250 Strada Strip Down

[Duccout]

Those who remember the saga of the ups and downs of getting my Mototrans Strada road worthy will be unsurprised that I have at last begun a full engine strip. I should have done this in the beginning, but I wanted to get it up and running and use it, so various jobs were neglected or bodged in order to achieve this. I can't believe that two years have gone by and the old thing is still running, but as a consequence of a petrol leak into the sump I can't put stripping it off any longer as the engine is really rattly now and I suspect that the big-end has terminal decline.

I found out when I bought the bike that the lower bevels were in a bad way, with several chipped teeth, so I have sourced a replacement set, and there is a lot of play in the vertical shaft joint that needs attention too, so it looks like now is a good time to get stuck in.

Apparently, flywheel pullers for the Strada and Forza are unobtainable; I emailed Jesus Guzman asking if he was likely to make any and he told me that there is no call for them because the Strada and Forza are rare bikes, which I find strange, because a search on Milanuncios (Spanish sort of Gumtree) shows loads of them for sale. Anyway, the result was that I had to spend two days in the garage making an extractor, and today the time came to see if it worked. There is very little depth of thread in the flywheel and I was worried that the extractor would just pull out and strip the threads. I sprayed the shaft with freezing spray before trying to pull off the flywheel, then screwed in the extractor, tightened the bolt, tapped the end and...... It worked! The flywheel was free. I was surprised at how heavy it is.

Anyway, that was it for today, next it will be head off, engine out and on the bench and the state of the big-end revealed.


Cheers,

Colin

[George]

Lesson to be learned there Colin. I have never trusted riding a new to me old bike including the ones that seller tells me is in good order. I always strip it down and if nothing is wrong I have gained peace of mind and if I do find things wrong better to find in shed than on the road. Good luck, at least you will now have time to sort fuel tank.

[Duccout]

Head and barrel off and on first inspection, big-end has no obvious play. Fingers crossed on that one, but I have not come across any obvious reason for the post petrol-in-oil rattle so far, although the cylinder head ports look strange and I am wondering if the petrol may have rotted the valve stem seals?

Might have the engine on the bench this afternoon.

Cheers,

Colin

[Duccout]

Not good news, although the crank spins smoothly, there is quite a lot of up and down play in the drive side main bearing, which might explain the rattle...... I can't see at the moment, but I suspect that the shaft has worn and the play is between the bearing inner race and the shaft.

Colin

[A.I.M]

Ouch! Hope you can get the problem sorted without having to part with too much money.

[Duccout]

It will be awhile before I can inspect anything - I can't get the cases apart! I believe that this engine has never been apart, and so there are 45 years worth of corrosion welding the cases together, and they ain't budging. If anyone has a magic solution please let me know.


Cheers,

Colin

[blethermaskite]

Colin, I have had a few stuck crankcase's in my time......bearing in mind that there are enough shafts trapped inside the case's to use effectively as internal drifts to get the them moving.......however in my experience this method will only work if you get the blowlamp out and get quite a lot of heat into cases especially around where you know the dowels are located because (unless somebody has been in there with the loctite) that's where things are stuck. I will only use a hide hammer to knock them apart (anything else will just break stuff).
I'm sure you have seen illustrations of the factory tool for the job which is basically a big plate that bolts where the primary drive case came off and has a couple? of big screws that bear on the internal shafts to force the cases apart, I have never seen this tool for real but a friend had a home made version for his race engines.
Cheers,
George

[Duccout]

Thanks George,

I read a post from Nigel where he states that he has never had to resort to making pullers, etc to separate cases, so this gives me hope, but after an hour of using the plastic mallet I have not the slightest gap in the cases. Nigel suggests tapping on the oil filler, breather and using an aluminium drift inside the selector drum as these points are near the dowels. I'll try some heat too.

Cheers,

Colin

[themoudie]

Aye Colin,

The '75 MotoTrans 350 MKIII engine had this same problem of corroded crankcases proving reluctant to part. Having been laid idle behind an Edinburgh tenenment for at least 15 years, chucked in a skip, retrieved and then sat in a leaking wooden shed holding the roof up, until I purchased the bits and housed them in a dry workshop in 2000.

I achieved succes by using the following method, having first stripped the whole of the cylinder head (mine was missing!), the barrel and piston, along with the primary transmission, the alternator rotor and stator, timing chest and contents, the final drive sprocket from the end of the secondary/layshaft gearbox shaft, the two cylinder mouth bolts and all of the crankcase securing allen set screws. Sit the engine bottom half in a large steel baking tray (this gets VERY MESSY!). Liberally sprary the whole of the outer join between the two cases with either PlusGas A, Bulldog BDX, or a diesel/paraffin mix and leave for at least 24 hours regularly applying more release fluid and at the same time using a nylon headed kinetic device to deliver short, sharp, shock blows to the whole length of the central mating join.

Then, re-assemble the cylinder head bolts back into their respective holes ensuring that they are threaded home, but do not foul the crankshaft or gears inside. Alternatively, use some M10 x 100mm or 150mm screws, or threaded rod, either a single length 1000mm or a pack of 6 x 300mm from Screwfix, along with some M10 nuts. You will also need 2x 5mm MS strip, 50mm x 150mm. I already have these taken from a local blacksmiths odds and ends pile, or you could try your local scrap dealer!

Drill an 10mm clearance hole throught the centre of one of the pieces of MS strip and assemble a rod, with two nuts secured to one end, locked and centre punched against each other and another nut threaded onto the rod. Then assemble as shown in the two attached images. You then hold the threaded rod in place with a spanner on the outer of the two "locked" nuts and another to exert pressure on the inner face of the opposite strip with the hole in it.

Do the nut up tight and then apply another series of blows to the join, using the nylon button hammer. I also applied force using the sharp end of a 300mm nylon tree felling wedge, hit with a 2lb ball pein hammer, with controlled hits (hit once, check for movement or damage, hit the opposing case, return). Tighten further the M10 nut and repeat. Apply more release fluid, especially to the area of the case dowels and repeat applying pressure, sharp blows. This will part the cases, but requires patience and applying progressive force/blows to the joint and cases. Beating the cr*p out of them will only result in a worse mess!

A mixture of carbonised oil/water/steel and alloy flecks and cotton rag fibres were in the bottom!

I hope that this decsciption and the attached images are sufficient information.

Good health, Bill

[Duccout]

Hi Bill,

Thank you for taking the time to write such a detailed report. I am exercising my grey matter (what there is left) and am readying myself for another attempt. Luckily, I did spray around the joint with Plus Gas last night, although I don't have much faith in it being able to penetrate. I will try your method and see if I can get it to move.

Cheers,

Colin