Gasket disintegrated?

[Borracho]

I'm in the process of cleaning/rebuilding the carbs on my 82 Heritage Special. Considering that it only has around 9K original miles I'm pretty sure this is the first rebuild this bike has seen. While removing the carbs I noticed there was no sign of a gasket between the manifold and cylinder head. Common sense tells me that there should be one but I am a noob and not sure. Could it have disintegrated over time? If so, I should have had a serious gas leak! Thanks in advance.

 

[xjwmx]

Between the head and the intake boot. The parts diagram shows one there. Maybe it's stuck to the intake and disguised as part of it? Not gas leak; you meant air leak. What has lead to the rebuild and what are you rebuilding? Former Austinite here. Good place.

 

[gggGary]

Yes there should be gaskets, unless the manifolds are JBM replacements they don't use gaskets. They also don't have the metal "cage" around them like the stock manifolds do. Manifold cracking is common even with low miles especially in hot dry climates

 

[Borracho]

Ha! Yup, air leak. Hello from Austin. Well, what got me to tearing into the carbs was a loss of power issue. Bike would idle fine but when I got on the throttle she would hesitate like crazy. It got to the point where I had to push it home one day because as soon as I would put in gear and try to go the bike would die on me. After some research I figured it may be a dirty carb issue. Any other ideas? I'll take all the advice I can get.

 

[Borracho]

Thanks for the input gggGary! Nope, all stock on this bike.

 

[gggGary]

Read the carb guide in the tech section "til your eyes bleed" then do the overhaul. It might save you having to do it twice. Throttle shaft seals, new float valves or float valve o-rings at the very least. Check diaphragms for holes or tears. confirm strong spark at the right times. Realize you will need to remove / drill out the idle screw blocking plugs.
R&R the petcock also, watch for a bad vacuum diaphragm in the petcock.
Before you do the rest check and confirm no vacuum leaks on the barbed fitting RH cap and LH vacuum line to petcock

 

[Borracho]

Good to know! Thanks again.

 

[xjwmx]

Don't take the boots off to get the carbs off. Getting the carbs off is a new experience in three dimensions, but it can be done. The second time is easier.

If everything is original, the single most likely problem is a bad o-ring around the needle seat, which lets gas leak past the valve and will have you running really rich or not at all. An original needle and seat itself is probably good, probably better than anything you could easily buy new. Are your plugs light or dark?

 

[Borracho]

Thanks xj. I replaced both o-rings and the needle. All I have to do now is adjust the floats to 27 mm if I remember correcly. Will have to order some gaskets now too. More $$$ to MikesXS!

 

[XSLeo]

On the gaskets the stock Yamaha used a thick material. Most after market use a thin material. The thin won't seal as well as the thicker. Getting them from Yamaha may cost a bit more but worth the extra to get a good seal.
Leo

 

[Borracho]

The rubber tip on the needles was pretty hard so I decided to replace them just in case. Will check the plugs when I get back to the house.

 

[xjwmx]

^Like I said the original needles are probably better than anything you can easily buy new. I did say it. 22 mm for your year on the floats.

 

[650Skull]

Makes it easier to understand if the correct terminology is used for the parts that are being talked about.

I assume your needles and needle seat is referring to the Needle Valve assembly.

The only needle in the carbs are attached to the Diaphragm assembly. If you ask for needles when buying parts you will get the wrong one

 

[xjwmx]

He is talking about the rubber tip on the needle. Do you think maybe he has it confused with the jet needle?

 

[650Skull]

^Like I said the original needles are probably better than anything you can easily buy new. I did say it. 22 mm for your year on the floats.

Makes it easier to understand if the correct terminology is used for the parts that are being talked about.

I assume your needles and needle seat is referring to the Needle Valve assembly.

The only needle in the carbs are attached to the Diaphragm assembly. If you ask for needles when buying parts you will get the wrong one

He is talking about the rubber tip on the needle. Do you think maybe he has it confused with the jet needle?

Needle Jet, Needle. No rubber on them. Are you really going to carry this on????

 

[Borracho]

Sorry about the confusion y'all. I was referring to the float needle.

The rubber tip felt pretty hard and not at all "rubbery". Figured it was bad so I replaced it. Chunked the old one so I'm SOL if I should have held on to it.

 

[650Skull]

No confusion. It is actually the needle valve from the needle valve assembly.

It was XJ that gave you the wrong terminology from the start.

 

[xjwmx]

I'm sorry you are confused, 650Skull.

 

[Borracho]

Going back to my initial question, upon closer inspection I did manage to find some remnants of a gasket. It was coated in white silicone which is what I spotted initially since the gasket was completely flattened.

XJ, the plugs were fouled up with black soot. Running rich I assume and the floats were off by a couple mm's which may turn out to be the culprit. Thanks again everyone! Ride safe...

 

[xjwmx]

You ride safe too bud, and save some brisket for me. I'll be back down there someday.