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Old 11-23-2012, 03:29 AM   #4876
WILL_S
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balancing

Well heres some stuff to get the juices flowing

Step 1 - Create a Jig

A jig is a gear that serves as a guiding tool or a holding machine. Construct a jig to hold the bearing and the crankshaft in place. Attach the bearing in the jig and the crankshaft unto the bearing. Take a new bearing and get rid of all the grease and immerse it in the break clean. This frees the bearing and allows the crank to spin the heavy spot down.
Step 2 - Weigh the Bobweight

Remove the piston, rod and wrist pin to weigh it in. The wrist pin is a pin attached at the end of a connecting rod either to a wheel, crank or piston. Take ¾ of the total weight as a guide for you to know the ideal bobweight you will need to wrap around the crank pin. Start spinning the cranks using the balancer machine and see where it stops. Make sure that the counterweight of the crank is heavier compared to the overall weight of the piston and rod on the crankshaft.
Bobweight refers to the reciprocating and rotating weight of the assembly. Reciprocating weight is computed starting from the middle of the rod upwards including the piston, wristpin, and rings. Meanwhile, the rotating weight starts from the lower half of the connecting rod.
Step 3 - Balance the Crank

Do the necessary cuts to obtain the ideal weight wherein the counterbalance must be heavier compared to weight on the crank pin. Place back the crankshaft into the engine which may seem that nothing is different. Start the engine and don’t mind the vibration.
Removing weight from the crankshaft to balance the assembly is simple. Use the drill and drill some holes unto the attached crankshaft counterweights. However, if the bobweight is lighter you may add metal to the crankshaft.
Balancing a motorcycle crankshaft also depends on the type of cylinder. There are three cylinders available-single, two, and multi-cylinders. The vibration which was mentioned earlier is normal especially for engines that do not have balancing counterweights. To reduce the vibration, single-cylinder integrates balancing weights.
Counterweights are installed on the crankshaft to balance the effect of inertia between a heavy piston and the connecting rod in two contrasting motions-reciprocating and rotational. The weight of the piston and connecting rod greatly affects the size and the placement of the counterweight. The heavier the piston-rod is, the heavier the counterweight to be used. Counterweights should be placed in front and rear of the cranks to lighten the crank without blocking the case of the crank.









Some good info on separating and rebuilding the crank halves here
but you need to be a member to view it
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Old 11-23-2012, 04:07 AM   #4877
DRjoe
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but what about the balancer shaft.


[QUOTE=jm-2008;20101936]
Quote:
Originally Posted by DRjoe View Post
thumper racing in the states can balance the crank and balancer for you but don't ask them how they do it because its apparently a trade secret.
Quote:
Originally Posted by DRjoe View Post
I think lots of complex maths is the secret to getting the balancer shaft and the crank shaft working well together


Not certain is that big a secret.
Ref Big Willy's comment a few posts up re balancing the Bonnie at 85%
You could allways tell if some one had their late 60's early 70's Trophy/Bonnevile's balanced as the front wheel would not shake when they idled - not a guaranteed give away but a good indicator.

Back to the question -
Deducing the correct precentage of rod/piston weight to use for the desired effect is the secret.
With the old Trumpet's (Triumph's) many a percentage was tried till the 85% figure was settled on as a good target to aim at.
As for balancing a counterweighted motor one would expect balancing both together (to an appropriate % would be a good start point.

Lots of quiet lurkers out there who will know, maybe we should seek their sage advise

(This might turn into another - Whats the best oil discussion )

For the sake of the discussion would be interested to know from the learned ones

JM
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Old 11-23-2012, 06:24 AM   #4878
ditchwitch650
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Hey is that my one DW?!
no mate the order still hasn't shown up yet travis

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Your bikes so clean.....it's nearly gay
yes it is a little gay but this is not my bike so W,H,F will have to keep looking for a chum

i have heard a rumor that there is a 07 plated XRR around Hervey Bay that has 200k's on the clock sitting in a shed
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Old 11-23-2012, 07:17 AM   #4879
johnno950
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I got this xrs engine stripped for a refurb in the new year,given it to my son so when he gets older he can come riding with me.....hes a few years off licence age so i should have it ready by then.Going to get a low c/f front mudgaurd and a c/f bashplate,and add the brace from the lhs footpeg mount to the rear of the subframe to help carry the load of the rear tank,should be a good thing
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Old 11-23-2012, 04:24 PM   #4880
WILL_S
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Quote:
Originally Posted by DRjoe View Post
but what about the balancer shaft.
Chuck it in the bin ,overrated
that might be where the secret is:

