CR250 Engine Build Part 9 (Final Part)

[dogger315]

This is the final part of this engine build and will cover head, reed valve
and carburetor installation. I will also perform a final leak down test.

Tools needed: Torque wrench, leak down tester, metric tool assortment

Apply oil to the six cylinder head studs and install them into the cylinder.
Torque the studs in three steps and in a criss cross pattern to 9 lb.ft.
Again use a stud tightener or two opposing flange bolts to properly torque
the studs.


Place a new head gasket with the "up" mark facing up and aft


Install the cylinder head and apply oil to the cylinder head studs and landings.


Install the six cylinder head nuts and hand tighten. Torque the nuts in three
steps and a criss cross pattern to 20 lb.ft.


Install the reed valve with a new gasket into the cylinder



Install the intake manifold with the intake oriented to the left. Apply oil to
the six intake bolts and install the bolts along with the throttle cable
retainer. Torque the bolts in three steps and in a criss cross pattern to
7 lb.ft.



Now is a good time to perform the functional leak down test. Cycle the
piston to bottom dead center (BDC). Install the spark plug and torque to
13 lb.ft. Install a exhaust plug to seal the exhaust outlet. Attach the
tester to the inlet and seal with a hose clamp.

Pump the tester to 6 psi and start timing. An acceptable loss rate is 1
psi/min. Less is better. This engine lost 1 psi in 4 min 32 sec which is
an OK value.


Remove the test equipment and the exhaust plug. Install the carburetor
aligning the tab on the carb intake bell with the notch in the rubber intake
boot. Tighten the intake clamp snugly and give yourself a big thumbs up
for completing a total engine build.

dogger

[DUDEONAYZ125]

dang your talented! how about a riding vid?

[Tonk]

don thank you very much for these threads there going to help me ALOT and many many other people, would be good to get some other threads to do with this build or any build that could be related.

once again thank you very much!
Ian

[Woody_393]

As we've come to expect, simply awesome.

I do have a question. Is their a reason you apply oil to all the bolts before tightening them up? Is that to stop corrosion? Also, I was under the impression that if you do have grease or oil on threads that you should take 20% or something like that from the normal torque values. So if the torque is 50 ft/lbs, you should actually torque it to 40 ft/lbs with oil on them. Is that not true?

Anyway if you could shed some light on that I would appreciate it.

[brucem]

very cool to follow along with rebuild. Thanks for all your work and to document for us - it will be helpful.

[bundyho1]

great info man.Just curious what gearing are you going to run 14 ?

[dogger315]

how about a riding vid?

Funny you should mention that. I have been thinking about getting one of
those trick helmet mounted cameras and taping some "hot" laps just for
entertainment purposes.

would be good to get some other threads to do with this build or any build that could be related.

Ian, I will try and document any build or restoration I do for the instructional
value the information might be to anyone.

Is their a reason you apply oil to all the bolts before tightening them up?

My background is aviation, conventional wisdom specifies some form of
fastner prep before torquing so that you get an acurate torque value
and not thread friction. Also, like you said, oiling helps with corrosion and
galling. It also helps with electrolysis from disimilar metals (steel vs
aluminum). I have heard of different torque values when using lubricants
but I believe that applies to applications where "dry torque only" is specified.

it will be helpful.

That's why I am glad to do it.

what gearing are you going to run 14 ?

Standard in 1993 was a 13/51. For every tooth you add to the countershaft
sprocket you subtract 2 1/2 from the driven sprocket. I plan to run a 53T
rear sprocket which will be 1/2 tooth less than stock. Since this motor will
be very "stout", it will more than make up for the higher gearing. I use 14T
countershaft sprockets on all of my late model CRs to optimize chain angles
and reduce suspension binding.

[Woody_393]

Originally Posted by dogger315

My background is aviation, conventional wisdom specifies some form of fastner prep before torquing so that you get an acurate torque value and not thread friction. Also, like you said, oiling helps with corrosion and galling. It also helps with electrolysis from disimilar metals (steel vs aluminum). I have heard of different torque values when using lubricants but I believe that applies to applications where "dry torque only" is specified.

