Carbs

[Anonymous]

Hey Everyone, I'm kinda here as an outsider, I'm currently running a Yamaha 83 Seca 900. I've just rebuilt (cleaned) the carbs and I'm having a hard time getting perfect retune. The carbs are Mikuni BS 35 CV (which were also run on Suzuki's. Do Ya'll have some sharp mechanics an can I ask questions ?

Thanks
MeCasa

[Anonymous]

Does anyone have knowledge of a site where I might ask questions. I love this old bike but the local Yam dealer has young mechanics with very little knowledge of older bikes not to mention they will not work on anything more than 14 years old. My question will be why there are only pilot screws on cylinders 2&3, 1&4 have aluminum caps on the pilot screw hole. does this mean the adjustment for 2 controls 1&2 and 3 controls 3&4, I have hesitation which drives me nuts as I am an aggressive rider....

[dgeorge]

MeCasa, those caps on 1&4 will come out, just take a self tapping sheet metal screw and screw it into them a little ways then use some pliers to pull them out. They are usually lead so they come out pretty easy. They were put there to keep people from messing with the mix's because of EPA regs. And I don't think you have to have a Suzuki to get some of the experts on here to help you. We have several that are very knowledgeable about older bikes in general. I have a question about your carbs did you sync them after you rebuilt them. That is probably where your hesitation is coming from if you didn't. It is very important that they be sync'ed. If you don't know how to do it is there a small independent motorcycle shop around where you live? If there is a lot of the times they can do it for you. Hope this helps you out.

[Anonymous]

There are some real experts here that might show up shortly. On my carbs, the screws with plugs are idle mixture adjustment screws in the small towers on the outside of the carbs (some of your plugs are missing). And though they might cause a slight hesitation on take off, (would affect idle the most) they aren't pilot jets.
These carbs are sensitive on air/fuel intake. Is the air filter element clean? Is there an element in the air box? If someone changed the exaust or air filter, did they change the main jet to match?

[Anonymous]

Thanks for help. This bike is stock and the carbs were in pretty good condition, air cleaner is clean and I own a set of gauges since Ive been running inline fours since 70, not counting a 4 year Norton stint which we all know is a true love/hate relationship. I am a little confused because this bike was built at the height of the EPA bull*@%^$*@%^$*@%^$*@%^$. To the best of my knowledge there was no adjustable parts on the inside of the carbs, which leaves the pilot screws and vacumn. I was concerned with drilling out those caps on 1&4 but will do so in the morning. The factory calls for 2 turns on the pilot so I will set all four at 2 or a little less before sync. This machine is a YICS which means it has a chamber behind the cylinder through which the vacumn becomes common before going to carbs, Yam called for a blanking tool while synching, which is nothing but a rod with rubbers to isolate every cylinder with it's carb. I cannot find this tool and I'm not sure just how important it is. I tried to make one with all-thread and O-rings but the O-rings were a c-hair tight. Does anyone know if this tool is essential or BS. Either way I will drill the 2 pilot screws, reset and resync. Maybe I need more octane?

Thanks
MeCasa

PS: Compression is mid 90 on all 4, valve shims are perfect and fuel petcock has been cleaned.

[Anonymous]

On my carbs the pilot jet is accessable only after removing the fuel bowls, under the rubber plugs, I believe. The outside front towers are idle mixture adjustment screws. My pilot jets can only be adjusted by buying a larger or smaller size. Someone suggested going one size larger on the pilot jet, (to correct emmisions downgrades) which turns out to be 2.5 larger where I get mine. Have done this on one of my bikes but the jury is still out on that. Opening up the idle adjustment screws will only help you at idle and just coming off idle, don't need to tell you hesitation can be very difficult to find. Did you use rebuild kits after cleaning carbs? Usually the mains in those kits don't match the bike set-up. Some put stock mains in for a bike with aftermarket equipment. Some kits come with a hugh main for a E model even thouth the catalog says its for a mild set-up. If you tanked the carbs with those aluminum plugs still in the idle adjustment towers, the little o-rings in there would have disolved. (on the tips of the adjustment screws). Are you looking at the spark plugs? they have that system for burning them and reading them, but if you're way off it will be obvious weather it's too rich or lean. Did the bike ever run right since you got it? Are the header pipes discolored? The experts you were trying to get are waiting in the sidelines for basic stuff to be gotten out of the way. I only ever owned a Yamaha twin, a long time ago. Friend of mine has a 1979 XS1100, owned it since new and has over 100,000 miles on it. A very sound bike. He has had to rebuild the carbs, change the ignition igniter, change the drive shaft, etc...

[Anonymous]

Hello, I'm using a Haynes book which is calling those tower screws pilot screws, the pilot jets are however on the bottom of the carb next to he main jet. This could be a matter of semantics and I'd be a liar if I knew. I believe even though Haynes calls these pilot screws they do the same as what ya'll are calling idle mixture since the book calls for a preset 2 turns out, at least, I guess they're the same, hahaha. I didn't use a rebuild kit because they are discontinued, this bike had 14,000 actual miles when I flew out to Oregon to buy it. I rode it back to Texas and lost #4 cylinder half way. It was then that I noticed no fuel filter and the screen in the petcock was laying down. I did a roadside breakdown (I bought the manual before the trip and this is my 4th Seca but first 900) and I did have a buildup of crap on the screen of the float needle valve seat and after it was cleaned I regained #4 but never got it retuned. The one thing I have noticed reading through ya'lls site is that these carbs are fairly generic, and parts jets etc. should also be generic, time to bust em down again ...MeCasa

PS: I had a CL-350 in 69(1st road bike), and a CB-750K1 in 72 with a CB-500(1st year they came out) in between, the 500 was a better ridin' bike than the 750'(top heavy) but I was a kid and I wanted fast, one of my Bud's bought one of those water buffalos, it was big fast an ugly, an he loved it haha

[Anonymous]

Just did about the same thing myself. Bought a GS1100GK in CA and rode it back to NY. I had to change the battery & regulator in a Walmart parking lot in AZ. Changed front tire in NM. Few other smaller things. I was fortunate, with break downs and the wind, I decided to stay in motels. Saw the floods, tornados, and huge storm fronts going on everywhere the last week of May. I altered away from my planned route and ended up not even getting wet once. Had storm fronts clearing out in front of me and closing in behind me. Now I have two 82 GS1100GKs, very nice bikes, sure I will find something to do with them.