One for the fuel guru's

[evo550]

A friend of mine has recently bought his son a '09 ktm 65 (the ones with the "husaberg" type motors)
He has been having a lot of trouble keeping plugs up to it, with a new plug the bike runs fine for about half an hour then starts spluttering, bogging, loading up, coughing, sneezing, then eventually gives up the ghost. Fit a new plug and away we go again.

He has had it back to the dealers a few time to ensure all the setting are as they should be and been given the all clear.

He received a call from his dealer yesterday saying ktm were about release a bulletin reccommending 65 owners NOT run any higher than 91 octane fuel in the bikes

He has always run BP Ultimate.

What do you think?

[E74]

My son has a 09 KTM 50SX same new motor styling, KTM Reccomend to run it at a fuel ratio of 60:1, does your mate know that this is the recomended fuel mixture for these new style engines? this maybe the cause if he is running it at a much richer ratio.

[Lozza]

What heat range is the plug?Type of plug?

[LWC82PE]

yep i would be looking at that, std heat range may not suit the riders riding style and they are not getting enough heat in the engine to burn off the carbon. see this sort of thing all the time and have to tune bikes to run on the fuel we have today. i find that i can ride bikes on their std heat range plug but many old guys who really ride gentle/easy need to have a hotter plug, but sometimes i wish they would just give the bike some more revs and ride a bit harder because they  think their bike will break but by riding the bike so gentle and letting it idle long periods is doing it more harm than good. Im not sure why they would recommend such a low octane fuel? usually its better to go as high as possible and use octane booster. 91 is shit. std carb jetting should be set up for oil ratio in owners book so do what that says.

[mx250]

Hmmmm, if I was gunna muck with an engine I would have a base of known settings which I know that works. The manufacturers recommendation including recommended fuel would be a good start . Try it and see. If it doesn't work you know who to blame . If it does work what more could you want .

Hmmmm, rhetorical question . If you want more higher octane fuel is an obvious. 91 octane does seem low for a racing two stroke (is that a fair dedscription of the 09 KTM 50SX?). The cycle you described, 96 BP ultimate, runs fine, misfires, new plug, 96 BP ultimate, runs fine, misfires, sounds like a fowling plug to me. Suggests one ot two things to me,

1/ wrong plug heat range (is the kid particularly novice and lugging the engine - if so try  'hotter' plug) or

2/there is something in BP Ultimate that the bike/engine/plugs does burn off and accumulates on the plug. This is possible. Oil ain't oil, Soul and fuel ain't fuel, mate. There are lots of additives and they vary from brand to brand. Try another high octane fuel such as Shell Optimax or whatever.

Is the bike gonna be a paddock basher or a race bike? If its gonna be a race bike and you want the max, ask the KTM dealer if there are various thickness base and head gaskets. KTM use to offer various thickness base and head gaskets for its two strokes and you could use them to good effect slightly raising and lowering ports and compression ratios to your hearts content or your ultimate frustration .

(60:1 seems lean on the oil to me . I would go with OEM specs).

 

[Mick22]

I think the problem with the higher octane pump fuels is the higher the octane the more additives they have these additves tend not to be carb friendly. I've seen a lot of bikes chewing thru plugs when run on high octane. These fuels are designed for fuel injected cars and don't work that well in carby motors. You can really notice when you pull apart a carb that has been run on Shell (VIC) high octane because of all the crap in the carb bowl.
On a 65cc two stroke there should not be any issues with detonation so running 91 should not have any effect anyway

[Lozza]

That's a symptom of SHELL there Mick, have easily tuned a Rotax Max kart engine at the point of detonation, each and every time it hits the track.Fuel is control of BP98, it NEVER varies from location to location or one batch to another.No waxy deposits in carbs, tanks or anywhere else.
Make sure you are NOT using an ethanol blend fuel either.

[E74]

(60:1 seems lean on the oil to me . I would go with OEM specs).

 

THAT IS THE OEM SPECS!

[LWC82PE]

you have to re-tune to suit the fuel being used. different fuels burn at different temperatures. if you tune for one fuel you will have to re-tune if you go to another fuel.

the only problem i ever experience with high octane premium is that the volitile chemicals dissapear quick and the fuel goes stale quick. usually best to drain float bowl after ride ( if your not riding bike ever couple of days) and keep fuel tank topped up. it has a shelf life in drums of about 3 months.

[jimg1au]

i use caltex 98 in my dt360 and my 70hp yamaha outboard.my dt is used for dirttrack.it gets flooded with fuel as i have a 38 mm carb.at one stage it ran with no rhs crankcase seal in it.nothing wrong with fresh fuel.a mate of mine has a few us mussel cars and if let sit with shel ultramax for 4 or 5 weeks they wont start.change fuel fires up straight away.the cars are perfect condition he has won 3 summernats with a few of his cars.old fuel high performence engines dot mix.
cheers
jim

[evo550]

Thanks guys,
Yep he is running as factory reccommends 60;1 with motul oil, the plugs aren't fouling as such (with big oil and carbon deposits on the tip) instead they just stop sparking. I understand this is a build up something over the insulator around the electrode which allows the charge to travel from the electrode over the insulator and to the earth, instead of jumping the great divide.
He has tried all of the heat ranges and from $2 plugs through to the $40 only get through your dealer genuine ktm ones. Same results.
It's a race bike and the kids no novice.
I just find it a bit hard to swallow the high octane fuel senerio, when you would expect it to effect a most bikes if the fuel was the problem.
He's getting slightly pissed off....not what you want when you hand over $6500 of your hard earned.

[Rossvickicampbell]

probably means nothing in this context but I usually run Silkolene oil - ran Motul when in Tassie as I couldn't ship any oil with the bike and this was the best I could find - my bike smoked a lot more?

Rossco

[mx250]

I can understand your frustration. I went through the same thing with the WR250F when it first came out (involving some looong pushs on some hooot days up in the Watagans ). It wouldn't run more than 30 minutes on Shell without fouling a $15 ubeaut plug (just long enough to get you deep down a single wheel track trail deep in the Watagans - Tojo's revenge ?. A change to Caltex, a couple of minor needle and jet changes, and then no probs .

I know some of the high performance (high compression) sports multi's have had similar 'teething' probs.

Good luck.

[oldfart]

Heres my two bobs worth, had a very similar experience with My Pe 400- and it drove me insane to point the  that I had the  stator rewound , changed CDI -coil -plus timing set , changing jets didn't work  
Must be the Fuel ---Shell to BP    no good
Hmmm,   ok change brand of plugs form NGK to Champion same heat range  problem solved   Why ?

[VMX247]

check the fuel breather tube isn't blocked  (just a thought)