inner clutch hub threads stripped

[ede]

The crack surface of the decomp looks like it was caused by vibration. First the material got weakened and then it broke since it wasn't strong enough anymore.
The markings on your piston look like the exhaust valves make contact (maybe due to wrong cam timing). In that case the piston pushes against the valves. That could cause the valvetrain to stop immediately or at least to decerlate instantly. Besides the high forces on every part in the valvetrain, the decomp flyweight would accelerate in opposite direction. When the engine is running that way, it makes the decomp flywheight oscillating at full force with high frequency....

...so it's just a guess and not much helpful.

Do the clay check is bushi said and carefully check every single part! Sorry for you BLUDGEONER

 

[bergiefe400]

Hi Steve, that looks very similar to an 650 engine I just bought, same type of cam with rocker cover and rockers machined for the lobes to clear, the ports have been opened up with the protruding valve guides removed but mine is a low compression piston, do you know who built it?
Regards
Matt

 

[BLUDGEONER]

What is the exhaust valve to piston clearance ?
Might be good to check it with clay as the Piston looks a bit odd and we don't know if that happened earlier when the valve timing was out or not

Well - not what I was expecting.... measured at - ex 2.4mm, in 1.7mm. I thought it should be round about .6mm??

 

[BLUDGEONER]

Hi Steve, that looks very similar to an 650 engine I just bought, same type of cam with rocker cover and rockers machined for the lobes to clear, the ports have been opened up with the protruding valve guides removed but mine is a low compression piston, do you know who built it?
Regards
Matt

Hello Matt. I've got an idea of who might have built it, but can't be sure. I'll pm you so's not to tread on any toes!

 

[bushmechanic]

Nice work !

Ok so if the exhaust valves are still straight everything should be fine

Love the pics thank you

 

[BLUDGEONER]

Nice work !

Ok so if the exhaust valves are still straight everything should be fine

Love the pics thank you

Thanks! Those clearances about right then?

 

[bushmechanic]

Yep

 

[BLUDGEONER]

:thumbleft:Cool, thank you.

 

[BLUDGEONER]

The crack surface of the decomp looks like it was caused by vibration. First the material got weakened and then it broke since it wasn't strong enough anymore.
The markings on your piston look like the exhaust valves make contact (maybe due to wrong cam timing). In that case the piston pushes against the valves. That could cause the valvetrain to stop immediately or at least to decerlate instantly. Besides the high forces on every part in the valvetrain, the decomp flyweight would accelerate in opposite direction. When the engine is running that way, it makes the decomp flywheight oscillating at full force with high frequency....

...so it's just a guess and not much helpful.

Do the clay check is bushi said and carefully check every single part! Sorry for you BLUDGEONER

Very helpful - looks like you spot on with your assessment. I'm guessing the damage was done while I was trying to start it with the timing slightly out.

 

[Taffy]

Hello Matt. I've got an idea of who might have built it, but can't be sure. I'll pm you so's not to tread on any toes!

don't even go there!

I would never put THAT piston in a 650. it's a 470 I think and we don't touch them, they are too low.

also, it's simple now, the valve timing was retarded. what you want to do is do the same test with it delayed one tooth and then if you have too: 2 teeth. knowing how it happened will help lay down your fears.

it could be a combo of a tooth out at the bottom and another at the top etc.

don't even start bludgeoner!

Taffy

 

[bushmechanic]

don't even go there!

I would never put THAT piston in a 650. it's a 470 I think and we don't touch them, they are too low.

also, it's simple now, the valve timing was retarded. what you want to do is do the same test with it delayed one tooth and then if you have too: 2 teeth. knowing how it happened will help lay down your fears.

it could be a combo of a tooth out at the bottom and another at the top etc.

don't even start bludgeoner!

Taffy

You really think that's neacesarry after he's checked the piston to valve clearance ?

