2 stroke maintainence

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Peter1230

Peter1230

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Joined
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central coast NSW
Hey guys,
i know this probably aint the prefect site to post this on but yeh...

i have just bought a cr125 2003 model 2 stroke
i am aware of the top end rebuilds that need doing frequently.
and they like good oil.
but wat else should i be aware of? i have heard the cod rods and main bearings go if not enough oil is in the fuel? the mixture is 32:1 but i will do 31:1 so more oil is in it to lube it.. it wont have the same go but still a very fast bike.
so yeh im just after maintainence tips.

Thanks!
 
well the conrods and bearings usually go from not enough oil in the gearbox/bottom end as for fuel mixture i run 50:1 and ive done probly 100+ hours on my old 80 just make sure ya always lube ur chain cuz they rape chains so qwuickc
 
ok so keep the right amount of oil in the fuel and good gearbox oil...
any other helpful things would be great!
 
if ya just putt around your going to foul plugs nice and quick so dont putt around too much try riding in band ... u might kill yourself but will save having to take 5 spare plugs when ya go riding ... instead you only take 1 spare plug
 
let the bike really warm up before you thrash it, don't revv and stress a cold engine, don't do burn-outs, they kill top-ends, clean your airfilter often, Two-strokes suck in a lot of air, and if the filter is filthy they will suck in dirt by the bucketloads. other than that you must keep an eye on your jetting, lean jetting equals less fuel in the mix, which in turn equals less oil...
 
umm, mate, i think ull be de-lubing it if you go down from 32:1 to a 31:1, cuz (for eg) 32:1 is 32 parts oil to 1 part fuel, so if you go down u will be de lubing the engine.

and heres a handy tip: for my rm 80, we bought a 10 litre drum so it was easy to measure. so if we run ( for eg.) 32:1, we can just measure out 320 ml and then fill the rest with straght fuel.
 
the easiest way to calculate how much oil you are gonna mix is doing it in percentage, I always mix my bikes with 3% oil.

and 32:1 does NOT mean 32 parts oil, that would equal 32 gallons of oil in a 1 gallon of petrol, it's the other way around, 32 parts fuel into 1 part oil...
 
31:1 would be adding more oil but cause it is 31 parts petrol to 1 part oil... and 32:1 would be 32 parts petrol and 1 part oil... just wondering if it will help the engine last a bit better with a tad more oil.
 
I've had my -96 KX125 for 7 or 8 years now, replaced 5 pistons, the thing still rips like crazy, I run Motul 800 oil only and mix it at 3%, as long as you don't goon ride it you should be fine, by top-shelf oil, let the bike warm up, don't torture it, ride it like it's supposed to be ridden and it should be with you for a long time.
 
nope, the bottom end is still the original from 96, no play in the rod, perfect compression, starts on the first kick always, the tranny still shifts perfect. the only things that have failed are the fork-seals.... and I credit the problem free years to good maintenance.
 
on the 03 cr 125s watch the jetting as they had a few problems in that year.
the carbies they used wernt the best but still do the job fine,the slides have a problem with getting stuck or sticky so its a good idea to check it every few rides and make sure its nice and smooth.also id be running the pro gear box oil(its red) as hondas 125s run a metri clutch and needs the higher quality oil,check your powervalves every once and a while as hondas run a compltely dif valve setup to other companies and tend to build up a bit of oil in there
 
i should be able to check powervavles with my manual right?
That would tell me what i need to do to "service" them, correct?
 
yeah the manual should show you how to maintain the powervalve. make sure the actuation of it is set correctly, as if you get it wrong, you will have no bottom end power, and it will run like a pre-powervalve air cooled pig...
another thing with the cr125's is that they have a wee appetite for reeds... might be worth replacing them... once they wear, you will lose a bit of bottom end clarity which can be confused with poor jetting, and they will flutter too much at high revs, causing a bit of "fluffiness"...
oh and Liljohn, my apologies for being curiously argumentative, but dont two stroke engines recieve their bottom end, top end bearings and con rod lubrication from the oil in the fuel mix? i may be well off the mark here, but i thought the air/fuel mix went in through the reed valve, sucked in under the piston, swirled through the bottom end cavity between the cases under the piston, (thus lubricating bearings and cylinder) and then into the cylinder itself through scavenging or transfer ports, usually on the sides of the bore before being ignited on the firing stroke?? is that the reason for fourstrokes having oil rings, and two strokes dont, as the bottom end doesn't run in a constant bath of oil? like i said, may be way off the mark here, more curious than anything...
oh, and with the bike being 5 years old, check all the usual bearings and repack em with grease.... ie: headstem, swingarm pivots, shockmount pivots, axles, wheel bearings etc...
 
