Dial indicating a crank

Neil_E. · Mar 1, 2008

I decided to check the crank since my engine is apart. I mounted it in the lathe and was surprised by the readings. Very similar on each side, but they indicate the crank has "spread" during operation. Measuring across the crank wheels confirmed this.

Months ago when I talked to Fryguy about some problems with this engine I commented that the crank end play seemed high at .015 inches. He said the end play has to be large because the crank tends to spread under load. When I looked up the factory spec, it listed .017"-.021", so I'm slightly below spec which is OK by me.

The dial indicator went from 0 to .007" on the ignition side, 0 to .008" on the primary side. Low side on both was at the pin. High side opposite the pin. The micrometer showed 2.361" at the pin and 2.373" opposite the pin.

Based on the fact that my crank has spread would anyone recommend pinching it back? My feeling is to leave well enough alone, particularily if it will only go back to this condition in use. Thoughts?

Photo:
http://www.husaberg.org/index.php?set_a ... _album.php

AUSBERG · Mar 2, 2008

Neil_E. said:
I decided to check the crank since my engine is apart. I mounted it in the lathe and was surprised by the readings. Very similar on each side, but they indicate the crank has "spread" during operation. Measuring across the crank wheels confirmed this.

Months ago when I talked to Fryguy about some problems with this engine I commented that the crank end play seemed high at .015 inches. He said the end play has to be large because the crank tends to spread under load. When I looked up the factory spec, it listed .017"-.021", so I'm slightly below spec which is OK by me.

The dial indicator went from 0 to .007" on the ignition side, 0 to .008" on the primary side. Low side on both was at the pin. High side opposite the pin. The micrometer showed 2.361" at the pin and 2.373" opposite the pin.

Based on the fact that my crank has spread would anyone recommend pinching it back? My feeling is to leave well enough alone, particularily if it will only go back to this condition in use. Thoughts?

Photo:
http://www.husaberg.org/index.php?set_a ... _album.php

With that amount of lack of parallel, and subsequent race misalignement, Im suprised you cant se a definite improper wear pattern on the inner races....

I recently did a KTM 2 stroke that only had the webs .2mm out of parallel, and you could tell there was something amiss by the uneven wear on the LHS NJ207

No way would I be putting a crank with those measurements you have quoted back "as is".
Time to break out the copper /brass hammers...

sparks · Mar 2, 2008

Hi Niel,

If you have got webs creeping on the pin simple fix, make sure the crank is true then have the crank pin welded either side problem solved.
We used to this with most of the pressed cranks during the eighties.

Regards

Sparks.

Neil_E. · Mar 2, 2008

RE: Re: Dial indicating a crank

I remember a thread with pictures of a welded pin, but I can't find the thread. Does anyone have an idea of how much welding current was used? Was it simply fused together or was it done with filler rod? I have access to a TIG machine.

Enginehardware · Mar 3, 2008

Neil_E. said:
I decided to check the crank since my engine is apart. I mounted it in the lathe and was surprised by the readings. Very similar on each side, but they indicate the crank has "spread" during operation. Measuring across the crank wheels confirmed this.

Months ago when I talked to Fryguy about some problems with this engine I commented that the crank end play seemed high at .015 inches. He said the end play has to be large because the crank tends to spread under load. When I looked up the factory spec, it listed .017"-.021", so I'm slightly below spec which is OK by me.

The dial indicator went from 0 to .007" on the ignition side, 0 to .008" on the primary side. Low side on both was at the pin. High side opposite the pin. The micrometer showed 2.361" at the pin and 2.373" opposite the pin.

Based on the fact that my crank has spread would anyone recommend pinching it back? My feeling is to leave well enough alone, particularily if it will only go back to this condition in use. Thoughts?

Photo:
http://www.husaberg.org/index.php?set_a ... _album.php

Hi.
We used a turnleathe before when checking the crank, most lathes have to much un alighments so its hard to get a correct reading.
Make your own stand with 4 bearings which you lay the crank up, with new inner races, then the indicators in each end you get a exact reading.
Our cranks are with-in 0.03-0.04mm aligned messuring the twist, and parallell about 0.01-0.02mm.
Then we weld them.
//Thomas

Enginehardware · Mar 3, 2008

Re: RE: Re: Dial indicating a crank

Neil_E. said:
I remember a thread with pictures of a welded pin, but I can't find the thread. Does anyone have an idea of how much welding current was used? Was it simply fused together or was it done with filler rod? I have access to a TIG machine.

Just a photo of the welding

Neil_E. · Mar 3, 2008

RE: Re: RE: Re: Dial indicating a crank

Nice looking crank, thanks for posting the picture.

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