Good Evening Ladies & Gents,

I have been working on a 1999 CRB900 RR that I saved from sitting in a barn for 5 or 6 years. I am a 60 year old very experienced hobby motorcycle mechanic that was a certified Honda/Suzuki tech many years ago.

Bike starts good and seems to run ok on the stand. Once under load it runs badly when the throttle is fully opened or at anything above about 4,000 rpm.

Carbs were real cruddy, they have been cleaned thoroughly and have stock jetting. Stock exhaust, some kind of funky homemade/aftermarket air filter that looks like a furnace filter element that has been installed into a nicely cut out piece of sheet steel. Filter element is correctly sealed on top and bottom to the air box.

Spark plugs were new but a carb float valve was sticking (all float valves have been since replaced) and flooded the combustion chambers badly.

Plugs have since been cleaned.

All plugs look way lean, especially #1 and #4.

New battery, charging system is operating within spec.

Air box has been cut open in the past but has been resealed.

Anyone know what the part #5 Duct Inner is in the OEM air cleaner parts drawings? I am missing that part.

Here is what I am thinking:

Replace plugs.

Get OEM air filter and new housing gaskets.

Install Stage one jet kit (I am told that all these bikes could benefit from this.)

Any of your comments/help would be greatly appreciated.



Thanks!