Running on one cyl when cold and higher fuel consumption

[Kox]

Merry X-mas y'all ;-)

My bike, a 2010 with about 50000km is acting strange.
I used to get low tank level at about 275-300km now it is down to about 200km. It has gotten gradually worse over the last 10000km or so.
I got the valves done about 3000km ago. New plugs as well. Done by a very good mech that I trust (and i watched ;-)). No moist in the cylinder wells. The bodies were synchronised as well. Didn't replace the air filter since it was not in stock.

Since the service I have been using a fuel injection cleaner in every other tank. On recommendation of the mech.

Is is quite cold in Denmark at this time of year. The bike has been running fine until now. Still has high consumption though. I am doing a lot of driving in the city at this time of year, just regular transport, no joy-rides. I have about 20km each way to job.


This morning the temp was about 2 deg C, and the bike was idling very "unsmooth" around 1000rpm (whereas 1200rpm is normal) and struggling not to stall completely. When I took off it felt like it was running on one cylinder only. Giving more throttle the bike would accelerate very slowly and stuttering until what ever is wrong cut out and the front wheel got air side. Not very comfy in the heavy morning traffic ...
When the bike is warm it is running just fine. I assume the consumption is still high though.
When I took off for home, it was exactly the same. I did a stop on the way - about 45min - bike was running fine after that. Guess is was not completely cold.


I know the air filter is (very much) past due - I am going to replace it with a new one tomorrow. Is there anything else I could check while I'm in there? Any input is highly appreciated!

 

[WJBertrand]

Were the throttle bodies re-synched after the valve adjustment and reassembly? Sounds like the symptoms one would have if one of the cylinders was "leading" the other doing most of the work.

 

[Kox]

Were the throttle bodies re-synched after the valve adjustment and reassembly? Sounds like the symptoms one would have if one of the cylinders was "leading" the other doing most of the work.

Hi Jeff

Yes, the sync was done after the valve check and reassembly.

 

[Squibb]

Quite a puzzle for us, without seeing/hearing the bike.

However, assuming she was running OK previously, it seems it has got to be something that has been touched/adjusted/removed when the valves were checked. It could be a sensor wire somehwere not reconnected, a failing coil stick maybe - the list could be almost endless, but I will try you with a few possibilities. However, it has to be worth asking your guy to check for any fault codes on the ECU before trying to second guess the issue.

When the throttle bodies were re-synced, did they need much adjustment? I only ask as this sometimes gives us a clue. The small caps on the sync ports can crack up with age & admit air. There could be an air leak between the TBs & the inlet ports, that closes up once the engine temperature rises.

A laser thermometer will soon tell you which cylinder is doing the work & which has the problem. We have seen errors made with valve clearances before now, so it could be a tight valve - did you/your tech keep a list of what shims changes were required? You could double check the maths.

Personally, I would get the bike back to the guy that you used for the service work & get him to check it over thoroughly, as soon as possible. It's seems unlikely to be the air filter, but this can be changed at the same time.

You say 3000 Km since service - rough running like this can do a power of no good to the engine/drive train, & could even lead to you having a silly accident in traffic or when taking a bend. So I suggest you park the bike up until it can be fixed.

Keep us posted........ KEN

 

[scott123007]

I would be focusing on a fuel system/injector problem, an air leak as Squibb mentioned, or possibly a faulty spark plug.

Although they are great suggestions, all of the problems mentioned, become a problem as the engine warms up, not the other way around. A dirty air filter may contribute to reduced fuel consumption, but not poor running when cold and ok when warm. It's just the opposite. Regardless, there is so much surface area with an OEM filter, you could probably never clog it unless you spent most of your miles off road while following someone.
And just like the air filter, the valves should also not be the problem. A valve's greatest clearance is when it is cold. A tight valve affects engine performance more as the engine warms up, not visa versa. For a cold engine to be compromised by a tight valve it would have to be at zero clearance when cold, and as the engine warmed up, it would run worse, not better.
A bad coil stick or coil, "usually" get worse as they get hot.
Lastly throttle body sync may contribute to a rough running engine, but that would not change, hot or cold, but as Squibb said, check those caps!

