Here we rebuild a failed Rotax Max FR125 Senior 2 Stroke Kart Engine The engine suffered a bearing failure on a practice day and some how the major components survived so it might live again!
always remove main bearing when big end fails ,u will find bits off bearing behind it ,thrust washer goes on water pump shaft not idle gear ,good video
Very informative video other than washer goes under water pump gear ,gear side crank seal should face outwards and water propeller seal should go flush with the case allowing weep hole to be clear,to remove old water seals there is a small hole where you can tap them out with a small diameter pic, case seals have 28 and 25 I/d numbers on them.
Great video, it's given me a lot of confidence to work on my own engine when the time comes. Do you have any videos of tuning a rotax engine / carb etc. Am new to karting and my kart sounds like it running bit rough. Thanks
I did many many rotax 122 engines back in around 2001 to 2005 I worked at an aprillia dealership. Many made over 33 bhp with a nice expansion chamber They came with a plastic cage on the main bearings, we usually put an NSK bearing , there was a lot of failures of these. The mitaka cylinder kits were a good replacement for the nikasil aprilia bores. The crank is actually quite easy to align if you have a press. And make sure the seal on the gearbox side of the crank is fitted backwards, or it will draw oil from gearbox 😳 You recently put the haltech on my Holden. Hello.
so i am rebuilding my rotax fr 125 right now i just got a 53.97 piston and i orderd a 53.98 the piston to wall clearance on the 53.97 i have is about 0.045 to 0.050 is that ok i do not race i just go have fun so i figured that would be ok and then do you recommend doing anything to the large starter gear / clutch it has no key to stop it from spinning on the shaft i put 637 locktite bearing retainer on mine not gonna lie do you think that was a good idea or bad idea im just worried about the clutch spinning on the shaft and loosing power i do still have the old style clutch too with the holes in the side are the new ones any different and how long do you think the bottom con rod needle bearing can go without replacement that is one of the only ones i have not replaced and probably has about 50-60 hours on it
@@killercane5183 You really want to do that con rod needle bearing if possible. It’s not pretty when it fails. All the aprilia engines I did had a keyway on the crank.
@@hoonaticbloggs5402 that is weird the aprilla engines do have a key on the non gearbox side mine just has a taper that the centrifugal clutch gose on with no key just weird to me and that bottom bearing I inspected it i has no play the race is in good shape so i thought it would be ok you really recommend swapping it im just really scared of having to line up the crank lol
@@hoonaticbloggs5402 u built these right can i ask you do you know any way to make these make any more power past 33hp i have this on a race kart and always looking to make more power i think they make a 150 kit for these but its like 1500$ for cylinder,piston,rod i think thats a bit expensive for whut it is but i might have to go for it
