Taking apart my KTM Duke 390 motor to replace the power output shaft and on the way in noticed a little side play in the piston rod. I have less than what you're showing but had no idea until I checked out your video. Just wanted to say thanks for posting this, it really helped me!!
'up and down play' is rare the bearings usually just explode plus you need side to side play for when everything expands; if you have a tight rod or one with very little side to side play it's mostly like to seize up, snap rod etc
I was taught the same thing when I first started wrenching back in the day, side-to-side play was perfectly fine, up and down play was not. I learnt that this was indeed wrong the costly way, blew some motors because of bad cranks that I thought was fine.
I'm years out of date with this but Maico specify the total movement of SMALL END side to side, big end side to side is irrelevant if the thrust washers are installed and not worn out. I can look up numbers for 1982 940 Alpha 1 as that's the only manual I still have for them. It's way easier to measure before you split cases,Push rod to side, measure movement. Push big end against other flywheel, measure movement. Average is what you got. If you don't have enough side clearance big end will probably be under lubricated. Rick was still living in New Mexico last time I was in touch with him (several years ago now) My 490 was dyno'ed at 63bhp at the wheel, it had been rebuilt for the 1982 Le Touquet beach race in France. Pretty sure your reading the manual wrong, have you had any training to re-build cranks? The 'Big 4' tend to give less information, clearances and lengths are for crank building. I really liked the YZ490 but with only 4 gears it was always limited use and on some tracks just couldn't be geared right. 125mph 'in the woods' on a big bore two stroke isn't as much fun as it sounds, plus, Metzelers lose the knobs off front tyre
Interesting video, I have seen quite a few videos where excessive crank end play and excessive big end play or sideways con-rod play features in work that must be corrected later. Is this an indication of engine wear or poor craftmanship? Can I ask you if you know what material has been you on those forged connecting rods the one attached to the left hand crank, as the colouration looks as though it could be a bronze aluminium alloy. And that colour is not just oil stain either becuase mine are that colour and when the oxide is cleaned off it almost looks like a coppery bronze colour.
You should have mentioned the washers to much side to side play is commonly caused by the washers that are made of a soft metal usually Cooper I had a bike that the washers between the rod and crank web was so worn out it split and came apart ! Had to press the crank apart and replace the rod bearing , pin and those washer of course!
Good informative video. I have bandit 1200 , 2006 model and had the same sounds comming from the engine. The bike started overheating and engine died. But now the noise is getting thicker and thicker. The mechanic says its the sound of connecting rod. I guess its the same problem?
Howsit man i pulled my motor apart to change rings there was no play on the pistons and conrod but the one cylinder got sticky as the temperature dropped. Could this be a big end?
ok if i still have the same issue with scraping walls after changing some stuff, like the oil pump, starter clutch cause why not, then i'll just replace this.
So, the problem is going to be the piston being able to go further up and down than it could as well as putting stress on the wrist pin unevenly. I wouldn't trust it. Depending on how the piston will now move, it could bang off the head. The bike is likely to run and who knows how long it would run for. I started a husqvarna 250CR 81 that the connecting rod was pink from rubbing on the crank, the piston had a large chunk out of the top because someone put a bolt through the side spark plug that was too long at some point, no compression and every bearing spun in the engine. So even if it runs you can't be sure what damage it may be doing. If you put the piston in can you move it in place up and down by any amount? These things can expand and the distance we are looking at between the piston and the top of the head is around 1mm or .40 or so inches so a little bit of movement could bang off the head. It could be fine and run also, I don't know how bad it was, but its just a question of taking the chance vs. the money it would take to replace the rod.
@@Maicowerk but when the bike gets hot there will be less play? I think this is how the cam works too. There can be a little play because the engine warms up.
The side to side play is called "rod gap" some (meaning very few) engine manufacturers publish the clearance tolerance for rod gap. But what I really want to know is, how come there is no bushing for the rod gap on both the big end and small end of the connecting rod. GM LSx car engines don't have them either. I've been researching for a week, so far no answer.
because the rod surface doesn't touch the crank! up and down, not side to side is what matters. when the motor is assembled, does the rod move side to side? no. its "locked" in place by the engine forces on the rotating assembly. with 2 strokes anyway, you need some some play to let in fuel + oil to cool everything down. ditto for the pistons... can't be too tight like a 4 stroke motor.
hi. I performed 67 hours on my exc tpi 250, and I have side to side play about 2 mm, it's ok? up and down I don't fill any.. but side to side it's fillble. I;m so confuse about that, realy I need to replace crank in 67 hours done?
I would say yes. My 2 stroke blew a couple of days ago, and before that, I could hear a tick as if it had valve rods. Normally, it would sound crisp and clear until that noise started, and later one day found myself walking 7 miles back to my truck. Turns out that bearing exploded and seized my rod to my crankshaft.
depends on how much side to side. The manual should tell you the side tolerance. If you can get it to scrape off the crank pushing it to one side when you rotate the crank definitely not good.
Manufacturers specify how much side play is permissible. It’s simple to measure. Simply observing some side play means nothing unless you measure it and compare it to specifications. All crankshafts will have conrod side play.
side to side play is important because it determines how much oil "flows" through the big end bearing.The wedge between big-end and cranck/shim let's the oil out.Too much and the bearing doesn't hold enough oil pressure, too little and the bearing can't get rid of the oil fast enough for cooling. (usualy because of wear it will be too wide)Courtesy off; Muscle car diy and John Baechtel
Cost of a connecting rod varies with the bike. Expect $100 to $200 plus labor to replace which could be $40. Side to side depends, there are tolerances specified by the bike. If you can push it to the side and it scrapes off the crank it's definitely bad. some bikes, like husqvarna, had washers on the piston instead so they had larger side to side than other bikes.
Tollerances are different for each bike. This one is actually ok but if it scrapes off the crank its definately bad. People only look at up and down but side to side can also be bad
Listen don't buy any other brand of crank other than oem your engine will love you spend the extra money and save you a headache from installing a cheaply made crank ( hotrods ) are made in china which is bad.... ( Prox) are made in Japan which is good (wiesco ) made in tiawan but assembled in China so thats no beuno