The valve timing was bludgeons doing. All clear and simple if you Read The thread from the start

Who done it ? It wasn't me precious. Gollum gollum, nasty shire folks

 

[BLUDGEONER]

don't even go there!

I would never put THAT piston in a 650. it's a 470 I think and we don't touch them, they are too low.

also, it's simple now, the valve timing was retarded. what you want to do is do the same test with it delayed one tooth and then if you have too: 2 teeth. knowing how it happened will help lay down your fears.

it could be a combo of a tooth out at the bottom and another at the top etc.

don't even start bludgeoner!

Taffy

I think you might have jumped to the wrong conclusion Taffy - I wasn't implying it was anyone on this forum. I know someone who previously owned/raced it, and they probably built it too, but that was going back a bit and it's had at least one other owner since, so anything could have been done to it. There's nothing wrong with the engine anyway apart from the original water pump seal failure (hopefully!). The rest was down to my ham fistedness - at least I'll be changing the head gasket as well now. I appreciate all advice given on here, and I'll most likely need plenty more of it! Cheers

 

[Taffy]

Who done it ? It wasn't me precious. Gollum gollum, nasty shire folks

its the signature of a norverner he put that piston in many a racer and never checked the compression mathmatically....but i have.

anyone wanna guess what the compression is with the 470 piston in?

go on, I bet nobody can get it in the first 5 goes.....

Taffy

 

[bushmechanic]

15

 

[Taffy]

nope, keep guessing. UPWARDS!

and bludgeoner: there are people on here that think that 'well known....' blah blah is me. so you need to be a little clearer. that was wrong OK?

several people (present company not included) who are not only mentally deluded but seriously sick! jesus, i thought Schwim was weird but at least he's harmless FFS!!!!

come on you lot, join in!!!!!!!!!!!

remember: deisels have a compression of over 18 to 1 (trying to remember college and 40 yeasrs later)

cheers

taffy

 

[bushmechanic]

Ok there is very little chance that a 550 berg engine with static Comp over 15:1 will last even 4 hours

Show us The calculations please taffy

You will find that it's more like 13 or 14 :1 and with this cam that is not a stupidly high CR

And IMHO bludgeoner posted nothing at all to imply this is your work.

You are overley paranoid That is wrong ok

 

[BLUDGEONER]

Please help - I'm losing the will to live.....!
Put it all back together and back in the bike last week. New head gasket, camchain + camshaft bearings, head bolts all torqued down to spec. New water pump seal and both o-rings. Fresh oil in, started and ran it for a minute, dropped the oil (to get rid of the last water contaminated oil). New oil and filter in, ran it for a minute, oil looked good. Filled the cooling system (just water), started it again and immediately got water mixing with the oil
Ok, so maybe not careful enough! Today - clutch casing off again, new water pump seal and both o-rings again. I was extremely careful about this - shink wrap and smear of grease on the shaft, smear of grease on both o-rings, very carefully refitting the casing. Filled/started/drained oil 4 times to make sure all the water was gone again. 5th time with new oil tried introducing water again and immediately got milky oil again:furious::furious::furious:
Is there anything else it could be - something I'm missing? Can only be the head gasket or the pump seal doing this right?
It's not the expense - it's the time that hurts.....
Runs beautifully by the way!

 

[Taffy]

the water jacket O ring could be undersize? the left cover gasket can be fatter and then the W/J |O ring then defo becomes undersize!

can cooland come out of the little front hole or is that blocked?

Taffy

 

[bushmechanic]

I hope it's those but it Can be liner o rings or cracked liner. Look for crack on the outside of the liner just under the flange at the top

Also when you have the clutch cover off Check the depth of the little o ring slot on the left hand crank case then measure the Thickness of the o ring. You would like to have about 1mm crush. Sometimes the groove is way too deep.

 

[bushmechanic]

Taffy where are your calculations for the compression ratio of a 550 with the 470 piston ?

You thought it was a 650 right ?