Seca 400 Posted April 27, 2010 Share Posted April 27, 2010 Hi everyone, I am a brand new member to this forum and I have a question about a 1982 Seca 400. I have had this bike sitting in my garage for almost 10 years and I finally decided to get it going again this year. I sent the tank to a repair shop that specializes in repairing and coating the inside and outside of gas tanks with a poly-uria coating. I changed all of the wheel bearings, rebuilt the front brake master cylinder and caliper, put new pads on the front, new drums on the back, had 2 new tires installed and balanced, bought a new battery, changed the oil, filter, spark plugs and repainted several parts of the bike. The bike was running fine when I put it away, so I decided to try to start it and see how well it ran without doing any engine or carburetor work (aside from the tune up and oil change, of course). I put everything back together tonight, turned the petcock to prime, and started to fill the tank with gas. After a few minutes, gas was pouring out all over the place. After searching for the cause of the leak, I realized that the fuel was leaking from inside the air filter compartment, and was getting in there through the carbs. In other words, fuel filled up the carbs and then just kept flowing out of the carbs and eventually into the air filter compartment. It's been a long time since I've used this bike, and I don't recall exactly how the petcock works, but I'm pretty sure that the carbs are not supposed to overflow if the petcock is left in the prime position. What is the likely cause of this problem, and is there any solution other than removing and rebuilding the carburetors? Is this a big job, and what parts would I need? I already have carb gaskets - I bought them when I bought all of the bearing and brake parts but I was hoping to not have to get into the carburetors this year. Would I likely need anything other than the gaskets? Any help or advice would be greatly appreciated. Link to comment Share on other sites More sharing options...
Seca 400 Posted May 1, 2010 Author Share Posted May 1, 2010 Thanks for the helpful suggestions everyone. I ended up rebuilding the carburetors (dual mikuni BS34's) top to bottom, using the rebuild kits that I had already bought (bowl gasket, float jet and float jet seat). I started the bike up tonight, and after a minute or so, it fired-up. I had to speed up the idle a bit to keep it running, and now it seems to be running a bit rough. It seems fine at idle (around 1,200 rpm on the bike's tach), but seems sluggish at take-off, until it gets into the higher rpms. I would like to try to get it running a bit smoother at the bottom end. What is most likely to help? Should I try to adjust the pilot screws (they were at 2.5 turns out and 3.25 turns out, and I set them both to 2.5 turns out), or should I check and adjust the valve spacers, or is there something else that I should try? I would prefer not to have to get inside the carburetors again. Any advice would be appreciated. Thanks in advance. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 1, 2010 Moderator Share Posted May 1, 2010 Thanks for the helpful suggestions everyone. I ended up rebuilding the carburetors (dual mikuni BS34's) top to bottom, using the rebuild kits that I had already bought (bowl gasket, float jet and float jet seat). I started the bike up tonight, and after a minute or so, it fired-up. I had to speed up the idle a bit to keep it running, and now it seems to be running a bit rough. It seems fine at idle (around 1,200 rpm on the bike's tach), but seems sluggish at take-off, until it gets into the higher rpms. I would like to try to get it running a bit smoother at the bottom end. What is most likely to help? Should I try to adjust the pilot screws (they were at 2.5 turns out and 3.25 turns out, and I set them both to 2.5 turns out), or should I check and adjust the valve spacers, or is there something else that I should try? I would prefer not to have to get inside the carburetors again. Any advice would be appreciated. Thanks in advance. did you really really clean those carbs? we've had peeps on here swear that they did and it ends up that all they did was a quick spray with a carb cleaner. after 10 years sitting, that fuel will be well varnished and I always recommend soaking and use ultrasonic cleaning. TBH i sent off my first carbs to a pro cleaner who also rebuilt them at the same time and he was amazed at the amount of crud that came out!!£100 well spent i got my own little ultrasonic cleaner now and had my latest carbs vapour blasted inside and out! hope that helps BTW to the forum Link to comment Share on other sites More sharing options...
Seca 400 Posted May 1, 2010 Author Share Posted May 1, 2010 did you really really clean those carbs? we've had peeps on here swear that they did and it ends up that all they did was a quick spray with a carb cleaner. after 10 years sitting, that fuel will be well varnished and I always recommend soaking and use ultrasonic cleaning. TBH i sent off my first carbs to a pro cleaner who also rebuilt them at the same time and he was amazed at the amount of crud that came out!!£100 well spent i got my own little ultrasonic cleaner now and had my latest carbs vapour blasted inside and out! hope that helps BTW to the forum Yes, I really cleaned the carbs. I removed them from the bike, and cleaned the outsides. Then I took them into the basement, completely unassembled everything, cleaned the gunk out of the bottom of the float bowls until they sparked, removed and cleaned all of the jets, removed and cleaned the floats, replaced the needle jet and jet seat, replaced the float bowl gaskets, cleaned up the pin needle and slide, removed, cleaned and inspected the choke assemblies and the pilot screws, and inspected the diaphram. Once that was done, I blew carburetor cleaner and then compressed air though every jet, passage and hole that I could find, and then very carefully put everything back together. They are clean. Link to comment Share on other sites More sharing options...
akronevan2 Posted May 25, 2010 Share Posted May 25, 2010 Yes, I really cleaned the carbs. I removed them from the bike, and cleaned the outsides. Then I took them into the basement, completely unassembled everything, cleaned the gunk out of the bottom of the float bowls until they sparked, removed and cleaned all of the jets, removed and cleaned the floats, replaced the needle jet and jet seat, replaced the float bowl gaskets, cleaned up the pin needle and slide, removed, cleaned and inspected the choke assemblies and the pilot screws, and inspected the diaphram. Once that was done, I blew carburetor cleaner and then compressed air though every jet, passage and hole that I could find, and then very carefully put everything back together. They are clean. So what's the status of your bike now. I think I may have the same problem. I don't really know for sure though. Link to comment Share on other sites More sharing options...
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