Author Topic: Exhaust smoking at head (Read 6091 times)

AgentX · **on:** August 18, 2018, 08:35:28 pm

Hi, all--been a while since I've posted...hope everyone's well.

Finally had a nice exhaust made up for my bike, replacing one I welded up with some guys in a shipping container in West Africa.

But with the change has come white smoke coming from the junction of the head and pipe, and oil spray on the front fender, downtube, and header. Smells like burning oil, too. I think, frankly, this may have always been the case to some extent, but the pipe wrap I had on the old exhaust (to hide its ugliness) mostly absorbed it. Took the pipe off and there was oil all over the shim encircling the pipe and the port itself.

This could only be coming from the rocker box, via

1) a crack
2) a bad valve guide

yeah?

Bike runs fine otherwise.

High On Octane · **Reply #1 on:** August 19, 2018, 03:03:19 am

A. Is the old pipe all coked up, particularly near the inlet of the exhaust?

B. Do you physically see oil running down the motor? Or just a must as you mentioned?

Misting out of the exhaust, yes likely a bad valve seal/guide. Running down the motor, you'll have to wash the motor clean and run it to pinpoint the leak.

AgentX · **Reply #2 on:** August 19, 2018, 03:26:06 am

It's a mist, but I can see a few beads have run down the pipe at some point. Bad guide is my thought, and actually my hope vs. a crack in the head itself.

Don't have the old pipe. I don't think it was particularly coked up. Every time I've been in the exhaust port previously, it's been dry and sooty.

AgentX · **Reply #3 on:** August 19, 2018, 03:42:51 am

https://youtu.be/KHQSsqd8nAI

ace.cafe · **Reply #4 on:** August 19, 2018, 02:35:28 pm

Check the rockerbox gasket and the oil line above the exhaust. Oil will run down.

It is very unlikely that much oil would be coming from a valve guide and then escaping from the exhaust joint.

AgentX · **Reply #5 on:** August 19, 2018, 03:56:38 pm

Hi, Ace-

It's not running on the outside of the head as far as I have observed while it's idling (and smoking), nor have I seen evidence of it after riding. Only the spray from the exhaust/header junction and the oozing along the underside of pipe.

Hopefully the video helps illustrate this.

Chumma may be down here in a week or two, so maybe he can take a look.

AgentX · **Reply #6 on:** August 19, 2018, 04:36:27 pm

If I can manage, today I'll get the tank off, take off the rocker box, and pour some oil in to see if/where it drains.

ace.cafe · **Reply #7 on:** August 19, 2018, 05:16:53 pm

Pull your spark plug and look at it.
If it is a valve guide, the piston and chamber and spark plug will all be oily, and there will be tons of smoke coming out the tailpipe when it is running.

AgentX · **Reply #8 on:** August 19, 2018, 06:56:59 pm

Will do.

There's a huge plume of white smoke at start, which I used to attribute solely to wet-sumping, but it abates after idling a bit and all I get is the smoke out of the header junction.

Arizoni · **Reply #9 on:** August 19, 2018, 07:11:30 pm

Quote from: ace.cafe on August 19, 2018, 05:16:53 pm

Pull your spark plug and look at it.
If it is a valve guide, the piston and chamber and spark plug will all be oily, and there will be tons of smoke coming out the tailpipe when it is running.

Will this be true if the intake valve guide seal is OK and it's only the exhaust valve guide that's leaking?

I've been wrong before but I'm betting the oil is coming from the rocker arm cover. Especially if it is getting blown onto the front fender (mudguard).

AgentX · **Reply #10 on:** August 19, 2018, 11:46:15 pm

I ended up opting to take my daughter for a 45-min ride on the bike. Had to put the pipe back on...wiped out all the oil that was inside the port and on the header. Had a little smoke during the ride but not a lot, also not a lot of white smoke out of the muffler on starting.

Did pull the plug and it looked dark but dry, to be expected as I know it still has richer winter jetting in it.

Still no sign of external weeping at the rocker box, feed banjo, or anywhere else.

Hrm. Still interested to take a look inside the rocker box.

