I've got an old motorcycle - an 89 Yamaha Radian YX600.

I've owned it about 2 years and I've rebuilt the carbs probably 3 times.

The problem is that I almost always have to keep the choke set - as in pulled out, extra fuel, to get it to crank and run. After it has been running for a long time - I'm talking 30 mins+ of riding, I can turn off the choke. I really don't know much of anything about carbs since I grew up in the fuel injection age. Everytime I rebuild it I make sure that the floats are floating. I always followed the manual to a T.

For what its worth, the spark seems strong (trust me, I've shocked myself, lol)

Any advice here?

Thanks

 

You really need to look close at the air bleed circuit on the side of the body and insure the float is set to the correct height in addition to operating freely. The air bleed works counter intuitive to what it works in a 2 stroke engine and will cause it to run lean very similarly to what you describe if clogged or varnished. If you can get acces to a good carburator solvent, I would allow it to soak in the solvent for 1-2 hours and apply compressed air to all of the ports, channels and venturis as well as air bleed and idle circuits. When you re-assembl e it, insure the float is set at the exact height called for in the manual or it will usually end up lean and cause the same issue you are experiencing again. M/C carbs are particularly affected by dirt and varnish due to the small sizes of the passages, so cleanliness and a good supply of compressed air will usually do the trick. Also if a fine mesh screen is covering the main jet, insure that it will allow fuel to flow through it unrestricted. Many times they look clean, but will not flow adeqautely and again create the same type of issue you are having. Also might be a good time to make sure the valves are in proper adjustemt since valves too tight can cause this also, as well as a vacuum leak at the carb boot to engine joint. Hope this helps.
Bob

 

Your post will help with my honda rebel,keep going with
the helpful post.I will have questions later.

 

That was a tremendous help.

I didn't even think about adjusting the valve lash. It's a 20 year old bike, so that could be worth checking.

The carb boots were fairly cracked and dry, but I just coating them with silicon and put them back on. Perhaps I do need to shell out the 60 bucks for some new ones.

 

wannaB,
The problem you described is exactly what happens when the jets get clogged/restricted. I just pull/unscrew them out (make sure you note the exact number of turns to get them back to the same spot) then what I do is take a single copper strand from some wire and stick it through the jet holes and clean that junk out.. Then reinstall and you are good to do.
And I always use Stabil in my gas to hopefully prevent/prolong carb jobs.