Engine renewal

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Re: Engine renewal

Beitragvon MaxNice » 12. Juni 2010 11:59

yes, you need a special tool or special method to,disassemble this, in german its calles "sacklochlager".
the original tools looks like this:
Bild
part 5+6 in combination with tool 1

now some selfmade tools from boardmembers:
#1 take a look on the pic with this little wooden board
#2 down in the pic is a row with three screws, above these you can see a long screw with a heavy load wall anchor, the big roll from steel works here as a pullhammer on the long screw so you don´t need a thing like tool 1 in the first picture.
there is another method, you can fill the space behind and in the beearing with a very thick grease or dough, then push a bolt through the bearing, wich closes the inner ring completely, so the substance behind the bearing will push it out
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Re: Engine renewal

Beitragvon Teemu » 14. Juni 2010 17:10

Hello,
Got the bearing out. No heating, just this. Helpful tool to have, 29 €.
Heating helped to get the new bearing in place.
Teemu

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Re: Engine renewal

Beitragvon Teemu » 25. Juli 2010 19:18

Hello,
Finally my bike is in running condition. :D
Everything works and no spare parts were left on the table... so everything should be ok.

Teemu

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Re: Engine renewal

Beitragvon motorradfahrerwill » 25. Juli 2010 20:12

It´s good to read something. :D

And now, some pictures please. 8)
MfG Kurt
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Re: Engine renewal

Beitragvon Teemu » 1. August 2010 07:44

Hello,
The fun lasted for six kms. Then the engine broke again. :roll:
So much for fixing the damn thing.
Next week I have to open it again.... I hope something small and cheap broke down. Hopefully not the piston&cylinder....
Teemu

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Re: Engine renewal

Beitragvon krocki » 1. August 2010 09:02

Hello Teemu
that's not good news. What happened exactly?
Disappointments like this are part of the game, don' let them bring you down.
"You try, you fail. Never mind - try again, fail better"
Carsten
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Re: Engine renewal

Beitragvon Teemu » 1. August 2010 09:59

Hello,
The engine just seized after six kms. Rear wheel locked, just got the bike to 96km/h. The engine still turns freely and seems to have compression still. Might be something to do with the gears. I have to take the engine in pieces next week. Today I'm not in the mood to do that. Funny as it did not give any warning this time. Last year it sounded bad. The only strange noise out of the engine was on the fifth gear, it sounded like a wolf howling. I can't explain better.
Teemu

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Re: Engine renewal

Beitragvon Henry G. » 1. August 2010 11:56

The engine had a piston seizure!
The aluminum piston has expanded too fast and jammed in the cast iron cylinder.
If the engine is still running with the complete power and makes no bad noises, you dont have to open them up again, i think.
You could only take the cylinder off once again, to look if there are some clamp traces.
Sorry for the bad english, i did it with an internet-translator.
With friendly greetings.. :wink:
MfG :wink:
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Re: Engine renewal

Beitragvon Teemu » 1. August 2010 12:09

Hello,
I could not start the engine yesterday again so I have to take the cylinder off the engine to see if that is the problem.
Bad luck or bad engine building by me.
Teemu

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Re: Engine renewal

Beitragvon Henry G. » 1. August 2010 12:12

it can not hurt the engine, if you take off the cylinder. Good luck.
And dont forget to take Photos of the piston and the cylinder.
MfG :wink:
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Re: Engine renewal

Beitragvon Teemu » 2. August 2010 19:12

Hello,
Piston seizure. Any opinions what to do next? Can this be fixed by new piston rings and taking cylinder to someone who can make it slightly bigger?
Pictures of disaster

