Revs from hell -- stuck throttle or bad mojo?

[stay_upright]

I'd check everything out - you don't want this to happen again!

Some additional things to look for

Cable - if cables wear often they fray as they enter the nipple at the handlebar end - this is difficult to see of you dont check for it specifically - flexing the cable right at the nipple would allow you to see it. I'd remove the cable completely and push/pull the inner cable in and out many times to check for smoothness, maybe sand is in there but only occasionally will jam. I would consider a new cable.

Cable again it could be the outer cable came loose a bit and did not re-seat properly which would result in a partially wide open throttle, exactly what you had, check turning the bars if this affects things as well.

Carb - inspect the slide and needle for score marks if you have any sand has got in there and could have jammed it.

Spring - on the KTM's the carb spring looses tension over time reducing the ability to close the throttle if the cable is a bit rough or some sand/dirt is in the carb. Consider a new one they are cheap.

Throttle - this happened to me the bottom of the throttle casing had broken but as it's bolted to the bars and covered in a rubber boot you could not tell except once when the throttle jammed open. Remove the throttle and inspect both castings.

carb - I'd remove if from the bike inspect and in particular look for and sand or sand sized bits of dirt in the float chanber or elsewhere - and scratch marks around the slide and needle areas.

I would guess it's not the bike running lean (at least as the only cause) since a riders first reaction is to shut the throttle - if the slide closed properly the motor will not have enough air to do anything other than idle - I don't think your slide dropped to the idle position properly, something stopped it.

[stay_upright]

Oh yeah glad to hear the rocks OK

[iancp5]

I had an unusual incidence of revving like mad.
I managed to put the wrong slide in, it was a shorter one from a 36mm carb

Couldn't work out what the hell was going wrong. Took a while until I looked at the slide close enough to realise it couldn't shut completely.

[AZRickD]

Did a Grand Prix some of which was in horrendously dusty conditions.

BTW, the former owner had safety-tied the cable into the twist-grip throttle housing. No way anything was going to come loose from that set up.

All is well.

[Skidad]

Still liking your gearing choice?

[AZRickD]

Yep. I still do.

Our next race is a Grand Prix which will contain a particularly difficult enduro-cross section (designed by Destry Abbot). I'll need every one of those 52 toofers.

Anywazye, in single track the 52T gearing spacing is very nice (not too close to be bothersome). On an MX track, on the other hand... 50T was just fine.

Time to start an RB-Designs carb mod thread...

If after the RBD work I find that my motor has even modestly "come to life," I'll have to consider a 51T when my current aluminum sprocket starts to wear out.