take off the top end then put it up to the light and look for any wear in the cylinder, if there is some minor scuff marks a hone might get it out and you'll be sweet for ages, if there are scratches then you need a resleeve or your rings will go really fast and you could seize the engine (happened to my RM250, cost $1500 to fix).
 
thump*140 said:
yeah the manual should show you how to maintain the powervalve. make sure the actuation of it is set correctly, as if you get it wrong, you will have no bottom end power, and it will run like a pre-powervalve air cooled pig...
another thing with the cr125's is that they have a wee appetite for reeds... might be worth replacing them... once they wear, you will lose a bit of bottom end clarity which can be confused with poor jetting, and they will flutter too much at high revs, causing a bit of "fluffiness"...
oh and Liljohn, my apologies for being curiously argumentative, but dont two stroke engines recieve their bottom end, top end bearings and con rod lubrication from the oil in the fuel mix? i may be well off the mark here, but i thought the air/fuel mix went in through the reed valve, sucked in under the piston, swirled through the bottom end cavity between the cases under the piston, (thus lubricating bearings and cylinder) and then into the cylinder itself through scavenging or transfer ports, usually on the sides of the bore before being ignited on the firing stroke?? is that the reason for fourstrokes having oil rings, and two strokes dont, as the bottom end doesn't run in a constant bath of oil? like i said, may be way off the mark here, more curious than anything...
oh, and with the bike being 5 years old, check all the usual bearings and repack em with grease.... ie: headstem, swingarm pivots, shockmount pivots, axles, wheel bearings etc...
Click to expand...

the gearbox oil also does the bottom end aka the crank and big end and shizzy like that down there it also lubes ur g/box and clutch and all that .....

not sure about the fuel swirling around down the wouldnt it contaminate the gear box oil??

tell me if im wrong this is what ive always believed right after pulling apart a cr250 motor
 
Thump140 ..... You're spot on dude ...... 2 stroke cranks are lubed solely by the oil in the fuel mix (unless they have a separate autolube system which runs straight petrol in the fuel tank , has a separate dedicated oil tank and pumps oil thru the centre of the crank) .... The spinning crank of a 2 stroke keeps the fuel atomised as a gas but the oil doesn't stay in suspension ... it separates , drops out , and coats everything ....... IF the fuel to air ratio is right ... the above happens ..... but if it's too rich .... the wet un atomised fuel "washes" the oil off the bore , rings , seals and bearings causing rapid wear ..... Leaving the choke on too long does the same thing .... as does loading an improperly warmed up engine so don't ride any 2 stroke until it's fully warmed up and the choke is turned OFF .... Also do not run the engine if the carb is overflowing (float level too high or float needle jammed open) or even too rich as you'll be causing it to wear faster due to bore wash ...

Two strokes rely on the reed valve to prevent fuel charge from being pushed back out of the crank cases and thru the carb under load .... That in turn allows the down stroke of the piston to be used to pressurize the crank case above atmospheric and force the charge up thru the transfer ports ... The effect is that of a positive displacement pump aka supercharger and is responsible for the rapid throttle response .... coupled with the expansion chamber ... 2 strokes are force fed thru the front and back door ....

Because of the fact that the crank case is pressurized .... it's critical to have a perfect sealing crank centre case gasket , crank end seals , cylinder base gasket AND piston rings that aren't worn and are giving the maximum possible compression with the least possible leak down rate .... Racers used to renew the rings between every single moto to keep the power as high as possible .... If they didn't stick to their rigorous ring change schedule , they gave their opponents who DID , a distinct performance advantage ....

The crank big end bearing of a 2 stroke engine is critical .... Since they are not bathed in straight engine oil , they don't get the cushioning/ damping effect that it offers .... Therefore up and down rod play should be kept to the absolute minimum to prevent the rollers and roller cage from getting "hammered" into the crank pin or the bearing roller cage from shattering and fragments of shrapnel gouging the bore , welding the rings into their grooves and embedding into the piston crown and head .... I'm sure someone reading this will have experienced a typical 2 stroke blow up .... :p
 
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