DT125R Went pop! *LASTEST UPDATE*

[twotakt]

Hi Everyone,

My yamaha dt125r (2000 reg) went pop tonight, went to kick it over and no compression. So I'm guessing (I'm a complete noob by the way) I'll definately need new rings and probably a new piston and maybe a rebore/new barell. However I haven't taken the cylinder head off to check whats happened yet though.

My questions

1. Where is a good place to source these parts from/get a rebore done? (I live in Bristol)

2. How much do these parts (generally) cost?

3. What are the best quality parts to buy, i.e. Mitaka, Genuine Yamaha etc?


Thanks in advance,

Jack
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R.I.P. Tareree Shiimi, 1985-2008

[Dischord]

Unless it seized I doubt it will need a rebore! A piston kit which includes piston, rings, circlips and pin will cost around £30 from a dealer - Don't get any special kind just a bog standard one will do for a DT as they're only mildly tuned.

If I was you I'd remove the head and then check the barrel, if it's clean order the piston kit and give it a go yourself - It's fairly easy and will save you loads.
____________________
2012 KTM EXC 250

Check out my vids - https://www.youtube.com/user/KTMSparky/videos

[twotakt]

Ta for the quick reply,

Yeah I don't think it's seized as I can kick it easily (Please forgive me if that was a noob statement). My girlfriends grand-dad is going to come around on the weekend and tutor me through it so there shouldn't be any problems in relation to that.

Thanks,

Jack
____________________
R.I.P. Tareree Shiimi, 1985-2008

[Dischord]

Let us know how you get on, the only tricky bit is putting the barrel back on over the new rings in such a confined space.

It's helpful to stuff a rag between the crankcases when the heads off incase anything falls down there - could get expensive then
____________________
2012 KTM EXC 250

Check out my vids - https://www.youtube.com/user/KTMSparky/videos

[darkangel]

i think the rings and circlips e.c.t are 30.00 and the piston and piston pin is 30.00, these are the official yamaha prices.
Dont get fooled into buying whole piston kits for 30.00 from somewhere like wemoto because they are SHIT, the build quality is terrible.
Get something with a decent japanese brand name or official parts.

[twotakt]

Yeah I'll let you know how I get on, I should be doing it this saturday.

Yeah Darkangel I'll definately get Genuine Yamaha parts, they ought to last longer than pattern parts and probably save me £ and time in the long run.

I've been recommended to go to Cooper Brothers in Avonmouth, Bristol to get the parts by a number of people now, so I'm off to there on saturday.

Thanks for the help,

Jack
____________________
R.I.P. Tareree Shiimi, 1985-2008

[ghettostan]

hope you get it sorted pal.

stan.

[twotakt]

Took the barrel and head off yesterday and this is what I found. Quite a big chunk out of the piston and lots of scoring of various severity. The barrel is also scored, some people are saying a need a rebore (and therefore oversized piston and rings) and others saying it'd be ok to leave the barrel and just have standard rings and piston. I'm more on the side of fence saying that I need a rebore but I'm still not 100% sure yet. Any advice?

Also I got a quote for genuine yamaha piston kit and gaskets from Fowlers, Bristol and it totaled for £85 for the lot

However the bloke on the phone also said some Japanese pattern parts are good like Prox, Mitaka and Weisco. What do people think of Mitaka? I'm asking because on

https://www.tinyriders.com/acatalog/Online_Parts_Store_DT125R_19.html

you can get a Mitaka kit for £40 which is pretty tempting.
Any advise in relation to this post is welcomed and please have a look at my piston below.

Thanks again,

Jack

https://aycu16.webshots.com/image/40535/2003343160381744664_rs.jpg
____________________
R.I.P. Tareree Shiimi, 1985-2008

[Vincent]

Mitaka are pretty good, also most Jap pistions are better quality than those from Spain and elsewhere. I'd use genuine Yam head gasket too. Any pics of the bore?

[twotakt]

Nope, no pics of the bore at the moment but I'll post some up for tomorrow. Its difficult to see the damage but I can feel where the bore has been scraped by the piston.
Maybe the damage is hidden a bit behind the carbon built up on the bore, should I give it a clean to fully be able to full assess the damage. If so, what should I clean it with?

Ta again,
Jack
____________________
R.I.P. Tareree Shiimi, 1985-2008

[Vincent]

[darkangel]

allthough i havn't heard about that brand of piston kits, i have heard of wiseco and people say good things about them

[Rasmus RS50]

if you can feel the barrel has been scrabed/damaged by the piston, u need a rebore!! I used prox piston, for min TDR125 (same engine).
Find a shop that does reborering, they´ll mesure it out, and find the right oversize for you.
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Rasmus
Yamaha XJ600S diversion. TDR125 for the winter.
Danish tax?s sux !

