Hi all, new to the forum but have been rebuilding my CRM MK1 for the past couple months.

I've currently got the engine stripped down to the bottom end, cylinder and head are off. Got a few questions.

1. What's an acceptable way to measure whether or not the crank/rod are still good? I have a dial indicator and some leaf gauges. The CRM250 AR manual states side clearance on the big end is 0.85mm or less, but I don't know whether that's a valid figure for the MK1 crank or if it even matters. I do not detect any axial play on the rod with the dial indicator, but there is a good 1 mm or possibly slightly more of gap between the thrust washer and the crank cheeks at the big end.

2. The rear shock is pretty well buggered and from what I can tell they're not really "rebuildable" (based on disassembly reports I've seen on other forums). What is the best swap option? An XR250 shock isn't out of the question.

3. I'm also considering right side up XR250 forks as a direct swap as I've heard they are better than the CRM units.

4. While pressing the bearings out of the linkage, the inside bore on one of the lobes of the linkage got gouged (damaged bearing shell cut some grooves into the bore). I smoothed it up a bit with some very fine sandpaper and the old bearings I pulled seem to install in the bore fine without any drag or damage - will this be OK? Will I need a different linkage for the XR250 shock?

Thanks for your answers in advance.

Answers -

1. From what I can tell of your big end it seems fine. AR specs are transferable.

2. The shock is rebuildable but it was pretty poor to begin with. I rebuilt 2 mk1s (see Motards /Specials /Rebuilds) and replaced the rear shocks with XR250 shocks. They are so much better BUT you need to replace the whole swing arm and linkage from any other Mk (they are all the same) AND relocate the top mount of the shock. I can send you some photos of the cutting and rewelding positions if you require (they were on here …blurred images are still there.)

3. XR250 forks are a direct swap for the originals but again they are much better. Springing is firmer and damping is much improved. I have a pair in very good condition that I can supply you with.

4. If they fit in snuggly without any movement then they are fine but bare in mind what I said in 2.

knackeredMk1 wrote: ↑

27 Feb 2020, 20:47

Answers -

1. From what I can tell of your big end it seems fine. AR specs are transferable.

2. The shock is rebuildable but it was pretty poor to begin with. I rebuilt 2 mk1s (see Motards /Specials /Rebuilds) and replaced the rear shocks with XR250 shocks. They are so much better BUT you need to replace the whole swing arm and linkage from any other Mk (they are all the same) AND relocate the top mount of the shock. I can send you some photos of the cutting and rewelding positions if you require (they were on here …blurred images are still there.)

3. XR250 forks are a direct swap for the originals but again they are much better. Springing is firmer and damping is much improved. I have a pair in very good condition that I can supply you with.

4. If they fit in snuggly without any movement then they are fine but bare in mind what I said in 2.

Hey, I wasn't expecting an answer given how dead the forum is, but very nice surprise.

1. Am I measuring the side clearance on the big end correctly? I'm putting the gauge between the thrust washer and the actual crank journal - I wasn't sure if I was supposed to do that, or between the thrust washer and conrod big end. I imagine the clearance should be the same either way, but eh...

2. I was really hoping to avoid having to replace an entire swingarm assembly. Is there a specific thing that the MK1 swingarm has/doesn't have that is absolutely imperative for the XR250 swap?

3. I appreciate the offer but I feel shipping a pair of forks to Russia would be a huge cost. I have found XR250 forks locally. I imagine it doesn't make much sense to swap ONLY the forks and leave the rear shock stock, as this would be an imbalanced suspension, so I'm holding off on buying until I know for sure that I want to get into the rear suspension swap.

Photos of suspension mount mods required would be great, thanks!

4. I figured as much, thanks a lot.

1) There can be an amount of sideways 'waggle' at the small end but NOT in the line of the connecting rod.

2) The sizes of the 'dog bones' and linkages are different but you probably could use the linkage to attach the XR250 shock to but I don't know. The reason for changing the swing arm and linkage to fit the XR250 shock is that the XR250 shock is identical in dimensions and better at damping and springing than the original CRM 250 Mk2 shock. If you keep the Mk1 swingarm and linkage I couldn't tell you where the new mounting point might be you will have to take an educated guess.

Hi everyone!

Been a while, eh? I've mostly been riding other bikes all spring and summer, and putting some work into the CRM when I have a chance.

What I've done so far:

1. All parts of the engine masked, stripped, blasted and powdercoated.
2. Got a cone pipe custom made to replace the stock exhaust. Stainless steel. I'll be making a silencer to match it myself.
3. Frame powdered.
4. Rear shock rebuilt. Swingarm and linkage completely rebuilt with fresh bearings and seals and bushings. I ended up using XR250 bushings for the swingarm pivots, had a machinist take the inner diameter out by 1mm to fit the CRM swingarm bolt. The linkage bushings were also ruined on mine, used piston pins from some sort of Soviet-era motorcycle, got the machinist to cut them to length and bore out the inner diameter to fit the linkage bolts.
5. Stockpiled all the bearings for the gearbox and crank and such.

