engine piston check
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Two strokes don't benefit from pottering around. You need to give them a blast every now and then due to the oily nature of them.
If there is a lot of carbon on the rings, then you'll get blowby and significant loss in performance, it's not irreversable or devasting, just dismantling it all and clearing the ring grooves and rings would probably address any issues. It all depends on how bad it is.
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here is a picture of it https://imgur.com/gallery/KX8mVti
and while it was on the cylinder the piston had a slight movement front and back it would tick a tiny bit -
here are some pics,only now i realised they were scratched
https://imgur.com/gallery/4C5Wk0J -
It costs nearly as much to hone (not polish!) the cylinder as it does to rebore it.
I don’t know how old your bike is or how many miles it has on the barrel, but they get oval after a time. Spending £100 on a rebore and new mitaka piston is the best money you’ll ever spend on your bike. When it’s rebored it’ll be a perfect fit.What head gasket did you do when you fitted a new piston? You say you had coolant loss?…
Edit: it looks like you’ve had at least a partial heat seizure. Probably from the ‘loss of coolant’ head gasket blowing…
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@SpookDog at the time that i did a piston change i did a rebore too bc my piston broke into pieces so its a 56.25, as for the head gasket it probably went bad it was never changed but the scoring on the cylinder i can't feel it with my finger or finger nails because i don't want to rebore it again,while the sylinder was still in the piston the piston hat a slight tap front and back,soo maybeee it will need a rebore for that bc it got oval but not for the scratches
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@SpookDog Beat me to it, looks to me like a heat seizure also. You need to understand why you've had a seizure, otherwise spending money here is fruitless as it'll just happen again. Unless it needs a rebore, a hone may suffice, but my recommendation would be to let the engineering firm decide on what' appropriate. I had a bike stolen and ragged, the engineering firm said the bore ovalised but managed to get away with just a hone. The barrel went on for many trouble free miles after.
To reiterate @SpookDog's point, make sure you're using genuine/Athena/Vertex gaskets. The pattern ones, at least as far as the head is concerned, do not work and you'll just throwing money away. Understand why it failed and look to address this, otherwise prepare for failure again.
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@Calum like i said the piston was brand new and i took both cylinder and piston for reboring it was perfect when i got it the only thing was that i used the old head gasket and that could of led it to seize.now,im saying that i will buy a new gasket and a new piston bc they have to be changed but i don't want to go on a bigger bore and if i can use the same piston size for the new one and hone the cylinder will it be fine with a new head gasket ?
and the wrist pin is stuck in the piston too,
so that maybe gives a more clear sign of whats happened -
here is a vid of the cylinder
https://imgur.com/gallery/HFiRhOS -
Like I said, the cost difference between a rebore and a hone is not worth pinching pennies over! A heat seizure has smeared the two metals together…
Also not all motorcycle engineers are the same. I’ve seen some shocking shit done by firms. If you are in the UK go to PJME for the work, not a ‘mom & pops’ corner place. The piston should of been matched to the rebore, without any movement or ‘ticking’. I’ve had places give me the same kind of fit. I only go with known, reputable places now…New gaskets every time!…
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Oh dear, you should not be reusing the head gasket, or any gasket really.
Sounds like to me, the head gasket has not sealed, it has drank all the coolant and the engine has heat seized. That bore looks pretty scuffed and at minimum is going to want a hone, but as @SpookDog says, looking more likely like a rebore.
Did you not have the temperature sender fitted when you were riding it? That should have gone into the head. Go into the radiator and stick your fingers into the top, I'd expect that to be full of two stroke oil by now so should be all slippery. Either way, you're going to need to flush the cooling system with some cleaning agent to remove all the two stroke residue, else the cooling system won't operate effectively, I'd imagine it's warmer where you are and therefore having efficient cooling is even more important.
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@erion1 Hmmm. something is not right there, definitely looks like a heat seizure to me, you see how it's scuffed on both sides, this indicates the piston expanded more than the cylinder walls. This can be down to one of two things, insufficient cooling, or too much load on the engine before it was up to temperature.
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Bud! I’m guessing that the ‘scratch marks’ are spaced around the piston in 4 places?
This is because you reused a head gasket (worst 15 £-€ you never spent!) It’s called a 4 point heat seizure. If you look up inside of the piston, the inside of the crown will be black and scorched from the heat seizure. Whether you saw it on the temp gauge or not; it overheated…Other thing is the piston shouldn’t ‘click’ back and forwards if it’s the right size. Neither should you have that amount of blow by past the rings! I think that the person who did your rebore may of done you wrong…
I’ve used old bits to keep me on the road, but never as an end plan! Even then I rode it like a grandad, never above 5-6K max, never like a ‘yoof’…
What country are you in? Somebody might be able to recommend a good motorcycle engineer to help you move forwards…
You’re going to have to put in a proper fitting piston. Why quibble about a rebore?…
If you want to ride and enjoy your bike to the max. Just fix it please!… -
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@erion1 These? I didn't know there was such a brand TBH, just looked them up and the website looks good. Encouraging they're available in .25mm increments as you get potentially twice as many rebore sizes:
Interesting they also offer a different piston kit for the '94 to '04 DTR; both kits start at 56mm (so not sure if the 1st link refers to the '88 3DB DTR as these and the original 2RH TZR125 had a 56.4mm bore as standard) but other dimensions are slightly different so there must have been changes during the '89 onwards DTR production run. Can anyone shed any light on this? Comparing the two webpages seems to indicate .5mm difference from the top of the gudgeon pin hole to the piston crown:
I always ran Mitaka and was happy with them (as long as you get the Japanese ones) but they only seem to be available in .5mm increments now.
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