Is this normal?

[Rusty Bolts]

Just painted the front timing cover and noticed this. The upper exhaust tract has a nice brown colour whereas the lower is more black. Neither are sooty though. It's the same on both sides. The lambda sensors are both a nice light brown/white so I'm sure all is well but just wanted to make sure.

(Note the rather stylish angle of the photo to add a bit of interest)

 

[Bendy toy]

The valve with closest clearance will always open first. Ideally, both exhausts should be the same clearance. Its worth getting them checked.

Hilltop (are reported to) say that some bikes run as low as 20:1 at low throttle settings.

 

[tanneman]

Just to make it clear for any newbies Bendy toy is referring to the air fuel ratio or AFR.

 

[(RIP) Miff]

Hilltop (are reported to) say that some bikes run as low as 20:1 at low throttle settings.

That's what the dyno sheets show..

 

[Rusty Bolts]

It's been sorted by Geoff so AFR is right. Good point re valve clearances, I'll check them. I thought that it could be something as simple the upper tract is hotter than the one below as heat rises.

 

[bone48]

I think its fine, my 2011 twin cam was the same, first spark plug always looked nice with good colour, secondary plug was always black and a little sooty.
I think the fuel must slightly pool in the bottom of the combustion chamber prior to ignition, and maybe more fuel is put in at some point to help cool the engine, maybe when the bike is stationary with high oil temp.

 

[Bendy toy]

We should be told.

Please can you could set the top valve to a wider clearance (opens later) than the bottom valve and have another look after a few miles.

Thanks

Heat rise is unlikely unless the engine is getting very hot in traffic. Fuel pooling is also unlikely as its all moving too fast for gravity to have much effect.

 

[bone48]

Unlikely, but not impossible, gravity will play a small part, and obviously the fuel is being injected at high pressure which may contribute to pooling.
It was the only explanation I could think of for one plug appearing to run a rich mixture and the other appearing fine, although thinking about it more, a lean mixture has a slower burn than a rich mixture, hence the second plug to assist with the slow burn, maybe thats how more fuel makes its way to the bottom of the cylinder due to the slower burn?

 

[andy79]

unless its running poor just put it back together and forget about it. Put up a picture of your newly painted bits instead.

 

[Bendy toy]

PS that was meant to be tongue in cheek.

Slow burn usually means hotter exhaust valves as the energy has not been extracted by the piston. Full on "afterburn" can quickly burn out the exhaust valves.

 

[bone48]

Of course, as a slow burn is a leaner mixture the temp is hotter and can lead to burnt valves.
Just trying to think of reasons as to why the lower port seems to expel a richer mixture, but have now decided to go to the pub instead


Sent from my iPhone using Tapatalk

 

[Rusty Bolts]

Just checked the valve clearances and they are identical so that kind of rules that out. I'm inclined to view it as a 'distinctive feature' and not loose any sleep.
Regarding the gratuitous picture request here you go.

 

[andy79]

top job !

 

[Rusty Bolts]

Cheers, hammerite smooth silver. Takes ages to dry but it does seem to stick well. After two days drying I helped along with a blast to Lynmouth for Fish and Chips. You could definitely smell the paint 'curing'.

The bus isn't doing too bad considering it's done just short of 90k miles.

 

[Bendy toy]

I had my front cover powder coated. Yeah yeah blah blah.
Noticed today there is oil staining below the black belt cover. So much for careful fitting and pvc tape to protect the oil seal :-(

 

[Rusty Bolts]

I had my front cover powder coated. Yeah yeah blah blah.
Noticed today there is oil staining below the black belt cover. So much for careful fitting and pvc tape to protect the oil seal :-(

I left mine on the bike and masked it up as I couldn't undo the pulley nut.

 

[Bendy toy]

I left mine on the bike and masked it up as I couldn't undo the pulley nut.

It probably did you a favour.
Mine is certainly looking good and I'm sure the finish will be very durable but its going to be a pain to have to replace that seal and probably the alternator belt as well.

**I got mine off with a 600mm breaker bar and the 'box in 1st gear.