Stanley · **Reply #11 on:** August 20, 2018, 11:27:30 pm

I just had a similar experience with my 2000 Bullet. White smoke, spray from headpipe joint with smoke.

My first wet sump.

AgentX · **Reply #12 on:** August 25, 2018, 05:03:14 pm

Well, I took the pipe off, wiped out the pools of oil in the exhaust port, and reinstalled pipe. Seems to be running fine, smoke-free.

Can't understand how all that oil got there, unless the world's worst wet sump forced that much oil up past the rings and out the valve?!

I guess I should stop worrying about it and ride, keeping an eye out for reoccurrence.

AgentX · **Reply #13 on:** August 25, 2018, 05:23:12 pm

Nope, wishful thinking.

After letting it idle for 3-4 min I shut it down. Came back and fired it up 20 min later. Already had oil seeping out of the pipe/head junction. Huge plume of white burned smelling smoke on startup. Wisps of smoke starting to come from the head again.

AgentX · **Reply #14 on:** August 25, 2018, 05:25:17 pm

And no, there is zero oil weeping out of the rocker box or the oil feed banjo. Totally dry and the oil is coming from the side/underside of the pipe.

AgentX · **Reply #15 on:** August 25, 2018, 08:14:27 pm

Loose valve guide. Through the exhaust port, I can see it moving along with the valve.

AgentX · **Reply #16 on:** August 25, 2018, 09:27:57 pm

That may explain why the oil was only in the port and not in the chamber too.

Adrian II · **Reply #17 on:** August 25, 2018, 10:18:20 pm

Oh well. Oversize guide time, could be worse!

A.

ace.cafe · **Reply #18 on:** August 28, 2018, 05:41:49 am

Those are custom made guides. You will need to copy the shape on new guide stock on a lathe. Just add the extra needed thickness to the shank O.D. to fit the head. Remember to make a few thou interference fit into the head because of alloy expansion of the hole when hot.
Ream the guide to 1.5 thou clearance for valve to guide.

I can't make any right now because the shop had a fire, and I have no access to any machines.

Arizoni · **Reply #19 on:** August 28, 2018, 10:44:40 pm

Rather than making a new guide from scratch, assuming the valve stem to guide clearance is about .0015-.0020, it might be a good idea to look into the idea of plating up the outside of the guide to increase its size.

Ideally a nickle or chrome plate would be used but if the guide is only a couple thousandths smaller than what it needs to be, a simple copper plating would work.

Copper plating is relatively low cost and it shouldn't require machining the outside of the guide undersize prior to plating. Just a thin coating of a couple of thousandths (.002-.003?) thickness of copper per surface is all that is required.
(Nickle or chrome plating needs a copper undercoat and the combined thickness of the undercoat plus the top coat can amount to several thousandths per surface. For that reason, often the basic part needs to be machined further undersize before the plating can be done.)

Getting the guide copper plated isn't a job for the shadetree mechanic but almost anyplace that does plating will have the ability to do copper plating.

The only thing to remember about using copper plating is, it is a soft material so it won't like being pressed into the cylinder head if the head is at room temperature.
Heating the cylinder head to 300-350 degrees F (149-177 degrees C) in an oven and chilling the guild in a refrigerator ice box will greatly reduce the interference so just a light tapping with a mallet should seat the guide fairly easily while leaving enough copper plating to maintain the press fit.

AgentX · **Reply #20 on:** August 29, 2018, 01:18:38 am

Quote from: ace.cafe on August 28, 2018, 05:41:49 am

Those are custom made guides. You will need to copy the shape on new guide stock on a lathe. Just add the extra needed thickness to the shank O.D. to fit the head. Remember to make a few thou interference fit into the head because of alloy expansion of the hole when hot.
Ream the guide to 1.5 thou clearance for valve to guide.

I can't make any right now because the shop had a fire, and I have no access to any machines.

Chumma's got the head now...

AgentX · **Reply #21 on:** September 22, 2018, 04:06:33 am

Apparently, the guide was in pretty bad shape. Chumma's working with a machinist to fab up a new one.

ace.cafe · **Reply #22 on:** September 22, 2018, 04:17:33 pm

I spoke with him about it.
It will be no problem taking care of it.