Bike Help !
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Post Fiend
Joined: Oct 2003
Posts: 6,214
Likes: 13
From: New Jersey
Bike Help !
I often take on "side jobs" trying to keep food on the table and I think I'm going to bite the farm on this one. It's a loss already and that's fine, I just need to get it the heck off my driveway.
It's a 1979 Yamaha "Special Seven" bike - a very nice bike actually, and when it arrived almost a year ago I was told it was "missing". I figured how hard could this be, air, fuel, spark, vroom.
I got air and spark working good
I can't seem to figure out the fuel part.
I'm not looking for anyone to spend hours fixing the bike, but instead maybe just listen to it (I'll jump it) and point me in the right direction, shoot the breeze a bit and enjoy a few grilled burgers and beer as a thank you.
My problem, I think, is I have no idea how carbs work. Everything I've ever owned was fuel injected, or immediately converted to EFI upon my taking it home.
Anyone?
It's a 1979 Yamaha "Special Seven" bike - a very nice bike actually, and when it arrived almost a year ago I was told it was "missing". I figured how hard could this be, air, fuel, spark, vroom.
I got air and spark working good
I can't seem to figure out the fuel part.I'm not looking for anyone to spend hours fixing the bike, but instead maybe just listen to it (I'll jump it) and point me in the right direction, shoot the breeze a bit and enjoy a few grilled burgers and beer as a thank you.
My problem, I think, is I have no idea how carbs work. Everything I've ever owned was fuel injected, or immediately converted to EFI upon my taking it home.
Anyone?
Freshman User
Joined: Apr 2010
Posts: 33
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From: McGuire AFB
Carbs are pretty simple some wikepedia style searching should get you the basic assembly info. Or you could just take it apart and remember what goes where. I would take it apart. Clean all of the pieces out really good after soaking it in turpentine overnight and replace any bad seals(you can also buy a rebuild kit if you can find one).
Adjusting it is another issue. One screw on the side is for the mixture and the other is for the idle you want to start out lean and turn up the idle until it will run by itself (without you holding the throttle open) then give it about a quarter turn to make it a little richer (it will increase rpms) then lower the idle back down. Repeat the last two steps until the rpms do not increase when you adjust the mixture. That is when it will be properly adjusted.
And of course check all of the fuel lines and tank and pump!
I hope this helps!
Let us know how it goes!
Adjusting it is another issue. One screw on the side is for the mixture and the other is for the idle you want to start out lean and turn up the idle until it will run by itself (without you holding the throttle open) then give it about a quarter turn to make it a little richer (it will increase rpms) then lower the idle back down. Repeat the last two steps until the rpms do not increase when you adjust the mixture. That is when it will be properly adjusted.
And of course check all of the fuel lines and tank and pump!
I hope this helps!
Let us know how it goes!
Thread Starter
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Post Fiend
Joined: Oct 2003
Posts: 6,214
Likes: 13
From: New Jersey
Some progress was made today.
After idling it in it's current state, removing the seat and various other things that were in the way, I was able to spray carb cleaner into the inlet while it was running, which would cause a really smooth jump to about 2000 RPM momentarily, sounding as a bike should sound.
After doing this on and off throughout the day, I went through all of one can and just started the second can, all four exhaust pipes now get hot, whereas originally only two did. So now I know *something* is getting through all four carbs. That's a good sign I think.
I guess I shall figure out how to take the tank off, then the intake manifold, then all the "I'm sure they're dryrotted and frozen" 2" (or so) rubber tubings between the intake and the four carbs, and the four carbs and the cylinder heads.
Thanks for the advice and such. I'll take it apart and soak it like you suggested.
Part of the "scary" factor is I have little to no carb experience, and this thing has four of 'em. A holley 4bbl I can get right, sometimes, something this complicated seems to worry me. It's also not my bike lol.
After idling it in it's current state, removing the seat and various other things that were in the way, I was able to spray carb cleaner into the inlet while it was running, which would cause a really smooth jump to about 2000 RPM momentarily, sounding as a bike should sound.
After doing this on and off throughout the day, I went through all of one can and just started the second can, all four exhaust pipes now get hot, whereas originally only two did. So now I know *something* is getting through all four carbs. That's a good sign I think.
I guess I shall figure out how to take the tank off, then the intake manifold, then all the "I'm sure they're dryrotted and frozen" 2" (or so) rubber tubings between the intake and the four carbs, and the four carbs and the cylinder heads.
Thanks for the advice and such. I'll take it apart and soak it like you suggested.
Part of the "scary" factor is I have little to no carb experience, and this thing has four of 'em. A holley 4bbl I can get right, sometimes, something this complicated seems to worry me. It's also not my bike lol.
Freshman User
Joined: Apr 2010
Posts: 33
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From: McGuire AFB
Oh it has 4 carbs? I have never adjusted more than two carbs at a time but what I did was turn the adjustment screws to the same position on both.
Sometimes the jets and stuff get clogged when they sit for a while or just from use.
Sometimes the jets and stuff get clogged when they sit for a while or just from use.
Thread Starter
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Post Fiend
Joined: Oct 2003
Posts: 6,214
Likes: 13
From: New Jersey
I found the air inlet, been feeding the bike carb cleaner 
Took me a while to get at it since unlocking the seat with the key didn't result in it flipping up - the lock is not connected to the seat so that makes sense.
It runs pretty good with carb cleaner sprayed in, nice and smooth and as soon as the carb cleaner is burnt off it goes back to a lumpy, horrible idle. It's definitely a fuel problem.
I'm in the north end of Woodbridge Louis, about 2 minutes from exit 131 on the Pkwy, if that's remotely convenient
Took me a while to get at it since unlocking the seat with the key didn't result in it flipping up - the lock is not connected to the seat so that makes sense.
It runs pretty good with carb cleaner sprayed in, nice and smooth and as soon as the carb cleaner is burnt off it goes back to a lumpy, horrible idle. It's definitely a fuel problem.
I'm in the north end of Woodbridge Louis, about 2 minutes from exit 131 on the Pkwy, if that's remotely convenient
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Thread Starter
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Post Fiend
Joined: Oct 2003
Posts: 6,214
Likes: 13
From: New Jersey
Very nice toy indeed.
It runs much better than it did before, but still not running well enough. I'm going to take off the gas tank so I can get at the carb and rip it out and soak it and pray I can take it apart and get it back together.
Gallon of carb cleaner helped a lot....
It runs much better than it did before, but still not running well enough. I'm going to take off the gas tank so I can get at the carb and rip it out and soak it and pray I can take it apart and get it back together.
Gallon of carb cleaner helped a lot....
