Plug reading help

[Tioli]

Hi
Any comments are welcome.

This plug is off a TY175 running auto lube With a nip of oil in a full tank.

what dorse it say to you?
- is the black soot at the edges normal?
- is the colour ok and where would you put it mixture wise?
- if you enlarge the picture the edge of the electrode is very clean

Plug

image.jpg (54.79 KiB) Viewed 7673 times

[Guy53]

It's a very hard question to answer since we don't know what you did before you took the plug out to take that picture and how long you did it.

Guy

[Tioli]

Very appropriate question Guy.
I have done my share of plug chops at the end of the main straight, clutch in and kill switch at the same time and roll, push it in to the pits.
How do you plug chop a trials bike?

I just stopped it at the end of the day which was trail riding. I don't have any experience or reference points for a old trials bikes.

I have played with the motor, carbaration and air box which is mostly in 'All about.... me - my long time friend the prancing horse' but there is to much meandering to ask anyone to read.

Please share your opinion
Regards
Eric

[Stork955]

Gday, it looks pretty good. If anything, a slight touch lean.

Cheers,

Stork

[David Lahey]

What plug is it and what fuel was it running on?

[Tioli]

The plug is a NGK BP7ES running on 91 octain with Autolube and a extra nip in a tank full using BEL RAY Si-7 synthetic

For some reason my bike doese not blow much smoke. My mates TY250 leaves a trail of smoke through the bush running on 30/1. I have to check twice that it doese blow any smoke. My mate says it doese smoke but not much. I have checked the pump and even ran a long clear line so that I could watch it move along at idle and revving it.

I have some concerns and welcome all opinions

- I can't say I have ever seen the edges if an electrode be silver before. Doese this mean its being eaten away by por timing or lean

- The black soot around the edge is strange in how thick and black dusty dry it is?

- The electrode and insulator are very clean which suggests a clean hot burn then why so much soot on the edge?

- The (forgotten the name) earth wire is clean al the way to the base which suggests heat.

Or it could all be normal

Plug

[David Lahey]

A 9 heat range NGK plug is pretty cold even for trail riding so by using that plug you are causing the centre electrode to stay cooler than it would with a more normal heat range plug. A 9 would normally be used for full throttle riding like road racing. The standard plug for a TY175 is either 7 or 8 and that is a very conservative heat range to use. For trials use only a 5 or 6 is ideal and for spirited trail riding a 7 would be good.
Using the colour of the insulator around the centre electrode as a guide to jetting is a lot tricker than it was when we all ran leaded fuel, because the lead oxide coating would produce a nice colour gradient depending on the fuel air ratio. Nowadays petrol is much more variable in what it is made of, and the colours it can produce on the insulator can be variable in the same bike, if fuel is changed. Your photo is not in focus, so we can't properly see the detail you are describing about the electrode tip. I can't see anything being eaten away in your photo.
If you enjoy playing with the jetting on your bike and want to get it right, fit an NGK B7ES, stick with the same fuel, and do plug chops at various throttle settings and various loads, just like you did years ago. Taking the plug out of a trials bike at the end of a trail ride really only tells you what was happening in there during the last part of your ride.
The other thing you asked about was the smoke factor. The oil you are using is designed (amongst other things) to minimise smoke formation. That means it will either burn with the fuel without forming soot (soot particles are why smoke is visible), or stay as a gooey oily residue inside the exhaust system. That oil will be very slow to carbon up your piston crown and cylinder head, for the same reason.
The other factor about the oil is that it is being injected at a rate dependent on RPM and throttle position, rather than proportional to the amount of fuel going through the engine. In the case of TY175 injection, that generally means that less of it will be going through the engine than would be if you ran premix at a normal ratio. Have you checked that that particular oil is suitable for being injected? Not all two stroke oils are made for injection.

[Tioli]

Thank you for your considered answer.

The oil is suitable for Autolube

One last question which you have already scirted for fair reasons but where do you rate it on the lean/ rich scale?

This plug was running on a 360 main. I'm not very acquainted with the flow scale for the TY jets. They are a flow rated style and only have a similarity with round style number jets at 100. After that they split quickly. I am presuming a 360 is large but it may only be like goi up 20 on a number.

I'm thinking a 400 which I don't have may be stupidly big but I don't know and only have the plug as a final guide. The motor feels ok but when you hold it flat out in 6th with a 16 front sprocket it goes better if you back off a bit and find the balance of what the motor will take. I don't think TYs run clean in the upper rev range. If you are doing normal squirting in the lower gears it has good rev out for a motor with a hose pipe as a muffler. . My opinion is these motors are sharpest down low and the rest is getting the best you can as long as you can.

I'm happy with how it goes with a 26mm carb

Rich to lean where do you place it?

Plug best I can do close up

[David Lahey]

Like I said before, it is impossible to judge the jetting of a motor from what the plug looks like and has not been chopped under controlled conditions.

If you are running a TY175 carby then your main jet at 360 is way too big for running on petrol. I have found great success with main jets between 190 and 210 on my TY175s that have had standard carbies and exhausts. There is something drastically wrong with the setup on a bike if it bogs (4 strokes) or dies on full throttle. Judging by your main jet size I would suspect that yours is too rich on the main. A standard TY175 even with standard jetting 240 main (which I think makes them a bit rich), will rev to (I'm guessing here) about 9000 RPM very cleanly with the torque tapering off as the revs go above about 7000 RPM. I've run them with well-jetted 26mm carbies too and they rev a bit higher before the torque starts dropping off with the bigger carby. Because those RPM ranges are quite irrelevant to 99% of trials riding, the standard size carby with its standard jetting has managed to please many thousands of trials riders for 35 years.

Seeing you have a 16T front sprocket, if you also have the standard rear sprocket, a standard TY175 with that gearing should run up to about 85 km/h in sixth gear on a flat smooth road with trials tyres at 15 psi. I know this because I used to ride along a freeway on mine to get to Uni in 1977 and I had a 16T front and standard rear. The speed limit was 80km/h and once it was wound up, it was slightly faster than the traffic. The speedo that came with it also read something similar but I wouldn't trust it for accuracy too much. For that sort of riding I used a B8ES plug and Castrol Super TT at 25:1 and never had a problem with overheating the plug tip or fouling the plug.
That high gearing was totally useless for the trail riding we did back then because even in first gear it did not have the power to climb the (steep and grippy) hills we rode.

[Tioli]

Thanks David.
I use the bike for trail riding and exploring where there are no trails. I don't think a trail bike could get to some of the places we have been. My JC model goes as you describe.

I'm happy with how this one goes on a 26mm carb just a few questions about the plug.

I will take it as slightly lean and go for a bigger main

The silver on the edges of the electrode I will monitor see if I can do some controlled plug chopes

Thank you