Topic: 73 CB500 "Slo Jet" Carburator Problem

[toobad]

Hopefully, someone has experienced before and can save me some work.  What is going on is this:  I start my bike normally and let it warm up before riding.  I runs great until I stop somewhere and turn it off.  This is where the problem begins.  After I restart the bike again, I now have what I will call a "dead space" in the initial take off which resolves itself in each gear shift.  This problem is mostly noted going from 1st to 2nd gear.  I have talked with the head Honda mechanic in my area and he said it could be a "slo jet" problem and I should clean and blow out all the slo jets.  I have some problem with this analysis since I would think intuitively that if the slo jet is clogged, it would occur all the time but what do I know.  I completely rebuilt all four carbs about 10,000 miles or so ago and it has ran great until this problem.  When I happens, it is like it initially looses power until it kicks in.  I have not noticed any issues once the carbs kick into the secondary.  I thought I would check with the forum before I start tearing it down.  Any thoughts or help anyone has would be greatly appreciated.  Thanks

[calj737]

It could be related to the choke. You don't state whether you need to use choke each time you start the bike. Only if the motor is warmed up, should you not require some amount of choke for some period of time to get the motor running hot again.

I agree with you, its not slow jet related. If it were, it would be persistent each time you ride the bike. It could be that you carbs are setup too rich on the pilot circuit, and you are slightly fouled on the plugs when you stop. Low throttle, cold engine will feel like a stumble until you reach higher RPMs and burn the plugs cleaner.

Is your bike stock? Do you have the stock airbox, exhaust and jets? Did you rebuild the carbs with aftermarket parts and/or change any of the stock settings to accommodate modifications in your bike? Pulled a plug out lately to inspect them? Simple things to check before you start tearing into the carbs...

[Deltarider]

This is what I'd do first.
1. Check ignition (all aspects including proper functioning of the advancer).
2. If all of the ignition is well, I'd verify the position of the airscrews. In your area they should be at two turns out, provided the needle clip is in 4^th slot from top. Whilst your at it, you could do this simple test: a) Have the engine idle or a bit over idle. b) Turn the airscrew of carb 1 fully home and then say three turns out. Either way you should notice a change in RPM as a result of this. c) Reset airscrew carb 1 at two turns out. d) Repeat this test on each of the other carbs. If a carb doesn't give this change in rpm, that carb has a problem in the slow circuit.
3. When bike is warm, does it smell of gas @ or near idle? That could indicate a too rich setting (actually I suspect this).
In general: CB500s don't like inline fuel filters. Remove and have the fuel lines at the proper length, 18 and 30 cm (models with the newer type petcock have 17 and 28 cm). Ideal internal Ø is 5,5 mm.

[jgger]

May or may not help, but here is something to think about. If your float level is border line high when the motor is shut off warm, the heat can cause the fuel to expand  and  flood the motor. That will foul plugs until they burn clean. It doesn't matter if the fuel is shut off, because it is the fuel in the bowl expanding that causes this.

I have had this happen to me, and I chased my tail for a long time trying to find out what was going on. You can see if this is the case by shutting off the fuel about a half a block before you stop to lower the level in the bowl. I would also think parking on the side stand could add to  this issue.

OR............maybe I'm the only one that weird crap happens to!
Good luck.

[TwoTired]

Is the bike in all stock cobfiguration with no mods to engine intake or exhaust?

Cheers,