Exhaust leak below head. loud squeak.

I am having trouble finding information regarding this problem in the forum so I will describe my issue below.

I have made a complete top end rebuild and checked the valve clearances as well.

However.

I have a loud squeaking sound when running the engine and visible exhaust fumes coming from the intake side of around cylinder #3 or thereabout.

From what I understand the new seal isnt sealing properly which might depend on uneven torqueing of the head bults or possibly the face of the top being uneven.

I rebuilt the head this winter just for fun but am now getting a little tired of dissembly/assembly.
My idea is to pull the head again and apply a thin film of high temp gasket sealer to both surfaces mating the head to base gasket.
This way I am hoping to acheive a tight seal.

Thoughts? Ideas?

 

What are your compression numbers - no use doing more work than necessary with another head removal.
How old is your gas - fuels have 30-60 day shelf life, and could cause funky fumes - just a thought.
You mentioned intake side, but did you replace the exhaust head to header pipe gaskets?

Someone more knowledgeable should be along shortly.

 

i am by no means more knowledgeable. just writing to claim there will be help along the way. RickCoMatic & bigfitz52 helped me out tremendously when I did the same thing.

assuming the top end rebuilt included new rings (?) then yeah there will be some smoking during the initial start up. mine was smoking because of all the hand oils and new sealant burning for a good 10 minutes til it was hot. also, you are confident the timing chain is properly aligned with cams (?) Lastly, cam chain tensioner was adjusted during top-end rebuilt (?)

wait til more ideas are thrown at ya from experts, to tear it apart again IMHO

 

Thanks for the replies fellows.
I do believe that my cam chain is correctly aligned and no exhaust seems to have backtracked via the intake valves.
As for the chain tensioner its a "automatic" tensioner set as described in the haynes manual.
If you are talking about piston rings I did not replace them as I had good compression number before the rebuild.
As i said, it ran just fine before. I just did this because I wanted to learn a little more about engines.

 

Hi again!

I am bumping my thread again because I have som more information. My hopes are that someone has a good idea on what to do next. Perhaps one of the gurus!?

I got off work early today and decided to pull the head (for the second time). Everything went a lot smoother this time and I can find some traces of soot where the compression has escaped (see pics)

When I pulled the head last time I did not put new rings in or pull the base since my compression numbers were in order. However, I do have the new gaskets for that (came in the package from chacal) so I guess I could pull it off just for the thrill of it (would need new rings though).

The gasket unfortunently separated a little when I pulled the head (see pic) but i managed to put it back and I figure that I will provide a tight seal once the head is put back on, anyone objects?

---

To sum up I am confused as to why there there seems to be leakage around and between several of the cylinders. I did not use a torque wrench but can that really be the whole reason for it not to seal tight?

Does the gurus recommend me to pull the block (or whatever the part holding the cylinders is called) in order to check ring wear and replace gaskets although compression numbers were in order?

My original idea has been to use a thin film of high temp silicone on both sides of the headgasket in order to make it seal better. What are the pros and cons of this?


Thanks again for taking your time.

 

Was the head checked for level while it was off the first time?

Without using a torque wrench how do you know you got the bolts tight enough? Did you follow the sequence? Those pictures look to me like a head gasket that was installed improperly. Get a new gasket and install with the correct torque and sequence. Any silicone is not going to hold up to the pressure in a running cylinder.

I don't think your problem is in the rings.

 

Anytime. If you're working without a manual, I'd get one. If you have a manual, FOLLOW IT. Which includes properly torquing the head, in stages, and the order the bolts need to be torqued in.

 

Thanks for the replys!

I do have a haynes manual and try to follow it. Got a torque wrench today and put i back together.
Checked the head as well and it seems to be true and level (used a flat metal surface for reference)

I tested the compression before deciding to mount carbs and exhaust but it showed up bad so now im a kind of perplexed.

#1 got around 130psi (used to get around 146 before when warm)
#2 & 3 got really poor compression. Barely 50 psi. Dropping oil into cylider helped only slightly
#4 got good compression

I know the engine is supposed to be warm but i just wanted to know if it was wothwhile to mount carbs and the rest, which it seems not...
It seems to me that it isnt the rings since compression was fine before i started fiddeling with the head.
Can i have the timing wrong?
Or is it just not sealing properly between head and block?

Any ideas on what to do next? I am thinking a) new gasket. B) permatex gasket (the way bigfitz described) or b) pulling block and head to plane them.

