Overfloating carb and smoke from intake manifold

[jyrki]

Hi, I checked valve clearances: in cylinder no 2 one intake valve was too tight and both exhaust valves were also too tight > causing high temperature > melting? some of vapor/gases escaped also to carburetor causing overfloating? Is this a school example what happens when there is not enough clearance for valves? I afraid that also mixture has been probably too lean, only 2 rounds open for mixture screw. Do I need to do something for cylinder head? See picture no 1. Also some markings in piston, picture no 2. Valves and valve seats looks like to be ok..

[great white]

it's always hard to tell from pictures on the internet, but the valves pictured don't appear to have any damage.

The cylinder head and piston crown look as if they've had previous damage. Looks like something came apart at one time and was bounced around, marking the head and piston crown.

Not ideal, but should be usable in a street driven bike.

If you're getting fuel overflow from the carbs, you need to get back into the float bowls and clean the needle shut off areas. depending on how neglected or molested the bike is, you may want to confirm the float levels are correct.

Get your valves set correctly, then get you carbs cleaned, then get the carbs properly set up and sync'd. this shoudl have the bike running at least acceptably.

Unless your compression is bad that is. But if you have the head off now, there's no way to check compression without putting it back together. If compression is low, you're looking at a rebuild. With that piston damage, if I was doing a rebuild I'd be going up an overbore to get fresh pistons in there along with a fresh bore and rings. It's a "if you're in that far, you might as well go all the way" thing...

[balky1]

Maybe polish the seats a bit with the paste? This is more of a question than a suggestion.

[ribbert]

..... Something for us to remember when I get to visit the land down under. Its been too long since my wife has seen family.

Mark, have you been to Australia and from which part is your wife's family?  If you feel like sharing, I'm curious as to how a yank got lucky enough to snag an Aussie Sheila for a wife?

Air fares have never been cheaper and the exchange rate heavily favours US visitors. It's also the off season for many of the things that will bite you, eat you or kill you.

Noel

[FJmonkey]

Noel, I will send a PM.

[FJmonkey]

I sent a PM...

[jyrki]

 Hi! I think I found reason for overfloating of carbs: I bypassed gasoline pump and cables from reserve switch I took off.... bike is 1988 model. No overloating any more. This hint I found from some UK site ( somebody had changed needles etc) Does anybody knows the reason for excess fuel pumping or function principle for fuel pumping?

[PaulG]

Check out this video. FJ1200 Faulty Fuel Pump.

Simple test - plug in fuel pump without fuel lines attached - put your finger over the outlet and turn the key on - a good pump will shut off immediately to within a few seconds - a faulty pump will run for much longer or not stop at all.  If this happens then the fuel pump will overflow the carbs.

If the pump shuts off then you can attach the inlet line & attach an outlet line and drain it to a container (e.g. water bottle) - turn the pump on and let it cycle - when it shuts off confirm if the gas flow also stops.  If the pump still gravity drains - and depending on your float heights - this may cause it to overflow also.

You can also check the contact points for the pump, but I think it just wouldn't work at all if they were faulty. (I'm guessing)

If it is doesn't shut off then you can only replace it with OEM ($$$$$), used, or aftermarket like RPM sells Electric Fuel Pump.

Good Luck

[jyrki]

Thanks! I will check tomorrow! Is there difference between inlet and outlet of fuelpump hoses? I wonder if I have mixed them causing this problem...

[Pat Conlon]

If you have the oem pump, both inlet/output ports face forward. The inlet (from tank) is the upper port, the outlet (to carbs) is the lower port.

[Firehawk068]

If you have the oem pump, both inlet/output ports face forward. The inlet (from tank) is the upper port, the outlet (to carbs) is the lower port.

On mine, both ports are at the same level to each other.

The one closest to the outside of the frame is the inlet from the tank.

The one closest to the engine is the outlet to the carbs.

[Pat Conlon]

Yep, Alan you are correct

http://www.partzilla.com/parts/search/Yamaha/Motorcycle/1989/FJ1200W/FUEL+TANK+NON+CALIFORNIA+MODEL/parts.html

[balky1]

Hi! I think I found reason for overfloating of carbs: I bypassed gasoline pump and cables from reserve switch I took off.... bike is 1988 model. No overloating any more. This hint I found from some UK site ( somebody had changed needles etc) Does anybody knows the reason for excess fuel pumping or function principle for fuel pumping?

But did you find a reason for the smoke from intake manifolds?

[jyrki]

Hi, I suppose it was fule fumes, not smoke... as there has been excess fuel. Damages in cylinder head and piston: I found some rests of sandblasting sand in valve stems (there is a minor slot around stems, there there was stucked some sand corns, bloody machinery company...). Next steps: checking function fuel pump, checking wiring, checking float bowl hight, adjusting carb balances, adjusting idle mixture, bypassing fuel pump, etc... Hopefully I get to ride this weekend.... Looks like that I have to really earn my riding, but anyways, this is interesting hobby! To get to know my bike...

[jyrki]

Hi again!
I noticed that there is big underpressure difference in second cylinder, when I tried to balance carbs. Underpressure was like 0,5, and other had around 0,1 bar. What is reasonable underpressure? I didn't suceed to balance that second cylinder carb... Air leakage somewhere? attached picture from cover of carb: it has given some back pressure hits also, as slide has hitten on top of cover... Mayby I should check all seals in carb number two...