Topic: Please help! - can't start it...

[Scout]

I'm the new guy with a 78 750K8... For completness, the bike has set in the garage for a year, but ran like a champ before that.

I changed the oil, changed the gas, got a new battery. It cranks great, but only one of the header pipes gets hot. I cleaned the plugs, still nothing. I then wanted to use the carb cleaner, so I tried draining the carbs, unfortunately, only #2 had gas in it. The rest were empty... So, what's easiest and simplest way to attack this?

Thanks for any help, I took a day off to work on the bike, hopefully I can get it runing today...

Scout

[M3JOC]

OK, Heres an idea for you. With the bike lying idle for so long the float needle valves are stuck in the carbs that are dry. Either take the carbs off and do a proper job, OR with the petrol/gas turned on open the drain screw one carb at a time, when its open if theres no gas coming out of it, hit/tap/rap the float bowl with the blunt end of a large screwdriver, remember the carbs are fragile so only hit it as hard as you need to free up the needle valve, IE not too hard, just a sharp knock to free the valve.
If that dont work its off with the carbs.
I dont think by your description that its a fuel blockage from the tank because you say that gas is coming out of carb No 2.
Just a thought.
Good luck,
Bob

[Scout]

Wow, it almost worked

I tapped on each of the carbs, and one by one, the started working!! I took it for a spin around the block, and I'm almost in heaven..........

Now the problem is that a) the front brake sticks, and b) the big one - I have to run it on partial choke, otherwise the bike dies....

So, what's the best way to run the Yamaha carb cleaner without taking the carbs out? Can I just pur the mixture into the fuel line to the carb and let it sit for the night?

Scout

[TwoTired]

Probably have a some slow jets plugged up.  The carb cleaner is worth a try to avoid taking out the carbs.  Drain the existing fuel out of the carb bowls.  Disconnect the fuel line at the petcock and fill the carbs with the carb cleaner. Let sit over night and if you can figure a way to agitate the cleaner (shake bike?) do so.
Next day, drain out the cleaner, refill with fresh clean fuel and "gee er a trey".  If whatever was clogging the slows was dissolvable, things ought to be better.

If you can catch and observe whatever drains out of the carb bowls, you might get a clue about what is causing the problem.  Any bits larger than about .016 inch will plug the slow jets.

Cheers,

[eldar]

The front brake should be torn apart. Remove the piston by squeezing the lever and the fluid will force it out. Remove the rubber ring inside the caliper. Then use a dremel with a wire brush to clean it out. A white powder builds up on the puck and the sides and causes a lot of drag preventing the piston from retracting. Check your piston also for large pits or spots where plating is missing. If you have these then you should spring for a new piston. Thats about $50-80. but they are usually fairly durable. Drain out all the old brake fluid.
Once the cleaning is done, put the rubber ring back in. There should have also been a plastic ring between the piston and the pad, put that back in too. put in fluid and start the long tedious process of bleeding the brake. This will take about a year of your life or so!

you can put the mix in the fuel lines and into the carbs.

[dusterdude]

if you can some seafoam buy it and put in the tank with good clean gas and run the bike a few miles.hopefully thats all you will need

[eldar]

Seafoam is good stuff. Almost as good as carb cleaner left in overnight.

[Scout]

Thanks for all the suggestions!

I have both Seafoam and Yamaha carb cleaner, so I put about half of the Seafoam into a full tank of fresh gas. So far it hasn't made a difference. I took the bike out a couple of times for about 30 miles total, and still have to run it on choke (about 3/4th, and it's very sensitive). Also, the two outside header pipes continue to be a bit colder than the inside two.

Oh, two more things. The bike seems quite slugish - makes a lot of noise but I have to really punch it to get ahead of cars. Also, when idling, it's rough. The 3/4 choke makes it idle around 1,500 - 2000 rpm...

And finally, the plugs are 7As, I'm not sure if that makes a difference though... I cleaned them well, and they didn't look too bad...

Scout

[Scout]

As far as the front brake, it seems a lot better, just squeaks. Part of my winter work will be cleaning the piston, replacing the pads, cleaning the rotor, and yes, the brake bleeding........ I've done it probably 50 times, and I hate it as much as ever... Hopefully it's easier than the hydraulic clutch on my old 1987 FJ1200, that was THE worst...

Scout

[honbonduc]

My 2 cents on brake bleeding. Actually it's somebody else's 2 cents that I read on a website, but it works. I was having an impossible time bleeding my front brake, tried all morning and gave up. Then I tried zip tieing the front brake lever down tight and left it for a few days. When I cut the zip tie off, the brake was nice and firm, better than it's ever been and has remained that way. You might bleed out all the old fluid first, then top it off and tighten everything up before applying the zip tie.

[TwoTired]

I took the bike out a couple of times for about 30 miles total, and still have to run it on choke (about 3/4th, and it's very sensitive). Also, the two outside header pipes continue to be a bit colder than the inside two.

#1& 4 carbs likely have the slow jets plugged.

Oh, two more things. The bike seems quite slugish - makes a lot of noise but I have to really punch it to get ahead of cars.

Not surprising with 3/4 choke.  The engine isn't getting enough air to make power.  You shouldn't even be riding it until you fix the carbs.  Won't be too long before the plugs on 2&3 soot up and foul (short) out.

Also, when idling, it's rough. The 3/4 choke makes it idle around 1,500 - 2000 rpm...

Jeez man, 2 of 4 carbs carbs are screwed up.  Of course its going to idle rough.  You can either fix them or whine about it. 
The choke knob also raises the idle speed with a mechanical linkage.  THAT's NORMAL.  Say thank you for not having to hold the throttle open manually.   

And finally, the plugs are 7As, I'm not sure if that makes a difference though... I cleaned them well, and they didn't look too bad...

Wrong plugs.  You should have D8EA if they are NGKs, a slightly colder plug.  It will help keep the engine from preignition when you get the carbs sorted.  They will also make the warm up period longer before getting good engine response.

Good Luck!