Spark Plug Colour

[southwester]

It's a pisser about the scratches on the brand new cyl but what's done is done filter, air box and carbs clean all joints in the intake train are tight I will have a blast around with the WD40 and see if there are any air leaks anywhere that could be letting some crap in.

[dadof2]

Lineaway & axulsuv = I cleary implied against re jetting at this stage. The engine is definitely rich and I suggested checks to do. The gasket misalignment would restrict coolant flow causing overheating. This engine is clearly rich / cold.

Those bore scratches should not be there - I have seen 15 year old well used bores with less.

Thouroughly rinse the barrel, piston and crank cases with petroil mix and pour into a clean bowl, allow to settle, pour off the clean liquid and examine the sediment under a strong magnifying glass or microscope.

Check the piston ring end gaps are within specification. There seems to be a bore sealing problem

Re assemble engine and check it turns over easily and smoothly. Run in for 10 hours using mineral oil at 25:1.

Grey plug can be due to lead in petrol but you should not be using leaded petrol in a 2t, nor do I know where you would now get leaded. and you state you use shell advance unleaded so I can't see that being the cause.

Edited January 2, 2014 by dadof2

[southwester]

Lineaway & axulsuv = I cleary implied against re jetting at this stage. The engine is definitely rich and I suggested checks to do. The gasket misalignment would restrict coolant flow causing overheating. This engine is clearly rich / cold.

Those bore scratches should not be there - I have seen 15 year old well used bores with less.

Thouroughly rinse the barrel, piston and crank cases with petroil mix and pour into a clean bowl, allow to settle, pour off the clean liquid and examine the sediment under a strong magnifying glass or microscope.

Check the piston ring end gaps are within specification. There seems to be a bore sealing problem

Re assemble engine and check it turns over easily and smoothly. Run in for 10 hours using mineral oil at 25:1.

Grey plug can be due to lead in petrol but you should not be using leaded petrol in a 2t, nor do I know where you would now get leaded. and you state you use shell advance unleaded so I can't see that being the cause.

Hi dadof2 head gasket in corrected position now, standard jetting, engine turns over easily and smoothly with plug out with plug in its hard as hell to kick over but was before pre having the cyl re plated? I know you mentioned before about checking the squish clearance re that comment but have not done so far.

Re petrol that's right I've been using shell super unleaded I've looked at plug since re positioning head gasket and it's still grey so that's made no difference.

I will take it back to the shop that rebuilt it show him the pictures and ask him to check ring end gap.

[copemech]

Lineaway & axulsuv = I cleary implied against re jetting at this stage. The engine is definitely rich and I suggested checks to do. The gasket misalignment would restrict coolant flow causing overheating. This engine is clearly rich / cold.

Those bore scratches should not be there - I have seen 15 year old well used bores with less.

Thouroughly rinse the barrel, piston and crank cases with petroil mix and pour into a clean bowl, allow to settle, pour off the clean liquid and examine the sediment under a strong magnifying glass or microscope.

Check the piston ring end gaps are within specification. There seems to be a bore sealing problem

Re assemble engine and check it turns over easily and smoothly. Run in for 10 hours using mineral oil at 25:1.

Grey plug can be due to lead in petrol but you should not be using leaded petrol in a 2t, nor do I know where you would now get leaded. and you state you use shell advance unleaded so I can't see that being the cause.

I would agree here with the fact the wear in pattern on the bore is looking all screwed up. And if that is what strawberry flavored oil does I want no part of it! I broke down my five year old Sherco and had less crap on the piston than that!

[southwester]

I took cylinder and piston to a proper trials mechanic today and he thinks there may have been very slight burrs on the edges of the ports or some debris in the passages he said to degrease it and wash it with soapy hot water and put it back in worst case synario it will seize but he doubts it!

Now I've cleaned it you can see the cross hatching under the scratches so the scratches arnt as deep as the cross hatching in most cases.

I will put it back together for the weekend up the ante on the oil and keep the revs down for long periods for the first few times out.

When assembling piston and cylinder I just give everything a lite coat of neat oil do I? and I didn't note which wat the piston went round is it arrow on top of the piston pointing to the exhaust and ring gap to the back?

I didn't chose the strawberry oil it was thrown in when I purchased the bike is it no good? It smells nice!

[0007]

The arrow toward the exhaust, the rings have a. Locating pin so you can't really do it wrong

I doubt it was rough ports, that would only drag straight up from the ports anyway, not all the way round

I believe in Ochams razor, the simplest most obvious answer is usually the correct one

That being dust through the intake or crud entered when you had the top end off

Just lightly oil the top end, you don't need a lot

And there's no point in breaking it in again, I'd say it's already happened, unless you are replacing the rings just ride it

Have you measured ring end gap? Only takes a minute

[southwester]

No I haven't measured ring end gap yet I put ring in cylinder do I and measure gap? Where in the cylinder does the ring need to be and what gap should it be.

