175TS with 125S engine project

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George
Posts: 83
Joined: Fri Feb 14, 2020 2:51 am
Location: Essex UK

Re: 175TS with 125S engine project

Postby George » Sat Apr 18, 2020 8:59 pm

Jon Pegler wrote:The Italian piston should fit fine.
The Italian and Spanish 125 pistons had similar part numbers.

Jon

Thank you for reply Jon. Italian available from Piston King. Will order when I feel more comfortable ordering from Italy.
George Essex UK

LaceyDucati
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Joined: Sun Sep 19, 2010 10:30 pm
Location: Wales UK
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Re: 175TS with 125S engine project

Postby LaceyDucati » Sun Apr 19, 2020 1:17 pm

Hello George

The circlip groove often breaks due to the groove being too close to the edge with some castings. This issue has been discussed on here some time ago and Jon's suggestion is probably about the best repair as weld repairs will most likely cause more harm/distortion to be viable. That said it is very debatable whether the circlip fulfils any function anyway, due to the direction of load on the gear.

I once received an engine for an overhaul after a successful season including a 3rd place in the Manx GP. On stripping the head I found the circlip missing (never in there) and no signs of any harm or distress......just saying :-)

On the subject of Loctite, I have never found it to be much use if the bearing is already tight or if used on a bearing at room temperature when it is loose and going to be subject to full engine temperature. If the bearing is tight at 100 degrees then I would just leave it. With slightly loose/creeping mains or gearbox bearings I fit/drop them into the cases heated to 100 to 110 degrees with the the outside of the bearing degreased and lightly wetted with engineering adhesive. A thin film of the loctite is formed around the bearing ensuring retention at temperature. When I first was building race engines I fitted loose bearings cold with loctite, On stripping the engine in a couple of years for inspection/overhaul the bearings were nearly always loose and no sign of the loctite. These methods do however rely on accurate temperature measurement and a bit of experience. If you use this method at too high a temperature there is a slight danger of the bearing being too tight in the casing at room temperature. If it is then it will have to be removed and start again.

Regards Nigel

George
Posts: 83
Joined: Fri Feb 14, 2020 2:51 am
Location: Essex UK

Re: 175TS with 125S engine project

Postby George » Thu Apr 23, 2020 8:09 pm

Trying to understand how top bevel bearing is fixed in head. The lip on the bearing housing is thinner than the recess in top tube flange, housing can move up and down with flange fitted to head without gasket. Should there be a spacer. I do not see how I can set up bevel gears without a fixed datum.
Hope I am explaining clearly.
Attachments
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George Essex UK

Duccout
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Location: Essex UK

Re: 175TS with 125S engine project

Postby Duccout » Thu Apr 23, 2020 9:05 pm

I can't answer your question, as the small engines differ in set up from the bigger ones, but I can see that your bearing steel housing has a cut out for a roll pin to stop it spinning; my 250 has this also and I thought that a PO had fitted it, but it must be a Mototrans modification.

Duccout
Posts: 261
Joined: Wed Feb 05, 2020 1:20 pm
Location: Essex UK

Re: 175TS with 125S engine project

Postby Duccout » Fri Apr 24, 2020 2:44 pm

George,

I can't see how the set-up can work either. The roll pin is listed in the Mototrans parts book for the Strada, so it is their modification, so looking at your pictures, if the cut-out on the lip of the bearing housing engages with the roll pin, then it looks like the housing will not press all the way into the head, and if shims go between the bevel flange and the bearing housing, then what purpose would the roll pin serve?

We need a specialist to explain!

George
Posts: 83
Joined: Fri Feb 14, 2020 2:51 am
Location: Essex UK

Re: 175TS with 125S engine project

Postby George » Fri Apr 24, 2020 4:48 pm

Duccout wrote:George,

I can't see how the set-up can work either. The roll pin is listed in the Mototrans parts book for the Strada, so it is their modification, so looking at your pictures, if the cut-out on the lip of the bearing housing engages with the roll pin, then it looks like the housing will not press all the way into the head, and if shims go between the bevel flange and the bearing housing, then what purpose would the roll pin serve?

We need a specialist to explain!


I have had another look at it today and cannot make sense of it. Hopefully someone with more knowledge will explain how top housing is held firmly in place.
George Essex UK

ranton_rambler
Posts: 275
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Location: Stafford UK

Re: 175TS with 125S engine project

Postby ranton_rambler » Fri Apr 24, 2020 9:16 pm

I don’t know if the 125 is the same, but looking at the cross-section in the workshop manual, the housing is pressed up to the shoulder on the outside by the outer race of the bearing. There is a little upstand on the bevel tube.
Figure 69, page 70. I think you have the same book.
Ian

George
Posts: 83
Joined: Fri Feb 14, 2020 2:51 am
Location: Essex UK

Re: 175TS with 125S engine project

Postby George » Sat Apr 25, 2020 12:22 pm

ranton_rambler wrote:I don’t know if the 125 is the same, but looking at the cross-section in the workshop manual, the housing is pressed up to the shoulder on the outside by the outer race of the bearing. There is a little upstand on the bevel tube.
Figure 69, page 70. I think you have the same book.
Ian

Thanks for reply Ian. My bevel tube does not have an upstand and there is nothing to stop bearing and housing moving up an down. Mototrans may be different with the roll pin added to stop housing spinning but surely expecting housing tight fit to hold in place is wrong. Mine is a loose fit anyway and has been spinning. Hoping Jon or Nigel will have an answer. The only thing I can think of is to add a spacer to lock tube flange to housing. Nigel has a replacement tube and housing put by for me perhaps they are different.
George Essex UK

Duccout
Posts: 261
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Re: 175TS with 125S engine project

Postby Duccout » Tue Apr 28, 2020 6:54 pm

George,

Are you sure that the bearing sleeve needs to go all the way into the housing in the head? Could the sleeve just be pushed into place by tightening the bevel tube flange against it? The sleeve cannot move down because the tube is preventing it, and it cannot move up because of the lip at the bottom of the bearing sleeve.

BTW it looks like the 125 engine has a different bearing sleeve, maybe that is worth checking out.

George
Posts: 83
Joined: Fri Feb 14, 2020 2:51 am
Location: Essex UK

Re: 175TS with 125S engine project

Postby George » Tue Apr 28, 2020 9:50 pm

Duccout wrote:George,

Are you sure that the bearing sleeve needs to go all the way into the housing in the head? Could the sleeve just be pushed into place by tightening the bevel tube flange against it? The sleeve cannot move down because the tube is preventing it, and it cannot move up because of the lip at the bottom of the bearing sleeve.

BTW it looks like the 125 engine has a different bearing sleeve, maybe that is worth checking out.


Thanks for reply
Problem is sleeve is loose fit in head and can move up and down even without gasket. In other words when tube is tightened up to head the sleeve lip is not touching head so not a positive stop. When I purchase replacement parts from Nigel I will have a word with him first.
Have put engine aside for now, stripping front end, wheel, forks and steering head, to see what else I should order.
George Essex UK


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