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Re: Engine renewal

Beitragvon krocki » 2. August 2010 20:35

Hi Teemu
did you mount the piston in the right direction, the arrow on the top towards the exhaust window?
Looks like a cracked ring. Are both pins still in place, in the ring groove?
The piston is done. Buy a new one next size, but not the cheap type which dilates much when hot (I seized one of these).
Then get the cylinder milled to 5/100 clearance to the piston. If you choose a more expensive forged piston, this clearance is different.
Have a look at the pin and the bearing, they might have got hit. And the crankshaft big end clearing, the tap test, you know?
Did you change anything at the window width? Chamfered the edges? Put on the rings gently with three stripes of thin metal or cardboard, without opening them too much?
Worked cleanly? One particle may spoil an engine.
Which parts were new, which used?
At least, it looks as if the bloc can remain unsplitted. Hopefully.
You wil get this one running, sure.
Good luck
Carsten
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Re: Engine renewal

Beitragvon Teemu » 3. August 2010 19:50

Hello,
Piston is in the right direction. Both pins still in place also rings seem to have melted to piston... I have to check the big end clearing, didn't do any alterations to piston or cylinder and I used beer can aluminum to put the rings in place and cleaned everything properly before putting the cylinder in place.
New parts were/are: piston, cylinder, cylinder head, crankshaft and all bearings and seals in the engine....
Why does the 300cc piston have only two rings as the 251 piston has three?
Bad luck with piston I think, I did not know there are different kind of them.
So I'll start looking for a new piston, this time from Finland, maybe faster.

It WILL start up again... :D

Teemu

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Re: Engine renewal

Beitragvon krocki » 3. August 2010 21:14

Hum, sounds good your work. But if cylinder and piston were new, you had to break them in slowly.
Sometimes even new cylinders have sharp-edged ports, then you better round them by hand.
Got oil 1:50 mix to the gas?
The 250 pistons are old style, therefore three rings.
300's are modern, two rings are sufficient. And they are even lighter than the 250's!
Your pics are not fine enough to see the details... and quite slow :oops:
I'm not the guru in pistons... maybe someone else?
Carsten
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Re: Engine renewal

Beitragvon Teemu » 4. August 2010 16:54

Hello,
Hopefully better pics in this place. At least faster... :lol:
Pics
I found a new cylinder and piston already so progress again... 8)
I still wonder why this happened. Maybe too tight piston? The rings were quite "big" . But I don't know. I have talk with the guy who sells me the new one, maybe he has a clue why it happened.
Teemu

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Re: Engine renewal

Beitragvon krocki » 4. August 2010 19:38

window edges look sharp, not rounded!
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Re: Engine renewal

Beitragvon Teemu » 8. August 2010 18:25

Hello,
How crazy or stupid idea is it to just buy a new piston and rings (same size that they were) and just get the cylinder polished?
Teemu

edit: the main reason for piston seizure could be too small piston ring end-gap? I forgot to measure that....

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Re: Engine renewal

Beitragvon krocki » 8. August 2010 21:45

Take the cylinder to a workshop to measure the diameter at the worn areas. They will tell you if a cylinder finish will do or if it needs to be drilled out to the next size (+0.5 mm).
You may have a clearance of 7/100 with the cheap pistons to prevent them from seizing, there will be less lifetime on the other hand. If the cylinder allows for that, it's worth a try.
Carsten
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Re: Engine renewal

Beitragvon Teemu » 9. August 2010 19:29

Hello
some stupid questions more: how do I tell the difference between a good piston and a crap one? If I get one via internet I have to rely only on sellers word...
There is only minor aluminium residue in cylinder so I think I'll take my chances on a new piston and rings only. It's worth a try I think.
Teemu

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Re: Engine renewal

Beitragvon Guesi » 9. August 2010 20:06

Hello

No I do not think it is a good idea.The cylinder looks damaged , you must install a bigger piston and the cylinder must be drilled to the next oversize.
If you have a piston with 75,50 mm then you can drill it to 76,oo mm.
But this does not eliminate the reason of the first damage.So this can happen again if you do not find the reason why it
was damaged.
Maybe the engine overheated ?
And you said you drove about 95 km/h.
With a new 300 ccm engine, I would not go faster than 80 km/h for the first kilometers...
GüSi

