My R25/2 restoration - few question

Begonnen von Al Capone, 12 September 2020, 23:22:49

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Don't mount this chain, take another one. Dismantle, put it on the table and try to pull and push, see what this does to the length of the chain...
This should be minimal with a new chain. Normally chains last very long, mine for almost 50.000 km up to now.




Morning Al Capone,

sometimes it is nice to find something in a box. In this case, after having watched your video I'd recommend to replace the timing chain. Doesn't cost a fortune. As Eppo says the installation of a chain tensioner makes sense, because even a new chain will also lengthen after time and you'll sit with the same problem.
umuntu ngumuntu ngabantu

Al Capone

Right! I need to order a new timing chain. However, I need to collect more items from the store because shipping costs a lot.

However, work does not wait and today I managed to sandblast and secure the seat bought on Mannhaim. I also have another seat for which I need to re-drill the holes. It looks identical to the one in the R25/2 brochure and is somewhat similar to the R25. It may have changed a bit over the years. Seat number 2 had no welds and appears to be stamped from a single piece of sheet metal.

Al Capone

Finally, the saddle frame is ready. I had to make new handles and drill holes. Looks pretty good after welding.

I have a problem with my Pagusa saddle cover. Of course, I read the topic on this forum first.

I managed to attach the front part to the cover but I don't know what to do next.
To use a device made from a car jack you need handles with screw holes. Unfortunately, I can't take them out.
Does anyone have any tips? 


Hi Al,

your saddle mounting frame looks like really good work  :thumbsup: and when it's been painted will look as good as new.

Too bad I found no pictures of when I was mounting the rubber on my saddle frame, but I hope I can describe it as good as possible.

You don't need to use a jack to stretch the rubber.

A good preparation is the half success.
So before heating the rubber in boiling water, check the two parts of the frame each separate of good fit as long as the rubber is cold.
Than you have to prepare some possibilities to hock up tension belts.
For the front part I use some flat iron, one end was put at the front thread and locked with a nut and at the other end of this flat iron I made a hole to put in the hook of a tension belt.
For the rear part I choose some angle iron and screwed it to the two threads. This angle iron has one additional hole in the middle of the opposite side of the angle iron to put in another hook of a tension belt.

Than I go out in the garden and searched for a pair of trees to hook-up the opposite ends of these tensions belts. If this was all done I disassembled all parts and heat up the rubber with boiling water.
Use some gloves and soap to put in the two halfes of the saddle frame, check for good positioning as long as you have the chance to adjust it, tighten the two irons on the threads with some nuts, put the hooks of both tension belts in each iron and tighten the tension belts slightly between the two trees till you can put both sides of the saddle frame halfs together. Than carefully loose the tension belts and check if the ends are sliding proper in the opposite sides of each frame half.

Hope this helps.
Geht nicht, gibt's nicht. Einfach kann ja jeder 😁.

Al Capone

Thank you for supporting Eppo. :thumbsup:  I finally got it.
Hot water was my best friend in this job. ;D
The hot water helped put the frame in and remove the handles.
Then I made a handle from the profile and welded it to my workbench. The next step was very simple, just reused the hot water and I was able to install the two parts of the frame together using only my hands.

Al Capone

hello guys

As I wrote some time ago, the cylinder was installed. Unfortunately there is a problem. The cylinder has a new sleeve pressed in and when I wanted to try on the head today, it turns out that it does not fit.

The cylinder liner edge is 74.2mm and the head bore is 74mm.

Will it be correct to grind the hole in the head by 0.1 mm with a dremel?
Or should I take the cylinder off and have it reduced on a lathe? 


By the way: Wrong spark plug. Threat is to short.
Ariel motorcycles... upon which the sun never sets.

Al Capone

The spark plug just wasn't screwed in all the way.

I am in the process of assembling the clutch. I have a new friction disc and the steel plates have been aligned.

Can anyone measure the dowel pins on the R25/2 flywheel?
The service manual says 15.8mm. On my wheel they protrude 11mm. I am afraid that the springs will be compressed too much and disengaging will be difficult or impossible.


hi Al,
you are lucky, I just have an R25/2 flywheel in hands - the pins are between 15,7 and 15,8mm long



Have you tried it with the Head Gasket in place ??

I have just measured a NEW fiber gasket, one with metal inside  & that is 1.35mm thick .

diameter for the cylinder liner edge is is 75.2.

If you alter the cylinder head, that is forever. get the liner outer edge reduced

Personally I would leave the head alone. Forget the Dremel, that will not be accurate enough, for the next 20 years.

All this is named, In England. " Part of the Fun !!!'

Good Luck



Yes. Better attack thy cylinder...tahts the part that does not fit. If it is replaced oe day, at least the head ist not d wide
reduce the oversized sleeve on a lathe until the cylinder head can be turned freely on the cylinder. Means probably you have to give it to someone with the equipment. Check also the gap between head and cylinder; should be a bit less than the gasket's thickness. e.g. 0,5 mm gap -> Gasket 0,75 mm. Gaskets exist in various thickness, or carve one yourself out of gasket paper 0,5, 0,75, 1,00 mm

Al Capone

A lot of time has passed since my last visit, but the project was suspended. I tried to disconnect the cardan shaft but it failed. On the forum you can read information that a 5-ton hydraulic press is enough. I used a hydraulic press with a pressure of 45 tons and it had no effect. Are there any ways to make this easier? ???


I wonder about the fixture You used, if 45 tons is not enough.
Can you post pictures ?
I suppose You applied a decent amount of heat ?

Think outside the box !


 If the cardan shaft is pressed from above without a pressure piece, there is the risk that this area will be deformed.
In that case the diameter of the shaft will be changed to higher values and it can´t be pressed out.


Leben und Leben lassen

Al Capone

I made a pressing tool from stainless steel. At 40 tons of pressure it started losing shape.

Heating and cooling looks to make sense if we have two elements. The Cardan shaft is a whole and will heat up as a whole. Hmmm.... If you think heating might help, I'll try it.

Btw. If it doesn't work, I bought an unpressed cardan shaft yesterday at Mannhaim, so I can try.


Heat doesn´t help - in case you have different metals (aluminium / steel) you can realise an effect.
May be that the area where both elements are in contact are corroded - ...

Leben und Leben lassen

Al Capone

Cardan shaft is finally dismounted. I made a new hardened tool and this time 30 tons was enough. Now i have to wait few weeks for new chrome.

In the meantime I started work with electricity and the first problems appears. As you can see in the picture there is a few rubber waschers that effectively isolating. I have no minus on handlebar and headlamp so that's why horn and speedometer bulb doesn't work. Do you know how was this problem solved orginally?


Originally you got the minus connection through your clutch and brake cables. You could lay an extra earth wire from the handlebar screw to the frame, often one of the screws for the identity plate was used for this.

In the headlight you do get a minus wire from the battery to terminal #31 on the switch plate. I made an extra cable from terminal 31 to one of the headlight attachment screws.

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