owned the bike for about 2 months now, within a week i blew the engine, had it rebuilt done about 400 miles on it then started going faster to check if its all working good top end, and it blew.
Engine is now rebuilt again, with a bigger carb and has been re jetted, took it up to speed again roughly 65mph held it for about 15-20 seconds today pulled in and checked the spark plug and its going lighter again so something is still wrong.
Runs fine at low speed and low revs but as soon as you give it more throttle and more speed problems happen, does anyone have any idea's?
Are you even running it in? Sounds like you're trying to rag the **** out of it before the engine is even ready :/ You need to do (they recommend 1000) enough miles to let the piston run in properly.
yeh im running her in properly, my local garage works on alot of enduro bikes, and he said if you take it up to speed she should be fine just dont go flat out for too long, (i was not near her top speed) he reccommended me doing it to see if the new carb and jets would cope with it but doesn't look like they are...
Can you be more specific - was it a seizure or did it hole the piston? If it seized, take a photo of the piston and post it on here. The marks on the piston will tell what sort of seizure it was.
I no longer have the piston so i can't take a photo, but there was a hole in the piston and the barrel was just destroyed.
Since i've had the second rebuild i've been taking it easy low revs and low speed keeping it under 50. Everything worked fine and spark plug was good, but took her up to speed and spark plug was going lighter in colour so i had to ease back off otherwise the same thing would of happened.
+1 colder plug required as a starter, but go through the plug chop procedure again to see if its making a difference to the colour of the insulator. I think I'd be inclined to go back to a standard carb and standard jetting as a bigger carb will require different jetting which complicates the whole show even more.
Iv just done my top end, An the bike is just, wow . iv not even opened it up yet im on 63km lol ... been reading about this easy run method supposidly being better for gettin more performance life span an ring seal check it out let me know what you think im givin it a go anyway, i aint really assed if i need to replace an do it all over again cant ride at 2000 rpm for 500 miles
Based on my experience, I dont agree with the take it easy method any more, but there are some conditions:
1. The cylindfer MUST have been bored and honed correctly, to the correct surface finish and at the top limit of the piston/cylinder clearance specified by the manufacturer.
2. The engine is DEFINITELY not running weak and is slightly on the rich side.
Give it some beans I say, in short bursts to start with. If you take it easy the bore will just glaze over, especially with synthetic oils which lubricate much more efficiently than traditional mineral oils. Also, light throttle settings mean less oil getting into the engine which risks overheating if you suddenly accelerate. About one hour of running in of this nature is required.
If you cant be sure of the 2 conditions above then maybe best to take it easy to prevent overheating and a seizure, but still give it some early brief bursts of acceleration to bed the rings in.
This is just my opinion, so I'd welcome other views as well!
running in wise, best bet is too ride calm, let it warm up and simply ride around under the power band, dont let the engine struggle either, up hills etc just keep it in the right gear. a couple of hundred miles will see a top end broken in fairly well. its just seating the rings and what not anyway. short birsts of speed and revs is ok after the first 50 or so miles, but dont take it too harsh, let the revs biuild up dont be snappy.
as for a hole in the piston, as said it can happen due to running too hot of a plug, or if the ignitions advanced slightly (modded cdi etc)
things too check are:
oil pump, is it working and bled? is it at the correct setting required to lube the piston enough to keep it cool
Spark plug, im assuming the dt runs a diffrent spark plug when full power compared to its restricted model like the rs does, have yyou got the right plug for the right power of your bike?
When rebuilding the top end are you using the correct thickness gaskets to get the right squish? too small a gasket is a big no no.
Carb jets, you need to do plug chops, which is difficult as your running it in so you cant really rev it up hard too do one. but you need to check that spark plug is nice and brown and not white. Maybe go back to a stock carb for run in with jetting thats easier to gauge via other users with similar set ups. Without the right jetting youl continue to blow top end and it will quickly start causing bottom end issues too
lastly is the engines temp sensor working right and the coolant changed and bled correctly? it could be getting hot at speed.
-- Edited by creamsodauk on Friday 16th of September 2011 09:08:33 PM
thanks for all the comments, ive put bigger gets in, and when i went to the garage they gave me the same spark plug used in the rs125 too see if that would do any good, ill give all these options a try and hopefully she'll be back to normal :)
what plug is that may i ask m8 i use br9eg same one used on the yz instead of the standard or the iridium ones.. cheers for the easy run in advice lads,,, yeah my bikes treated pretty well anyway best oils , and iv always warmed to temp before opening it up. short slow bursts iv not gone over 7 k either m8 yet 105km on the clock this mornin soon ill be tearing along again
only a little
