Honda CRM250 Mk2 Rebuild Project

[Hallsy]

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 '91 CRM250 MK2, 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:

https://farm7.static.flickr.com/6205/6097306941_5219fc09cd_b.jpg
IMG_20110827_110330 by Hallsy01, 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):

https://farm7.static.flickr.com/6010/6097855556_feb61740d0_b.jpg
IMG_20110828_123124 by Hallsy01, on Flickr

Here is the piston as removed:

Fairly normal carbon pattern?

https://farm7.static.flickr.com/6132/6097307733_2eb8dfbe9b_b.jpg
IMG_20110828_120649 by Hallsy01, on Flickr

Intake side:

https://farm7.static.flickr.com/6197/6097854128_1b09affb12_b.jpg
IMG_20110828_120700 by Hallsy01, on Flickr

Exhaust side:

https://farm7.static.flickr.com/6195/6097854912_a513703c07_b.jpg
IMG_20110828_120718 by Hallsy01, 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:

https://farm7.static.flickr.com/6121/6097306207_45b869e47f_b.jpg
IMG_20110828_123359 by Hallsy01, on Flickr

https://farm7.static.flickr.com/6192/6097850992_c824ddd96f_b.jpg
IMG_20110828_123339 by Hallsy01, on Flickr

https://farm7.static.flickr.com/6006/6097304793_4b1656a88e_b.jpg
IMG_20110828_123326 by Hallsy01, on Flickr

https://farm7.static.flickr.com/6068/6097304091_c0b2cc15c2_b.jpg
IMG_20110828_123255 by Hallsy01, 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? Pulling the conrod up & down when at TDC I can't feel any knocking that would suggest radial wear, but the rocking seems to suggest 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.

[Hallsy]

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 than usual and start leaking.

https://farm7.static.flickr.com/6079/6097310689_b18e3aa706_b.jpg
IMG_20110828_123222 by Hallsy01, 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!!

[mad4it028]

that barrel looks far from ok to me , looks ok to be rebored..lol
____________________
always looking to buy bikes crashed ,unfinished projects,none runners pm me
currently riding kawasaki z1000 only bike ive ever loved

[Hallsy]

I said above it needs a rebore, lol!!??

Maybe the camera flash makes it look worse, but most of the bore looks OK, apart from the very obvious damage just above the exhaust port.

It will be getting a rebore, no doubt!

[dangerousdave]

I saw a good bit of info on the CRM 250 mkii here:

https://www.offwidth.co.uk/bike/crm_rebuild/index.php
____________________
1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50

[Hallsy]

Thanks Dave, I've read that write up a couple of times, no doubt it will help a great deal if I need to rebuild the bottom end.

At a minimum I will do the balance shaft bearings as those along with a siezed swingarm spindle seem to be the common CRM250 problems.

I found a link to the site above in the FAQ section on CRM250.com, a great site for info

[Hallsy]

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.

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), although it may have been a 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!

[dangerousdave]

The gear change does need a bit of movement from the back wheel to move up the box. Helps the gears engage.

For example, trying to go from neutral to fifth gear while the bike is at standstill won't happen. Might select third, but that's about it.
____________________
1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50

[Gazdaman]

Project looks good, more photos needed!

That exhaust flange looks ok to me, once the exhaust gasket was sat in there, I think that'd seal just fine.

Gaz

[Hallsy]

Cheers guys

Gazdaman - I did think that about the exhaust when I first saw it, but it may well be more vulnerable to vibration. I'll sort something out, as I say, either machine the lip and press in a new lip as such, or maybe machine a piece to fill in the part that's missing and get it welded or brazed in place.

As for pics, I've taken a few as I've been going but nothing too exciting happening at mo. Stripped forks today, want to replace oil & seals, but also the uppers have been repainted which is flaking off. The uppers have a few scrapes which is probably why they were painted but I want to strip them back to the original anodising. Hopefully the decals I want to use will cover the grazes. Unfortunately my turn to paint stripper - Nitromors Automotive seems to be out of production now (EU regs about some of the chemicals in it), so have had to order an alternative.

