Slight surging after tune up

[2and3cylinders]

I did the 26000 mile maintenance a little early.
 
As I posted in another thread the valves were very tight and they were adjusted to loose side of spec.
 
I installed an ape cam chain tensioner it was a little loose on Startup but I've now got it adjusted so that the significant rattling stopped when I turn the adjuster a hair more. I've checked it three times and it seems okay.
 
I change the air filter and the spark plugs, and at 8,000 miles I had had vcyclenut Flash the ECU.
 
The throttle body synchronization was still pretty much dead nuts on.
 
Prior to the tune up performance and mileage had been down which I put down to the tight valve lash.
 
I also adjusted the accelerator position sensor down to the lower end of spec.
 
When I started it up I noted a surging I have never experienced before and when I give it the gas and let off, when it drops to near idle there's a slight hiccup.
 
I thought since the only thing I really changed from before the tune-up was the aps, I reset it back to where it was. The oem setting in diagnostic 14 at 17 /101, and in diag 15 at 16/100. I had brought it down in diagnostic 14 to 12 / 97 and in 15 down to 12 / 96. It's now back where was before I touched it and it didn't make much of a difference so I'm going back down to where I originally adjusted it to.
 
It's very hot today but I'm in my air condition shop, albeit with the door open and fans going due to the exhaust running the bike. The engine temperature got up to 199 which is where I had David vcyclenut set when the thermostat should go on.
 
I'm going to button it up and and go for a ride and see what happens.
 
Any helpful input would be appreciated.
 
 

[2and3cylinders]

As an added note the surging seems more subdued but when I take it up and revs and let off the gas and it drops down to idle there's a little hitch before it settles into the idle I wouldn't call it a hiccup more of a single stutter

[2and3cylinders]

At 8 thousand miles I connected vacuum lines to the throttle body ports and ran them so I can check synchronization without removing anything and there are fitting with the oem caps on them and I did check them.
 
The surging is actually more pronounced than I thought initially and the stutter or hiccup when it drops down to idle caused it to die a couple of times,
which in traffic not a good thing.

[2and3cylinders]

I can double-check the vacuum lines where they connect to the throttle body ports but I actually double checked the synchronization with everything together, and it was spot-on.
 
 
Now it could be that the one or more of the hoses cracked or came loose during assembly but the synchronization being what it is, it's unlikely. Also, I had everything apart then reassembled and then disassembled and reassembled again when I rechecked the sync.
 
If by the PCV you mean the hose from the Breather, no that's connected for sure along with the side hose to the airbox.
 
I don't know of any other vacuum lines there may be, and the TB bodies were never removed.
 
I just think, as it runs very well, that the problem may be electronic in nature.

[norcal616]

just a thought... maybe its a good idea to reset the ISC after a TB sync? maybe its the ECU trying to correct/compensate your TB sync? just food for thought, not saying you need to do it, but asking what others say...

[skipperT]

Good idea, but no ISC on this bike.
The YCC-T handles the job of an ISC motor, by opening/closing the throttle plates.
 
There is a “learned” value IIRC, but this is accessible only with the Yamaha diagnostic software. That value usually changes due to carbon build up in the throttle plates/body as the ECM compensates for the lower idle speed.
 
-S

[skipperT]

Btw, I think Piotrek meant Power Commander V? As opposed to Crankcase Breather hose.
 
But not entirely sure.
 
-S

[2and3cylinders]

No PCV valve. TB sync checked before and after APS adjustment but its easy to recheck the APS again if that matters.
 
I checked trouble shooting sections in the shop manual and nothing pops out at me, and no trouble code displayed.
 
I'm 99% sure I properly torqued the spark plugs.
 
In reinstalling the cams with the APE CCT, it was wonky to try to line up the punch marks in the cam with the cam bearing caps. the punch marks did not quite line up (cannot remember if the did exactly before either), and with valve stem loading of the follower under spring tension against the cams I couldn't get the punch marks closer at 120 BTDC. Again, I think I have the cams phased correctly and it rotated over by hand with no unfortunate noises, and started right up, ran well and was not overheating or making bad noises...
 
So why the surging and stutter after dropping to idle???
 
 

[2and3cylinders]

Idea: What about loosening the APE CCT a little and let it rattle just a bit to see if the surging and drop to idle hiccup disappears?
 
Too tight cam chain???

[koth442]

Worth a shot.