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Classic Bike Trackdays

RG250 Crank Assembly

 
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how69



Joined: 28 Apr 2018
Posts: 21
Location: Belfast

PostPosted: Thu May 17, 2018 6:56 pm    Post subject: RG250 Crank Assembly Reply with quote

I am about to start assembly of my crank.
as the one that came with the bike was scrap due to the web with the fixed crank pin past servisable use.
I had intended to have a go at removing the pin and boring a hole to accept
to accept a new pressed in crank pin, but I bored it too large and needed another web.
so I bought a bottom end at really decent money and pressed that crank apart and to my plesent surprise the web with the fixed pin was in good condition so no need to machine that.
It has taken a bit of time to collect the seals and con rod kits due to the expense as this bike rebuild is on a very tight budget.
If I can fix or repair something I do that before getting a replacement.

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Last edited by how69 on Fri May 18, 2018 3:01 am; edited 1 time in total
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yamfan



Joined: 11 Jul 2016
Posts: 122
Location: Ireland - South east

PostPosted: Thu May 17, 2018 8:46 pm    Post subject: Reply with quote

Lots of nice things in that pic,

I also see the tips of your "very nears" Laughing

If you use the BC code option for the photos, the img one - the photo will appear in your post. Check with the post preview.
Also you may need to resize to a smaller size such as 600 or 800

Will be very interested in seeing how you rebuild the crank Cool
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how69



Joined: 28 Apr 2018
Posts: 21
Location: Belfast

PostPosted: Fri May 18, 2018 2:58 am    Post subject: Reply with quote

The old trusty verynears never leave home with out them.
Thanks for the photo tips hopefuly this looks a bit better.
you can click on image and it brings you to a larger version.
All the parts where bought over quite a period of time.
but have all the bits for the crank now, so started to press it together and I used my trusty alignment jig I made over the last couple of months.


it has been hard to get any information on how to press together a twin lots of singles but no twins.
so the only way I thought to time the crank pins 180deg apart was to make up a pressing jig.
the top plate has a 25mm centre hole with a 22mm hole in alignment and the correct distance from the centre, the bottom plate is made just the same but with the 22mm hole on the opposide side ie 180deg apart.
the first thing to do was to press in the new crank pin.



as I am going to press from the centre out
I put on the seals and centre bearings onto there desired positions making sure they where loaded correctley.
I did not want to press it apart again if I buggered it up.

Then I loaded one side into the bottom 22mm pin into hole on th left

then loaded the other side into the top plate with its 22mm pin to the right
then lowered the top plate down until the two halfs aligned over the centre.[url=https

I had pre calculaited the width the webs should be apart and had pre made height stops to use when pressing down.

and to my amazement every thing worked as planned.


Thats all the time I had at the moment it will be next week before I get back to it.
hopes yous all enjoy.
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how69



Joined: 28 Apr 2018
Posts: 21
Location: Belfast

PostPosted: Fri May 25, 2018 2:10 am    Post subject: Reply with quote

got a bit of time this week to have another rattel at the RG crank.
I made up some spacers to go into the middle part of crank to stop it crushing down when I add the end webs.
They were made with some cut outs in the middle to miss the seals so I could push them in as far as possible

you can see them in this pic loaded into the centre,
this is the web with the taper I am fitting first.
I only noticed when fitting this that the height of the bearing location face is .018 thou higher than the web outer edge this mucked up my calculations for the press stops I made but I got round it by using
.020 thou shim around the web edge and under the press stops.
so all good.
this is the 2mm thick conrod thrust washer that is no longer available from Suzuki so I made one from phospher bronze

this is the 3 webs together and the 50mm spot on of the 2 webs together my gcse maths pulled me out of a hole that time

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Last edited by how69 on Sat May 26, 2018 3:11 pm; edited 3 times in total
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how69



Joined: 28 Apr 2018
Posts: 21
Location: Belfast

PostPosted: Sat May 26, 2018 9:53 am    Post subject: Reply with quote

Again I had to make up a spacer to put between the webs to stop it crushing when pressing on the 4th and final web
Sorry about the glare I used the flash to get better light on the subject
you should see the spacer in the top web
This is it all placed in the press for final assembly

Looking back on it now I maybe should have turned the crank up the other way so I was pressing the free web at the top but it worked ok the way it was.
I did check that the webs where in alignment with each other by using a square set at the edge with a light behind it so i could see any mismatch
and adjusted there position until I was happy.
and pressed it together.
and just to check any run out the manual allows .05mm
(about .002thou)

on checking the runout is .003thou
thats not too bad but I will see if I can get the crank to run a bit better to bring it into tolerance.
by giving it a good whack with a big copper hammer.
I really started this becouse I was going to repair the solid pin web by machining it off and boring the hole the correct size to accept a standard crank pin.
I did not think any of the crank rebuilders would use the web I was intending to send them,so it was do it yourself or dont get it done.
it did not work out that way in the end as I had to use a good solid pin web.
As I had allready made the crank press it was going to be used.
and you see it can be done.
I dont know if it was worth while for Just one crank but I just wanted to have a crack at one
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Last edited by how69 on Sat May 26, 2018 2:20 pm; edited 5 times in total
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yamfan



Joined: 11 Jul 2016
Posts: 122
Location: Ireland - South east

PostPosted: Sat May 26, 2018 11:35 pm    Post subject: Reply with quote

Wow, great job,

Thanks for taking the time to post everything.

It may not be worth it for just one crank, but now you have the know how and experience - which make it worth it Cool
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gammaguy21



Joined: 07 Jan 2011
Posts: 70

PostPosted: Tue May 29, 2018 11:47 am    Post subject: Reply with quote

Great stuff!
Do you do other cranks too?
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how69



Joined: 28 Apr 2018
Posts: 21
Location: Belfast

PostPosted: Tue May 29, 2018 5:12 pm    Post subject: Reply with quote

Thanks.
I just done this crank for my self .
I am afraid I could not take the responsibility for someones elses
Crank.
If I messed my own up That would be a dissapointment.
If I messed someone elses that would give me a headache.
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