[twotakt]

From the majority of opinion I'll definitely need a rebore, I think it's about £20 from Piston Broke, Bristol. Then it means oversized rings and piston which I'll order once the rebore has been done and I know the size that I'll need. I'll phone them on Monday.

Anyway heres some pictures of my barrel

https://aycu35.webshots.com/image/37354/2002793386753276915_rs.jpg

https://aycu38.webshots.com/image/40037/2002771199457543134_rs.jpg

Vincent, from the opinion of a few of my friends (car mechanics) my con-rod looks fine with no excessive play. However is there a particular way in which I can check this to ensure that their opinions are fact?

Darkangel, I couldn't find any Wiseco pistons on the internet for my Dt, if you've got any links that would be greatly appreciated.

Rasmus, where did you get your Prox piston from? I've heard some really good things about them. I love the TDR although I haven't seen the 125 in the 'flesh', my friends got the 250 in Blue and Yellow its sooo nice.

Also, once I've undertaken the work and have got the bike running is it worth replacing Piston and/or rings at certain intervals as a part of preventative maintainance.

I was asking this because I've been recommended to replace my Aprilia Rs125 rings at 6,000km and to replace the Piston and rings at 12,000km.

Also would the procedure to replace piston and/or rings be the same/similar in relation to any 2stroke motorbike? (whether they be single, twin and so on cylinder) I'm asking this because I'll need to do this on my Aprilia at some point and was wondering if there was any variance in the procedure between my Dt and Rs. By procedure I mean: take off airbox, carb, fuel tank etc. remove cylinder head and so on.....

Thanks again for the help,
Jack
____________________
R.I.P. Tareree Shiimi, 1985-2008

[stirlinggaz]

hi,
have mitaka barrel & piston in my aprilia & had no problems.
very common on rs's instead of replating original barrel & buying proper aprilia stuff which costs loads more!
example full top end rebuild kit,piston etc for less than £200!
& mines is lasting well!
so dont be put off by non original manufacturers stuff, just dont buy the chinese crap!
cheers,
GAZ

[twotakt]

Cheers gaz,

I ordered the Mitaka piston kit (0.5mm oversize) and gaskets from pj engineering for around £50. I'm getting the rebore at Boden's in Patchway Bristol, for £30 which is going to be done once the piston arrived so they can measure it up accurately.
Hows the Aprilia running now by the way? Have you got the 34mm carb on there at the moment? I got the 125 as well but its standard apart from an Arrow exhaust. I really want to get the 250 at some point though.
____________________
R.I.P. Tareree Shiimi, 1985-2008

[Dischord]

£80 all in all sounds good, I remember my mate did the same thing...his bike ran for about 5 minutes and then bits of his old piston went through the ports and nackered everything up again big time. If I recall his next bill was close to £400 - just make sure you check as thoroughly as you can for bits of scrap around the cases
____________________
2012 KTM EXC 250

Check out my vids - https://www.youtube.com/user/KTMSparky/videos

[twotakt]

That's harsh for your mate Dischord, I'll definately be throughly checking everything before I put everything back together.
____________________
R.I.P. Tareree Shiimi, 1985-2008

[twotakt]

Hello again,
Got the barrel back from the shop yesterday with it rebored 0.5mm oversized. Got home gave it a clean and put everything back together. Kicked it a fair few times then it fired up, gave it a run and its riding well. Been out on it today, did 25miles and it hasn't skipped a beat so I'm happy.

First top-end rebuild done!

Thanks again for the help everyone,
Jack
____________________
R.I.P. Tareree Shiimi, 1985-2008

[ghettostan]

nice to hear its working again

im doing mine at the moment too...

just need to get the piston set and gasket, even though my piston is okay iv been advice to get a new one anyway just incase...

[Joeb46]

glad to hear its working but remember to run it in propperly, no more than 6000rpm for 80- 100 miles
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Current- Drz400sm- For sale
Kawasaki er-5 race bike# 106

[twotakt]

Best of luck with your rebuild Stan

Went out on the bike again and clocked up another 30miles and still no problems, its running lovely. How long do you think it'll need until its fully run in? About 500miles?

Also, what's the best way to run in the bike?

At the moment when I've been running it I've tried to alter the revs (not exceeding 7k rpm) and gradient/types of roads.

Thanks again,
Jack
____________________
R.I.P. Tareree Shiimi, 1985-2008