Slow starting '82

[Rockosmith]

Last week I acquired a nice '82. It runs nice after it starts. When warmed up it starts fine. Only from cold, when it has not been run in a few hours is it hard to start. It acts like only a few cylinders are "choked". Is this likely or is my starting technique faulty?

[asacuta]

CBXs are known for being hard to start when they are cold. I think it's a combination of the vacuum-operated fuel valve and a tendency to boil the gas out of the carb bowls when they sit hot. I find that if I prime the carbs by using a small vacuum pump to activate the fuel valve, the bike starts much easier. That's a hassle, so one of these days I'm going to add an on-bike bulb or something. I haven't checked this forum; maybe someone else has already built something.

[Rick Pope]

If memory serves me, on the back of the vacumn shut-off is an unused nipple. By putting a length of hose on said nipple, one is able to blow gently into the hose, overcoming the little spring which closes the valve when there is a lack of vacumn. So, fuel will flow to replenish what has evaporated due to engine heat.

[daves79x]

Rick's correct, but Honda put a long hose already on the vent side of the valve and ran it down the right side of the top of the airbox and down the inside of the frame tube. Pull it free on the end, clean it up and blow into that.

Several other factors might be in play here also. You accelerator pump is likely non-working and that would help a lot. Try pumping the throttle a dozen times or more before you start. If it's working, it will load the cylinders with fuel and make starting easier - don't worry, you can't flood these things.

Possibly the chokes aren't working either. Check cable adjustment and make sure they're fully opening and closing.

If you don't know the history of the bike, a carb rebuild might be in order.

Same applies to timing, valve adjustments, cam chain adjustment.

Dave

[Rockosmith]

Thanks all. Today I pumped the throttle 8 times and it started right up. The carbs were rebuilt in '08 and it has been lightly ridden since then. It seems to run right so I believe all is in order.

[asacuta]

Mine's the opposite: if I pump the throttle to have the accelerator pump "prime" the intake, the bike is harder to start. It prefers to have the throttle left alone until it fires. Cranky beasts these are. Even after 6 months storage, my fuel-injected Rune fires on the first touch.

[daves79x]

Al:

Yours would be the first CBX I've seen that didn't benefit from pumping the throttle several times prior to start-up. It's a moot point if the accelerator pump does not work, which most don't after many years.

Rocko - try this: If you know the bike will sit a week or so without running, drain the carbs. Then when you're ready to start again, fill the bowls by blowing into the vacuum valve vent, as discussed before. Then full choke, no throttle, and I'll bet the thing starts instantly and runs on all cylinders immediately. It's just the way these are.

Dave

[asacuta]

Several of the bikes in the local CBX club, when it was still around, behaved like mine. The accelerator pump does work, but maybe not to original specs.