the curious incident of the bog in the bike-ride.

[HeadSmess]

the facts.

i run 50:1 oil, always have, always will.

ran a 0.5 jet out to the bearing shop.
swapped over to 0.55 for the ride back home.

ride out involves hairpins, some dicey corners...not just WOT.
ride back involves a 4km(~2.5Mile) uphill, at WOT. 20km(~13Mile) each way in total.

had recently fitted a champion RJ19HX. insulator still spotless after a week.

ride out to shop was fine, except for not being able to fully open the throttle. ie, too lean.
ride back home, upon nearing the top of the hill i suddenly lost all power.

ten seconds later, started fine, ran fine. then the same thing happened. a struggling engine. felt very "stiff", then just bogged down and died.

coped with half throttle to get back home. even the odd WOT for short periods.

engines still running hard as always now

can anyone figure out what the problem was?





sorry, there arent any prizes available for correct answers just personal satisfaction

 

[Fabian]

i run 50:1 oil, always have, always will.

You silly, silly man.
Get some 25:1 in your engine ASAP.

 

[crassius]

sounds either too lean on oil mix, or too lean at the carb - richen up both & see what happens

 

[butre]

little bit of vapor lock maybe?

 

[HeadSmess]

all above answers are wrong! nasty, arent i?

hint... the plug colour is a dead give away

and that it would start up again, after a short "rest".

remember...i had the larger jet in when it happened.

 

[HeadSmess]

you people are no fun no love of mystery! sherlock holmes, if he was even real, would be rolling in his grave

champion 19 is equivalent to ngk 2. very very hot!

simply mild pre-ignition brought on by 4km of full power. answer was instantly obvious by the way the plating on the plug blistered off!

technically, butre came closest, it is a form of (hydraulic)"lock" due to heat


deceptive, huh?

 

[Fabian]

Why haven't any of my engines suffered from your listed problem?

Maybe because they run 25:1 and are jetted to perfection.

 

[HeadSmess]

fabian,

go get hold of an ngk br2hs (if it even exists), and try it yourself... not the 5 or 6 or 7 that we normally use

or the plug i used, rj19hx, available from bunnings (or the mower like i did, with its thin electrode i thought it might be a platinum/iridium...it isnt!) if you really dont believe me champions heat range numbers are all over the shop. with 7-8 being in the middle and much the same as ngk.

https://www.ngk.com/learning-center/article/225/heat-range-conversion-chart

this also has never happened to me before, using cj8 or br6hs or similar, cooler plugs. ive never seen the hex of a plug turn blue from heat before either.


you trying to say i dont know how to jet an engine? or that, despite it running perfectly fine for the last week with the good old bpr6hs back in, that it has seized up?

this is the fun of experimenting strange things can happen


(all i can find is ngk bpr2hs and thats old stock, all sold...)

i doubt anyone got the reference to sherlock holmes in the thread title... this was a story i already had the answer to

i gave out the facts, some misleading, and you made an assumption.

i said i was nasty