What should my piston look like?

[HD]

Yesterday I rode about 60 miles and my bike was running like an absolute pig, completely down on power. When I got home, I found that the spark plug cap wasn't securing on the plug properly. So I changed the plug and now it is in there nice and tight so I assume that was what was doing it? Haven't ridden it today as I'm in need of some 2 stroke and the place I normally go wasn't open today so will see tomorrow if that worked.

While I was changing the plug I thought I would have a look at the top of the piston just to see what it was like. I was bored and it was hammering it down so I just fancied a bit of tinkering. Took the tank off and took some pictures of it but what should I be expecting?

It was quite coked up tbh. Very black and maybe a bit sooty? Bit like a too rich spark plug.

TL;DR - What colour should my piston look like when peering through the spark plug hole with a torch/camera?

If it is wrong, should I just whip the head off, clear off the crap, polish it(?) and then just buy a new gasket and put it back on then look at the mixture as it isn't the best runner in the world...

Ta
____________________
Rusty '02 Vito Camper + CBR600F3

[Kickstart]

Hi

Pretty much always black. Only be a bit concerned if there is a thick black layer

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[HD]

Any way to check without taking the head off?

And if it was thick, how thick is thick? And what would that mean?

Sorry
____________________
Rusty '02 Vito Camper + CBR600F3

[Kickstart]

Hi

With a 2 stroke I would expect a noticeable layer, but maybe half a mm or so tops, and easily scraped off. If due rings soon I would leave it until then.

With a 4 stroke I would expect a far thinner layer.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[HD]

Only about 2-3k since last top end rebuild so I may just get a head gasket and sort it. Something to keep me busy haha.

Ta
____________________
Rusty '02 Vito Camper + CBR600F3

[pits]

[Kickstart]

Hi

Very much down to the particular model of engine, and rare (if ever) by using a different head gasket. Different base gaskets are used on some (Aprilia and Cagiva 2 stroke 125s for example), but plenty do not need this care.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[HD]

No pits I didn't mean any old gasket

I would buy another proper one for my model.

Reckon it's worth a shot? And if it is 'thick' what does that mean?


____________________
Rusty '02 Vito Camper + CBR600F3

[Kickstart]

Hi

OK, bit more detail.

Some bike makers use different thicknesses of gasket to tailor the compression ratio for different models and / or to compensate for manufacturing tolerances. Normally by using a different thickness of base gasket.

If you use a gasket that is too thin you will land up with too high compression ratio and possibly hole a piston. Too thick and you will be down on power.

How critical this is varies. Aprilia supply 2 base gaskets in kits for the RS125 I think (0.5mm and 0.3mm from memory, makes about 0.5cc difference, and VERY roughly have a point difference to the compression ratio). Cagiva seem to supply about a dozen with a very small difference between them.

However don't know if the engine used in your bike has this, and I would doubt the head gasket thickness varies.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[HD]

No I meant the thickness of this layer on top of the the piston
____________________
Rusty '02 Vito Camper + CBR600F3

[Kickstart]

Hi

Thick buildup probably means running a bit rich. But that could easily be from using the choke for too long, or just not thrashing it enough.

Fairly thick soft buildup I wouldn't worry about. It will probably disappear when you next thrash it anyway.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[HD]

[Xenocide]

TBH is the plug wasn't firing properly and not burning the fuel properly then you'd expect it to clog up a bit. Give a spanking with the new plug and have another look
____________________
KTM LC4 400 | Honda VTR1000

[HD]

Nah I just think it is too rich. But put some redex in there yesterday and road it with this other plug in today and seems the same.

Had a fuel leak today and presume it was from when I lifted the tank up yesterday and the hoses came lose. So took them off, cleaned it all up and connected it back up. Now it won't idle and seems almost choked. Needs like half throttle to even stay running.

The only thing I can think of is that I connected the hoses up wrong? I ran out of light so will have a crack tomorrow.

Any other ideas just in case it isn't that?

EDIT - NOW ON COMPUTER:

Basically the bike ran how it does now; splutters at lower revs, hits the powerband and revs smooth and in 1st and sometimes second will splutter at the top of the rev range.

So dropped the needle and it ran lovely! Only thing was it idled a bit high. So tryed adjusting the idle screw on the carb and it did nothing. My dad fannied around with both screws (no idea what he did and he couldnt remember) and managed to lower the idle but now it runs the same as it did before, unless it is around 50 degrees (on my eBay temperature gauge )

When I have the BR8 plug in, it shows a perfect colour. However when I run the BR9 plug (as several people have recommended so I dont blow a hole in the piston or anything) it shows a black/rich colour. It runs the same with both plugs in, well no difference that I can tell so I leave the 9 in but surely with the BR8 in it should run lovely? Clearly not.

Now it doesn't bother me so much because when I thrash it, I keep it in the 'normal' rev range because it doesn't move unless I scream it but when someone comes to buy it in the next few months, then they will say its not working right. And I also have to slip the clutch a lot to get it into this rev range when coming out of corners and stuff. So its also knackering my clutch...

So how do I get it back to what it was like when it idled too high? Surely turning screws only alters the low speed side (as I have been told)?

Note, it doesn't take any choke to start and will cut out when ran on the choke, normally. Does this mean it is too rich and I should drop the main jet a bit? But if I have the BR8 in and drop the main, then it will be too lean?

I'm confused
____________________
Rusty '02 Vito Camper + CBR600F3

[satelliteone]

Just curious, what 2T oil are your running?
____________________
Honda XLR125R - Project
TZR125RR Belgarda 4DL - Sold
Chinki Project done n Dusted/sold** DTR125 2003 - Finished/sold

[HD]

[HD]

Any thoughts on this idle business? Should i up/drop the pilot jet or something?
____________________
Rusty '02 Vito Camper + CBR600F3