Motorcycle and Scooter appreciation

Lidl is the newer, younger competitor of Aldi! People don’t realise Aldi came first!

Guess how deep I got before lunch…

Looking at the insane play in the little end bearing, but the relatively minor scoring on the piston… I am going to try to reassemble with just a new bearing for now.

I want to do my research into people who can provide me a piston as well as the bore and hone. Then I can make a call whether to do the work or sell on the bike.

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We don’t have Aldi here. Lidl is common and very handy for underwater welding equipment 😂😂😂

Well done for getting this far into it. Seems like assessing the situation yourself, before getting some help, is always a good move. If anything it's good experience and you're saving a few quid too. Fingers crossed the new bearing does the trick.

Good work. Post some pics of the piston and bore. Is it a steel liner?

Scoring on the piston skirt?

See problem could be anything, only know when you take it apart.

You are missing out...

Shed-loads of movement with the piston in the barrel, head removed. Rotational play as well as side to side (rocking).

Some fine scoring nothing mega-deep. A couple you can feel with fingernail but also the rings move beyond the indexing/stopper points.

It took a couple hours of hanging out at the mechanics before the main guy had time to look at it, but he thinks it needs a new piston and bore/sleeve. He thinks it’s too far gone for a light clean and rings, says I’d be lucky to get 500 miles with a new bearing without proper engine work.

The numbers inside the piston look like it’s already oversize but maybe I’m wrong.

I left them there but they won’t have time to get a quote from the machinist until late this week. I’ll swing by tomorrow and grab them to ask a local business recommended by another rider.

There’s play in the rod, loads of side to side (unacceptable level), and also a little bit of up-down in various stroke positions.

So. Looks like total engine rebuild and all that comes with it!!

Bugger. But I guess I’m learning. Very late in the day of 2T to be learning this stuff, but I guess it’s experience I won’t soon forget.

Now, on one hand I could reassemble with new little end bearing and deal with reduced piston slap and compromised compression. It’s supposed to be a beater bike. But on the other hand I’ve gone this deep, I might as well rebuild it properly and have an engine that works properly.

I’ll be spending a lot of money on a bike with practically zero value. By the time I do a complete nut and bolt rebuild, I doubt I will see any increase in resale against leaving bottom end noisy sold as seen with “slight rattle”.

So, if I sold it now with only the new bearing and gasket, maybe I lose a couple hundred on resale as a ‘project’. If I do a full rebuild I’ll lose a couple or a few hundred in resale as a fully working bike. My heart says rebuild it, my head says get shot.

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Could always just assemble it yourself. Get the bearings and seals from a bearing supplier.

Now let's talk about enlarging the transfers for more power

Local bearings supplier is researching the needle cage bearing and large o-rings on top of the cylinder. May just have to buy them from Rotax UK.

So, as I understand it, this crank bugger can’t be ‘easily’ disassembled to replace the big end bearing. Not impossible, but it will be easier to replace the assembly. I’m calling the UK guy with NOS parts to see what he has in stock tomorrow. He has the entire piece for a ‘fair’ price apparently.

Assuming that since I’m in the bottom end, I should replace any and all bearings while I’m in there. Whatever ‘mains’ are.

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Now let's talk about enlarging the transfers for more power

You mean dremel the ports to increase in-out flow?

I was told about using a needle file to smooth the sharp edge of the ports to speed up the flow.

We were always in the garage porting the 50cc bikes we had. You could get a few mph quicker but that was all you needed when you were all racing on 50cc.

That looks like a plated cylinder to me, probably Nicosil - in which case, you don't bore them. They get replated and honed, usually at a fairly extravagant cost. It looks worn, but you really can't tell unless you measure it. Generally if you can't see any evidence of hone marks, plated cylinders are usually in need of redoing.

If you've up and down play in the crank, it needs rebuilding for sure. Unless new cranks are very available and cheap, you usually press out the pin (with a bloody great 20ton press) and fit a new rod kit with big end bearing as a set. It would be weird to do all that and not replace the rod. It shouldn't be too expensive.

I'd look around on the bay for a less used cylinder - Nicosil bores last a frigging age if they're looked after. I'm surprised to see that wear on a trials bike - my CR250 is 2001 and on the original cylinder!

It’s from ‘96 so very old, and likely revved long beyond when the bearings wore out.

There’s only one used cylinder available on ebay for £150. Considering there’s at least one stud with nut still on the outside, I bet it needs some work too.

As I understand it looking at the parts stockist, the rod alone (if available) will cost as much as the NOS crank assy, even before labour on top. Maybe I just bite that bullet on the new assy.

I wouldn't piss around with the porting - it's a trials bike. Most of the power from two stroke engines comes from the exhaust. Expansion chambers are tuned to provide a supercharging effect, that's dependent on the port timing and engines expected RPM operating window. You really need to modify stuff as a system to be effective.

Damn that sucks. Are there any Rotax specialists in the UK you can ask about bits / compatibility? It sounds like a money pit if you can't get parts easily. In fairness, if you do rebuild the crank, replate the cylinder etc - it'll probably last for bloody ages as a trials bike but it won't be cheap. Only really worth it if you love the bike....

I said talk, not do ;)

Have a few stories of enlarging the ports for moar power and destroying cylinders.

Would getting bits from the EU be any cheaper?

Orings are orings, as long as you have the right material then diameter and size. You can shorten bigger o rings to size.

Thought most bearings in two strokes are usually standard iso sizes. Or just wander to the machine shop and they have the parts. Different country I suppose and 2 stroke bikes are far more common.

Main bearings have different internal tolerances so you need to be careful you’re fitting like for like. I think C1-5 - I always try and use OEM for mains, unless they’re coming from someone that really knows their stuff.

Sometimes it is worth confirming that the correct bearings (clearances) have been fitted in the past.

The experience I have had with 2 strokes was in Italy, even my rgv and rs250 bits came from Italy.

SO much for taking my own advice. I was out last night dremelling the ports on my RM (chamfering the windows.) I'm going to do the absolute dirt and just bung it back together. I measured the cylinder and bore and they're actually fresh - looks like the previous keeper cold seized it. Cleaned up the piston with a bit of 400 wet and dry and have bunged my el cheapo hone down the bore. I think it will work. For a bit....

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Did a quick audit and I think I have most bits to build a motorcycle in all the boxes…

Do itttt

Seems like a good plan!😁

I was out last night dremelling the ports on my RM

Do as I say not do as I do ;)

How is the car going ;) You know one project at a time, move on once finished ;)

Think I’ll start pulling apart the Scorpa/Rotax bottom end this week/weekend. Assess the situation before investing in the parts. Top end is waiting for the mechanics to get a quote from their chosen machine shop.

In other news,

The Blackbird is in for fork seals and front pads tomorrow AM. I drove it to Cheddar and back, felt a little…easy. <40mpg is painful after smaller capacities though! Especially when the bike never goes above 6k! Ha!

Sherco needs swingarm bearings. Gonna get that done before my first ever trial in a fortnight.

XJ is still stored, and DR350 is sat looking sad waiting for me to have time and energy to do some lanes.

What's the hivemind on removing your front sprocket cover? On a dirt bike. Cleaned the bike after getting it very muddy then removed the front sprocket cover to find all manner of gunk. I like the idea of this area being cleaner but also quite fond of my fingers.