175TS with 125S engine project

[blethermaskite]

Think about how hot the stator /windings get when the engine is at normal working temperature, you are not heating the rotor hub up much more than this and only momentarily for effect. Just apply heat carefully and for as short a period as possible.
Cheers,
George

[George]

Had my tea break thought I would tidy shed, gave rotor one more try no heat no hammering just tightened a touch more success.rotor is free.
Will stop now on a good result. Start again Monday. Thanks for help. Tea breaks and patience is the answer.

[Duccout]

Tea breaks are the answer to everything - at least in Britain!

[blethermaskite]

I'll drink(tea) to that

[George]

The crankcases are split. Cleaned bearing cage bits, piston ring parts and lots of alli pieces from sump! Oil like tar and oil filter lying at bottom of sump. Sludge traps and crank oilways blocked solid with dry carbon and alli. particles causing oil starvation.
All new bearings, bushes and conrod kit ordered and delivered. Crank and barrel/new piston dropped off at my local engine machine shop. He asked me why the piston has two oil rings and thought that the bottom one would just cause more drag lose horse power and asked is it necessary. Has anyone got an opinion on that.
Gear cluster in good condition. Small parts sent away for chrome plating.
Petrol tank has been getting cleaned with electrolysis method. Almost ready now, not helped that previous owner sealed the tank without cleaning tank leaving rust under seal. No leaks tank steel is thick on these bikes, sealer not going back. Will coat with two stroke oil to preserve while waiting for paint job.
Working on this engine has been a struggle, Looks like there has been a recent rebuild with the previous owner doing everything wrong he could think of. I feel that I have turned a corner and looking forward to engine rebuild when I get all the parts.
To celebrate I got on the Moto Guzzi 750 and had an enjoyable ride out

[George]

I forgot to mention that sludge trap screws were not very tight, easily undone with screwdriver, is this normal. Any advice is welcome.

[Duccout]

Hi George,

Well done getting to this stage. Nigel will enlighten you, but AFAIK, the sludge trap screws are always very tight and the ends are punched to lock them in place, so it looks like the previous rebuilder did not tighten them up properly. Nigel sells plugs with an Allen head top that are much easier to use. As for the extra oil ring at the bottom, I don't know what that is used for, but it must cause extra drag and I would have though that a modern single ring would be more efficient, allowing the lower ring to be omitted?????

[Ventodue]

<snip> As for the extra oil ring at the bottom, I don't know what that is used for, but it must cause extra drag and I would have though that a modern single ring would be more efficient, allowing the lower ring to be omitted?????

Nigel and the other engineers to advise, but I understand double oil scraper rings is a bit, 'ancient technology' ..

[Jon Pegler]

I would guess that you are OK leaving off the bottom scraper ring, but I would just check that the oil drainage holes in the piston are large enough to remove the scraped oil.
The holes are usually about 2mm diametre which should be sufficient.
If they are smaller than 2mm, I would stick with the bottom scraper as there may not be room through the holes for the oil to be removed and it may blow past the ring.
I have a theory that the modern Omega pistons use in some Ducati V-Twins are getting a lot of oil into the combustion chamber because the oil drainage holes total cross sectional area in the piston are less than a quarter of the cross sectional area of the holes in the Borgo pistons that they are replacing.

Also, the sludge trap screws in Mototrans 125 motors are threaded M10x1, not M18x1.
The allan headed screws that Nigel Lacey sells are the larger size and will not fit the Mototrans bike.

Jon

[LaceyDucati]

Jon as we we supplied those Bevel Twin pistons, I will add a comment.

The oil issue experienced by some customers with our early batches of Bevel Twin "standard" Omega pistons only effected some customers. The fact only about 10% of twin customers reported issues means that the issue was not entirely piston design related. The high comp pistons available at the same time did have different oil drain holes (partially out of the groove) and none of those customers reported the same issue. This does therefore indicate that the drain design was potentially an issue, but the fact that some customer engines only suffered on one cylinder and no singles using the same pistons reported issues, would indicate other contributing issues.

Needless to say all Omega twin pistons from 5 years ago have different oil drain holes and all pistons now utilise NPR rings as used by most other piston manufacturers. We have not had any reported issues with any of the Bevel twin Omega pistons sold over the last 5 years. Most if not all customers who reported issues have been given or offered replacement pistons. That still leaves a few hundred customers out there 5 to 10 years on still using them or maybe sitting on there bench. who knows! Whatever we move on.....

Best Regards Nigel