Need help diagnosing a problem

If you have fuel leaking out the left air filter your float is sticking open or is adjusted wrong or fuel soaked.
The only way gas leak out of a carb is through the float valve. Pull your carbs, clean them check the floats for fuel soaked and ajustments.
Leo

It's too bad you didn't test the coils before getting new ones.
At first I thought your problem was the filter inside the tank. I would definitely remove that and clean that anyway. Especially chrome spray paint? :doh:
The float needle valve - not closing - is allowing it to flood over. Take carbs apart and from square one make sure floats are adjusted to proper height. Also (like a problem I had) after adjusting float heights hold carbs upright then turn upside down making sure the floats move smoothly to close the needle without catching or sticking before moving against the needle. That would cause flooding.
The spark plug on the flooding side is just fouling up maybe and overrevving it might get it to spark, like you were doing.
 
I guess I should rephrase. Would it be worth it to replace the floats themselves? I bought a rebuilt kit for everything else.

Shouldn't have to replace, just require careful bending for adjustment and look for both sides to be even. Only replace if you break them or if they have fuel inside any of them.
 
It's too bad you didn't test the coils before getting new ones.
At first I thought your problem was the filter inside the tank. I would definitely remove that and clean that anyway. Especially chrome spray paint? :doh:
The float needle valve - not closing - is allowing it to flood over. Take carbs apart and from square one make sure floats are adjusted to proper height. Also (like a problem I had) after adjusting float heights hold carbs upright then turn upside down making sure the floats move smoothly to close the needle without catching or sticking before moving against the needle. That would cause flooding.
The spark plug on the flooding side is just fouling up maybe and overrevving it might get it to spark, like you were doing.

I ended up buying a new gas cap altogether, should be in this week.

I also bought a carb rebuild kit, will do this right.
 
You would gain nothing by replacing the floats,unless they're leaking.Make sure the tab doesn't allow the float to go down too far as to bind on the way up to shut off the gas.I have a Dt400,'75 model,and I cleaned,adjusted,and tried everything I knew of,and it would run well a while,I'd smell gas,look down and see gas coming out of the overflow hoses.I cleaned the float needle set to no avail.Finally,I bought a new needle set,and no further problems. Maybe you should consider getting a couple of sets. lha
 
You would gain nothing by replacing the floats,unless they're leaking.Make sure the tab doesn't allow the float to go down too far as to bind on the way up to shut off the gas.I have a Dt400,'75 model,and I cleaned,adjusted,and tried everything I knew of,and it would run well a while,I'd smell gas,look down and see gas coming out of the overflow hoses.I cleaned the float needle set to no avail.Finally,I bought a new needle set,and no further problems. Maybe you should consider getting a couple of sets. lha

The kit I bought has the following:
2 float bowl gaskets
2 float needles (VITON tipped to survive modern fuel)
2 #135 main jets
2 #42.5 pilot jets
2 pilot jet rubber plugs (VITON to survive in modern fuel).
2 mixture screw o-rings
 
Where are the overflow hoses? I know it smelled like gas when I brought it back to the garage last time.

Is that a trick question :laugh:
Iha was referring to his Dt400,'75 model
If float needles don't close you will see gas flowing out of the airbox. Although you won't see all the gas getting into the cylinder.
 
Is that a trick question :laugh:
Iha was referring to his Dt400,'75 model
If float needles don't close you will see gas flowing out of the airbox. Although you won't see all the gas getting into the cylinder.

Cut me some slack, only my second year :)

Do I need to worry about fuel flowing down from the carb into here, since it's hooked up to the filter boots?
 

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If it overflows / floods enough, sure, the fuel would probably make its way into the connecting air ass'y joint piece and down the crankcase breather tube. By that point you would already have fuel flowing into the cylinders making its way into the crankcase anyway. Then time for an oil change :wink2:
 
I took my carbs out and cleaned them 4 times finely HoughMade suggested to pull them completely apart and boil them in 25% vinegar 75% water solution turning the carbs every 20 min or so. Then blow compressed air through every hole and then hit with a bit of carb cleaner in every hole until it flows out nice. Worked awesome for me.

There is also a brass emulsion tube that the main jet screws into that has very small holes that need to be cleaned be sure to tap them out.

Other things you might check is make sure the diaphragms don't have holes in it. Hold it up to the light.
 
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So if I am to put everything into perspective.

(Root cause) The carb floats have an issue, left side staying open, which is causing fuel overflow.
(Primary issue) Air and fuel flow issue on the left side is preventing cylinder firing , killing the left side of the engine, explaining why it works fine when the carb is drained.
(Secondary issue) Fuel is leaking from the carb through the boot to the air filter
(Tertiary issue) Fuel is leaking from the carb through the boot into the crankcase, contaminating oil, causing more issues in the engine.

I'm not a greasemonkey at all, with limited knowledge, but could that sum up the issues here, or am I looking at this completely wrong?
 
Did you get the carb rebuild kit, ST?
Do you see fuel dripping or flowing out when petcock is on prime? With the airboxes both off and with a flashlight, put it to prime and look (left, then right, etc.) to see if fuel flowing into intake. Maybe, maybe not.
When you have the carbs apart get them good and clean and make sure floats are at the correct height for your bike.
Fuel contaminating oil shouldn't cause real issues if oil is changed. I would even say as long as there is more oil than gas and it wasn't running for long, just an oil change.
Not much of help, but take your time with getting the carbs right and all passages clean.
 
Did you get the carb rebuild kit, ST?
Do you see fuel dripping or flowing out when petcock is on prime? With the airboxes both off and with a flashlight, put it to prime and look (left, then right, etc.) to see if fuel flowing into intake. Maybe, maybe not.
When you have the carbs apart get them good and clean and make sure floats are at the correct height for your bike.
Fuel contaminating oil shouldn't cause real issues if oil is changed. I would even say as long as there is more oil than gas and it wasn't running for long, just an oil change.
Not much of help, but take your time with getting the carbs right and all passages clean.

I did get the kit, still waiting for it to come in. The bike is apart right now. I will definitly hook it up and test the prime without air filters once I put everything back together.


In theory could I do this with distilled water while its out of the bike?
 
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IF you are having trouble removing the pin that holds the float on use a good quality penetrating oil like PB Blaster or Kroil. WD40 is a great water displacement spray but has limited value as a penetrating lubricant.
 
The pin come out fine, but I believe it is partially responsible for the flat not closing, or not opening.

Could just be the needle though.
 
Finally got some time to work on this.

Now the bolt holding the oil in under then engine seems to be stripped somewhat (can't get it with a ratchet). Until i can do that, how bad will it be if I hook the carbs up to test (but not ride anywhere)

*EDIT* So I did the above procedure. Set the fuel to gravity, carbs fueled up, and didn't overflow. Engine turned on pretty fast, I let it run for a minute, did not see fuel going into the boots.

I turned it off, did see the smoke from the gas in the crankcase. Now I just need to get the oil plug off and I can change that and really test.
 
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Well gents, I got the bolt off today, did the oil change (which the old oil smelled like gas, not oil) and we seem to be off and running!

Went for a few miles today to give it a quick test, no issues so far. Idle was a little high, but I lowered it at home, and now have a steadt 1.5k idle.

This was the old filter. Completely drained all the oil.

Now back to the first world problems, like why the speedometer is having issues. :)
 

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