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348 engine problem.


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#1 mrandy800

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Posted 29 March 2011 - 09:49 PM

Hi there my monty friends i just got myself a 348 as a little project i broke side casing off and noticed a lot of damage on the crank shaft and the inside of the casing just wondering if anyone has any ideas whats gone on here and is there anything missing off the end of the shaft i looked at a few pics on the net but cant really see what the end of the shatft is meant to look like to see what meant have gone wrong hope some one can help me thanks Andy


http://s1235.photobu...f433/mrandy800/

Edited by Andy, 29 March 2011 - 10:09 PM.



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#2 belldane

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Posted 29 March 2011 - 11:11 PM

Hi there. Just let me say that your little project has turned into a big one. What has happened is that the end of the crankshaft has snapped causing all sorts of untold damage in there without looking at it closer. At the end of that shaft there is a small flywheel attached to it and when the shaft broke the flywheel has continued to spin inside the case causing that big round scrape inside the case. I hope you got the bike cheap !! and obviously who ever sold it to you must have pulled the cover off and removed the broken bits before putting it back together and selling it either wise the motor would have probably not turned over. For a start you are up for a new or second hand crankshaft, another flywheel, most probably new cases and when you split those cases there could be damage to the gears as that motor appears to have been traveling at quite a few revs when the shaft broke and everything would have probably suddenly stopped. My suggestion to you is to find another motor, try to salvage as many parts as you can from your existing motor and rebuild one out of the two. Not really good news but I hope it helps. See ya

#3 mrandy800

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Posted 29 March 2011 - 11:52 PM

Or great lol cheers matey the side cover had been welded on the outsde i thought it had just be built up with weld ready for reshaping due to wear from gear changes now i no different like you said the shaft has broken and in turn it split the side casing.

Would the bike run with this little fly wheel and shaft broken off because when i got the bike the gentlemen said it just stopped and he didnt no why ??? nothing looks damaged in side clutch looks ok and selector to but maybe breaking the crankcase would unearth more secerts.

Cheers belldane thats a great help even tho it was bad news haha

Cheers Andy

#4 belldane

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Posted 30 March 2011 - 12:34 AM

Yes, the bike would run without that flywheel but it is the flywheel that gives the motor the torque and I really have no idea how the bike would perform without it. You have another problem, though. At the end of the crankshaft there is a big nut that holds the flywheel in place and stops the primary gear from coming out. The primary gear is on a tapered shaft, that is no woodruff key to stop it from spinning loose when things are going on in there. So, sorry but no cigar. You would have to do a blotchy job and weld the gear onto the shaft but I would not recommend it as there are no guarantees how the bike will run without the flywheel. The gentleman you bought it off says it stopped !! Bloody oath it would stopped quick smart and I reckon he knew what the problem was other wise where has the flywheel gone ? Which country are you in. I might be able to give some some leads to source another motor. Your other option is to take the bike back to the gentleman and tell him to stick it you know where and get your money back . See ya Manuel

#5 belldane

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Posted 30 March 2011 - 03:44 AM

Hi Andy. On reflection I may have been a bit harsh on the bloke that sold you the bike as he may have also bought it with the problems you are having at the moment. If that is the case and the gentleman accesses this forum, please accept my apologies. Thanks. Let me know if I can be of any help. See ya Manuel

#6 mrandy800

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Posted 30 March 2011 - 01:01 PM

Yeah maybe he did matey but al never no so looks like am after a engine god knows were i start looking for 1 off them ??. I am from the uk matey shame sounds like you could have been a great help with sourcing a new motor.

Looks like al have to put it on the back buner till i can get another motor

You been a great help belldane even tho you were the bearer of bad news :D

Cheers Andy

#7 bigshineybike

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Posted 31 March 2011 - 11:59 AM

[The good news is that engine didnt stop that quick.
The shaft ground itself to a point and that means there was an almighty noise while the very round flywheel simply rubbed its self to a halt in the casing with I expect the engine running on.
Do you have the flywheel?
I have a spare in Surrey if its of use.
I saw a photo of one of these that had been welded, not a bad repair until you need to do the crank seals!
You will need to do the economy maths but francetrialclasssic do sell a half crank as this is a common enough problem with these engines.
I was very lucky to buy one on ebay recently that came from Sandifords.

In my opinion the woodruff key is too big for the diameter of the shaft. if the flywheel is not a good enough fit on the shaft or not torqued up enough it vibrates which in turn opens the keyway up leading to splits and then to catastrophic failure of the shaft.
I have a spare engine that has run for a good few hours with the chunk of shaft that splintered off, soldered back in place and hand dressed with a file to be a tight fit.

There are always engines on Ebay, If you do buy one be looking out for the condition of the crank

#8 bpilgrim

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Posted 31 March 2011 - 06:22 PM

Hi,

I have a 348 with your very exact problem, before I acquired it, the flywheel had snapped off with quite a bit of the crank, and has eaten part of the casing, as well as putting a hole in the front of the casing (which has been fixed with a very hard filler). I have ridden my bike (quite aggressively) for about 20hrs and it has been fine. The primary gear is only half on the end of the crank, and it hasn't broken off yet...(I hope I haven't just jinxed my next trial!) It also seems to run fine without mass of the flywheel, I believe riders used to skim the flywheel anyway to take some mass off it and make the bike rev quicker. I'm not sure about the torque, as I haven't ridden a 348 with the flywheel on, but I'm sure it would make a difference.

I have (eventually) managed to get my hands on a complete 348 engine (with an intact crank and flywheel), so I plan to swap the crank as mentioned above.

Here's some pics off my bike: (if you skip to picture 29, that's probably the best pic of the crank, and the primary gear only just on it)
https://www.facebook.com/album.php?aid=59664&id=1497248461&l=b591644882

I've also got some electronic copies of 348 manuals if you need them.

Ben

#9 mrandy800

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Posted 31 March 2011 - 09:50 PM

Cheers lads, Ben i see yours has a nut on the end now has the crank been threaded for that or has it been welded on???

Does this missing flywheel make a noticable difference or not, i was thinks about breaking it up and selling the bits on ebay to make me money back but now am starting to think other wise may sort it out now, but i still need a piston i got a price from inmotion and was not expecting 200 plus the 12 pound for the little end bearing so i dont know.

I thought my 280 pro was pricey for bits.

Cheers Andy :thumbup:

#10 feetupfun

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Posted 31 March 2011 - 11:51 PM

Cheers lads, Ben i see yours has a nut on the end now has the crank been threaded for that or has it been welded on???

Does this missing flywheel make a noticable difference or not, i was thinks about breaking it up and selling the bits on ebay to make me money back but now am starting to think other wise may sort it out now, but i still need a piston i got a price from inmotion and was not expecting 200 plus the 12 pound for the little end bearing so i dont know.

I thought my 280 pro was pricey for bits.

Cheers Andy :thumbup:

The motor is still nice without the flywheel. I test rode a friends 348 that had the flywheel removed (deliberately) and I did not even notice anything different on his at the time - he told me about it later (I ride a 348 with the flywheel in place)
There is nothing good or bad, but thinking makes it so

William Shakespeare


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#11 toofasttim

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Posted 05 April 2011 - 12:15 AM

Come to think of it the 330 did away with that flywheel.

#12 belldane

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Posted 10 April 2011 - 07:48 AM

Hi Andy

If you are going to weld that primary gear I suggest that you make sure all six gears engage correctly and put new crankshaft seals before you do anything. To split the cases at a later stage will be an angle grinder job and you will need a new crankshaft. By the way the best of luck with getting the primary gear off. It can be a real *******. Manuel




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