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Re: Engine renewal

Beitragvon Teemu » 13. August 2010 15:02

Hello
Now I have a new cylinder (again) for the bike. Of course piston and seals too.
What is the proper way to break in the engine? Last time when I got the cylinder drilled I rode for a week at about 80 km/h. Then went on as normal, that is no mercy to the engine.
Now I do not want to shatter the cylinder again so how should I do it?
Teemu

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Re: Engine renewal

Beitragvon Guesi » 13. August 2010 18:39

Hello


The cylinder you bought first was with a "RING" between the cylinder and the cylinder head.It helps to bring the cylinderhead centric on the cylinder.

Is this ring also on your new cylinder ?
If not, you cannot use this new cylinder with the cylinderhead you have.
This cylinderhead fits only with the kind of cylinder you had first.
It fits only as a SET, not with any other cylinders...
GüSi

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Re: Engine renewal

Beitragvon Teemu » 13. August 2010 19:51

Hello
Do you mean this ring?
I'll take picture of the new cylinder on Monday.
This can't be really so difficult?
Teemu
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Re: Engine renewal

Beitragvon Guesi » 13. August 2010 20:15

Hello

Yes, exactly.Normally, when drilling the 250 cylinder to 300ccm , this ring is drilled out.
In your first set, this ring is being reproduced after the drilling by taking away material from the place, where the gasket lies later.
And the cylinder head is changed to fit to this new ring.
So you only can use this 300 ccm SET together(cylinder and cylinder head).

GüSi

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Re: Engine renewal

Beitragvon Teemu » 14. August 2010 12:09

Do all cylinders have the ring? When I tried the cylinder head to the new cylinder it seemed to fit nicely. But I'll take a picture on monday. Teemu

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Re: Engine renewal

Beitragvon Teemu » 16. August 2010 17:53

Hello,

New pictures.

This is new cylinder.

Teemu

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Re: Engine renewal

Beitragvon Guesi » 16. August 2010 18:41

Hello

This one is a reproduction cylinder. I do not sell these because of the poor quality. You see for example the holes in the area where the gasket is .
I do not know if it fits to your other cylinderhead...

GüSi

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Re: Engine renewal

Beitragvon Teemu » 16. August 2010 20:44

Hello,
The cylinder fits nicely to the cylinder head. I decided to buy this cylinder from Finland as I get it faster and hopefully the seller can help locally if something goes wrong. And I can't say that quality in Germany is any better.... at least not everytime. Or then I'm just unlucky. Or something. As long as the bike works it's ok for me. And when it breaks down, I'll dump it in a swamp and get something else. Bicycle probably, cheaper to repair :lol: I've heard that a total renovation of a 251 machine would cost about 500€ including work. How is that possible when parts cost more?

Teemu

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Re: Engine renewal

Beitragvon Guesi » 16. August 2010 20:48

Teemu hat geschrieben:Hello,
The cylinder fits nicely to the cylinder head. I decided to buy this cylinder from Finland as I get it faster and hopefully the seller can help locally if something goes wrong. And I can't say that quality in Germany is any better.... at least not everytime. Or then I'm just unlucky. Or something. As long as the bike works it's ok for me. And when it breaks down, I'll dump it in a swamp and get something else. Bicycle probably, cheaper to repair :lol: I've heard that a total renovation of a 251 machine would cost about 500€ including work. How is that possible when parts cost more?

Teemu


It depends on what you do on the renovation.
And buiding a 301 engine from a 251 engine is surely not part of a renovation for 500 Euro.
And the price for the parts of my own engine renovation was about 500 euro(only the material).

GüSi

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Re: Engine renewal

Beitragvon Teemu » 22. August 2010 17:04

Hello,
despite all the odds the bike runs again. It remains to be seen for how long...

Is it possible to put the Superelastic to a 251 with out the mounting brackets? Maybe cheaper/easier to buy a bike with it already.

Total cost of renovation now is approx 700€.
Teemu

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