First bottom end Rebuild

[JIM77]

So I've been buying and selling my house for the last 6+ months and haven't even touched my CR250 resto, until this weekend.

After taking firko's advice I decided to give it a go for myself and bought the right tools etc. The good news is the cases are apart and I didn't cock anything up yet.

I need some guidance on a couple of things though, hoping you blokes can help0:

- Stud removal, head and cases. I want to get these zinc plated before reassembling. Is the 2 x nut method the best option for removal, or can I expect the stuff the studs and a fair bit of suffering.

- I want to zinc plate the case bolts, firko suggested getting all new bolts, whats the theory behind this? And will a standard zinc plate finish have any issue going into the Aluminium case, corrosion etc?

- I need to remove the bearings from the gear box and the main bearings, before I can aquablast. Some are easy to remove, others are blind, any tips for removing these without a bearing remover? Put the whole case in the oven at 100-150c and watch them fall out?

- Anyone see any problem using the gear box bearings again, assuming I can remove them gently? These feel tight and look good, I don't want to waste money for the sake of it, Main bearings and all seals will be replaced.

Any help appreciated.
 

[pancho]

 The two nuts locked together is my preferred method fo removing studs.
 Rarely that won't work, in that case a good quality stud remover is the best bet to minimise damage to the shank of the stud, vice grips do damage. A bit of penetrating oil and a bit of heat can help.
 New bearings are relatively cheap, replace the lot. Don't damage sealing edges of housings.
 Enjoy.
 cheers.

[80-85 husky]

be very carefull with long studs as they can snap easily. I would give them a good sand down and paint them with galmet.if they don't come out easily.

check the bearing numbers in the gearbox and go down to a bearing service and get a price. they can be cheap if they are std bearings and not special one offs

all new bearings may be 50 bucks all up. but if they are ok, why disturb them?

bolt your barrel down to each half of the crankcase and see how the transfer ports match the barrel. mark up any edges with txta and grind them smooth. match the base of the barrel to the gasket outline so you have a smooth transfer port
cheers

[hagon_84]

If u have gone to the trouble of stripping it down replace all seals and bearings might as well do it right the first time don't want to get it running and it shits itself thru bearing failure, remember when reassembling it to have all your mating surfaces clean and free from damage seal with 510 locktite all the gaskets that need it and every nut and bolt u don't want to come loose including cradle bolts lock tighted with 222 low strength u want no leaks anywhere preparation is the key 

[JIM77]

The galmet option on the studs sounds like the go, I was only wanting to remove them for Zinc platting. I do have to replace 1 case stud though, I'm assuming you just put them In with 2 nuts, anyone know if Loctite 262 or 243 would do the job?

The only reason I am taking the gear box bearings out is so I can aquablast the cases, otherwise they are in good enough condition to just leave alone, they are smooth running with no play in them.

If I heat the cases in an oven, will the case expand faster than the bearings and the bearings basically fall out? or the bearing will expand with the case? The manual I have says that direct heat(torch) around the bearing seat will ruin the case hardening, whats you fellas thoughts on this? A bit over the top maybe?

[Montynut]

set up soft wood on a hard surface. Arm your self with heavy leather gloves to handle the hot cases.

Wait until your other half is away for the day. Make sure the cases are 'clean' - kitchen clean not shed clean 

Preheat oven to 120 deg C heat cases for 10min and then bump the cases on the soft wood with the bearing exit side down. The bearings should drop out.

Bearings and seals are cheap compared to a second strip down in a couple of weeks or months

[JIM77]

righto then, sounds easy enough.

your wife doesn't allow you to bake engine parts?

[Montynut]

not officially - burning some toast at the same time tends to do the trick

[Tim754]

your wife doesn't allow you to bake engine parts?

It's Yes here, as long as she can cook my next steak with the Oxy set......

[Montynut]

 
That is why I wait for a day when someone is not at home

It is one of those understandings. As long as there is no 'tell tail' signs when someone returns nothing is said and I don't scrutinise the credit card account too much.

We understand it is going the be what it is but just accept it

A nice oven in the shed would be perfect and better but then the credit card wou.......................

[Lozza]

no need for an oven

http://www.bunnings.com.au/ryobi-2000w-corded-heat-gun_p6210387

[Montynut]

Have two of those but the heating capacity is just not there and very slow and tends to be unreliable as far as expanding the case. The heat source is concentrated whereas the oven brings everything up to the same temperature together so less chance of distortion. But whatever works for you.

I use heat guns more for electrical cable repairs or where a concentrated 'non flame' heat source is required

[Lozza]

Have two of those but the heating capacity is just not there and very slow and tends to be unreliable as far as expanding the case. The heat source is concentrated whereas the oven brings everything up to the same temperature together so less chance of distortion. But whatever works for you.

I use heat guns more for electrical cable repairs or where a concentrated 'non flame' heat source is required

Distortion?     

[Montynut]

Have two of those but the heating capacity is just not there and very slow and tends to be unreliable as far as expanding the case. The heat source is concentrated whereas the oven brings everything up to the same temperature together so less chance of distortion. But whatever works for you.

I use heat guns more for electrical cable repairs or where a concentrated 'non flame' heat source is required

Distortion?     

dis·tort  (d-stôrt)
tr.v.dis·tort·ed, dis·tort·ing, dis·torts
1. To twist out of a proper or natural relation of parts; misshape.
2. To give a false or misleading account of; misrepresent.
3. To cause to work in a twisted or disorderly manner; pervert.

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[Latin distorqure, distort- : dis-, apart; see dis- + torqure, to twist; see terkw- in Indo-European roots.]

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I am obviously referring to definition 1 where uneven heating of press fit components can cause distortion. when heated evenly in an oven the bearings usually just fall out. If a heat gun works for you then that is fine.

[tony27]

not officially - burning some toast at the same time tends to do the trick

A friend of my father used to stove enamel part for his triumphs in the oven while his wife was at church, cooking a good curry provided the perfect covering smell