I rang Beta uk this morning and they said don't worry about the ring end gap if the cyl has been plated to new piston he said vertical lines in the bore is what happens and isn't a problem unless it can be felt with a finger nail.

He also said they say 100-1 when breaking in and 70-1 after and recommend putoline oil.

Edited January 3, 2014 by southwester

[dadof2]

I think you are now in the unfortunate position of having conflicting advice from different sources any anyone could be overlooking something that they assume the others will have done.

Beta Rev 3 handbook recommends 10 hours running in and permits use of mineral oil at 25:1. Engines do not always run in properly on fully synthetic, this is possibly why Beta UK have suggested a far leaner than normal ratio of 100:1 for running in although this is certainly not something i would advise.

check the edges of the ports, they should be radiused / smoothly rounded, NOT SHARP. Its just possible the borer / honer has forgotten to do this.

Edited January 3, 2014 by dadof2

[southwester]

Well with 20 hrs or more on this plug it seems as if the tip of the electrode it's getting a darker grey and the oil seems to be moving from the base of the thread along the electrode towards the tip where there is a fleck of oily residue after the last ride.

[0007]

You should only consider plug color on the trail when it's hot

You can't do it hours later or next day

The piston crown is a much better way to jet an engine but it's not easy on a Trials bike

I would look for any amount of carbon buildup on the ctr of the the crown even the size of a nickel, if you have nothing then it's rich but do some hard riding before you check any jetting, idling around will tell you nothing

No carbon means low combustion temp, cold burn, cold piston, wash down

[southwester]

You should only consider plug color on the trail when it's hot

You can't do it hours later or next day

The piston crown is a much better way to jet an engine but it's not easy on a Trials bike

I would look for any amount of carbon buildup on the ctr of the the crown even the size of a nickel, if you have nothing then it's rich but do some hard riding before you check any jetting, idling around will tell you nothing

No carbon means low combustion temp, cold burn, cold piston, wash down

Ok thanks it seems to be running ok to my ear any way

[0007]

Oh and you need some moisturizer for that dry skin.........LOL

[crowley]

Plug chops are notoriously difficult with modern fuels owing to additives, even after hours on a Dyno tuning my Ducatis and Buells, the plugs can give contradictory readings to the info I get on A/F ratios which are logged. In any case, the chop has to be done after the motor is cut as quickly as possible, and even then you need to distinguish between colouration caused by the fuel and the colouration caused by the heat range of the plug. (There used to be a good NGK site detailing this)

I'm interested as to why someone is saying that leaded petrol shouldn't be used in two smokes, since lead is not just used as a valve lube. In addition, many motor manufacturers now use synthetic as first fill and the engines run in just fine; - yes I've heard all the internet wisdom about synth being 'too slippery' and causing rollers to skid rather than roll (a favourite on Harley Davidson sites), and causing rings to not bed. I always suggest that they throw a handful of sand into their oil if this is the case

I discussed this 'issue' with the UK ex Head of SKF at the Ulster GP last year and he said that their company used to get clogged with Emails asking these questions - which is why these type of questions are banned in the Tech Section of a bike site that I moderate on

[dadof2]

Interesting post,perhaps I can offer a few answers

Fuel ratio affects colour of base ring of plug, section of earth electrode close to base ring and centre electrode insulator deep inside plug. Protruding part of centre electrode insulator, centre electrode and tip of earth electrode are more indicative of heat range of plug. On a trials engine both should be a chocolate brown to pale tan colour.

Leaded petrol is bad for 2 strokes because its deposits increase wear and corrosion on the steel (Fe) based bearing metals. In 17th-century England, Samuel Pepys (then serving as Admiralty Secretary), agreed to the removal of lead sheathing from British Royal Navy vessels to prevent the mysterious disintegration of their rudder-irons and bolt-heads, though he confessed himself baffled as to the reason the lead caused the corrosion.

Modern engines are machined to finer tolerances and better metallurgical properties than the engines in use when synthetics first became available and that it is why it is now probably OK to run on synthetic from new.

On 2 strokes good, high film strength synthetics such as Belray MC1 prevented the wear that was an essential part of the running in process. When the engines were subjected to full power use post running in, problems, usually piston / bore seizures occurred because the parts were not actually fully run / bedded in. These problems became quite well known in karting and 2 stroke road racing in the late 1970s / 1980s. Mineral oils contained impurities that

"chemically" burned off high spots during running in whereas synthetics do not.

During the 1990s Honda were recommending running on mineral oil, not synthetic until the second oil change. It had been noticed that clutches and bores

had not run in properly when run on synthetic from new.

In the same era Yamaha were specifying manual removal of high spots on 2 stroke pistons after an hour or twos running as they did not wear off when using Yamalube R.

[slicktop]

Evo 300

I'm running Avgas 100ll 4:1 with Sunoco 110 leaded race, mixed 80:1 Maxima super. Am I doing the motor a disservice running leaded?