That stuff above is general info not xr specific ,might help someone split a crank and play around.

also not a xr but back in the day these weirdos used a *#!650 motor,renowned for not being overly powerful, jammed in a 250 chassis for racing.They removed the counterbalancer.
Why would one want to make the xr motor better i was under the impression they was pretty good.
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Old 11-23-2012, 04:59 PM   #4881
DRjoe
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That's a pretty trick bike you got there northy.
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Old 11-24-2012, 01:36 AM   #4882
Growelly
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Quote:
Originally Posted by johnno950 View Post
I got this xrs engine stripped for a refurb in the new year,given it to my son so when he gets older he can come riding with me.....hes a few years off licence age so i should have it ready by then.Going to get a low c/f front mudgaurd and a c/f bashplate,and add the brace from the lhs footpeg mount to the rear of the subframe to help carry the load of the rear tank,should be a good thing

Looks like someone has set that bike up well at some stage. Well done.
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Old 11-24-2012, 01:38 AM   #4883
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How much does that tank combo hold?

Had to post this because it looks so good.

It's big, it's red, but it's not a pig.

[/QUOTE]
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Old 11-24-2012, 02:29 AM   #4884
KASUYAHO
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Cruz, under seat is 14lts from memory. total 38lts.
Made by Acerbis to sponsor John Canpbell Baja fame for DAKAR.


Thesame bike Johno ?

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Old 11-24-2012, 02:33 AM   #4885
Cruz
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Originally Posted by KASUYAHO View Post
Cruz, under seat is 14lts from memory. total 38lts.
Made by Acerbis to sponsor John Canpbell Baja fame for DAKAR.


Thesame bike Johno ?

Thanks, very nice setup. Looks more balanced than Digga's Exxon Valdez setup.

Did they increase the engine oil amount, oil cooler or fan on the race bike?
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Old 11-24-2012, 02:44 AM   #4886
Sean-0
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they weren't a great success Cruz .. they keep the weight to high and raised the seat hight .. were known to split ....digga's is the best setup ..the ergos on the bike are like the stock tank
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Old 11-24-2012, 03:02 AM   #4887
KASUYAHO
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Thanks, very nice setup. Looks more balanced than Digga's Exxon Valdez setup.

Did they increase the engine oil amount, oil cooler or fan on the race bike?
To my knowledge they never did any of those things to the bike.

Yeh i would say it is more balanced than the Safari setup.
They just followed how the Rallye bikes are setup with front and rear tanks.
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Old 11-24-2012, 03:07 AM   #4888
johnno950
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Quote:
Originally Posted by KASUYAHO View Post
Cruz, under seat is 14lts from memory. total 38lts.
Made by Acerbis to sponsor John Canpbell Baja fame for DAKAR.


Thesame bike Johno ?

Thats it,had actually sold it and ended with it again which was good.Yes the underseat tank does split,has had a repair and was always going to do the footpeg to rear subframe brace to stop the tank flexing/cracking so its getting done.Very tall bike with the acerbis underseat tank,from memory the shock maybe a longer modified unit which adds to the seat height,looking forward to giving this bike a bit of a refurb etc next year.The young fellas got a few years to grow into it so in the intrem i will ride it.
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Old 11-24-2012, 03:11 AM   #4889
KASUYAHO
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they weren't a great success Cruz .. they keep the weight to high and raised the seat hight .. were known to split ....digga's is the best setup ..the ergos on the bike are like the stock tank
Sean-0,
What do they do with the KTM690RR stock tank ?
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Old 11-24-2012, 03:13 AM   #4890
KASUYAHO
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Originally Posted by johnno950 View Post
Thats it,had actually sold it and ended with it again which was good.Yes the underseat tank does split,has had a repair and was always going to do the footpeg to rear subframe brace to stop the tank flexing/cracking so its getting done.Very tall bike with the acerbis underseat tank,from memory the shock maybe a longer modified unit which adds to the seat height,looking forward to giving this bike a bit of a refurb etc next year.The young fellas got a few years to grow into it so in the intrem i will ride it.
Yeh TEKNIK did the suspension on that bike.

Did you buy it from the original owner ?
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