And so it begins.......... Mk2 rebuild

Hallsy
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And so it begins.......... Mk2 rebuild

Post by Hallsy » 30 Aug 2011, 21:36

Those of you that have seen my 'newbie' post will know that I've just bought a Mk2 CRM 250 in bits!! Not ideal for everyone but I like doing things the hard way!!

This is the first bike I'll have rebuilt, so there will undoubtedly be some head scratching and newbie questions asked. Hopefully I'll have a bit of a chance as I'm an electrical engineer by trade with access to a fairly well kitted out workshop, and have tinkered with cars since I passed my test.

So, to the bike, it's a white Mk2, '91, imported into UK in '98. The guy I bought it from seemed like a genuine guy, interested in bikes, spoke a lot about older 2 strokes, and said he had rebuilt a couple of KH250's. He had bought this for greenlaning but found that the swingarm bearings were nackered. Sounds like he had fun getting the swingarm spindle/bolt out, but it is out. He then carried on stripping the bike, but lost interest/time.

Looks like it's pretty much all there, no doubt there are some fixings and small bits lost, but definitely the bulk is there. He hasn't stripped it quite as methodically as I would have done, but I can see some of his logic!!

So from a quick look over my intial plans are as follows:

- frame to be shotblasted & powder coated satin black, considered getting swingarm one the same but thought it might be a waste as it would get scuffed/chipped and soon look tatty - thoughts?

- service shock & forks, forks feel pretty soft at the moment. Are there any common mods to the internals to make them a little better, or is it a case of trying heavier oil or different oil levels?

The fork uppers have unfortunately been painted gold (I'm guessing that the original anodising was tatty), but this just gets scraped where the yokes are fitted/adjusted. I plan to strip the paint off, if the anodising is poor I'll consider getting them re-anodised. Has anyone had this done? Pricey?

- rebuild engine as necessary.............

- generally tidy as I go, replacing any bushes/bearings as necessary

- Pass my test and take it for a spin!!

So, how do you get a CRM in the back of a Volvo? Like this:

[url=http://www.flickr.com/photos/25266351@N06/6097306941/][img]http://farm7.static.flickr.com/6205/609 ... 09cd_b.jpg[/img][/url]
[url=http://www.flickr.com/photos/25266351@N06/6097306941/]IMG_20110827_110330[/url] by [url=http://www.flickr.com/people/25266351@N06/]Hallsy01[/url], on Flickr

He was nice enough to let me have the boxes!!

So, had a better look at the engine. Seller had removed the barrel from the crankcase, and it looked to be in OK condition, but the head was still on so couldn't see properly. Back in the workshop I could see why head was on. Even though all the nuts were removed, one stud had bitten into the head and wouldn't come off. The thread on the stud had been mauled as well. Welded a nut on and removed stud. There are a few marks in the squish area, from debri I'm guessing (sorry for poor pic quality, I only had my phone cam at work):

[url=http://www.flickr.com/photos/25266351@N06/6097855556/][img]http://farm7.static.flickr.com/6010/609 ... 40d0_b.jpg[/img][/url]
[url=http://www.flickr.com/photos/25266351@N06/6097855556/]IMG_20110828_123124[/url] by [url=http://www.flickr.com/people/25266351@N06/]Hallsy01[/url], on Flickr

Here is the piston as removed:

Fairly normal carbon pattern?

[url=http://www.flickr.com/photos/25266351@N06/6097307733/][img]http://farm7.static.flickr.com/6132/609 ... be9b_b.jpg[/img][/url]
[url=http://www.flickr.com/photos/25266351@N06/6097307733/]IMG_20110828_120649[/url] by [url=http://www.flickr.com/people/25266351@N06/]Hallsy01[/url], on Flickr

Intake side:

[url=http://www.flickr.com/photos/25266351@N06/6097854128/][img]http://farm7.static.flickr.com/6197/609 ... fb12_b.jpg[/img][/url]
[url=http://www.flickr.com/photos/25266351@N06/6097854128/]IMG_20110828_120700[/url] by [url=http://www.flickr.com/people/25266351@N06/]Hallsy01[/url], on Flickr

Exhaust side:

[url=http://www.flickr.com/photos/25266351@N06/6097854912/][img]http://farm7.static.flickr.com/6195/609 ... 3c07_b.jpg[/img][/url]
[url=http://www.flickr.com/photos/25266351@N06/6097854912/]IMG_20110828_120718[/url] by [url=http://www.flickr.com/people/25266351@N06/]Hallsy01[/url], on Flickr

