83 xj900 seca

I'm working on this bike. It has sat for a few years with gas in the tank. I cleaned the tank. The carbs were cleaned with a ultrasonic cleaner and reassembled. I didn't see any problems with the diaphragms. According to the manual, the timing is set and correct plugs are used. It starts easily with the choke, but doesn't run well after being warmed up. I have taken clear tubing and attached it to the fuel bowl drain ports. After loosening the screws, the fuel bowl levels are all the same. I ran the motor using a remote tank,( I had to use teflon tape on the screws to keep them from vibrating out) the levels all remained constant. The outside pipes run about 100 degrees, the inside run about 160. If I try to hold a constant speed on the motor, such as 2,000 rpm it will drop to about 1,500, then rise to 3,000 and repeat this with out moving the throttle. With the drop off in engine speed, I thought it was a defective diaphragm or 2, but i don't think it will cause a rise in engine speed. I sprayed WD 40 around the carbs and manifold to find an air leak. None that I can find. If I turn the choke on, the motor runs better. I can use it like a throttle to rev the motor up and down without touching the throttle. This is makes me think it is running lean. When I tried to balance the carbs, I could get them close, but they wouldn't remain constant, just mildly fluctuating. The plug wires were cut off at the ends because some corrosion and plug caps cleaned up and screwed back on. It Has a K&N air filter on it. Could this be the cause of the lean running? The original exhaust is still on. the bike has a little over 14,000 miles on it. It's a long post, but I wanted to cover everything I've done. Are there some thoughts on what the problem could be? Thanks for any ideas Dazed

 

WD-40 won't work to check for a leak as it isn't flammable enough. Using propane is the best method or starting fluid. I only use WD-40 to clean dusty parts-that is all it is good for.

The choke is actually an enrichment system, so it will always act that way as it is essentially a small fuel circuit just making another path for fuel to mix in. When your carbs are right it will over-rich the mix once the bike is warmed up.

Your symptoms do point towards an air leak, but you might also have pilot/mixture circuit not supplying enough off-idle mix-usually a clogged passage (unlikely in your case) or the o-ring, washer, screw/plunger assembly isn't correctly installed or faulty. Also if you can't get a balance on your carbs that will cause throttle issues.

Have you checked your valves? They must be in spec for you to get the carbs right.

 

Get the valves in spec. FIRST.

Accurately wet-set the float levels using fuel and clear tubing. Just being the same is no good if they're all too low or too high. The carbs need to be level in all directions for this; it's easier to do it with the rack off the bike.

Do an accurate bench sync. THEN block the YICS and vac sync.

It may very well need re-jetting or just some tweaking to get it to run correctly with the K&N; but the other steps need to come first.

 

I have a seca 900 motor on my 650 maxim. I had to super clean the carbs. I prodded and poked every nook I could to get these carbs clean. Now with about 40K I have not had one idle or throttle issue with my Maxim. So take your time & clean clean clean. But first check valves specs.

 

Dazed.........have you given me the info on your bike for the 900rk registry? If so, great. If not.....PM me, please.

Thanks,

Dave Fox