Hello and thank you all for the inputs. I'll answer as much I can best to my knowledge.
My Ninja 650 has seen only touring miles. I never use it in the city start stop traffic.
The distances I do are usually anywhere from 100-800 miles in a single day.
The weather here is mostly very hot 40*C+ (100*F+) and in summers the air is dry. Also my radiator fan comes on at any speed below 30 kmph.
Also I've done a lot of distances in the Himalayas at high altitude roads (10000-18000 ft) where the Ninja seems to be running ultra lean due to the adjustment it makes for low oxygen levels at those altitudes. Due to running lean the radiator fan comes on quite often.
However one area of concern that the airbox has oily dirt in it which seems to have come from the PCV. Can there be more oil vapour generated due to running hot or have a made a mistake and overfilled a bit ? Should I install an oil catch can in between the pcv and airbox ?
Lastly I've never used any injector or fuel additive to clean the engine as I didn't think they would work. Are there any non snake oil products that actually work ?
This is what I would do;
I would replace all vacuum lines
Do a valve shim check.
What is my take on the condition of the valves, to me it looks like possibly tight valves and combustion gases are coming back into the intake, possibly burn valve seat on the left cylinder. As to cleaning or anyone else opinion, the person I would put 99% faith in is Invader or Fasteddie or a number of other members including our other mod Gigitt .
The valve clearances were all in spec but on the tighter side. Two valves which were out of spec where just 0.1 mm to 0.2mm out on the tighter side.
If a valve seat is burned what's the remedy to that ?
Originally Posted by fasteddiecopeman
W/out anything to compare it to - to me it appears that it's been either 'backfiring', or the intake valves are so tight that they aren't fully closing (BUT I'm only guessing...) thus letting the 'burn' ALSO occur in the intake.
I recently checked the valve clearances and it seems the valves are in spec and just two of them where out of range on the tighter side of clearance. I reshimmed all the clearances to the looser end of the clearance specified since all valves were running near the tighter side of clearance.
To me it looks normal for a bike with that mileage and run on low detergent gas-needs a fuel cleaner run through it a few times to clean up the exhaust valves and a little contact cleaner on a rag will clean the intake throttle plates also due to the gas-if the valves (exhaust) were tight the exhaust valves would be almost white due to hot gases escaping
The fuel here unfortunately is RON 91 or 87 Octane. Premium gasoline is hard to come by unless in a tier 1 city. However I don't think the Ninja needs a higher octane fuel due to its relatively low compression ratio.
My question would be how does the bike run? If it runs fine with no misfiring then I would perform normal maintenance and not worry. You will always get carbon on the back of the throttle plates and on the back sides of the valves. depending on the fuel used can make it more or less. There will always be some flow reversion in the intake due to cam timing. At the end of the exhaust stroke the intake stroke is starting so the intake valve and exhaust valve are both open and due to the residual pressure in the cylinder it will cause a small amount of reversion at the start at low rpm. At higher rpm the flow velocity is higher and the inertia of the intake flow will overcome the reversion and actually improves cylinder scavenging and filling. Depending on the amount of valve overlap and the rpm operated at can affect carbon build-up.
Yes the bike runs absolutely fine. It's just that this is the first teardown I've performed on the bike and since no one else in India has done this there is no cross reference data at all.
Hence the hesitation to dismantle the engine for inspection. However I wanted to be sure if the intake valves, seals, seats are fine as I don't have an idea how they're supposed to look.