Gurus needed;fouling plugs

[Husk72]

I was going to throw this in the Yamaha thread but,decided it would get more looks (and hopefully answers) in Tech Talk from the knowledgable ones. This is gunna be long winded,so people can see exactly what I am using/running for fuel,oil,plugs etc.
The bike in question is my '83 mod IT490.
The past few times I have ridden the bike it is getting harder to start,and fouling plugs. I normally run B8ES NGK plugs,sometimes going to the B9ES in the summer.I usually run premium 95,with Penrite 2T,mixed at 35:1.
In September after a camping/riding holiday,and pushing the thing more than actually riding it.I changed the oil,stripped off the seat,tank,and cleaned all earth contact areas,checked the ignition,kill switch,etc.The plug was pretty black and oily,(rings?).Put in a new plug,replaced everything,and it fired up third kick.Drained tank,and parked it.
Fast forward to last week. It kicked over,but didnt want to know about starting.Took plug out,and the thing was fouled with oily fuel.The only spare plug I had,a B7ES,was used.About 5th kick it started,whilst it idled I put my gear on.Chucked it in gear,went 100m,and it died.Plug removed,and it was fouled as before.
Ok,due to my where I am presently located,I could only get ahold of Havoline Super 2T oil to use.I am still running 95 premium,and mixed at 35:1.
Yesterday,in 35 degree temputures,I put what I thought was a B9ES,only to discover it was a BR9ES.I went with it,and it started fourth or so kick,the bike didn't seem at all very crisp.Went riding,after maybe 10 mins,the bike stalled.Same problem,plug fouled with a slime of brown oil.
New plug in,same type BR9ES,and it didnt want to start at all.Ended up push starting it,started and went really well,bugger all smoke,and was hitting the powerband no probs.Rode for maybe 20 mins,and it again stalled.Push start,and away I went again.This time rode for 15 to 20 mins,till we were done riding.Haven't checked the plug as yet. When I say push start,there is a big hill which was used to start it on. It didnt want to start on moderate slopes,or by kick starting either.
Other things to consider: I am running an air pod,recently acquired an original airbox which is going in asap.I checked the carby out maybe 18 months ago,re-aligned the floats,the needle and slide are aged,but don't seem worn.Is there anything I've missed? Anything tests I can run?
Is it time for a new piston,and rings?
Any help,or pointers would be greatly appreciated.


                                                                              Cheers,Mark.

[bigk]

Whilst I think you have more than a spark plug problem, chuck the ES series plugs and use EG series. Virtually none of my bikes run with ES series plugs for long, yet no problems all season with EG plugs. Try to avoid resistor plugs as well.
K

[bazza]

Had you done a plug chop when bike did run well? To eliminate jetting. Compression,spark or plug. Try new plug and 98 or av gas,some 95 will even fowl lawn mowers.

[tony27]

If you're getting oiled plugs it probably wouldn't hurt to measure how much oil comes out of the gearbox next change, has to be the cheapest check you can do

[Lozza]

A combination of jetting/ignition. Check to see how much of an air gap the ignition can make a spark jump.

[GMC]

I had a similar problem with a KTM 300 a few years back.
Kept fouling plugs from cold start but would then settle down for the day, and then other days it would be fine.
All the Guru’s were telling me I was…
#   Using the wrong fuel
#   Using the wrong oil
#   Using the wrong oil ratio
#   Using the wrong spark plug range
#   Using the wrong spark plug brand
#   Had the timing set wrong
#   Had the wrong jetting
#   or just holding my tongue wrong

In the end it turned out to be a Main bearing on its way out causing intermittent main seal leaks.
Eventually it got bad enough to become obvious. New mains and seals and it was fine after that, no matter what fuel or oil I used.

[DOK]

Hi Husky72
I am a bit rusty on all this bizzo but I can suggest a few things.
First up have your compression checked ( it might feel like its going to break your foot kicking it over) pop into the local bike shop it should upwards of 140 psi.

When it is running check the exhaust. hold your hand over the end to make sure it isn;t blocked.
Both of these (blocked exhaust & low compression will cause plugs to fail.

good luck and let us know how you get on

DOK

[lms6201]

 gmc is right ,main seal on the clutch side , dead giveaway ,

[Husk72]

Fantastic response guys. I thank you for all those tips.Invaluable advice!
Today,I removed the DG exhaust on the bike, as it didn't line up and fit as it should. Whilst it was off I thought I would check out piston movement in the bore,by putting a finger in there and pushing the piston. Say no more.Loose as.
I thought it needed a rebore at best,and reading GMC,and Ims replies it,could be more critical than that.
DOK, you're spot on about the comp. This thing is quiet easy to kick over,and I reckon that the comp wouldn't be anywhere near 140psi. So problem solved. Rebuild time.
Anyone recommend a good bike shop,who can supply the parts,and rebuild this motor from pretty much anywhere between Mackay and the  Gold Coast?
Thanks again.

                                                                                     Cheers,Mark.

[chrisdespo]

Rule of thumb a compression test is a good thing to do and for the time it takes remove clutch and ignition covers and check for play in crank main bearings.