Hi all.

I just got an 89 600F last month and have only put on about 200 miles so far. It has 15K and was "serviced" by the dealer who sold it to me (not a Honda shop, just an independent guy) and the carbs were cleaned and reassembled.

I know it will need a new CCT because it is making the exact same noise my 90 600F used to make prior to replacing that one. Otherwise it starts fine with not choke needed, and idles well. As the bike gets hot, like in stop and go traffic, it will stumble quite a bit off idle, and then again at exactly 4K RPM.. It sounds like a misfire and the exhaust note turns really horrible as it stumbles, then once past 4K it will rev just fine. Before I did anything drastic, I replaced the fuel filter and added a few ounces of SeaFoam to the tank. I thought it helped at first, but here I am with the same problem. I am guessing that it might be a fuel/air issue? Does that make sense as it comes and goes with the temperature?

What would be a good starting point in troubleshooting this sort of thing ? vacuum lines, spark plugs, etc... where should I start? I am going to take the bike to a Honda dealer in the spring to have the carbs looked at and synchronized, but for these last few weeks of warm weather it would be nice to fix this! And BTW.. it has a full D & D system which I am beginning to hate... I have a bit of a theory that the aftermarket system is not helping the overall health of the bike ;-)

 

Mine always needs a little choke (for a few minutes) when it is completely cold when it is warm outside. I am sure the carbs on an 89 are different than the 90 model so I would check the idle mixture screw, the jets, air filter etc.

I would think it is probably running rich at idle.

Does it get worse as it warms up?

Try running it without the air filter and see if that improves things. If it does, then you are way rich.

KongBastard

 

Thanks.. I will look at that. It does get worse as it is warmed up... when I first go out on a "cold" morning, the bike runs best. As the temp gauge is half or more, it stumbles more at the 4K mark, and below sometimes. I will take out the air filter. Yesterday I took off the tank and checked things out.. turns out the airbox was drilled and it has a K&N air element - neither of which I was too thrilled about. Along with the D & D full system, I think that the bike is pretty wacked. I will get an OEM filter and a new lid for the airbox ASAP.

 

Usually a too rich setup will get worse as the bike warms up.

I would keep the K&N. They are a good filter. Tape over the holes in the airbox cover (temporarily). The holes let a lot of extra air in and lean things out but if you are still having a stumble it is quite possible that the previous owner richened things up too far to make up for the various problems that crop up if you don't do a full rejet and needle replacement

You will be running very rich then and should have to rejet. The D&D replacement back to stock will also require some jetting changes.

Shut the fuel off and drain one of the carbs that you can reach and see if you can pull the float bowl without taking the carbs off. you can then pull out the jets and see what is in there. If you have to pull the carbs because you can't reach it takes a lot more time (we are just on a fishing expedition here)

The other thing that happens is sometimes the diaphram in the carbs get pinched and a person will overjet to make up for the problems that causes. It doesn't fix it, just masks some of the symptoms.

Good luck.

KongBastard