Gen 3 surging

[Festus]

I have photos from the scope. I’ll have to get them uploaded. Two valves in every cylinder and only 1 of the 2 in that one cylinder was gunked up.

[FJRoss]

I have photos from the scope. I’ll have to get them uploaded. Two valves in every cylinder and only 1 of the 2 in that one cylinder was gunked up.

Odd - probably not caused by fuel injection if only one of two intake valves.
I would still do the compression/leakdown. Might not tell you why there is a problem but will tell you IF there is one related to valves.
I wonder if a valve clearance adjustment error was made somewhere along the line and that intake wasn't closing???

[Festus]

I checked the valve clearance about 20,000 miles ago. It was good then, but I also wonder if 1 is out. It’s at 70,000 miles or so, I think. Probably never adjusted, only checked.

[raYzerman]

Carbon on an intake valve not unusual as they run colder than exhausts. Does piston have carbon on it? Inspection camera may be magnifying an issue that isn't there. A bad clearance wouldn't likely have caused carbon, riding like grandma does, but odd that one has carbon and the other doesn't. If it's the outside one perhaps it runs colder. A leakdown test will confirm if that valve is sealing, note a certain amount of leakage is allowed.

Coils - FSM page 8-169 describes resistance check of primary and secondary... where the red/black wire connects to each, put your positive meter lead on it. Negative lead on the other terminal, primary resistance should be 1.19-1.61 Ohms. To check secondary put negative lead on the sparkplug connector, secondary resistance should be 8.50-11.50 kOhms. If that is wrong on conventional spark plug adapters, it is most likely a corroded/oxidized connection of the spring/resistor/spark plug fitting... do not know of coil on plug has removable parts... if you look up the spark plug end and see a screwdriver slot, remove it, clean it, reassemble, recheck secondary resistance.

[Festus]

I didn't do any leak down test. I don't have the tools to do that, but we can certainly get them.

In my opinion, riding these bikes back to back, is that this bike is running a little rough. It's very small, but it's noticeable when swapping from bike to bike. Accelerating, you can't tell it, it feels the same, but just tooling along at one speed, there's a little vibration in the seat that I don't feel on my bike and at idle, I swear I can tell a difference. Viper Dad says he doesn't notice it, but he hasn't ridden both bikes.

Here's a few random photos. Sorry for the poor quality. I didn't think they would be relevant so I wasn't paying as much attention to them as I should have, I was just snapping photos because I hadn't poked a camera into an engine before.


Piston top - Piston Top - Side view of open valve
intake valve on far left of bike - same - random cylinder wall and bottom of different valve
A little crud - pretty clean - crud

[FJRoss]

I have seen worse but not sure what to expect on an FJR.
Go at it with a few tanks with Yamaha Ring Free. I think it is more effective than Seafoam.
I would still like to know if anything is leaking past...

[1911]

^^^^^what he said^^^^^^

viewtopic.php?t=5178

[raYzerman]

Referencing 1911's post, I mentioned I'm not sure RingFree is the answer, or any fuel additive.... to remove carbon without disassembling the head, either remove airbox and spray atomized water..... or (in former days... and I can't find anything suitable now), one could spray a combustion cleaner directly into a hose attached to the sync port (I wouldn't necessarily recommend that with water). Seems all the good combustion chamber cleaners were discontinued......
Seafoam is mostly naptha, need something stronger with benzine or harsher chemicals in combination......

As for leakdown, I recently bought a compression tester that had various size spark plug hole adapters and a long nipple that would accept an air hose fitting.... this is what you use to do a leakdown test. Piston at TDC and say 90 psi or so of air, if a leaking valve it will come back out the intake port... normally you would warm up the engine and do the compression test first...

[Festus]

We will work towards that as time permits. He's getting the bike back this week some time and is going to ride it for a little bit to see if the problem is still there. I couldn't replicate it, but maybe he can.

Do you think that the the one valve being cruddy could be a result of a miss? That would back up the bad or weak coil theory?

[Powerman]

You must have infinite patience. I would work on it intensely for a week and then set it on fire.