Eating Plugs

[eiger]

I'm currently using a ty175 with a WES exhaust fitted (no silencer box) For some reason it keeps destroying spark plugs (whiskering).So we have gone up to a hotter plug but still it destroys them it also doesn't run cleanly at the bottom end.

Apparently the previous owner had the mains and big ends done and it was rebored to first oversize, however the piston currently fitted has square shaped skirt ports which i am told is the piston out of the yam dt as the ty pistons (which are apparently no longer available) have round skirt ports

has anyboby got any knowledge of what plug or piston should be in the bike or any ideas asa to the problems we are experiencing

many thanks Eiger

Edited April 25, 2004 by Eiger

[bullfrog]

Maybe our definitions are different, but "whiskering" the plug indicates (pick one, or more): too lean, plug too hot, compression too high. So, to me, going to a hotter plug when you are already encountering "whiskering" would only make it worse.

[t-shock 250]

In the UK, whiskering generally means small strands of metal shavings spanning the plug electrodes!!

If you have this problem then some component in the engine is busy "machining" another one away!

[feetupfun]

You can successfully use pistons intended for many Yamaha 175cc bikes singles of the same era in the TY175. Some include 1973 CT3, 1974 and 1975 DT175 and all TY175. Wiseco pistons for these bikes are fine also. All these pistons provide the same compression ratio. Don't worry about the shape or size or even complete absence of the holes in the back of the piston.

More information needed about the whiskering please. First what do you mean by whiskering? We need to clarify this because you seem to be saying that the whiskering is "destroying" the plugs. If one of my plugs whiskered I would just flick the whisker off and put it back in again for more use.

Spark plug whiskers can be composed of steel or cast iron or carbon.

If you are getting steel whiskers it could be that the engine work wasn't very sanitary or the port edges weren't chamfered or there could be something rubbing metal to metal where it should not. Check a whisker with a magnet. If it sticks it is steel or cast iron.

If the whiskers are carbon and the engine has just been rebuilt, then there is something pretty amazing going on in there because carbon whiskers are usually (1) old carbon being loosened up by a change in engine operation ie lots of heat in an engine used previously for lots of gentle slow speed work or (2) a change in fuel type or premix oil type which loosens old carbon. If your engine has just been rebuilt, it shouldn't have any carbon deposits anyway.

I suggest you use an NGK B7ES or B6ES sparkplug, high quality fuel, high quality premix oil at between 25 and 35 to 1 ratio and when you get another whisker, see if you can work out what it is made of.

I just thought of something else. I remember a friend once added graphite to his premix on the advice of a graphite salesman and he managed to ride for about 20 minutes before the first carbon whisker formed on the sparkplug of his otherwise perfectly tuned bike. He cleaned the fuel system out and then spent the next few weeks replacing sparkplugs as the graphite (carbon) worked its way out of the engine!!

If you want more help, please provide more information about the way you ride, the fuel you use, the ignition timing, the carburettor type and size and jetting and how long in time the bike runs between whiskers.

David Lahey

Australia

[kevin j]

If you are getting little aluminum balls or specks, its a sign of detonation or preignition or both. melting off the piston and a very bad sign.

as previous post wrote, look for air leaks, too lean, too much advance, bad gas, etc. but deal with it quickly.

kcj

[endo kid]

HI EIGER THIS IS ONLY A SUGGESTION. IF POSSIBLE NEXT TIME YOUR SPARKPLUG FOULS UP MAYBE YOU COULD KEEP IT AND TAKE A CLOSE UP PHOTO OF IT AND PUT IT ONTO THE COMPUTER WITH THE OTHER INFORMATION SO THAT FEETUPFUN CAN SEE IT. HE SEEMS TO KNOW WHAT HES TALKING ABOUT AND MAY BE ABLE TO HELP YOU FURTHER. GOOD LUCK ENDO KID

[eiger]

Thanks for the replies folks, sorry I've not been on sooner but the computer has not been well lately. To clarify, after an hour or so whether its in a trial or practising the bike begins misfiring and a couple of minutes later it cuts out. I then remove the plug to find a couple of whiskers of what appears to be carbon across the electrode, it also has the appearance of running slightly rich despite having altered the needle position, air screw etc, cleaning the plug makes no difference - its had it! So in goes a new plug and its fine again (but not for long). Also the bike seems to choke itself up a lot on small throttle openings and tends to 'fourstroke', I am going to renew the carb 'o' rings and the needle valve this week and see what happens, I will also fit a set of points and condenser I've got and hopefully we'll see an improvement.

Thanks Eiger.

[kevin j]

Thought of something else: If it is really bad overfueling, check the o-ring around the center needle jet where it fits into the bowl. On the TK carb, the main jet is in the bowl, removable from outside. That's great, but if the o-ring from needle jet to bowl leaks, the fuel goes around the main jet and on its way.

Usually only shows up as overfueling at mid range or more, but I have seen this issue several times.

k