PISTON & REBORE advice

[Gunnar_HH]

Currently I cannot find an offer for a +0.75 piston.
This has +1.00mm and can be delivered from Australia to the UK. The cylinder must then be bored to +1.00mm.
Anyway, if it runs it will last 30,000 km.

Many greetings
Gunnar

https://www.ebay.de/itm/151635411224?ep ... SwKdZgmjii

This one will be also OK, but the seller wont send to Germany or UK. Take a look.
https://www.ebay.de/itm/161648036737

[Kristian]

Direct link to the +1,00 mm piston:

https://www.cruzinimage.net/2017/08/17/ ... -oversize/

[hiha]

Anyway, if it runs it will last 30,000 km.

At least 30.000. If you always give the motor-oil enough time to warm up before you burn down the road, the piston/cylinder-combo can last more than 60.000km.

Good luck,
Hans

[hiha]

Engineer felt a slight groove in bore then said they'll rebore/hone for the .5 and see if the groove is gone.

Sometimes those grooves result from a too thick O-Ring rund the lower side of the cylinder-neck. The cylinderwall thereby is choked, and wears. If you remove the cylinder, the choke-force is lost, and leaves a slight groove.
Next can be corrosion-rings, which occur when the bike was stored for a longer time after riding it under very wet conditions. The piston-rings corrode into the cylinderwall and leave rusty grooves.

Gruß
Hans

[baldock]

thanks for all of your advice.

Engineer rang today and said the +.5 rebore went perfectly and the groove is no longer visible.

I was surprised at how cheap it was too at only £46.

I mentioned that I have new NOS valves and NOS valve guides and new guide seals. Engineer said that Honda deliberately made the guides too big so as to be machined to fit. £84 to fit guides, 3 way cut valve seats and lapping. He said to bring head when I collect the cylinder and he'll check it first to see if it even needs the new guides.

[Gunnar_HH]

Hello Baldock,

this reads great. I think we need such a smart craftsman here in Germany who charges such prices.
What exactly does he mean by the 5th stage? Is it the piston with 90.00mm.
Baldock, where do you live? How did you get the XL500? We are all interested.

Greetings from the North Sea coast
Gunnar

[baldock]

hi Gunnar,

I live in England in a county called Hertfordshire (40 miles north of London).
I had an XL250 field bike when I was 18 ( https://www.youtube.com/watch?v=rHTZStrHQL8 ).
I'm 56 now and saw a white 1982 XL500R on eBay and decided to buy it as I weigh a lot more now and think I need the extra cc to pull me along
Anyway, 40 year old vehicles don't need road tax or an MOT, and are very cheap to insure in the UK, so I thought it would be a good project to take my time with and finish by 2022.
Every part has been taken back to bare metal and either sprayed or powder coated. Every bearing replaced and every seal changed for new. An incredible amount of NOS parts have been found, like front mudguard, chainguard, all handle bar levers and controls, pistons/rings, camshaft, cam chain tensioner, lights (front and back) etc. etc. etc.
It's all in parts now, waiting to be assembled like a giant Airfix kit when the engine is finished.

Unfortunately, I don't speak German and the translator on this site makes a few mistakes so it can be hard understanding some of the posts.
The engineer didn't mention '5th stage'??? The engine had a standard piston, but the cylinder bore was too big. Its now rebored to match a NOS Honda piston 50.

Incidentally, does anyone know what exact size it should have been bored to for a 50 piston so that I can check it?

[Gunnar_HH]

Hi Baldock,

what a funny video, I am rather impressed and all without helmet and wearing in slippers.
Most of us are also near to 56

How to bore a cylinder?
Normaly you have bought the next piston first and then you go to the engine repairer, he wil measure the piston, add 5 or 6 hundreths and this is new size for the bore at the cylinder. Because of the piston differ a little bit to the manfacturer.

- normal (original) piston has nearly 89,00mm
- first oversize is 89,25mm
- second oversize is 89,50mm
- third oversize is 89,75mm
- fourth oversize is 90,00mm (but the fifth piston)
--- After that you have to ask special companies for larger pistons like Mahle or Wössner.
--- And never use a Wiseco-Piston (high compression-Racing), you cant handle this beasty part.

What's your tipp for Tuesday?

Cheers
Gunnar

[baldock]

Germany have got to win. Our matches have been embarrassing. Like watching a school football team in comparison.
Germany 2 England 0

[hiha]

Im Übrigen:
Profifußball ist scheiße und gehört verboten.
findet der
Hans

[PeterB]

Nun ja mein lieber Hans,

das Spiel gerade zwischen S und F war spannender als jeder Tatort. Und, btw. Jugendfußball ist die beste flächendeckende Integrationslösung, die unsere Gesellschaft ausserhalb der Politik und Kultur zustande gebracht hat.
beste grüße
peterb

[hiha]

Sorry for my german OT about soccer. We will discuss that offline...

Incidentally, does anyone know what exact size it should have been bored to for a 50 piston so that I can check it?

I would say, you needn't check the enigineers work. What you told us sounds very competent, this man seems to know what he is doing.
The video reminds me in my youth. Yamaha DT50, barefoot riding and jumpin' over Rocks.

Cheers,
Hans, 57

[PeterB]

I tried some hillclimbing with my DT80 and fell over backwards several times. The Honda MT80 of my buddy made it . With the XLs 500 I owned one year later it went way more smoothly despite the extra 50 kg...
What an unfortunate thing for the german team that sympathetic Bavarian Müller lost the game.

kind regards
peterb

[Gunnar_HH]

In football, you have to score goals. The better team won, I still wish the winner good luck.
My first cross attempts were with a 50 cc Vespa scooter, but I was never successful with it.

Back to the XL and the little problems.

Cheers Gunnar (58)

[PeterB]

Hi Gunnar,

Vespas run pretty well on snow and icy roads because of the low gravity of the whole setting. Try once.
beste grüße
peterb