Crankshaft bearing blew to bits :(

Questions regarding the DR800

Crankshaft bearing blew to bits :(

Postby Monodoggie » Mon May 14, 2018 8:28 pm

I finally finished working on my Big last friday and got it up and running.
I replaced the balancer chain, cam chain and guides + the camchain tensioner. I also got the head and valves cleaned and machined at the local shop. All was fine and the weather was perfect. Shame that I only got to ride it for 2 days before the magneto side crankshaft bearing blew into bits today :tdown:

Now I have to take it all apart again and hope that there is not any significant damage done to the engine. Atleast the stator and magneto + cam and balancer chains seem to have survived without any noticeable damage when I took the magneto cover of to have a look. There were big chunks of metal from the bearing stuck to the magneto, couldn't see the balls from the bearing anywhere so I guess they are still in place.

I didn't notice any strange noise prior to the bearing breaking other than a occasional rumble when idling that would only last for a short time and go away. My last Big also made the same noise from time to time so I tought its normal. Seems it was the bearing on its way out, I wish I would have realised that and saved myself alot of trouble. When I was replacing the chains I checked if there is any play in the bearings but couldn't feel any so I was convinced they are fine :crazy:

Not a great start for the summer but hopefully I'll get her up and running soon enough, wish me luck :D
User avatar
Monodoggie
Virgin - be gentle
Virgin - be gentle
 
Posts: 8
Images: 2
Joined: Mon Feb 19, 2018 2:34 pm
Location: Kuopio, Finland

Re: Crankshaft bearing blew to bits :(

Postby nug » Mon May 14, 2018 11:04 pm

Very strange that it failed so dramatically. Bearing don't always show play in the early stages of failure. The races could have started to break down causing the rumble which then led to rapid failure. Very bad luck.
User avatar
nug
Site Supporter & all round Good Egg!
Site Supporter & all round Good Egg!
 
Posts: 3123
Images: 14
Joined: Sat Jan 23, 2010 10:46 pm
Location: Lincoln

Re: Crankshaft bearing blew to bits :(

Postby BigBob » Tue May 15, 2018 8:16 am

One of the main bearings on the original 1988 DR750 was not up to the job and consequently it used to make a noise after a few thousand miles.
Often this was a pronounced knock which would drive owners mad as it sounded like the engine was about to explode, but the bearing never seemed to fail like your one has.
In 1989 Suzuki uprated the bearing and no more problems were encountered.
I lived with my 1988 750 making this noise for nearly 175,000 miles and then it was a camchain tensioner failure that eventually killed it by bending all the valves :tdown:
I`ve never heard of a SR43 crank bearing failure before except when someone has had the clutch cover off and damaged the crank end seal in the cover which means a dramatic loss of oil pressure.
If you have removed the clutch cover then I would check to see if the seal is OK.
There is a small plate underneath the engine held on by 4 bolts. If you remove this you will probably find lots of bits of bearing
Good luck with the rebuild
User avatar
BigBob
Admin
Admin
 
Posts: 3552
Joined: Sat Jan 23, 2010 10:46 pm
Location: ESSEX

Re: Crankshaft bearing blew to bits :(

Postby Monodoggie » Tue May 15, 2018 9:46 am

I didn't touch the clutch side when I was working on the engine. However when I bought the bike the last owner told me he had done some work on the clutch, so this might explain things if he managed to screw something up while fidling with the clutch :prob:
User avatar
Monodoggie
Virgin - be gentle
Virgin - be gentle
 
Posts: 8
Images: 2
Joined: Mon Feb 19, 2018 2:34 pm
Location: Kuopio, Finland


Return to DR800

Who is online

Users browsing this forum: No registered users and 1 guest

x