Most of the barrel looked to be in OK condition and is still on original bore (66.0mm), but just above the exhaust port you can see and feel some marks:

[url=http://www.flickr.com/photos/25266351@N06/6097306207/][img]http://farm7.static.flickr.com/6121/609 ... e47f_b.jpg[/img][/url]
[url=http://www.flickr.com/photos/25266351@N06/6097306207/]IMG_20110828_123359[/url] by [url=http://www.flickr.com/people/25266351@N06/]Hallsy01[/url], on Flickr

[url=http://www.flickr.com/photos/25266351@N06/6097850992/][img]http://farm7.static.flickr.com/6192/609 ... d96f_b.jpg[/img][/url]
[url=http://www.flickr.com/photos/25266351@N06/6097850992/]IMG_20110828_123339[/url] by [url=http://www.flickr.com/people/25266351@N06/]Hallsy01[/url], on Flickr

[url=http://www.flickr.com/photos/25266351@N06/6097304793/][img]http://farm7.static.flickr.com/6006/609 ... a88e_b.jpg[/img][/url]
[url=http://www.flickr.com/photos/25266351@N06/6097304793/]IMG_20110828_123326[/url] by [url=http://www.flickr.com/people/25266351@N06/]Hallsy01[/url], on Flickr

[url=http://www.flickr.com/photos/25266351@N06/6097304091/][img]http://farm7.static.flickr.com/6068/609 ... 15c2_b.jpg[/img][/url]
[url=http://www.flickr.com/photos/25266351@N06/6097304091/]IMG_20110828_123255[/url] by [url=http://www.flickr.com/people/25266351@N06/]Hallsy01[/url], on Flickr

So, looks like it will need a rebore. I'll get a borrow a bore micrometer tomorrow and see if I can meaure the bore around the damaged area to get an idea of how much it will need taking off.

In the meantime, I have had a very quick look at the bottom end. The crank feels smooth by hand, but what is a concern for me is that the conrod can be rocked from side to side. I understand this can be normal, but how much is too much, if any? Likewise, does anyone know the specs for side to side movement (not rocking), I only have the Leisure Trail manual at the moment. Pulling the conrod up & down when at TDC I can't feel any knocking that would suggest radial wear, but the rocking seems to suggets otherwise. As this is a needle roller bearing rather than shells, is that what causes the slight wobble, or a sure sign the big end is nackered? The big end bearing doesn't look discoloured at all.

I understand the original mk2 workshop manual is all in Japanese, is the AR manual a worthwile download or will very little be the same?

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Re: And so it begins.......... Mk2 rebuild

Post by fallenmikethebike » 30 Aug 2011, 22:18

Side to side movement would suggest some wear in the big end,and side thrust washers are reaching the end of their life.
I fully under stand it's more expense, but if you're unsure, it's really worth having some one evaluate the wear.
Putting all the bike back together, then for the bottom end to let go would be heartbreaking.
I would highly recommend have the balance shaft bearings replaced at the juncture you're at as well, as this is a well know short coming on CRMs.
Mike
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Re: And so it begins.......... Mk2 rebuild

Post by knackeredMk1 » 31 Aug 2011, 03:16

Some side to side movement is fine on the big end. If there is any hint of vertical movement then you need to replace.

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Re: And so it begins.......... Mk2 rebuild

Post by Hallsy » 31 Aug 2011, 15:18

Thanks for the advice, I work with a guy who used to work with Stan Stephens doing machining & revuild work, and although he hasn't seen the bottom end yet, he did say that some rocking is usually OK. As Knackered said, just to check for radial play and any discoloration of the big end bearing.

As I say, by hand at TDC I can't feel any radial knocking, I know feel doesn't tell you much, but ime you can usually feel movement. I'll try to put a clock on it and pull it up & down, although it won't be an ideal way of checking.

Fallenmike - I had read the rebuild thread from the FAQ section and the guy mentions about excess side to side clearance on the big end, but I've not found any actual figures. Do you know what this movement would be from factory, and what the allowance is?

I know the pictures above aren't visible at the moment, I have donated to the site, but Paul is away at the moment so said he would upgrade my account when he was back. Hopefully they will become visible once I have been upgraded?

I forgot to mention that the flange of the exahust port has been damaged. It looks like it would still seal OK as the mating face is complete and celan, but it would be lacking in support and possibly vibrate more.

