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Hi! introduction and inevetible questions! 2007 rm125

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earlier in the year i became the proud owner of my first 2 stroker and decided ball to it and picked up a beautiful 2007 RM125. its a bit excessive for a field come farm bike but damn is it fun!

the Guy i bought it off had clearly looked after it well (it was raced but kept up with the service schedule.)

it runs like a dream still fills me with terror occasionally and has to be the most stable dirt bike ive owned. very pleased!


that is until ive come to do the top end rebuild......

im a former service engineer, and general engineer so stripping the thing and putting it back together is childs play.

however i have hit a wall at the piston removal when i noticed scuffing to the rather nasty racing piston (im a engineer i dont like ali pistons!)

on inspection of the cylinder bore i was devastated to see a 8mm square max flaking in the nikasil plating just above the exhaust port.

there is little in the way of actual scoring to the nikasil just this chip.

and whilst the scuffing on the exhaust side of the piston is quite alarming again this is the only damage, ring looks ok.


What i want to do is buy a cylinder body (or sleave dependant on advice) so that i have a spare that can be fitted while one is off at plating, however my pockets dont run that deep at this second.

will i get away with continuing the rebuild, hone and reassemble put a new oem suzuki piston in (i know it will sacrifice the piston in quite a short time) knowing in a month or so ill have a spare lining?


pics included, bike after the other weeks clean, cylinder and piston please excuse the quality i can do better but would like to know how to proceed asap cos i missed my ride last week. and a picture of my pet baby goat.


many thanks in advance!










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yes you could hone and put a new piston in there.


issue with doing that?


if anything falls into the bottom end (chip of coating) its toast, costing you a lot more.


it sucks to not be able to ride, but your saving yourself a ton of money and head aches.


moral of the story......do it right the first time.  

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that is what i thought it does look almost like someones tried to fill it? (if thats possible)

im a recreational rider and dont scream it, and the piston pics show IMO im clearly not beating the shit out of it enough lol being as it does get ridden every other week and ive had her 6 months (and i guess previous owner put the new piston in with the sleeve damaged)

ill look into getting it recoated as it would appear to be cheaper anyone know somewhere with a good rep and turnaround (UK)?

im ashamed to say i kindo guessed the hours :jawdrop:

any other hints and tips gratefully recieved (eg does my engine seem to be jetted right piston health etc.)

if i do put it back together it would only be for a month till the wallet allows and would go easy. Pleas Do call me a pikey and shame me into not doing anything till i get a new sleeve or coating.


thanks so much for your help!!

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no way to tell if the jetting is right without knowing whats in there.


you said it was raced but kept up, to be honest the best used bike you can get is a prior race bike. these guy's (90% of them) treat their bikes better than their wives/girlfriends, they are trying to win races and a old clapped out bike just would not cut it.


its hard to tell how many hours are on a bike unless you know the seller personally.


the top of the piston does not look that bad, depending on actual hours.


like i said, if anything breaks in there because you could not wait it will cost a bunch more for the bottom end.


now I am not saying it WILL  break, just with cylinder damage the risk is higher, basically turning a 3-5 hundred dollar job into a close to 1 k job, plus the extra down time.


be patient and get it done right, unless you have a terminal illness you have lots of time for riding.

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thankyou and well shamed sir! warning heeded, its amazing nothings happened thus far.


and i agree wholeheartedly people in fields kick the swhit out of em with no maintenance.


as for hours he said 6 races and ive done at least 8 hours riding on it.

putting oem suzuki piston back tho as i hate ali.

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check the bottom end when you have the top end off.


up down play is a no go, side to side is ok as long as not excessive.


the best advice is treat her right, she will treat you right.


also, every other ride remove the exhaust and have a look inside, this can save a ton of issues that could have been avoided and only takes a few mins.


you see the damage as it occurs (hopefully) and not after it has messed stuff up.

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i have booked it in to be sent off tomorrow or monday, at langports of weston super mare in the UK. looking at a 1.5week turnaround (spose it keeps the mrs happy!) which is very good and should only cost £105gbp or 135 if they have to build the casting back up.

TBH IMO as an engineer it'll be 105.

lesson learnt??

when someone offers you a cylinder body for £140 if you dont have the money go and make it!! ill have to hope santa brings me a spare cylinder body for christmass.

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In my opinion, you should absolutely not use that cylinder until it's been replated. An OEM Suzuki piston will be fine, as will many of the diffrent aftermarket ones. Hate to break it to you, man, but 100% of them are made fron a very similar aluminium high silicon alloy. Hope you don't hate each and every high performance piston in the world.

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Lol, thanks guys excitable has made me see the error of my ways,

I want to do things properly and already have full top end oem kit, the thouget of wrecking the bottom end does scare me as I have expensive tastes 🙂

I'm supraised they are all Ali, the suzuki one looks and feels a lot more rugged than that.

Learn summit new every day!

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It's back and I'm very happy with how it looks, it cost that much because they had to build the casting up where it had been fettled out so it didn't catch the ring for sale.

I shall pop it back together later.

What pressure can i expect at a compression test?

And I presume through the exhaust I'm looking for linear scrapes?

Also there is a small nick in the Ali exhaust piece that has been stoned back n all.

Thanks for your help guys looking forwards to a ride this weekend 🙂

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  • 2 weeks later...

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