The second project...'Tiggy'

[Steve H]

Not sure how extra power would cause the failure. I cant remember of the flywheel was removed/lightened, if so this would allow the engine to spin up much faster putting extra load on the balancer shaft gearing. The balancer shaft drive has a 'cush' drive in it, is this still on one piece ?

[Steve Lake]

Steve... not had a close look at it yet.... didn't know about the cush drive... is this peculiar to the SZR bottom end?

trying to find a socket to get the nut off the crankshaft...

as can be seen from the pics, most of the teeth are missing from the crankshaft sprocket

[attachment deleted by admin]

[Steve Lake]

last pic

[attachment deleted by admin]

[themoudie]

Aye Steve,

Refer to pages 3-34 and 3-35 in the SRX600 manual and you'll see the culprit.

From viewing your piccies it appears that fatigue and then the old adage "One out, ALL out!" then applied, as shock loading from missing teeth moved onto next tooth on circumference.

Where your 'dot' marks on the gear and the internal buffer aligned? Can see in your last image the 'dot' mark on the gear, but suspect the other is masked by the slotted washer.

The weights 'driven' gear appears to be made from a different material to that of the one on the end of the crank.

And here I show my engineering 'numptiness', if you are putting 60bhp through the rear tyre, does that mean you are putting nearer 70bhp through the gear on the end of the crank into the clutch? Therefore, you must be putting the same through the gear into the balancer, yet it is less than half the bearing surface of the primary teeth!!!!!! I stand to be shot down in flames, if wrong.

Also read I think on the 'Thumper' site that someone had removed the weight when racing, so as to release extra bhp and remove the risk of this happening.  I realise that this might destroy the 'Tiggy' frame, with the jack hammer vibes you might release. Crank balance factors etc!! Maybe 'Mr Slipstream' would care to comment. A thorough strip, flush and complete new set of bearings, sump oil filter and oil pump look in order as a minimum.  I hope I am proved wrong.

My regards, Bill.

[Steve H]

And here I show my engineering 'numptiness', if you are putting 60bhp through the rear tyre, does that mean you are putting nearer 70bhp through the gear on the end of the crank into the clutch? Therefore, you must be putting the same through the gear into the balancer, yet it is less than half the bearing surface of the primary teeth!!!!!! I stand to be shot down in flames, if wrong.

Bill, the load through the gear driving the balancer shaft will be due to the balancer shafts inertia when the engine is accelerating/decelerating, if the flywheel has been removed then the engine inertia will be less and the engine can accelerate faster, putting extra load on the gears. I doubt its enough to do the damage though.

Steve, the 'cush' drive is sandwiched into the drive shaft, there are a bunch of springs and stuff in there that I have not give much thought to before. Oddly on your last picture the driven sprocket looks to have teeth which have been damaged at the rear rather than completely removed.

The other thing to consider is that the balancer shaft weight can hit the crank if if left loose, so you may find the end of the con-rod has taken a beating as well.

Also another option is that the crankshaft woodruff key has sheared, knocking the balancer shaft timing out ?.

Steve

[andy230]

Its quite common to replace the "cushed" balancer shaft gears in this motor with solid ones.  Presumably without the cush they are more resiliant...?

I opted not to change them as they make a terrible racket (allegedly, never done em), and presumed those that were there would be ok...

Clearly not.

a

[themoudie]

Steve, the 'cush' drive is sandwiched into the drive shaft, there are a bunch of springs and stuff in there that I have not give much thought to before. Oddly on your last picture the driven sprocket looks to have teeth which have been damaged at the rear rather than completely removed.

The other thing to consider is that the balancer shaft weight can hit the crank if if left loose, so you may find the end of the con-rod has taken a beating as well.

Also another option is that the crankshaft woodruff key has sheared, knocking the balancer shaft timing out ?.

Steve

Aye Steve, I understand about the inertia and thank you for setting it out. I too was puzzled by the reduction in width of the teeth on the counter balance shaft. Are you thinking "sideways" movement after failure of the woodruff key? The timing going whizz won't have helped the end of the rod or maybe the flywheels. It's all a bit tight in there!
Hope it's not as bad we fear when Steve gets back to us, if he wants to!

My regards, Bill.

[themoudie]

Its quite common to replace the "cushed" balancer shaft gears in this motor with solid ones.  Presumably without the cush they are more resiliant...?

I opted not to change them as they make a terrible racket (allegedly, never done em), and presumed those that were there would be ok...

Clearly not.

a

Aye Andy, Bit like a Duke with straight cuts, rather than bevels! 

Regards, Bill.

[Steve Lake]

Yes Steve, you are right, the balancer gear would appear to be damaged on the inner 3/4's suggesting a misalignment.
Bill, i'm not sure the balance shaft cam be removed successfully, as it is hollow and acts as an oilway.... I guess it could be replace woth a tube of similar dimensions, but i've not heard of it being done.

You're right about the flywheel/bigend taking a pasting from the freewheeling balancer..... that's what i could hear when i passed the bike at cadwell. It remains to be seen what damage has been done when i split the casing.

still looking for a socket, when i get one it's not going to be easy, the reccomendation in the manual is to jam the sprockets with a rag prior to torquing up....
they wrote that assuming there were teeth on the sprockets!! :-)

[themoudie]

Aye Steve,

Old chainsaw trick of a piston 'stopper' threaded through the plug hole, or rag fed in through the plug hole. If you are further stripped out, with the head and piston out of the way, a long 1/2" extension supported between blocks of wood either side of the crankcase mouth and with cloth wrapped around it prevents crank rotation.

As for the counterbalancer, if they have been hammering each other, one last interlocking of crank and counterbalancer with rag in between and then plenty of steady torque applied isn't going to further damage the jack hammer damage you may have suffered already. Or an air wrench if you have access to one.

Tell me to P*** O** if necessary, it's you that has the beast and I'm 450 miles away tapping on a keyboard!

All the best with whatever you resolve to do.

My regards and commiserations, Bill.

[Steve H]

Air wrench is the way to go. I have a cheapo Aldi compressor and a £25 air wrench, solves many problems including getting the flywheel off.

[Steve Lake]

thanks guys.

Steve...do you know if the crankshaft/balancer sprockets are the same on this lump (SZR/MUZ) as the srx/xt? (also is there a match on the srx 400)

[andy230]

hi steve

counter balancer can be removed.  bill Jurgenson has done it.

It has pros and cons tho:

the whole blog will be interesting to you, also re gears -->

http://cembalobill.blogspot.com/

C/balancer removal -->

http://cembalobill.blogspot.com/2007/12/balancer-shaft-and-myths.html

I had thought there were some pics somewhere tho....  He uses a replacement dummy shaft...
 
a

[Steve H]

thanks guys.

Steve...do you know if the crankshaft/balancer sprockets are the same on this lump (SZR/MUZ) as the srx/xt? (also is there a match on the srx 400)

I will have to pass on that. It would expect them to be pretty close, if not identical, but you will need to compare them side to side

[Dave Pearce]

Steve
Don't even think about removing the balance shaft. That chassis has lasted 20 years
so be gentle with it.

Dave Pearce
Tigcraft