There's a few things that still need doing:

- order a rod rebuild kit from Leisure Trail. My crank seems to be fine but I would rather have a freshly rebuilt one and not worry about it for a few years.
- take my cylinder to the local shop and get them to bore it out to get rid of the egging and order a oversize replacement piston.
- get seals and such in order

I have a question about the seals - original crank seals seem to be hard to find. I believe I managed to find an OEM generator side crank seal. Finding the clutch side crank seal (the big one) is hard. I ordered one from my local shop and they ended up refunding me my $70 or however much it cost. I did some cross referencing of sizes and found that the mid 90's RM250 and RMX250 have an identically sized crank seal - has anyone tried using one of those?

Suzuki p/n 09283-38018 - crank seal 38x52x8

The one difference I see is that the Suzuki unit has a little metal bit on the outside of the seal.

Alternatively - is it possible to use the later CRM Mk2/3/AR seal 91202-KAE-731 ? It measures 38x52x10 instead of 8mm. I will measure the seal seating area on my crankcase half and see if there's any room to spare in there...

Thanks for all the help!

Crank seals are generally available I believe - you don't need OEM.

I thought LT required you to send in your crank so they could get a contractor to do the work required to replace the rod?

I have a set of XR250 forks that are a direct swap. Just fit and forget swap for the original CRM ones. They have far better springing and damping. Also adjustable damping.

Thanks for all the help Knackered.

I spoke with Leisure Trail on the phone a week or so ago and they said they could just send me the rod kit - sending them a crank would be prohibitively expensive when I could just have one of the many old-timers who've been doing it for decades rebuild it for me here in Russia.

I have found some seals that are similar in size, but the crank seals on the CRM appear to be special in some way (dual sided, maybe a specific geometry or material) and I don't trust a 2 dollar generic seal from China to do the job just as well as the OEM unit. If you can suggest a part number or specific manufacturer I'll be happy to have a look.

I think that next winter when I've ridden the CRM for a bit I'll think about whether or not I want to go further into the mods as far as fork swaps and such. I'll either keep it the way it is with the stock suspension all around and just use it for tame rides (passenger pegs means I can haul a girl on the back and have a nice little picnic in the woods). I am itching for a new project that isn't a 31 year old bike with unobtainium parts, so I think when I finish the CRM that'll be it for that particular machine.

I just dropped the cylinder off with the machine shop to get it checked and bored. Is there a specific make of piston you recommend? Wossner, Pro-X, Wiseco seem to make TRX pistons that will work with the MK1.

Another question is - do you recommend keeping the oil pump? I personally don't mind premixing gas. I had the oil hoses and everything else removed when the frame was getting blasted and powdered - I could just cap off the open bits, make a block-off plate for the oil pump and use a CR intake boot without a spigot for oil injection (planning to use Boyesen RAD Valve if I can find one). We've all heard horror stories of oil pumps going bad but the one I took off the CRM looks perfectly fine and I'm sure it's still got a lot of life left in it.

Sorry i am no help here but jut wanted to say, looking forward to seeing some pictures.

Hi everyone, long time, no post, I have been very busy lately with other bikes and projects, and life in general. That being said I do have some stuff to share:

1. I decided to go with OEM crank seals after all, despite the exorbitant price they wanted for a clutch side crank seal (something like $45-50 dollars).
2. I'm keeping the stock forks. I did manage to rebuild the rear shock, the seal is in good shape, just needed an oil change and some fresh nitrogen. Seems to be doing OK so far, but haven't tested it yet.
3. Pro-X piston for a TRX250R in 0.50mm oversize is sitting on my shelf waiting for me to drop the cylinder off at the machine shop. Haven't gotten it done yet but will do soon.
4. Frame has been powdercoated. New steering stem bearings and races pressed in. I'm waiting for the weather to get better (temps above zero) so I can start using my new parts washer in the garage and get the plastic bits all cleaned up. Swingarm has been cleaned up as much as I could, all bearings and seals replaced in linkage and swinger.
5. Engine has been powdercoated as well to go with the mid-80's "works" CR theme I'm going for.
6. Cone pipe has been made out of stainless steel by a local fabber based on my technical drawings. I did some minor tweaks to the cone shapes and lengths, but tried to stay close to the overall shape and size of the stock pipe. The new pipe is less than half the weight of the stock unit. I am currently looking for a good silencer to mate it to, looking at a KTM 250 can this weekend.

The jury is still out on my crank. I will likely get the tin cans welded and the crank itself rebuilt. Don't really have the money to spare for a rod kit at the moment though. Later this spring.

A photo to tide you boys over for the time being.