DT125R ARCHIVE

AndyYam · Guru

RE: Top end rebuild

Calum122 · Guru

Well it looks like there are a million and one ways to break engines in and how much truth is behind them i don't know.

www.dirtrider.net/forums3/showthread.php

That one there mentions using a lower grade oil then switching to synthetics to wear out imperfections in the bore. It's the way i've always been told and it's served me brilliantly.

AndyYam · Guru

www.yamahamotorcyclespares.co.uk/product/yamaha/3BN124141000/gasket,%20cover?uid=0

AndyYam · Guru

Calum122 wrote:
Well it looks like there are a million and one ways to break engines in and how much truth is behind them i don't know.

www.dirtrider.net/forums3/showthread.php

That one there mentions using a lower grade oil then switching to synthetics to wear out imperfections in the bore. It's the way i've always been told and it's served me brilliantly.

An interesting read. Its for race machines though rather than road going bikes. From what i could see they havnt mentioned whether they are plated or steel bored which obviously need different break ins. Nikasil plated bored just need a few heat a cool cycles where as the steel bore with cross hatched honing it will obviously need more running in. I'll stick with high quality oil and long break in 300-500 miles but thats just my preference.

AndyYam · Guru

Sorry just read it in full. Im at work so just skim read it originally. What Trick2stroke is saying is use a petroleum based oil.

"If it's a two stroke, you can add a bit of extra pre-mix oil to the fuel, set the oil pump at a slightly higher than normal base setting, or both for the first tank of fuel, but I'd use a petroleum based oil."

This is a very good read Cal, good spot. Might be worth copying n pasting it into a sticky for "First run of a rebuilt engine".

Very good point about leaving the choke on. I've never thought of that before. The extra fuel will wash the oil away and severly reduce ring life.

Also on not revving an engine thats not under load. I had my RD out the other day and was warming it up. My dad suggested it was revving it too high and explained why its a bad idea. This guy is saying the same. It's easy to do as it sounds nice :P

Back to the original point, I don't think he's saying use an inferior quality oil but a different style of oil nd thats aimed at 4 strokes in particular i think. Very good read though.

Energized · DTR Legend

+1 Andy.

Exact same preference as me, i'd stick to a good quality oil (silkolene) and give it the old 500 mile bench mark for anything steel lined.

Then for Nikasil like you've said, you can get away with heat cycles. This is proven by the run in tenchniques they use for crossers (which have the nikasil bore). smile

yamahadt125 · DTR Senior Member

So i could of made a base gasket instead of buying a top end kit oh well but yeah ill make
a gasket for thermosta Thanks for help!!!

NEV · Guru

Aye deffo a good quality oil for running in, but cheap detergent type oil if cleaning or flushing out.

Calum122 · Guru

Stuff that experiences big pressures i'd buy a gasket. So engine gaskets. The rest i'd just make.

AndyYam · Guru

Yeah i wouldnt make a base having never made gaskets before. n athena top end kit is 20 quid.

yamahadt125 · DTR Senior Member

athena gasket i bought £ 23

NEV · Guru

I use the Athena Italian site, and have found that they're cheaper than buying Athena uk. I paid about £8 for each top gasket, so bought 3 at that price.

NEV · Guru

Try here www.athenaparts.com/eng/blog/easy-gaskets-la-nuova-linea-di-serie-guarnizioni-per-maxiscooter

Victor · Guru

oem top end gaskets are 13 quid part number 3bn-11181-02

i re-used one(no sealant) and still hold's 4 months later well worth it

Calum122 · Guru

I went to Yammy to get my head gasket and base. £40! Couldn't believe it. It's gone up by so much.

yamahadt125 · DTR Senior Member

so got piston and gaskets but there is 2 piston rings and a zigzag ring? whats is that for also the rings dont have a top or bottom marked on it but there is an R marked on it ??

dread123 · Moderator

make sure you install the expander ring- cant remember if goes top or bottom..the rings will have a marking on them -one may be slighlty different when comparing the other

dread123 · Moderator

expander ring on the bottom pal- then install rings over it :p looiking at my spare piston kit- there are no markings on the ring- but if there are then it will tell you which is top :p

infact there are differnces in the ring thickness. the thicker ones wont fit in the top or vice versa :p

-- Edited by dread123 on Wednesday 22nd of January 2014 05:29:53 PM

yamahadt125 · DTR Senior Member

okay but can you stick a ring upside down or wrong way thats what i meant expainder ring hmm only one and there 2 ring ? never seen one before

Calum122 · Guru

Yes. Depending on the type of ring some will need to go the right way round. Should be blinding obvious if it's the wrong way though since the rings won't close properly.

dread123 · Moderator

yeah only 1 expander- goes on bottom- you cant fit rings wrong way- look at the ring ends- they are designed to sit under the pins on the piston- the thicker ring is for the bottom...

yamahadt125 · DTR Senior Member

well i got told you can stick them upside down the shape of the end of the ring is cut and should points some wayi dont know dont worry....

dread123 · Moderator

just post some pics after :p

yamahadt125 · DTR Senior Member

okay will do later

yamahadt125 · DTR Senior Member

i understand but what do the wavy ring do also the rings hve an R printed on them should the face up ?

Calum122 · Guru

The wavy ring i believe increases tension in the piston ring. Although my £90 piston kit does not have this.

The pistons have a ring locator. The piston rings slot into that locator.

To be fair I'm really stating the obvious here.

Something that moves up and down 12,000 times a minute might have the tendency to move. This may come as a shock to you but a two stroke barrel has holes in the side of the walls. If the piston ring were to ever move during its cycle it could risk snagging the ports and thus breaking.

The pin locators stop the rings from spinning. Thus the rings must be carefully located to ensure this does not happen.

-- Edited by Calum122 on Wednesday 22nd of January 2014 07:18:01 PM

dread123 · Moderator

the letter on the rings faces up pal :p

yamahadt125 · DTR Senior Member

that what I've been asking letters face up thanks

yamahadt125 · DTR Senior Member

also the ring at the bit where the gap is cut normal but my old ring are cut different id was going to do a pic but all blury

Calum122 · Guru

There are various piston ring methods. I would have to look to tell you them all.