engine out turned into top end rebuild :D rs 125

rite it all started with a splutter at 4-6000 rpm after i put a new 34mm carb on, tryed diff needle positions and jets, even went back to the standard air box. with the standard air box on it was noticeably better at low revs but wouldnt rev over 7000 rpm <like hittin a wall lots of vibration and splutters> decided while i had the farings off to dump the gear oil ! there was only 250 ccs that came out ! my first question was weres the other 350 ccs ? as there is no visable leaks. filled it up with new oil and took for a test run still wouldnt rev over 7000 rpm now dumped the oil today and out of the 600cc i put in i only got 400 cc dumped ? so were has the oil been going ? by this time id had enough and decided for drasratic action lol as its due new rings any way

so took the farings,carb,airbox off and removed the gear changer linkage and rear brake foot pedal






then drained all the fluids from the gear box and cooling systems and removed the oil pump and clutch cable





found some small metallic deposits in the gear oil only slight ones tho




then disconnected the plugs to the igniton pick up and temp sender




then took the front sprocket cover off




then released the tension on the chain on both sides of the wheel



removed the rear brake calliper




and put the bike on axle stands supported by the rear sets




then removed the front sprocket and noticed there is no leak from the output shaft seal




then removed the rear spindle from the rear wheel




then once the wheel was off and the bike was supported on axle stands undone the swing arm lock nut and loosend the allen key bolt the tool used is for a cbr 125 ive filed it down to fit the rs 125



then withdrew the swing arm bolt just passed the crank cases



then un done the the suspension arm bolt that connects to the swing arm




and the upper and lower front engine mount nuts



then supported the engine with a trolley jack and with drew all the engine mount bolts and lowerd the engine to the floor



engines out cant beleive the state of it as it hasnt even been a year since i last had it out



took the top end of the engine and was greeted by this








notice the dent in the piston caused by DET which i think was because of the stepped woodruff key i fitted to advance the ignition and the blow by on the piston wall


cleaned the engine up a bit




just waiting now for the new top end kit too come went with a vertex piston in the end

heres the piston cleaned up

 

Anyone fancy a pint?

 

Good work pego, nice and detailed :snack:

Dont see many bikes with the chain and sprocket on the RHS.

Ended up blowing my 2-stroke 125 quite afew times and became accustom to doing the top end :rant:

 

anyway ^ lols
its been niggling at me about this oil thing so decided to split the cases today and find out what if anything is going on


pics of the crank seal



there was gear oil in the starter mounting bolt were it screws in <hate the smell of this gear oil stinks of piss


all case bolts undone


split



pic of the left crank housing cant really tell if any thing been burning off not much discolouration TBH


there was some slight "blueing" on the crank suggests to me that its been runnin lean


thorts comments and opinions welcome cheers

 

If its burning transmission fluid I think its a sign that a crankseal has gone.

You could do to pressure test the engine when you have rebuilt it to make sure its not leaking.

 

yeah gonna do that cheers
the crank seal looks ok tho only 5 months since i did a whole bott end rebuild bearings seals etc etc
scratching my head on this 1 maybe my bike just absorbs oil lol

 

got the gear shafts out to day and inspected the pinions and needle bearings all seems well



new piston came too




discoverd the balance shaft bearing the one on the left case was shot ! loads of play and rattled when you shake it in your hand lol
just waiting for the new bearing, gaskets and seals to come
just want to say a big thanks to paul@pj for some good advice and excellent customer service :+1::+1::+1:

 

rite update all the parts came to day so started rebuilding
fitted the new balance shaft bearing and crank seal


fitted the gear box in and rejoined the cases



then fitted the pri drive gears with there new circlips and aligned the timing marks



then fitted the new vertex piston



and fitted the clutch and the oil pump gear etc etc


couple of problems along the way snapped 2 crank case bolts whilst torqueing them up
got them out tho got to wait for new ones left the cooling sytem plug out and the case bolt underneath it for now
and once fitted the topend after spinning the fly wheel noticed a leak under the reed block once i took it off again noticed the gasket was ripped how i dnt know lol fitted new gasket bolted down seems to be good now

gonna fit the engine tommorow back on the bike
again thanks to all the people with comments and advice and a big thanks to paul@pj for the excellent customer service and top advice !!! highly recommended !!!

 

Not bad progress there pal considering the time scales.

Are you going to continue trying to get the larger carb working with the engine ? or go back to original and save the heart ache lol ?

 

yeah gonna fit the bigger carb with the standard jets and standard air filter box think that were the probolems came from using the open filter :s gotta few things to iron out the primary drive gears are set wrong gotta align them properly plus snapped two crank case bolts whilst setting touque also snapped a bearing retainer screw needs to be drilled out and replaced am getting on this today so hopefully monday/tues i can begin refitting the engine into the bike

 

Doesnt bigger carb = more air = bigger jets ?

Its a bit of a black art messing about with two strokes ! I gave up with my RGV trackbike as it gets costly when it goes wrong.

 

yeahh put the standard aibox on and rejetted the carb to the standard settings for the rotax 122 engine which is
k57 needle on second from top notch
B40 idle jet
60 choke jet
160 main jet
its rich now but gonna run it in rich to be safe and the do some plug chops think it could go soen to a 155 or 158 main sounds and revs a lot more responsively at low rpm now am made up, hard work tho on me own puttin the engine back in prob the hardest part tbh

 

am gettin to old to be doin all this puttin the engine in on me own has killed me off !! lmao
heres a pic b4 it went in

 

[youtube-vid:1sj90zzh]http://www.youtube.com/watch?v=DAL_Fe38Tz8[/youtube-vid]

well happy with the way it sounds now so much more crisp and quieter then wit the open filter