86 200x

[Joshuart311]

I have an 86 200x that I've been working on for three months. When I got the bike it smoked terribly so I found another motor that ran great and swapped it out. Carb is freshly rebuilt. New air filter. Valves have been adjusted. Adjusted decompression cable and even took it off with no change. The problem I'm having is the bike runs like crap without the choke. It will idle some but bogs down. It has power loss without the choke on. I've tried every setting on the metering rod. All setting on fuel screw and idle screw. This bike has been a headache. My next step is to check for some sort of air leak. It has to be getting air from somewhere. I don't have a compression gauge to test compression. With the choke on the bike runs like a scalded dog. If the choke is off it acts like it's missing and just bogs. Also new plug with good blue spark. Any help would be appreciated.

[webbch]

Since you changed the whole motor out with one that ran great, it eliminates a lot of stuff. Timing is therefore not a likley culprit in this case IMO, although it's always good to verify.

Since you need the choke on in order to run, that suggests the engine isn't getting enough fuel (or you have air leaks, but that's fairly easy to verify by shooting carb cleaner/starting fluid in the likely leak areas and listening for changes in the engine speed). When a motor isn't idling well, I generally crank in the idle screw in until it will run without me touching the throttle, whenever possible. Then I go and start adjusting the pilot/fuel mixture screw (after checking for air leaks). As things improve (this won't happen when your pilot jet is the wrong size), the idle generally increases and I have to re-adjust the idle speed, which I do with my timing light that has an RPM readout.

Before playing with the jetting, you'll want to double-check the carb to make absolutely certain it's clean. This means soaking in carb cleaner and blowing out the jets with compressed air at a minimum. You also want to verify the float level, in case you accidentally tweaked it when rebuilding the carb earlier. Float level adjusts fuel mixture in low, mid, and high range, and is pretty important. Also remove the pilot screw and make sure it has the spring, washer, and o-ring on it. My experience has been that the o-ring is frequently missing, which throws off the mixture. You can compensate to a degree by turning the screw in a bit more*, but it's not the correct way to do it. Thankfully the oring is included in most carb rebuild kits.

As a general rule, you start with the pilot screw in the position recommended in the manual. If you have to go 2 turns or more in any direction off the stock setting, it generally means you need the next size up or down on the pilot/slow jet. At either end of the pilot screw's max adjustement, you should be able to stall the engine (when idle speed is set properly).

*I'm assuming it's a fuel mixture screw, and not an air screw.