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Post by eean on Mar 31, 2011 20:18:00 GMT
any tips or how do you do yours? been told to fit into case first then fit cases together tapping gently with a rubber mallet, reputable source and he has fitted a few like this successfully, but how do you do yours I've always heated mine up with a blowtorch and fitted to crank first, risked it but it is wrong way isnt it
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Post by amazombi on Mar 31, 2011 20:35:38 GMT
No, it's not. It's the officialy correct version. You heat the bearing and use a tube which sits on the inner ring only to drive it onto the crankshaft. It's an interference fit there. Then you heat the flywheelside casing and fit the crank with the bearing into that one. This is designed as a floating fit at the engine's working temperature. Then you slide the crank through the driveside bearing where it's not a tight fit and easy to fit. That's the way described in the official Piaggio workshop manual, and it also makes sense because no bearing is unduly stressed by being hit with a hammer.
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Post by eean on Mar 31, 2011 20:42:25 GMT
Cheers for that Mathias, how do you heat the bearing? been on the skf site and it suggests using the oven but no higher than 125 degrees C
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Post by amazombi on Mar 31, 2011 20:47:41 GMT
I use an adjustable electrical blowtorch with the temperature preset to 150. Cost about a tenner more than the basic one, and well worth the money. I also use icespray to cool the crank down. If all that is done correctly the bearing simply falls into its place. Maybe that's a bit overkill though.
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Post by eean on Mar 31, 2011 20:53:05 GMT
ok thanks, but after reading on the skf site saying you should not use an open flame to heat the bearing I'm reluctant to do it and fancy the oven now and put crank in the freezer maybe
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Post by amazombi on Mar 31, 2011 20:58:35 GMT
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Post by Jimmy D on Mar 31, 2011 21:18:31 GMT
I put the bearing in the freezer overnight (probably overkill) and the engine case in the oven for 5 mins at about 220C.
Bearing dropped right in - stopping about 2mm short of all the way in. I had an old bearing of the same size that was damaged so put that over the top and whacked that with a rubber mallet to get it fully in position.
Bear in mind you have around 2 seconds before the bearing is heated from freezing to boiling and is therefore locked tight.
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Post by tony on Mar 31, 2011 22:28:10 GMT
No, it's not. It's the officialy correct version. You heat the bearing and use a tube which sits on the inner ring only to drive it onto the crankshaft. It's an interference fit there. Then you heat the flywheelside casing and fit the crank with the bearing into that one. This is designed as a floating fit at the engine's working temperature. Then you slide the crank through the driveside bearing where it's not a tight fit and easy to fit. That's the way described in the official Piaggio workshop manual, and it also makes sense because no bearing is unduly stressed by being hit with a hammer. But remember that the crank is pulled hard to the drive side bearing.. so be careful not to load the flybearing if using this method Lauro makes a fantastic tool if you are using a solid bearing on the fly side with his crank... ( i would use it on other cranks too) What you do is fit the 6303... bolt up the crank with a primary... Fit the 6204 into the fly side... fit a gasket and then use the tool to pull the crank into the 6204 fly side and thus closing the cases at the same time... You therefore have located the crank correctly and have not loaded the bearings laterally.
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Post by amazombi on Apr 1, 2011 8:37:51 GMT
You are aware that everytime you warm up or cool down the engine the ally crankcase expands and contracts much more than the steel crank, which would lead to lateral loads? Just like the flexing and bending of the crank around the big end pin when the engine is running leads to a permanent in- and out movement of the crank in the bearing. Because of that the flywheel side bearing seat of the old style ballbearing is not a press fit, and it's not secured by a circlip either. At working temperature the bearing floats from left to right to compensate for heat expansion and flexing. That's why quite a few people actually prefer to use the later design with the needle bearing. Even though it doesn't like squint as much as a C4 ballbearing it does have it's advantages.
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Post by tony on Apr 1, 2011 11:28:31 GMT
Are you saying that if I fit a solid bearing like a 6204 to a flywheel side it moves during engine running?
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Post by amazombi on Apr 1, 2011 11:54:46 GMT
Yes. It was designed to do exactly that. That's basic engineering. How else would you take care of the different expansion rates of the materials and of the flexing of the crankshaft? There's nothing wrong with that, it's done in quite a lot of engines. One side of the crankshaft is supported by a bearing which is fully defined in all directions (smallframe driveside: bearing position is axially definied by bearing seat, laterally by the circlip, the shoulder of the crank's shaft and by the primary on the other side), the other side is definied axially only to compensate for the above.