Honestly I'm not sure myself. I do know that when I've had grease on a bolt and try to torque it to spec, I've stripped the bolt (done that 2-3 times) which is why I ask.

I'm very particular anymore and make sure to wipe off any grease/oil just to ensure the bolts don't start coming apart.

I had heard some percentage, but I can't for the life of me remember, so I've used 20% less just to be safe if it has any sort of lube on it. I just hate stripping bolts.

[Tonk]

thanks again for these amazing threads don. ive decided rather than just tryin to repair my problems untill something bad goes wrong i mite aswell take the plunge and start the long needed REBUILD! i am going to take the bike apart this week end. and kick start the whole process of stripping and cleaning.

is there anything cheap you can reccommend for cleaning the engine parts or any such cleaners i would need once i got it apart? i wont be buying any new/replacement parts for a week or two but i just want to get it all stripped, cleaned and start working out what i need to get. im assuming i need new bearings, seal, and any circlips/ washers i see.

as im a complete newbie to this and this is going to be my first time takin any bike apart, which is the best way to order the parts i need?? as i take it off the bike see where its come from and make a list as i take it off? ill be next to the computor to do it, so i can check part numbers and then order the parts from service honda? if that makes any sense to you.

thanks again don

Ian.

[dogger315]

I just hate stripping bolts.

I know what you mean, it can be very frustrating.

I used to get lots of broken or stripped bolts from all the vintage projects
I do. What I found in many cases was 1) the fastener was old and fatigued
2)the fastener had been over tightened before 3) the threads on the
fastener or recieving part were compromised to some extent causing the
fastener to seize or 4) the fastener was rusted and corroded and I
didn't use enough penetrant, heat or patience to extract it properly.

What I have learned from this is to use new fasteners to the max extent
and if I have to restore an old one, I use the lowest torque value listed
on the range of torques. Also I chase the threads on everything just to
make sure. And last, never force the issue. Finesse is better than force
most times.

The last time I broke a bolt, I was restoring the ignition on a 1979 CR250.
I had already removed and installed the bolt in question for test fitting,
several times. I was removing the bolt (it was a cad plated pan head
screw), when it got difficult to turn. Then, without warning, the screw
snapped off a couple mms below the surface. This was a classic example
of seizure through disimilar metals galvanization - the bolt was cad plated
steel in an aluminum casting. Also, when you break a fastener during
removal, it is much harder to remove the remainder than if it breaks during
installation. If I had prepped the screw with oil, grease or anti-seize, I
wouldn't have had a problem. That failure cost me a small fortune and a lot
of time because the screw and the ignition cover were NLA.

I guess it all comes down to what works for you and what you feel the most
comfortable with.

i mite aswell take the plunge and start the long needed REBUILD!

Outstanding Ian!
Make sure you thoroughly clean the bike first and also clean a section of
your workbench where you will work. CLEAN, CLEAN, CLEAN - I can't
emphasize it enough.

is there anything cheap you can reccommend for cleaning the engine parts or any such cleaners i would need once i got it apart?

There is a cheap way and a really cheap way. The really cheap way is to
buy an oil drain pan, some stiff bristle brushes and a bunch of aerosol cans
of brake cleaner. The cheap way is to buy a small bench top parts washer,
some stiff bristle brushes and a gallon of parts wash concentrate.

which is the best way to order the parts i need??

Since this is your first time, I recommend using a digital camera to take
pictures of the engine before disassembly and after you remove any parts.
The pictures will come in real handy during reassembly and also, if you run
into problems, you can post them here for help. As far as parts orders,
Look at an exploded parts diagram on the website of your choice. Those
diagrams will show you everything you need to place your orders. I
recommend you go ahead and order the seals, bearings, thrust washers
and circlips. After you have it disassembled, you will be measuring all the
gears and shafts to see what is good and what needs to be replaced.
Hopefully, everything is good to go and you will get off with just bearings,
seals, washers and circlips at least on the bottom end.

dogger

[Tonk]

this is still going to be a challenge haha i was planning on taking pictures of everything because i know for a fact im going to need help =P.
ill look into the consentrate stuff.
i need to get hold of myself a torque wrench so i can put it all back together...
this is probaly most stupid question you ever heard but what is a thrust washer =[
i had a look at the exploded diagrams on service honda and they look so complicated to work out especialy seing as i dont have a clue what half of it is =D
would i also need a micrometer thingy i keep seing you all talk about?

thanks don.

