81 GS550T Engine Ticking Noise

[sosedoff]

Hi all,
I've got 81 GS550T, all stock with 8k miles on it.

Before i cleaned the carbs (stock jetting, adjusted float heights) it was running pretty rough, with all 4 cyls getting
too much fuel, now its much better, spark plugs look good, but im still having issue with cyl #2. The header does not
get hot as on other cyls, suspecting its not firing under some conditions: it def gets fuel, and coil works (did a test swap).

After carb rebuild i ran the bike for ~30 miles and friend riding behind told me its smoking from the left pipe under hard
accel and constantly on the highway. White smoke, not thick. Not sure if it was smoking when i got the bike, but i never noticed it.

Yesterday, started the bike and checked #2 header it was much hotter this time but i noticed a new noise coming from top end.
It was easy to hear by leaning on the tank, def not the regular engine noise.

Here's a quick youtube video:
https://www.youtube.com/watch?v=PeuwcrqBLLU - You can hear the ticking noise at the beginning.
https://www.youtube.com/watch?v=r87niZ7o9jQ - Smoke

I just ordered a few tools and a new valve cover gasket (its leaking) so while i'm waiting i thought maybe someone could
help me troubleshoot this. I have not checked the valves yet, that would be my next step.

Any thoughts on this noise?

 

[Nessism]

Bike is not running on all 4 cylinders in first video. Hard to say about the second video.

You may want to check the Newbie Mistakes thread linked in my signature. You need to do more maintenance before you can start to figure out what's wrong.

 

[sosedoff]

@Nessism, just curious, how do you know its not running on all 4?

After a minute after start the #2 header was pretty hot, although cooler than others, other times it was just warm.
Btw, i don't think the bike was running right on all 4 in the second video either, the header was not as hot. But judging the spark
plug it was def firing at some point, it looked pretty rich and had bunch of unburnt fuel all over it.

Thanks for the link, i'll check it out. I've only worked on a smaller kz400 engine, so inline-four dohc is above of my knowledge right now.
I don't know the exact background of the bike, aside from it being running when i got it. I did a cold compression test last month and
3 cyls were ~130psi with an exception of one being ~145psi.

 

[tom203]

#2 header not hot, suspect the vacuum line to petcock leaking gas into #2's throat due to failed petcock.
Spend lots of time carefully cleaning old gasket residue off camcover surfaces or new gasket will likely leak too!

 

[sosedoff]

I took the vacuum line off the tank/carbs a few times now and i don't think i've ever seen any fuel on it.
Will check the petcock this weekend.

Anything to add about the noise?

 

[tom203]

Pulling off vacuum line is not conclusive.

Try this... remove both lines from petcock: get some clear vinyl tubing that fits snugly on petcock vacuum fitting. In "on" and "res" fuel,show flow when you suck on this tubing- otherwise it should not. Any signs of fuel in the tubing means the petcock diaphragm is likely leaking.maybe just when bike is running but maybe at alltimes.​

As to the noise...since this is a new to you bike, lots of things need checking/adjusting.

 

[Brendan W]

Something else you could try is swap the HT leads on 2 & 3.
If the cool header moves to 3 you might be looking at a corroded connection at the cap end of the #2 lead.

 

[sosedoff]

I did swap the 2 & 3 leads, no difference. I checked the spark as well - strong and blue.

Today, however, i went to the garage to start the bike again and listen for noise - it wont start, usually it starts right up.
Switched to reserve, with choke - same deal. Thought i was out of gas or something. Spent like 10 mins, then gave up.
Then i realized some time ago i had the same issue, gas/battery/spark was all in good shape but no start.

As soon as i opened up the gas tank cap - it started right up. Is that just an issue with the cap or a symptom of a bigger
problem?

 

[Brendan W]

On the face of it the tank vent is blocked.
You may have more than one issue.
With the tank cap loose is #2 header still cooler?
A blocked vent would lead to fuel starvation across all carbs.
Maybe one is more sensitive bit I can't see it making a plug sooty.

 

[sosedoff]

Ok got some clear gas/vacuum lines.
The petcock gas flow works like it should, no gas when ON/RES, flows freely when on PRI. No fuel comes out of vacuum line.

When i set it on RES/ON and suck on vacuum line i get a bit of fuel. Should there be absolutely no fuel under any conditions?
Also, i don't know how much vacuum does the engine produce, maybe the leak gets worse with RPM's.

Did confirm that gas gets into the engine too, i checked the oil level and its way over full.
Last time i changed oil/filter it was slightly under full.

As for the noise, i filled the tank just to check if i was hearing the noise before - looks like its less noticeable with full tank, so
most likely i had this problem for a while.

 

[fbody_mike]

No fuel should make it to the vacuum line. The petcock diaphragm is probably ripped.

 

[Tom R]

Did confirm that gas gets into the engine too, i checked the oil level and its way over full.
Last time i changed oil/filter it was slightly under full.

Sounds like your problem is the petcock diaphragm.

 

[sosedoff]

Update: installed and tested new petcock - the issue with #2 not running hot is fixed, all four are about the same
temp right after start. The spark plug is no longer wet after riding. Changed oil as well.

However, after a few mins of test running in the garage i noticed some faint smoke (appeared to be white-ish) coming out of left muffler.
I went for a very short ride around a block to get the engine hot - now getting good amount of white smoke on anything >3k rpm from both
sides. Stopped by and revved up to ~7k and was seeing more blue-ish smoke color.

Going to test compression tomorrow again.

Not sure what the problem is, i haven't seen smoking on the right side since i bought the bike.

 

[sosedoff]

Looks like im going to need piston rings replacement.
Cold compression test: 120, 130, 130, 130, with a bit of oil: 140, 160, 160, 170.

 

[Big T]

Adjusted your valves yet?
Your compression numbers look pretty good

 

[sosedoff]

Adjusted your valves yet?
Your compression numbers look pretty good

No i haven't yet. I was reading through manual and learned that i need a special tool
to get the valve shims off, so had to order it as well.

On the other note, how would valve adjustment help with poor compression and leaking piston rings?

 

[Guest]

only 8 k miles, if it were me, I would adjust the valves then ride the snot out of it for a while before tearing into anything, a little time at temperature and redline might just do wonders...also, no desperate need for a special tool, you might search "zip tie method"...