 

My suggestion would be to torque the head and let it sit for a day. Maybe mount the carbs, run the engine as best as it will, basically heat it up some and let the head / gasket seat itself a little. The gasket will compress some when torqued properly, it is part of the design. After you do that, double check your torque on all cylinders.

Another thing to keep in mind, once you torque the head (starting on the inside working out), as the outside bolts torque to spec it loosens the strain on the inside bolts, so they will need adjustment. I ran into this exact same issue, and it turned out my problem was just the uneven compression from not going through and double/triple checking the torque of each and every head nut.

Good luck with it, I hope you figure it out!

 

OK here's my 2 cents.
I'm not sure but looking at the picture, it looks as if there is gasket material on the tops of the cylinders...!?
Is that the original gasket from when you pulled the head the 1st time?
It looks used!?
You should use a new gasket before you do anything! And you need to clean off all the old gasket thouroughly.....
while the head is off check the head with a straight edge to be sure it isn't warped. (if you don't have one, then you need to go to a machine shop)

Whatever you do now, DON'T cut corners on this job!

When you get the gasket surfaces clean and you start to go together you REALLY DO need to torque the head to the right value and in the right sequence. (this will need to be done in stages)
Also see what the gasket maker recomends regarding any sealants!!!

Keep us posted..

 

BTW notice the burnt spot on the 3rd pic where the compression is escaping?
You ABSOLUTLY do need a new gasket!!

 

Thanks guys!

I am going away for a week but I will post once I continue to make progress

 

Update:

I have pulled the head and block and am going to have them planed.
Now I just need to order a new head gasket. I can find them here in europe for a bit cheaper than from the states (with the added fees for duty and so on) but I can not seem to find a new cam chain tunnel seal.

Question:
Do you think I can reuse the old (new but installed) tunnel seal together with a new head gasket?

 

Sorry I don't know, not seeing what youre seeing there.
You might look up Chacal here on this site, he has all kinds of stuff like that.

 

Thanks.
Sent an email to chacal. Will order new gasket and possibly new tunnel seal.
Will keep you posted. Maybe throw in some pics as well..

 

Ok.
Here is a quick update before i go away for the weekend.
Got a reply for chacal straight away. I have ordered stuff from him before and he gives no nonsense straight aswers without trying to make you buy things ghat you dont need.
I have therefore decided to try and reassemble with the "old" head gasket and see if it will provide a good tight seal before ordering a new one from all the way across the pond!
Will get the head and block back early next week so fingers crossed! Will post when I get going with it.

 

Update:

Received the head back from the shop and it has been planed. The block was checked for straightness and is good.

So.
Today I put it all back together and just ran a quick (cold) compression test.
Got around 140-145 psi on #1 and #4 but #2 #3 barely got 50 psi.

I have a theory though!
Can it be so that the cam tunnel seal is too thick and thus creating a leakage in between #2 and #3?
When I installed the gaskets I noticed that there was a difference in thickness between the head gasket and the cam tunnel seal.
When I installed the head I torqued it down according to my haynes manual.

What are your thoughts on this?
I can order a new head gasket from the UK but it will still be some 100USD.

 

Compression problem Solved!

Hi everybody!

I finally got my new gasket from the UK and proceeded to install it.

I have neglected to check the length of the protruding "studs" that hold the engine together but decided to be very prudent this time around since it was my forth time taking the top off! =)

I then noticed that one of the "studs" hade become unwound and was "taller" than the rest. It was an easy fix then I torqued the head down according to the manual.

Got everything assembled and did a quick compression test which was allright but in no way super.

Ran the engine. It started with starter gas but did not maintain any idle.
Ran another compression test when the engine was warm. Wasnt overwhelmed which was quite dissapointing. Managed to wreck one of the studs that hold the exhaust as well so had to helicoil that.

Then:
today i retorqued the head again to specs and rode the bike for a couple of miles. Redid compression test: again not too good but even. Checked valve clearances: all in specs!
But:
I had forgotten to open the throttle when I did the tests! stupid me!! well well...
Redid the compression test yet again and this time with flying colours! all around 143-150 psi!


To sum up:
Check that none of the studs holding the engine together has come loose so that the dome shaped nuts cannot be torqued down correctly.
Have the throttle open when doing compression tests.

Thanks to everyone who has taken their time to try and help out!


So now it is a matter of syncing the carbs to get the idle right i believe.