Derbi senda Gearbox/engine/drive Problems.!

LJColeman · Borekit Bruiser Joined: 10 Jun 2010 Karma :

Ive got a Derbi Senda X-Race 2009 sm, Its been running fine, its got a gianelli pipe, 14t f sprocket, blah blah,

But Last saturday and today i was out for a blast and i was in 5th gear about 9000 rpm and suddenly the back will locked up and the engine sort of died, i kept it under controll and when i pulled over, i put it into nutrual and it started straight away and was fine!!

it has only ever done it twice and only in that gear at high rpm!!

Any ideas guys?
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Old Git Racing · World Chat Champion Joined: 08 Aug 2009 Karma :

Sounds like it has seized the piston then freed off. Is it running hot? has it been jetted for the pipe? Running the correct oil mix with good quality oil?

Best sort it out cos repeated seizures will kill it eventually and one day it might lock up on a corner and either chuck you into the roadside scenery or into oncoming traffic and kill you.

OGR
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fiery tupp · Trackday Trickster Joined: 24 May 2010 Karma :

I'm guessing it could have seized temporary , cooled sightly when you stopped , & allowed you to restart ? if so , you are lucky not to fek it up completely,
Smoker experts on here will be able to tell you better Neutral

edit, old git was faster typing Very Happy

connornrg · Scooby Slapper Joined: 05 Jul 2010 Karma :

just do a quick check for us please and remove your spark plug and check the colour of it.
Milky = To Lean! (UPJET)
Chocolate Brown = Perfect!
Black = To Rich! (DOWNJET)

Also i would be weary of the condition of your bore now, maybe look at installing a new one or upgrading to a 70?
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LJColeman · Borekit Bruiser Joined: 10 Jun 2010 Karma :

Had a look at plug, all fne, had the head off, piston is fine ! , and nothing appears to be worn or overheated,

put the bike up on my bike ramp and let the wheel spin free, put it in 5th and reved to 9000 rpm, and the chain was leaping all over the place, and sprocket was moving a large amout,...

so im thinking maybe the chain jumped on the sprocket causing it to momentarily lock the rear, and because of this stall the engine? im going to put a new chaain and sprocket on and see how it goes..
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