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Post by eean on Apr 1, 2011 16:23:20 GMT
Cheers Mathias, I'll go and dig my hot air gun out and give that a try, thats when I get this other bastard off with the new bearing separator I just got lol. Jimmyd, its the getting the bearing on the crank thats the hassle mate not getting it into the casing but thanks anyway Tony, I wish I had one of those Lauro tools to have a go with, sounds good Thanks everyone for the pointers Its got to be the smallframes bastard bearing to fit this ;D
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Post by amazombi on Apr 1, 2011 17:11:13 GMT
I haven't seen Falc's tool, but I guess it is a more elaborate version of a length of tube whose inside diameter is a mill or so larger than the shaft diameter. Outside diameter needs to be smaller than outside diameter of the cases you use, in your case that would be less than 32mm. It sits on the inner ring of the bearing, and you use the flywheel nut to pull the crank in. Have a handfull of spacers ready to use when you run out of thread. You fit the oilseal after the crank is in place. With a lathe and a lenght of round ally bar stock this could be made somewhat nicer, I suppose.
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Post by eean on Apr 1, 2011 19:42:41 GMT
;D ;D ;D I'm a happy bunny ;D ;D ;D sorted it, ok I was changing crank and bearing, heated the case to get out and with my mate saying put bearing in cases first I had already fitted it so didnt have to heat case twice etc., then put this thread up to see what everyone else does, looked for my heat gun, couldnt find it so thought well I may as well get the bearing back out ready so heated the case with blowtorch, as I was doing this I thought hang on, this should heat the bearing via capillary/transfer of heat action shouldnt it without discolouring it so kept the heat on a little longer to heat soak the bearing, got crank ready, tapped the case on worktop to get it back out and quickly put it straight onto crank and straight back into the case and left it to cool down naturally, re oiled it and put cases back together and I swear its the smoothest running crank I think I've ever had lol
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Post by Tommy on Apr 1, 2011 19:47:15 GMT
You are aware that everytime you warm up or cool down the engine the ally crankcase expands and contracts much more than the steel crank, which would lead to lateral loads? Just like the flexing and bending of the crank around the big end pin when the engine is running leads to a permanent in- and out movement of the crank in the bearing. Because of that the flywheel side bearing seat of the old style ballbearing is not a press fit, and it's not secured by a circlip either. At working temperature the bearing floats from left to right to compensate for heat expansion and flexing. That's why quite a few people actually prefer to use the later design with the needle bearing. Even though it doesn't like squint as much as a C4 ballbearing it does have it's advantages. This has happened to me vespatronic flywheel used to move and rub off the flywheel cowl as the engine warmed up,flywheel and primary gear cog was tightened up 50Nm so then i taught flywheel side crank bearing had gone stripped motor to investigate, bearing seems fine.So you are saying this is normal then amazombie
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Post by amazombi on Apr 1, 2011 19:55:15 GMT
Heat expension is something around 0.2 of a mm. Enough to put sideload on a bearing if the bearing doesn't move, but not enough for the flywheel to start touching something. Check distance to flywheel cover when cold, if it's very little check cover for small dents or for elephant footprints (there are elephants in Ireland, aren't there?). If cover is as it should be I think you'll need to check inside the engine again. Check driveside bearing too, is the circlip there? Does it have excessive sideplay?
Eean: Did you actually manage all that without burning your fingers?
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Post by eean on Apr 1, 2011 19:59:45 GMT
Mathias, I did mate with my heatproof gloves on ;D
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Post by Tommy on Apr 1, 2011 20:34:11 GMT
Heat expension is something around 0.2 of a mm. Enough to put sideload on a bearing if the bearing doesn't move, but not enough for the flywheel to start touching something. Check distance to flywheel cover when cold, if it's very little check cover for small dents or for elephant footprints (there are elephants in Ireland, aren't there?). If cover is as it should be I think you'll need to check inside the engine again. Check driveside bearing too, is the circlip there? Does it have excessive sideplay? Eean: Did you actually manage all that without burning your fingers? Checked all bearings,circlip and made sure everything tightened up 50Nm and everything seemed fine last time will check everything again.
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Post by jonnysnatchsniffer on Apr 2, 2011 8:46:47 GMT
ah the beauty of an nu204, no fucking about, cases come apart and go back together with no heat and no fuss granted the 6204 will spin faster ok to 38000 rpm or so but the nu204 is good for at least 16000 and also has a grater axial load tolerance around 3-4 times that of the 6204 the only reason i can see to use the 6204 is price or if you have a 20000rpm rev monster or am i missing something ? dont say brain cells cos the 3 i have seem ok
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Post by Tommy on Apr 2, 2011 11:17:48 GMT
Think i may have found what is causing flywheel to move slightly outwards when engine warms up fully and rub the flywheel cowl the flywheel side bearing wasn't on the crankshaft cone fully off by about 1.5mm would this cause the problem? can anyone confirm this for me? sorry for hijacking this thread
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