2001 xc250 connecting rod side clearance

[70455]

Im preparing to split my cases, and measuring/ observing as much as possible before i get into it (waiting on one last bearing to arrive also).

My rod big end has 0 play radially but approximately 2mm side clearance.

Is this right? Last kx250 crank i rebuilt was at. 010".

Im thinking of pressing the two halves in my press together and save the crank rebuild for later date.

Reason for teardown was unresolvable jetting problems (burning atf from gearbox) caused by leaking seal, potentially caused by radial play of 0.5mm in rhs crank bearing.

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[jostby]

STD .8mm, MAX is listed at 1.00mm My manual doesn't list a minimum for side-to-side clearance.

[hannesd]

Originally Posted by jostby

STD .8mm, MAX is listed at 1.00mm My manual doesn't list a minimum for side-to-side clearance.

tis clearance , how do you measure this?
is this by pulling the rod up and down on the rod, or 'tilting' it side to side (not as sliding it over the axle from 1 to the other crank half)
it's hard to explain this i guess...
does anyone have clear understandable words to clearify this?

hannes.

[jostby]

the manual says to push the big end sideways to the crank and measure the clearance on the opposite end with feeler a gauge

- Measure the play of the connecting rod big-end by pushing
it to one side and inserting a feeler gauge on the opposite
side.
Connecting rod big-end play STD: 0.80 mm
Limit: 1.00 mm

[70455]

If all looks well, ill press the two crank halves together to meet the 0.8 to 1.0mm spec.

Has anyone had the crank separate over time?

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[hannesd]

Originally Posted by jostby

the manual says to push the big end sideways to the crank and measure the clearance on the opposite end with feeler a gauge

- Measure the play of the connecting rod big-end by pushing
it to one side and inserting a feeler gauge on the opposite
side.
Connecting rod big-end play STD: 0.80 mm
Limit: 1.00 mm

ok that's clear, but there's more play to measure, right?
it's the up and down play on the big end of the connecting rod,how do you measure that?

[hannesd]

Originally Posted by 70455

If all looks well, ill press the two crank halves together to meet the 0.8 to 1.0mm spec.

Has anyone had the crank separate over time?

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you mean that the crank halves met go over time, by riding it?
i've heard of guys who race the bigger thumpers that tig-weld there big ends to the crank halves so they wouldn't "twist" and become untrue.
personnally i don't thinks that's nescesary for our gassers going only up to 300cc and being 2 strokers.

[70455]

Crankshaft must have been built incorrectly originally. It has vesrah 5001 rod. Is this oem?

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[jostby]

Originally Posted by hannesd

ok that's clear, but there's more play to measure, right?
it's the up and down play on the big end of the connecting rod,how do you measure that?

the manual doesn't specifically state how to check up-down play or give any specs for it. My thoughts are if you can feel it then it's too much. Maybe someone else will chime in on this.

[70455]

Looks like root cause was crank bolt backing out, hitting rod and side loading crank web. Causing side clearance to increase. Can see polish marks where bolt head was hitting the rod.





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