Top end noise that won't go away

[Meista007]

Correct, the original pipes end about 4 inches behind the front foot pegs.

[BA80]

That's where the internal breaks occur, in the downpipes.

It'd be nice if that's all it is.

[Meista007]

Well the exhaust is going to come off as soon as the new gaskets arrive..so by this weekend I'll have them off and will inspect everything.

I have softball tonight and a concert tomorrow so unless we get some rain tonight I won't have a ton of time till Saturday but I will fit in anything I can.

[MPittma100]

Noise

If you haven't already done so, make sure that you do not have a damaged (wiped) cam lobe on either of the cams.

Mike

[Meista007]

If you haven't already done so, make sure that you do not have a damaged (wiped) cam lobe on either of the cams.

Mike

Is there any way to tell without a micrometer and measuring all the lobes?

I inspected them visually and they all appear fine but I haven't measured them.

[TopCatGr58]

Hey there,

Checking for an exhaust leak around the HOT headers can be a problem. I've heard of using a long stem match and holding it lighted around the exhaust junction and look for it to get blown/wiggled.

The cam lobes on the same cam should have the same amount of lift, so if you don't have a caliper, you could take a piece of plastic or something, and measure the total height from the cam shaft base to the height of the cam lobe, and then just compare it to the others, they should be the same size/height. However, a flattened/worn cam shouldn't make as much noise, because it won't lift/push the bucket down as far???

You're not describing the sound as a KNOCK, but a tick! Sounds like Greg is onto the right idea, a broken off piece of the dual layered header pipe sounds like the right type of problem. And matches the symptoms....happening while riding but otherwise no performance hit! Good Luck.

T.C.

[BA80]

Hey there,

Checking for an exhaust leak around the HOT headers can be a problem. I've heard of using a long stem match and holding it lighted around the exhaust junction and look for it to get blown/wiggled.

The cam lobes on the same cam should have the same amount of lift, so if you don't have a caliper, you could take a piece of plastic or something, and measure the total height from the cam shaft base to the height of the cam lobe, and then just compare it to the others, they should be the same size/height. However, a flattened/worn cam shouldn't make as much noise, because it won't lift/push the bucket down as far???

You're not describing the sound as a KNOCK, but a tick! Sounds like Greg is onto the right idea, a broken off piece of the dual layered header pipe sounds like the right type of problem. And matches the symptoms....happening while riding but otherwise no performance hit! Good Luck.

T.C.

The easiest way I've found to check for exhaust leaks around the gaskets is just a simple piece of 3/16 - 1/4" vacuum hose about 18 or 24" long. Put one end in an ear so it seals up and run the other open end around the gasket area. Trust me, you'll KNOW when you find a leak.

Works for pinpointing other noises too.

If you've got a cam lobe going flat it's pretty easy to see the rough wear especially on the tip of the lobe. Once it wears past the hardened surface of the face it will start to kinda flake off and have a pitted look. I don't think that's what it is though. The engine would start running rough and doing weird stuff.

[Slimbob]

Hello,
Just jumping in here. I just got my 81 XS11 SH and have not had it running and have not worked on it yet. I do have a 77 XS650 and have adjusted the valves many times over the years. You say you let the engine cool down, but it should really sit over night or so before setting the valves.

1. You said you read the clearance on #3 exhaust at .08.
BA80 said the spec is .008. That is a big difference. What is the actual spec?

2. You also said and showed in the picture that one of the cams is off to the right a bit. Not knowing this particular engine, but I would think that that alignment mark is there for a reason. Maybe try to readjust that cam to line up correctly.

Maybe someone with this engine experience can chime in on that alignment.



Slimbob
Don't get blinded to the possibilities. The trees are not in front of the forest.

[BA80]

That was an intake and .008" ( eight thousands of an inch) is the wide end of the clearance spec for the 78 - 79 engines.

.006 - .008

[Slimbob]

BA80,
My bad, Intake it was. Still .08 and .008 are worlds apart for valve clearance.

Do you have any ideas about the cam alignment? Could Meista007 be off a tooth on that cam?

Meista007,
Did you have a typo when you said the clearance on #3 intake was .08?

Just my 2c.
Slimbob

[Meista007]

Yeah, just a typo...it's 0.008

I picked up a mechanics stethoscope and will try to pinpoint the noise this weekend. I have plans to do a few things that should help me isolate the location of the noise.

If the timing was off I would expect to have the noise the same on both sides but it sounds louder on the right side of the engine. I'll update when I've had time to work on it tomorrow.

[Meista007]

After spending the weekend working locating the issue I can say with confidence that it is valve noise and it is coming mostly from #3. So I will be swapping the shim on #3 out for one size larger as soon as it arrives in the mail. The mechanics stethoscope was a huge help.

I would love to be able to get out on the road to ruin her around but I'm waiting on foot peg adapters to arrive. ScootWorks has had a run on them lately and won't be making more till the middle of this week. So if you're waiting on them you'll need to keep waiting a little longer.

[Slimbob]

Please excuse my ignorance. Foot Peg Adapter?

Slimbob

[Meista007]

There is company that produces an adapter that allows you to use any pin type foot peg. This is great for anyone looking to get away form the stock pegs but would rather not have round pegs.

http://www.shopscootworks.com/ScootW...catalogId=-799

[Slimbob]

Ahhh, OK!

Thanks,
Slimbob