Kmx help needed..

[Medicinal_Motocross]

Hi all, im new to this site i have a 94 kmx 125 which i have owned for 6months now im looking to get the engine rebuilt as i can hear my small end bearings worn, i have 2 spare engines but one has no numbers(dont fancy putting it in my road bike) and the other was heat seized barrel isnt that bad damaged few scratches & a lip by exhaust port i havent got round to taking it to bike shop ask his opinion on whether it needs plating but guessing it does i have checked the crank play very little or none up&down wise how risky is it using the bottom end which was top end heat seized? i have ordered Koyo crank bearings & seals, a piston kit, small end bearing, gasket set all off ebay... any ideas as to if im gonna be playing with fire using one of these aftermarket piston kits in my road engine? https://www.ebay.co.uk/itm/KMX125-Std-Piston-Kit-/261266625597?pt=UK_Motorcycle_Parts_13&hash=item3cd4b4543d

they claim to have 12month warranty but cant see it myself..i know you get what you pay for and i should of saved to get a Mitaka one or similar but i could only afford that one at the time has anyone had problems with aftermarket pistons? before getting it fitted i would of used better quality rings but someones input would be appreciated.........

[dangerousdave]

[Medicinal_Motocross]

Thanks for your reply. im no bike mechanic by any means but i get the basic principle of how they work its definitely small end bearing in manual says if theres vibration in the foot pegs/frame then bottom end is on its way out i can feel a bit but not excessive.. but im guessing if it is the original engine/bore as its over 26000miles now in need of a full rebuild.. how risky would using the heat seized engine bottom end (which does seem fine con rod play wise) with a usable barrel? it was would it be worth taking to bike shop get him check it or is it a case of he can only see the same as you without it being split? do i need a bore micrometer for mesaure bore/piston clearence or can it be done with a half decent normal micrometer?

[dangerousdave]

[quote="calisi103] its over 26000miles now in need of a full rebuild.. /[quote]

yes, usually by 20K the barrel will be showing wear. some hard-used bikes are out of action long before this.

At 26K its ripe for a rebuild, but if the barrel is undamaged and the wear is not excessive, you may get a few more thousand miles out of it by freshening up the piston/rings.

If you have a fresh piston to hand, run that into the bore and see if there is any clearance on it. If you can rattle the new piston in the bore at all then it needs a replate. This rattle will eventually cause the piston skirt to shatter which will break up and ruin your engine.

However, if you're in any doubt, take it to a motorcycle shop where they do rebores and replating and get a second opinion.

I have myself run a bottom end after the piston seized in the cylinder. I'd do it again. I wouldn't got to the expense to replace all the bearings after a seizure, if they felt ok.

As long as there's no vertical (up/down) movement on the con-rod, and just a few mm horizontal movement then its fine to run again.

You can check the main bearings by checking for any movement on the flywheel too.
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1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50

[nathan k]

Am i missing something here? If it's the small end, replace it. You don't even need to take the engine out the frame. If the barrel needs it, get it honed and use a over sized piston.

[Medicinal_Motocross]

Forgot to mention my shift shafts worn and needs replacing i was planning on re building the one that was heat seized it did have a top end rebuild when my mate acquired it but ran it with no or hardly any gearbox oil& didnt give it chance bed in but all together ive got 3 barrels surely one wont need replating as to nathan k's reply i thought these cannot be honed due to the thin nickasil plating? or can they be lightly honed? if i was to split the crank case i was watching a video on youtube of a guy using a tusk case splitter/crank pusher on a kdx engine is this needed on a kmx or can it be done by hand just the same? i will double check the vertical movement and get a picture of barrel

[nathan k]

[Medicinal_Motocross]

If you mean how bad worn is the shaft then very as in there isnt a spline left on it kind of thing? if you mean cylinder i will get a picture of both spare ones i have tomorrow for hopefully someones advice on whether any are usable or not what kind of noise does it give off if theres piston slap mate?? am i looking at buying a dial indicator or 0-1inch micrometer to measure crank up/down play? its very minimal if any but if the engines going be getting me around every day i want it to be spot on

[Medicinal_Motocross]

Does anybody own a rm 125? or know how much a dynamo and coil pick up sensor would sting me ?

[Medicinal_Motocross]

Quick couple of questions if anyone will shed some light please.. i bought a pair of indicators from Hong Kong and the seller told me they do not flash is this possible? i cant get them to flash on my bike just stay on & is it possible to change gear shift with engine in frame on a kmx? im in the process of stripping my spare engine down but the crank suddenly seems hard to turn cannot be done by hand & its scoring the crank when turning as iv noticed any ideas?