[url=http://www.flickr.com/photos/25266351@N06/6097310689/][img]http://farm7.static.flickr.com/6079/609 ... a706_b.jpg[/img][/url]
[url=http://www.flickr.com/photos/25266351@N06/6097310689/]IMG_20110828_123222[/url] by [url=http://www.flickr.com/people/25266351@N06/]Hallsy01[/url], on Flickr

One idea we looked at today was to machine out the inner step that is partially there, and turn up a new steel ring to same dimensions (with the outer part that's broken added as well), then press it into the gap, so that when the exhaust is bolted up it will seal on the same face, and use the steel step ring as support.

Looking closer though we wonder if a previous bodge is what caused the damage to the bore. There is some type of resin around this broken piece, and on the underside of the piston you can see a small deposit of what looks like blackened glue. Likewise the marks on the piston are black. Wondering if after this bodge the engine was started and it sucked in some of the glue, which casued it nip a little in the bore on the exhaust side and cause the damage. Far fetched? Maybe, but it's a theory!!

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Re: And so it begins.......... Mk2 rebuild

Post by fallenmikethebike » 31 Aug 2011, 18:18

:( No sorry I don't know the tolerance that's permissible,and as Knmk1 says some movement is tolerable.
I think, it's usually measured with a couple of thou, feeler gauge, on the thrust washers to bottom end side face.
Mike
VFORCE REEDS-MUGEN HEAD AND BARREL-WHITE POWER-ALL ON MY WISH LIST!!

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Re: And so it begins.......... Mk2 rebuild

Post by Hallsy » 31 Aug 2011, 18:19

No problem Mike, looking in the AR manual they suggest 0.85mm iirc, but I don't know for sure how much of the AR manual specs I can use on the MK2.

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Re: And so it begins.......... Mk2 rebuild

Post by Hallsy » 09 Sep 2011, 12:46

Not loads happening at the mo, been away for a few days and had other stuff on.

Stripped and cleaned the carb in an ultrasonic bath, looked to be clean internally anyway, but was pretty shitty on the outside. Jets looked to be clear. There is the odd o-ring missing and the float bowl gasket has gone hard so will need a gasket/o-ring kit.

Cleaned up the frame ready for powdercoating, I plan to bung the 2-stroke oil entries/exits, and mask up any bearing faces, hopefully this will resist the shot blasting. Probably a silly question, but as I've only seen this bike in bits I'm not sure, but what I assume is the 2-stroke tank (top tube of frame) has two filler holes, why is this? Or is one for something else?

Stripped the wheels down ready for new bearings, it looks like the wheels, or at least the spokes/hubs have been painted which is annoying as it's going a bit flaky and the spokes underneath look to be mild steel. I'm assuming someone has painted them to tidy them up (although the rims aren't painted), or was this factory finish? Stainless spokes would clean them up, but probably unnecessary expense at this stage.

Not put a feeler gauge against big end yet to check thrust washer clearance, but while I was there I tried selecting gears (visually the gear selectors look OK, doesn't look like it has been apart anyway), I seemed to be able to select them OK but would have to rotate the crank, then something would click and I could select again, although now it seems at a point where I can only select two gears. My question is, am I being an idiot, would I need to remove the clutch (or depress it if I had the lever connected) to be able to select gears like this, or should it be fine with engine not running? I'll be splitting cases anyway to clean them out, replace bearings/seals, etc so will inspect the gear mech then but thought I'd ask the question!

I've had a bet with a few of my workmates that I'll have a rolling chassis within 2 weeks!! Best get on then!

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Re: And so it begins.......... Mk2 rebuild

Post by back off road » 09 Sep 2011, 20:33

top hole is the filler bottom hole is the oil warning light sensor
Im thinking about a bike with more valves than a powervalve

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Re: And so it begins.......... Mk2 rebuild

Post by Hallsy » 15 Sep 2011, 21:45

Thanks BoR :)

So, still waiting on bits, namely some decent paint stripper (seems that due to new EU regs Nitromors Automotive (was stronger than normal one) is not available :evil: ) and a few bits from David Silver - Swingarm bolt & nut, dust caps and a couple of bushes.

So nothing too exciting going on really, stripped back wheel, tried to clean it up a little but someone has painted the hubs & spokes previously and it's a bit flaky now. I'm not keen on the idea of painted spokes, but no need to relace at the moment, so I may just repaint them again for now just to tidy up a bit - undecided on that one for now. The rims I tried polishing quickly with Megs NXT metal polish, but think I'll give them a hit with my mops - or are they lacquered?