Since you are going to replace the air filter any way, I would, just to be on the safe side, replace the spark plugs again too. If there is no improvement, I would focus on the fuel system.

Good Luck!

 

[WJBertrand]

I think valve clearance may actually increase as the engine temperature rises. The cams, are held in aluminum which has more than twice the thermal expansion coefficient than steel, stainless steel or titanium* (I don't think we have Ti valves though do we?). This means the cylinder head material which is holding the cams, valves, shims and buckets will grow/expand faster than the valve train parts themselves and tend to separate the parts from one another, increasing clearance.

I recall a story on one of the ST1300 forums where an owner was having a hard time starting his bike and once started it ran poorly until warmed up where it then ran acceptably (according to the owner). He'd gone something like 50,000+ miles never checking his valve clearances. Upon being urged to do so by responses to his forum post, he found multiple valves at less than zero clearance (based on the shim sizes needed to bring them into spec) when cold. The cylinder head designs are similar between the two bikes. Once corrected, the bike started and ran normally. He was lucky not to burn an exhaust valve.

Such a loss in clearance at that mileage is highly unusual for a Honda ST, but the lack of maintenance, implies general neglect which probably include oil changes, explaining the wear rate.

Is it possible your mechanic made an error on the valve adjustments?

*http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

 

[scott123007]

I think valve clearance may actually increase as the engine temperature rises. The cams, are held in aluminum which has more than twice the thermal expansion coefficient than steel, stainless steel or titanium* (I don't think we have Ti valves though do we?). This means the cylinder head material which is holding the cams, valves, shims and buckets will grow/expand faster than the valve train parts themselves and tend to separate the parts from one another, increasing clearance.

I recall a story on one of the ST1300 forums where an owner was having a hard time starting his bike and once started it ran poorly until warmed up where it then ran acceptably (according to the owner). He'd gone something like 50,000+ miles never checking his valve clearances. Upon being urged to do so by responses to his forum post, he found multiple valves at less than zero clearance (based on the shim sizes needed to bring them into spec) when cold. The cylinder head designs are similar between the two bikes. Once corrected, the bike started and ran normally. He was lucky not to burn an exhaust valve.

Such a loss in clearance at that mileage is highly unusual for a Honda ST, but the lack of maintenance, implies general neglect which probably include oil changes, explaining the wear rate.

Is it possible your mechanic made an error on the valve adjustments?

*http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

Some engines may be exceptions, but generally, if the speced exhaust valve clearance is greater than the intake valve clearance, it is compensating for a greater reduction in clearance when hot.

 

[Kox]

Thank you all for your input!

The valves were checked 3000km ago. The consumption was already higher before that.

The "one cylinder" issue began yesterday morning without any warning. I trust the mech beyond reasonable doubt. I am going to pull the plugs and replace them and visually check the fuel injector and check all connectors. And all vacuum hoses. Diesel start, right?
I think I can read the fault codes from the display if there are any, right?

 

[Checkswrecks]

Especially with an older bike in the environment you have, I'd start by swapping the ignition coils between the left and right cylinders. My guess is that your problem will move from one cylinder to the other with the swap. Even though the things are expensive, with 6 years in Northern European cold and wet, replacing all four would be a good idea because if one has gone bad the others will follow.


Yours is not the first:


http://www.yamahasupertenere.com/index.php?topic=14736.0

 

[Kox]

The coils on cyl 2 and 3 sure don't look pretty. And the plugs neither.
Oh, of course the plugs are on backorder ...

 

[Kox]

BTW the one on the left in the first pic is from the right cylinder.


I hope that is enough to cause my problems - its the only thing I foundation

 

[WJBertrand]

Some engines may be exceptions, but generally, if the speced exhaust valve clearance is greater than the intake valve clearance, it is compensating for a greater reduction in clearance when hot.

I'm sure there are exceptions considering all the different engine and valve train designs out there. I always thought the larger clearance on the exhaust valves was to allow them more "seat time" between openings in order to transfer heat away to the cylinder head?

 

[Checkswrecks]

I'm sure there are exceptions considering all the different engine and valve train designs out there. I always thought the larger clearance on the exhaust valves was to allow them more "seat time" between openings in order to transfer heat away to the cylinder head?

