Poor fuel mileage since valve adjustment

Ohendo

Site Supporter
I adjusted the exhaust valves a couple of weeks ago, 5 of 8 were OOS tight, others were close. After adjustment, lash was middle of the spec. link to forum post (#87) --> Valve adjustment
Rode through a tank of fuel, calculated thirty something MPG's. Couldn't be right, I thought. Performed a throttle body sync, was way off, link to forum post (#183)---> Throttle Body Sync Pics.
Filled up the tank again. Just finished that tank, low MPG again. Exact calculations were 37.5 MPG (I used to get 47.5 consistently).

Bike is running rich, can smell it in exhaust at idle. No other symptoms that I know of. No misses, back fires, sooty exhaust, loss of power, etc. I pulled the spark plugs last night to take a look, pic below. Seem to confirm rich condition.
Also have a link to 30 seconds of idling if that's worth anything. Almost seems like the cam chain is noisy but not sure if it's always been this way.

- checked TPS, steady values throughout throttle range (17-102).
- tire pressure is 36psi cold front and back.
- no brake drag, can spin front tire 3-4 revolutions, rear spins freely as well (as much as it can with chain on sprocket)
- lifted tank, all seems right with the airbox; all hoses connected, clean filter.
- I have an S1, so no O2 sensor


Could improperly adjusted exhaust valves cause a rich condition and poor mileage? Any other ideas on the cause? I may crack it open again and double check the clearances, even though I triple checked after adjusting. Argh.

Idling video: --------> https://photos.app.goo.gl/Bm3jWGpexTZswy479

 

TownsendsFJR1300

2007 FZ6
Site Supporter
Plugs don't look bad...

If you can smell un-burned fuel at idle, I believe you and points towards your issue.

Is the bike staring normally, cold-with a slightly higher idle, then dropping down as it warms?
(I can smell mine cold but goes away in a minute or so).

Any aftermarket fuel systems/gizmos?

You did confirm before buttoning up after the valve adjustment, all was within spec, correct?

In the "sync post", you mentioned not being able to adjust the idle like before. Looking at your procedure/ manometer, all looks good... Did you double check TB plastic plugs (blocking the sync hoses) and other lines all in place?

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Motogiro

Vrrroooooom!
Super Moderator
Moderator
Elite Member
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Some times after performance changes in engines you have to dump the volatile memory the ECU learns over a period of start and warmups etc. If you haven't, disconnect the battery for 30 mins -1 hr and see if the mileage gets better.
One of the things Two Brothers racing recommends is disconnecting the battery when installing the new exhaust. I don't think it because they're worried about a short.
 

Ohendo

Site Supporter
Thanks for the replies, sorry for the delay. Was spreading mulch all day!

To answer some questions:
-Bike starts normally... RPM’s at 1100. After a slight delay RPM’s jump higher, return to 1100 after a couple of minutes. (Not sure if it’s just me... but the delay before going to higher RPM’s seems longer than normal. If I remember it used to be right away, now it idles for about a minute before increasing
-No aftermarket gizmos or controllers
-everything was in spec valve-wise before buttoning up
-TB sync hose plugs were installed, I’ll go double check that.

Cliff- the battery was disconnected for valve adjustment. You’re saying I should reset ECU for the TB sync also? Easy enough, will give that a shot.

Performance-wise, if I skipped a tooth on the timing chain, wouldn’t it be more evident? Engine seems to run the same as it always has, if not smoother than before.

I’ll report back with any findings- thanks for your input!
 

TownsendsFJR1300

2007 FZ6
Site Supporter
You are correct, on cold start up, the rev's SHOULD be higher right at start up.

That NEW delay isn't normal, but I have no idea what's going on there (never heard of that behavior before)

I believe coolant(via hose/line), at the TB's, when cold, activates the high idle initially. As the coolant warms quickly(especially during summer), the idle drops..

That may be something you want to check, that coolant is flowing thru there easily. Yamaha doesn't show the unit broke down at all. Probably not the issue, just throwing that out there, dunno...

If you removed the TB's for the valve adjustment, they are fully seated, all 4 hose clamps tightened?

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bigborer

Site Supporter
Many engines have 1-2 teeth offset allowance before the valves and piston touch. Some even install it offset on purpose for "poor man's race cams". If it's offset I can't tell you how it would feel or to what extent the ECU might compensate
 

Ohendo

Site Supporter
-Verified plugs are in the TB sync hoses.
-disconnected battery
- verified TB’s fully seated, clamps are tight.

I’ll reattach the battery later tonight, ride the heck out of her tomorrow and see if rich condition/ MPG’s are better.

If no change, I’ll verify timing is correct.

Will report back once I have some info, thanks again guys.
 

Ohendo

Site Supporter
Ran through 3 gallons today. 39 MPG, slight increase due to highway miles. Apparently resetting ECU had no effect (thanks anyway Cliff!).

Next I’ll verify timing... and clearances while the valve cover is off. Anyone ever try to get the valve cover off by just removing radiator? Only need access to exhaust valve train. Seems tight, but I’ll try it out.
 

bigborer

Site Supporter
The coils can stay on the tray, and if you don't pull the leads out of the mat the mat will be much easier to put back.

Just remove the air box and battery, push the mat and battery tray a bit, remove the leads and then push a bit more. This should give you enough room to remove the battery cover. Just for checking the timing it won't be necessary to take it out entirely, just lift it a bit. Taking it out entirely will require a bit of patience- it will seem like there is not enough space but if you find the proper angle it will come out with the radiator and fan installed. Still quicker and less messy than removing the radiator.
 

Ben sIII

Junior Member
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assuming I can do maths that's a little over 6L/100km that you are getting which on low octane fuel doesn't seem bad at all depending on the riding you are doing, around town on 91 octane i am getting around 6-6.5 L/100km, granted hwy is closer to 5 but it depends how spiritied you're riding and stop start etc
 

Ohendo

Site Supporter
assuming I can do maths that's a little over 6L/100km that you are getting which on low octane fuel doesn't seem bad at all depending on the riding you are doing, around town on 91 octane i am getting around 6-6.5 L/100km, granted hwy is closer to 5 but it depends how spiritied you're riding and stop start etc
I’ve always averaged close to 5L/100km. Dropped to 6-6.5 immediately following the valve adjustment. It’s not a huge deal really, bike runs fine; would just like to find out how I screwed up!
 

TownsendsFJR1300

2007 FZ6
Site Supporter
I'd be REAL careful when pulling the valve cover up.

It's real easy to have that large, odd rubber seal move out of place on ya...

Then you get a "do over" for newly made oil leak from the valve cover... :(

I dunno how your going to re-check valve clearances (if doing so), W/O pulling the valve cover
completely off.

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