Shock was leaking oil from banjo connection on the body, so this will need replacing. Also gas needs recharging. I know I can get it serviced for £100, but I'm tempted to have a look myself, found some guides on the 'net and it looks similar to MTB shocks which I have done before. Only thing I wouldn't be able to do is Nitrgoen refill, but I can possibly get this done through work, if not I'll pay someone to do it properly.

[dangerousdave]

Just a thought, might be worth replacing the cylinder complete. By the look of the scoring on the barrell you are probably looking at 120 quid (ish) for Nicasil coating. Then the repair to the exhaust flange.

There's one on eBay for 110 quid which if its in good nick could be worth considering ?
____________________
1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50

[dangerousdave]

https://www.ebay.co.uk/itm/4711-HONDA-CRM250-CRM-250-BARREL-/400237777261
____________________
1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50

[Hallsy]

Cheers Dave, I had seen that one when was considering my options.

It's not Nikasil plated though, I think only the AR's had that. So just a rebore would be needed. Exhaust will only cost me time & favours, that's the benefit of working in an engineering workshop with fitters, machinists & welders (I'm electrically biased)! Some of the guys at work have rebored at work, but we don't gave a proper hone tool as far as I know so I'd rather have an engine builder do it!

If a good cylinder came up cheap enough it would be worthwile, but still a good chance of a used one needing a rebore.

I'm kicking myself as i forgot about a swingarm i was watching that sold for less than £10!! That's possibly a tale of woe for tomorrow though!

[Hallsy]

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 ) 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 - unless they are lacquered.

Not so clean:

https://farm7.static.flickr.com/6065/6150617803_40e3f25a9f_b.jpg
IMG_1332 by Hallsy01, on Flickr

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

https://farm7.static.flickr.com/6195/6151168144_1bf0fce7b7_b.jpg
IMG_1333 by Hallsy01, on Flickr

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

https://farm7.static.flickr.com/6180/6150619179_4494923e97_b.jpg
IMG_1335 by Hallsy01, on Flickr

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!!

https://farm7.static.flickr.com/6198/6151174950_14b25f6b67_b.jpg
2011-09-15 19.40.02 by Hallsy01, on Flickr

The screw in cap that is fitted to the sprocket side 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:

https://farm7.static.flickr.com/6156/6150616299_4b6613bb42_b.jpg
IMG_1330 by Hallsy01, on Flickr

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.

https://farm7.static.flickr.com/6209/6151165506_77073634ab_b.jpg
IMG_1329 by Hallsy01, on Flickr

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 Phone pic - sorry!

https://farm7.static.flickr.com/6175/6150621787_ef654cdfb2_b.jpg
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 ones which are a bit wider than standard, should last longer) 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. Have the fork oil & seals ready, as well as new front wheel bearings:

https://farm7.static.flickr.com/6086/6151173366_c717ecdd14_b.jpg
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)

[Hallsy]

Finally got my heavy duty paint stripper through on Friday, so tried some on my fork uppers. It worked well, but unfortunately the uppers are in quite a sorry state underneath. A few scuffs & scrapes, uneven shade of anodising, so unfortunately I will have to paint them again. Probably go with the same satin gold that I'll repaint the engine casings with, will have some pics tomorrow as I've not done anything with them all weekend.

Other than, I'm still waiting on bits from David Silver. Doesn't look promising for 7 day delivery as I ordered them last Tues and it still says they're on backorder

New rear wheel bearing retainer has been made (thanks to a couple of workmates ):

https://farm7.static.flickr.com/6167/6156169923_d8cf530244_b.jpg
2011-09-17 18.16.54 by Hallsy01, on Flickr

Been out & about this weekend so nothing else going on, will crack on prepping fork uppers and flatting swingarm tomorrow.

[dangerousdave]

coming on well mate
____________________
1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50

[Hallsy]

Been doing a little bit to tidy the forks up cosmetically this morning.

Scuffed uppers have been filled and one of them pretty much prepped, will hopefully get these finished & painted tomorrow.