No, it's because with the hot exhaust gas they get longer in operation. The bigger gap will close up quickly when they get hot, so they have the proper operating clearance that the engineers wanted them to have.

 

[Checkswrecks]

The coils on cyl 2 and 3 sure don't look pretty. And the plugs neither.
Oh, of course the plugs are on backorder ...

Try swapping them yet?
The coils are common to a number of other Yamaha products, so if you do buy just one you could figure out which is the bad one.

 

[Kox]

Especially with an older bike in the environment you have, I'd start by swapping the ignition coils between the left and right cylinders. My guess is that your problem will move from one cylinder to the other with the swap. Even though the things are expensive, with 6 years in Northern European cold and wet, replacing all four would be a good idea because if one has gone bad the others will follow.


Yours is not the first:


http://www.yamahasupertenere.com/index.php?topic=14736.0

Actually it was a leftover - so it has only been running from 13-14 where it got about 10000km on the clock. Then the PO got a back injury and it sat for about a year until I bought it last year.

I am not going to replace the coils just now. I am waiting for new plugs to arrive. And will swap the coils when i put it all back together. Unfortunately, when I fired her up today she was running on both cylinders - I had the camera ready ... Then after about 200m it was down to only one cylinder for a couple of km. Didn't have the chance to stop and check which cylinder is bad. But if it is still bad, I will check for next time.


Reg. the possibly faulty coil - if only one coil is bad, will it leave the cylinder totally out?

 

[Checkswrecks]

It could if the other coil is also weak, but not necessarily.


And new plugs with nice sharp electrodes may make up for a weak coil for a short time.

 

[scott123007]

Kox, those plugs do not look like they were changed out 3000km ago unless it has been at least 6 months of really shitty weather you've been riding in. Also, that engine is only 2 cylinders with 2 plugs per cyl. It appears by your picture that you have a crappy plug in each cylinder.

Try Ebay for your plugs. Here's a link...http://www.ebay.com/itm/4x-NGK-Spark-Plugs-for-YAMAHA-1200cc-XT1200Z-Super-Tenere-TS-10-No-6607-/322162629053?hash=item4b026399bd:g:hq0AAOSw-4BXaVHm&vxp=mtr

 

[Kox]

It could if the other coil is also weak, but not necessarily.


And new plugs with nice sharp electrodes may make up for a weak coil for a short time.

But if the cylinder cuts out totally - then there is more wrong, than just one coil, or? I mean, if one plug/coil performs well, the cylinder should be running to some degree?

I am just reluctant in buying new electrodes - "just because", and not knowing if they are really bad. I have just read, that I can test the coils by means of a multi-meter, which of course i will first thing when I'm back in my work shop. Is there a better way to test them - with professional equipment I mean. Or can you assume that they are good if they ohm'well?

 

[Kox]

Kox, those plugs do not look like they were changed out 3000km ago unless it has been at least 6 months of really shitty weather you've been riding in. Also, that engine is only 2 cylinders with 2 plugs per cyl. It appears by your picture that you have a crappy plug in each cylinder.

Try Ebay for your plugs. Here's a link...http://www.ebay.com/itm/4x-NGK-Spark-Plugs-for-YAMAHA-1200cc-XT1200Z-Super-Tenere-TS-10-No-6607-/322162629053?hash=item4b026399bd:g:hq0AAOSw-4BXaVHm&vxp=mtr

No it sure don't look like they got in November 4th (this year!) They did! I saw it with my own eyes - both of them ;-)

The left most coil had a lot of moist on/in it too. But the plug is not corroded to the degree the others have. But yes, the 2 middle plugs look really bad, i.e. one in each cylinder.

Oh, and the weather - you wouldn't believe the kind of shitty we have to put up with ;-) and we think salt on the roads is the solution to everything in our country.


Edit: I bought from that exact seller yesterday - 2 set ...

 

[OldRider]

Or can you assume that they are good if they ohm'well?

No. My experience is that if something ohm's bad, it almost always bad, but if it ohm's good it can still be bad under a load.