[Woody_393]

Originally Posted by dogger315

I know what you mean, it can be very frustrating.

I used to get lots of broken or stripped bolts from all the vintage projects
I do. What I found in many cases was 1) the fastener was old and fatigued
2)the fastener had been over tightened before 3) the threads on the
fastener or recieving part were compromised to some extent causing the
fastener to seize or 4) the fastener was rusted and corroded and I
didn't use enough penetrant, heat or patience to extract it properly.

What I have learned from this is to use new fasteners to the max extent
and if I have to restore an old one, I use the lowest torque value listed
on the range of torques. Also I chase the threads on everything just to
make sure. And last, never force the issue. Finesse is better than force
most times.

The last time I broke a bolt, I was restoring the ignition on a 1979 CR250.
I had already removed and installed the bolt in question for test fitting,
several times. I was removing the bolt (it was a cad plated pan head
screw), when it got difficult to turn. Then, without warning, the screw
snapped off a couple mms below the surface. This was a classic example
of seizure through disimilar metals galvanization - the bolt was cad plated
steel in an aluminum casting. Also, when you break a fastener during
removal, it is much harder to remove the remainder than if it breaks during
installation. If I had prepped the screw with oil, grease or anti-seize, I
wouldn't have had a problem. That failure cost me a small fortune and a lot
of time because the screw and the ignition cover were NLA.

I guess it all comes down to what works for you and what you feel the most
comfortable with.

The most recent one was the bottom bolt on my RMZ450, which was brand new. I removed it to grease all the linkage etc on my new steed. So unless from the factory (which isn't impossible) they messed it up, it should have been fine.

Anyway, I'm off-topic so I'll stop Though I do have to wonder if maybe oil might be a tad better than grease (maybe not as slick). though I do use anti-seize on a lot of bolts since I've been down the dis-similar metals corrosion road before, and that was NOT fun.

I think you are right though, finesse seems to be more key than anything. If I'm going slow I can usually tell when something starts to stretch or slip, which is a good time to back it out and check before a small problem turns into a huge one.

Anyway, Thanks for the info.

[dogger315]

i need to get hold of myself a torque wrench

Yes you do and dont worry about the micrometer, you can use
a dial or digital caliper for all your measurements.

what is a thrust washer

Thrust washer = flat washer. It is placed between gears or at the
end of the shafts to control runout (the amount of play allowed for
that gear or shaft). Look at the exploded parts diagram and you
will see quite a few thrust washers on each gear cluster and
throughout the engine assembly.

the bottom bolt on my RMZ450, which was brand new.

That sucks. I don't know how to explain that one. By the way, what kind
of torque wrench do you use; dial, beam and pointer, clicker, digital?

oil might be a tad better than grease

I would agree with that statement.

dogger

[Woody_393]

It was/is a craftsman clicker (5-80 ft/lbs --> this one Craftsman Digitork® Torque Wrench, 5-80 ft. lbs., 3/8 in. Drive)

I think I'll continue to make sure and get grease off my bolts

[dogger315]

It was/is a craftsman clicker (5-80 ft/lbs

An excellent wrench, I have three. 10-150 lb.ft 1/2", 5-80 lb.ft. 3/8"
and 25-250 lb. In. 3/8". I get each one calibrated once a year to
maintain accuracy. Sears offers the service for a nominal price.
My 10-150 was the first torque wrench I ever bought. It is 30 years
old now and just as reliable as ever.

dogger

[Woody_393]

Oh they do? I was not aware of this. I am going to have to go get it calibrated then because I've wondered if it's still accurate. I've had it for 5 years or more. I'll look into that for sure. Thanks

[OLDMXRACER 393]

Outstanding as always Dogger.