Hi .I was fitting my new bgm crank tonight n i fukd up ,I've fitted 2 before with shitty old cranks and went together smooth as cream but this time iv had a big hitch .The bearings went in fine and with out a problem. I then froze the crank and heated the cases to attempt to get the crank in the vari side then the fly wheel side on that was bein heated at the same time. As i lowered the crank into the vari side it went most of the way in then i wobbled ,it touched the side and expanded i'm assuming. Causing it to stop about 3 mm from being fully seated .the bearings and crank are brand new i gave the crank about 5 sharp taps with a bit of wood covering the threads, hoping it would slip in but it didnt . how can i ensure it seats propperly next time .should i get a new bearing .or should i just lower the other half on and tighten it down until it fits snug .im guessing not the latter as pressure side ways on bearings aint a good idea hence i shouldnt of hit it . dan
If you hav`nt fitted the magneto side yet (the crank is stuck in the vario side) heat up the vario side and get the crank out. Remove that side bearing (the force of removeing and improper fitting will have indexed the side and stressed it) put a new bearing on there (freeze down that crank and heat a new bearing up in a bath of hot used 4t oil and drop it on) then start again :mrgreen:
lol nibs ive done this before, ,dw m8, learn from your mistakes..your now more experienced in fitting a crank so next time this shouldnt happen
Yh lol shit realy does happen ,waste of 40 quid but you're rite ill be more precise next time .Thanks dwarf ,i think your talking about the method in the haynes wich i think i SHOULD have used lol .I put the bearings in the cases first rather than the bearings over the crank then freeze that and heat the cases and insert I shall use this method in future . My main thing was i wasnt sure weather i needed new bearings but now i do .Thanks again
i prefer the bearing in case method myself.. but each to there own. just gotta be fast and spot on with temp's or this will happen again and again. knowing what is best to do in whatever situation is all learnt through experience. doing it wihtout everything equaling temperature would have saved this happening in the first place, simply nock the crank out holding the crank race on the other side as it would only take a tiny tap to remove the crank and heat the bearing inner a little more/more evenly
i do the same way as you too minor and heat is deffo the key i nearly fooked up my first time but noticed before i even tryed putting it in that the crank had heated up a bit. i learnt from my mistakes andnow do crank fitting on the kitchen table lol
Ive only ever put the bearings in the case first? this works for me i'd be scared to try somethign different incase i fuucked it up lol
i used to do it bearings on crank then assembely into cases (the normal practice basicly) singles you get away wiht bearings first if you know what your doing, means the end float is amazing without a single nock on the crank (again if you know what your doing)
I was told by a mechanic that used to fit my crankS to heat the cases till i can spit on them and it sizzles but ive never realy been told how long to freeze the crank/crank n bearings. Bearings are never a problem to get in the case they go in EASY its jus the crank afterward i struggled with .So i thought it might be easier to do the bearings over crank method as im fine at puttin the bearings in . How long should i freeze the items im cooling anyone. thanks
this "mehnic" has basicly gven instruction on how t warpcases... th trick is just hot enough to get the bearng in fricton free BUT without getting it to th pointit starts to move abot (supprisingly close to instalation temperature) bsicly heat it bit t atme n ke trying the bearing'... i dont freeze the crank/barings anymore.... best if your learning out, try every way you can/have been told and make your own mind up about it all... just DNT get it that hot ffs
its a joke aint it lol he studied as a bike mechanic and worked as for 1 for like 15 years n he still aint got his shit right. jus shows you not to trust a certificate i spose. thx
ye, 15 years backwards from now and they still wouldent have done 2 stroke rebuilds.. 4t mechanics shouldent tougch 2 strokes simple as.. there built differently and confuse mechanics as they cant see past the parts infront of them
i agree my mates works with suzuki bikes fuck me he has not got a clue about 2 stokes they should train them with both
at college we learn about both but they are pretty much all 4 strokes we work on like 4t zips and ybrs etc. But we should have a dyno in our new work shop so should be sick, I'm going to stick my runner on there as it is now and then try it after a 172 is on and see what the gains actually are sorry for hijacking thread LOL
rite had another go 45 quids worth of bearings n it went straight in was realy stiff at first but tapped it a few times until it spun free as a errrm spinning top fuk knows .yh all good now
