Yesteday I came very close to coming off my bike on the way home from college, with absolutely no warning the back wheel locked up rolling off the throttle doing about 45/50mph, really don't know how I didn't come off but I somehow managed to keep it from going over, so had to push the ****er back about 2 miles home.
So I'm guessing this means the engine has seized, what number of things can cause a seizure? if it was getting to hot the temp sensor light would of come on but it didn't so can't be overheating. There wasn't any strange knocking before or as it happened, it just cut out and then locked up.
I'm really considering just getting a new bike at least then that would mean I could keep the dt and fix it in my spare time and maybe enjoy doing so. I just have no time to be ****ing around with this right now with college and work commitments.
I don't trust the DTRE temp sender. If that fails you would have had NO way of knowing whether or not it was overheating or not.
What is the mileage, etc. When was the piston last changed, that wants doing every 15K. Oil pump failure, poor bad oil. Poor fuel. Air leak. Sometimes it can just fail. It's all mechanically moving parts and sometimes they break.
You could have the engine rebuilt in a day. Very easy job and can have a fast turn around. If it's top end failure and the bottom end is okay then that can be fixed very cheaply and fast!
Ultimately the bike is fcked now. So best thing to do, strip it down and inspect the parts. As to why it's failed, usually poor maintenance. But sometimes parts fail.
Get some pictures up of the bore, piston and spark plug and that'll indicate what has gone wrong.
If you haven't replaced things like gearbox fluid then that can cause issues. There is no single point of possible failure on engines. Usually its a combination of factors that has cause engine failure, but this can more than often be because the engine has not been maintained.
Oh lmao. Just read it rolled whilst rolling off throttle!!!! Mate the oil pump is controlled via the throttle. Rolling the throttle at high rpm on a two stroke is a no no. Since you starve the engine of oil. I always set my pump to pump oil in even when the thrrotle is closed.
Well I've done 20850 miles, maintenance wise I change the oil (10w 30) every 1000 miles with new iridium spark plug, I've had the top end rebord over 250 miles ago with new mitaka piston kit. Haven't gone above 40mph for the most part and only gone 50 when necessary but very rarely.
I was coming off a main road about 45 ish so I rolled off the throttle then changed down and then just died suddenly and locked up, wasn't even off the throttle for very long. Not a bad idea to have the oil pump set like that, something I'll be doing if/when I get her back on the road...
By the sounds of things then you've looked after it another. The only thing I can think of at this moment is, piston ring end gap did you measure it.
Have a good look at the sparkplug, my money is on it ran dry of oil for whatever reason. Assuming the installation was correct then I would say something caused it to fail. Scrim swears by the oil pumps on the DT. Car oil pumps seem to do ridiculous mileage before failing so I can see where scrim is coming from. After 20K miles is nothing really.
I was aware that there should be some degree of clearance, I just assumed that this was taken into account when the rebored barrel was returned to me with the piston kit. Surely if there was any incorrect clearances the bike wouldn't have ran for very long and would of just failed straight away?
Yeh the rebore service included Pv machined down. It's so strange this has happend, I mean it was running so sweet for the time I've been using for work and college.
In the past 2 months I've spent £250 on the whole top end, rebore,gaskets piston kit ect... I've been quoted £207 from pjme for re-sleeve with piston kit and gaskets. Can't even get this done until I can be sure the bottom end is sound. Really I need the bottom end looked at and have everything replaced bearings and gasket wise. All this with a £500 budget...
When I removed the barrel the piston was completley coated black like it was sprayed black and was very sticky.
By the looks of things mate, no bits of piston have broken up, the bottom end should be alright. Check the usual play but that looks like oil starvation, perhaps oil pump has packed up, or the plastic cogs that drive it have broken up.
Shame you can tell that that hasn't been ragged though. The rest of the bore looks fine. Notice how it has seized on the 'cool' side of the barrel. That's very strange, usually it'll be the 'hot' exhaust size where it will fail. So to me that looks like there has been little or no oil coming in and it's just seized. Sorry about that.
Also that won't need a resleeve mate. That's fine for a rebore, £30. New mitaka piston, £40. New gaskets, £40 and if it were me, fck the oil pump off and go premix.
-- Edited by Calum122 on Thursday 2nd of October 2014 06:53:11 PM
Probably know what has happened then. Did you modify the powervalve mate? Get some pictures of the powervalve. With that size OS you need to shave the powervalve to allow for the bigger bore.
Yeh the power valve has been modded by grampian motors. I'll try and get pic up tomorrow, but It seems flush with the barrel, I'll clean it up tomorrow and have a close. look.
Should not be flush with the barrel!! there would be no room for expansion!, you want a good mm gap. The last power valve fail I saw took out the rings so not 100 % that's it. It does look a bit starved of lube. I have seen worse bores so if it is not deeply scored then I would just get another piston, shave the power valve with a dremel or file (I normally take a couple of mm off to be on the safe side with no ill effects) and then get it going using pre mix. While it is running you can then check the pump is working by pulling the pipe off of the inlet.
Might just have to give that a go, but the barrel has this one secstion with a bit of a flat spot, so unsure really if that would be ok, I don't really have to run it for very long to see if the pump is working I suppose???
When I say flush I mean its not protruding into the barrel.
-- Edited by L_COLE on Friday 3rd of October 2014 10:27:46 AM
Ok so I'll get the barrel honed and take some off the Pv, then run it with a new piston for a very short period of time premixed, then check the pump like how zooankski said and if the pump checks out ok I'll adjust it like in your video.
If worse comes to worst just wondering if anybody knows how much a new oil pump would cost?
I'll be finding out soon if I'm going to need a replacement pump, I may have to take you up on that so I'll let you know. Mines a 2005 so thats fine.
Just wondering, my neighbour is a bit of a old school engineer so I was speaking with him and he noticed that I've sprayed the rad and he thinks that this has affected the cooling effect of it and this may have caused the seizure?
Spraying the rad will have an effect, although very minimal since it doesn't lose heat via radiation. Black colours will radiate more heat and actually household radiators should be painted black. Although household radiators don't heat up the room by radiation actually by convection. So they should really be called convectors. I digress.
Yz125 radiators are light in colour. So is the aftermarket radiator on my car. So no colour isn't going to seize your engine.
Unless of course you have clogged up those precious fins with paint. Stopping the cold air passing through the mesh and taking the heat away. But again it would be so noticeable you would have known.
Powdercoat their radiators? Hmm, yes mate. If you look at ANY radiator you will see how thin the metal is. It's thin because it needs to dissipate heat quickly. Powdercoating it, adding layers to this metal, effectively insulates the metal, making it more work to dissipate heat from it.
I've not seen people powdercoating them before, I wouldn't have thought it would be very good though. But there is a difference between powdercoating and the rattle can. The molecules out of the powdercoating machine will be electrostatically charged causing them to attract to a disperse evenly. Allowing a smooth finish of finite distance between molecules. Again I don't know what effect this would have, just from imaging it, I can't see it being any good.
