Engine stalls at top speed, Aprilia SX50.

Krakken · L Plate Warrior Joined: 09 Jul 2013 Karma :

Hi guys,

I have a niggling problem with my bike and was hoping someone may have some ideas on what to do.

The bike is an Aprilia SX50 on a 57 plate (the one with the D50B0 engine in it), it has no mods and is completely standard as far as I know.

At first the bike was fine, nipping along at around the 50 mph mark, lately though it seems to stall as soon as you hit 50 and continues to not respond until you get down to about 25 - 30 mph, at which point it fires back up and pulls normally up to around 50 again.

At first I thought it was perhaps a vacuum in the tank, so I tried cleaning the cap valve which was clear, also tried riding it without the fuel cap on, still same problem. Have also tried running it slightly leaner and richer without success.

The annoying thing is, it ticks over fine, revs fine, will pootle along at 40 no problem. Its only when the engine is at max speed that the problem occurs, Any ideas? Question

windows95 · Two Stroke Sniffer Joined: 08 Jul 2013 Karma :

Very strange issue.

I would hazard a guess at it being an issue with the reed valves

Have you checked they are ok?
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Current Bikes: Kymco Pulsar 125 2011 & Honda CB125TDC Super Dream 1982
Past Bikes: Typhoon 125, AP50, BWS 50, CBR125, Kymco ZX 50, Gilera Runner 125, 180 & 172, Honda XLR 125, KMX 125 x2, Piaggio NRG x3, x2 110 Pit Bikes, Pug Trekker 50, Honda Sky, Speedfight 50 & 100cc, SR50 x2, Suzuki Love, Chinese Fym 125 (yuk), Honda Varadero XL125-V1, Honda Vision 50 & 70cc, Honda X8R-S, Symjet 50, Suzuki Zillion &... Yamaha TDR 125.

Krakken · L Plate Warrior Joined: 09 Jul 2013 Karma :

I haven't removed anything from the bike as yet, was hoping for some ideas on where to look first, I guessed it might be a problem somewhere in the carb but after reading some other posts on this forum it seems as though an iridium sparkplug (which it does have) could be the cause.

I will pop and get a normal NGK br9es, which is the recommended one this afternoon as they are only a few quid and see if it makes any difference. As 2 strokes are pretty plug dependent it wouldn't surprise me if if it were that simple, lets hope... Wink

Drake · World Chat Champion Joined: 01 Oct 2010 Karma :

In b4 fuel starvation. Check fuel filters.
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was: derbi senda, aprilia sx125, nsr250 mc16, cagiva mito, cb600 hornet now: mk1 bandit, KR1S, landrover series 3 light weight 2.5 petrol, 5speed box