Not so clean:

Image

Headset press I made for my MTB's was just the right size for pressing in the new bearings:

Image

Fitted the new brake disc that the previous owner supplied, not sure who makes them, but hopefully they'll be OK:

Image

The bearing spacer looked like it had been chewed up by a bulldog, one of my workmates offered to make a new one so who was I say to deter him!!

Image

The screw in cap had seen better days so a new one of those has been made as well, just need to put it on the mill to drill the peg spanner holes.

Moved onto the forks. The uppers have been repainted gold, it wouldn't have been too bad a job, but the paint makes them a bit big for the yokes and it's flaked off in places. The uppers have a few scuffs on them so no point on getting them anodised again, I'll just strip the paint (if my paint stripper ever arrives!) and use decals to cover the scuffs.
In the meantime I've stripped them down ready for new oil & seals:

Image

The springs spacers have some corrosion on them which makes me think the bike has been sitting for a while.

Shock was in a bit of a mess as well, it had no Nitrogen in it and had an oil leak from the body where a copper washer was missing. This will be sent away for a rebuild.

Image

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Re: And so it begins.......... Mk2 rebuild

Post by Hallsy » 15 Sep 2011, 21:45

Dropped the frame and subframe off at the powder coaters yesterday and I had a call from him this afternoon to say it was ready to collect :lol: Phone pic - sorry!

Image
2011-09-15 17.23.07 by Hallsy01, on Flickr

I'm now in two minds about the swingarm, this was fairly rashed in places, so I started to rub it down to aim to retain the original brushed ally look. Trouble is some of the pitting & scrapes are quite deep, and now I can see that it was originally lacquered (which seems quite durable, maybe PC?). I may end up getting it powder coated, but I'll try tidying it up for a few hours first to see what I think. I've polished car wheels before and always get to that half way point when you ask yourself why you started!!

Once that is done I have the bearings & seals ready to be fitted to swingarm (went with the 18mm wide ones) and will need to make a solid dust cap to stop a small crack from spreading where original dust cap is fitted. Swingarm bolt is on the way, bushes I will make, just need to get the swingarm bolt to confirm the bore needed (they are 63mm wide as far as I have read?). Have the fork oil & seals ready, as well as new front wheel bearings:

Image
2011-09-15 19.45.24 by Hallsy01, on Flickr

For the linkage I got away with cleaning & polishing the old needle bearings & bushes, which is good as they were quite pricey, even from a bearing supplier.

Should still be on for my little bet of having it rolling by Wednesday (apart from shock service) :)

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Re: And so it begins.......... Mk2 rebuild

Post by knackeredMk1 » 15 Sep 2011, 21:49

Moving on :) .

Looks like the fork bushes need to be replaced. Bare copper - not so good.

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Re: And so it begins.......... Mk2 rebuild

Post by Hallsy » 15 Sep 2011, 21:53

Trying too!! Trying to keep it paced otherwise I'll spend too much too quickly (trying to keep overall spending from getting excessive!).

I did wonder about the bushes, but I must admit I have not looked at them since I stripped them as I still need to thoroughly clean the lowers & internals. Should have added a pair to my David Silver order :oops:

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Re: And so it begins.......... Mk2 rebuild

Post by back off road » 15 Sep 2011, 22:00

Hallsy wrote:Trying too!! Trying to keep it paced otherwise I'll spend too much too quickly (trying to keep overall spending from getting excessive!).

I did wonder about the bushes, but I must admit I have not looked at them since I stripped them as I still need to thoroughly clean the lowers & internals. Should have added a pair to my David Silver order :oops:
;) sorry Hallsy but its gonna get expensive
Im thinking about a bike with more valves than a powervalve

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Re: And so it begins.......... Mk2 rebuild

Post by Hallsy » 15 Sep 2011, 22:05

Well, hopefully now I will only have to spend out money on the engine, apart from tidying little bits here & there. If I decide to start uprating bits, or blinging the bike up then that will come later once it has been rebuilt to a (hopefully) reasonable standard.

Nack - I'm guessing it's advisable to replace the bushes in pairs? Any reason not to trust aftermarket? Wemoto have the inners for ~£8 each and the outers for ~£3 each. LT want ~£50 for a bushing 'kit'.

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Re: And so it begins.......... Mk2 rebuild

Post by fallenmikethebike » 15 Sep 2011, 22:24

Not replacing the bushes would be a false economy,as the seals will inevitably blow again.
Mike
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