile without finding a way to the observatory, I started up a promising looking road. Turned out to be a closed fire road (paved though!) that someone had left the gate open to. This began to dawn on me when I realized the people I passed on horseback were shooting me disapproving looks and gesturing back towards the entrance. Didn't care. How could we pass on the opportunity to test the bike out on miles of empty winding road with views of the whole city?! Followed the twisties along the ridges towards the Hollywood sign assuming I'd find a way out eventually. Spilled us out right next to the observatory! Had to maneuver the bike through the pedestrian path around the gate to get to the main road.

Funnest thing I've done in God knows how long. I've been restoring this thing for about 8 years on and off. Today it became a real bike.

Got home. Pulled the (D8ha) plugs. Mouse brown.

A new way of life. Definitely.
Couldn't have done it without the help of this forum.

Thanks,
nander

[e3steve]

A British expat in Spain? I'm imagining Ray Winstone on a Superhawk.

I ain't quite his stature, my son! But he is one of my acting heroes. I swear he and Vinnie Jones would be tuff enuff to anhialate the Alien all on their own! Unlike that wooss (as in 'pussy woossie' -- Brit English for 'softie'!) Sigourney, who needed a small platoon of rough tough space commandoes...... Girlie!

EDIT: or even commandos.....

75 degrees and sunny in Los Angeles. Borrowed a second helmet. Rode down to Little Tokyo two-up through traffic and had some celebratory shabu shabu (corny? seemed appropriate). Headed back toward home, but reconsidered.

Nice! I'm more of a sushi mixta and ebi tempura man, myself.

Great result, nander! Who'd have thought a mainjet could work its way loose? Don't overlook float heights, next time you pull the carbs.