Yesterday I decided I would get the swingarm powder coated. The original anodising was worn in places and to get it uniform I used a flap wheel in a drill, which worked really well, but couldn't quite get in all the nooks & crannies, and unless you had a very steady hand, the brush lines were not perfect. I wasn't looking for something perfect, just uniform, but it would need protecting. I'd figured I would give it a couple of coats of 2K lacquer, but unfortunately it won't ahdere very well unless I use an etching lacquer, which is pretty pricey apparently. So I ditched that idea and will be getting it powder coated. Satin black or satin silver, undecided so far!!

I'd mentioned before the small crack where the dust seal fits on the bearing housings. Welding was discounted as unsure about it messing with any production heat treating, that and it would be a bit thin to make a decent job of. So as the bearings will support the inner, I decided to use a cap in place of the Honda dust seal to support it exteranlly and help prevent cracking. I'll use something like Loctite bearing retainer in the crack and between the housing and the cap.

Here's the small crack (sorry phone pics again as was at work!):

https://farm7.static.flickr.com/6170/6175768356_513355d58c_b.jpg
2011-09-23 18.00.02 by Hallsy01, on Flickr

And here is the original dust seal next to the cap I'll use:

https://farm7.static.flickr.com/6171/6175787098_772e791371_b.jpg
2011-09-23 17.59.29 by Hallsy01, on Flickr

And in place:

https://farm7.static.flickr.com/6174/6175225073_a6d9ec267a_b.jpg
2011-09-23 18.00.15 by Hallsy01, on Flickr

Also made up some new bearing sleeves for the swingarms as I didn't have the originals, but these are being heat treated at the moment. Got my swingarm pivot and few other bits through from David Silver now, so once the swingarm has been coated it will be ready for rebuild.

Also painted the linkage and dog bones:

https://farm7.static.flickr.com/6160/6175300175_7cea4d2509_b.jpg
2011-09-23 17.58.44 by Hallsy01, on Flickr

Moving along...........slowly!!

[Hallsy]

Tonight was quiet so I decided to try to clean up the shock a little, which then lead me to stripping it down!! I'd been advised to leave it to suspension experts, but I had to have a look!!

I'd already disconnected the resorvoir as there was no nitrogen in it, and it was leaking oil from the banjo due to a missing copper washer.

The spring seat was caked in mud, grease and rust. There was no way the seat was going to 'tap' away from the centre piece and spring clip. Some Plus Gas and a hammer & drift sorted them out!! Looks like the two parts had rusted together so cleaned them up with a wire wheel, fit together nicely now.

Removed the bladder from the resorvoir, looked to be in good condition, but I have not yet pressure tested it.

The fun began when I started to strip the shock body. Seal head was tapped down and circlip removed, but trying to pull the seal head out wasn't too easy, the o-ring gets stuck in the recess for the circlip and needs quite a bit of force to remove it. I didn't have a slide hammer to hand, so decided to put an air fitting in the shock body and pressurise it force the seal head out. 6 bar later and the seal head was slowly moving, unfortunately I didn't fully consider how far the shaft would 'fly'!! Yep, the shaft went flying across the workshop into one of the doors!! In hindsight I should have rigged up something soft or something to catch it. Reassurlingly a workmate said when he did his 'it just popped out and slid across the bench'!!

Anyway, internal looks OK, but unfortunately I have damaged the piston slightly, so will need to source a new one. I've contaced a few suspension specialists to ask about serving costs, etc, but if spares are available I'll probably replace the o-ring and dust seal on seal head and the piston that I've damaged. Refill with oil then take it to a specialist to have it re-charged. I know that a specialist would be able to adjust the shims & piston to suit weight and riding style, but as I'm a total newbie I'm not convinced I'd know any better at the moment.

I'll replace the hose as well, it's not damaged as such, but it pretty hard & tired looking!

Anyway, shock stripped down (I'd put the bladder back in at this stage):

https://farm7.static.flickr.com/6169/6176191358_b040bb85ec_b.jpg
2011-09-23 20.49.08 by Hallsy01, on Flickr

and the damage I caused

https://farm7.static.flickr.com/6172/6176189082_26bda37108_b.jpg
2011-09-23 20.49.16 by Hallsy01, on Flickr

[steven_191]

If the barrel has a nikosil coating get it replayed by Langcourt

Also good luck with the project. When I pick up my first bike I needed a transit to get the two and a half bikes worth of boxes in.