Hmm now what (A Rebore!)
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I'd be rebuilding that bottom end too. Or chance it and hope nothing went down into the mains...
@Calum I've had a little check over and I'll take the risk, I'm more of a when it breaks fix it kinda guy, Plus I'm tired of the traffic in my car, miss giving my 26 year old smelly french whore a daily seeing too :grinning_face_with_smiling_eyes:
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So the head.....
They didn't do much by the looks of it, just a quick clean of the mating surfaces
Not particularly happy with that so far so have not refitted yet, gonna sit here and have a play and tidy it up myself. Head is pretty accessible so can always come back to swap it out with another later down the line too.
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So the head.....
They didn't do much by the looks of it, just a quick clean of the mating surfaces
Not particularly happy with that so far so have not refitted yet, gonna sit here and have a play and tidy it up myself. Head is pretty accessible so can always come back to swap it out with another later down the line too.
@Pablo13 It's not as simple as that.
There really isn't much you can do.
If you take away the marks, you alter the squish band. If you only alter the squishband, then you'll reduce the compression and the bike will be down on power.
You need to alter the squish, according to a piston dome design, then alter the compression ratio by using a thinner base gasket, or machining the head down.
It's a very complicated process.
A tuning company ought to be able to sort it out for you.
But I wouldn't want to run that head like that, it'll be down on power and increase the likelyhood of detonation.
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@Pablo13 It's not as simple as that.
There really isn't much you can do.
If you take away the marks, you alter the squish band. If you only alter the squishband, then you'll reduce the compression and the bike will be down on power.
You need to alter the squish, according to a piston dome design, then alter the compression ratio by using a thinner base gasket, or machining the head down.
It's a very complicated process.
A tuning company ought to be able to sort it out for you.
But I wouldn't want to run that head like that, it'll be down on power and increase the likelyhood of detonation.
@Calum Yes I understand and will most likely get another head down the line to do correctly. For now I'm going to tidy it as best I can while being sympathetic to the compression ratio but at the same time loosing any sharp edges that will be hot spots and prone to kickstarting a det situation. Basically I'm going to do the best I can with what I've currently available to me :winking_face:
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@Calum Yes I understand and will most likely get another head down the line to do correctly. For now I'm going to tidy it as best I can while being sympathetic to the compression ratio but at the same time loosing any sharp edges that will be hot spots and prone to kickstarting a det situation. Basically I'm going to do the best I can with what I've currently available to me :winking_face:
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@Pablo13 Heads are getting rare now unfortuantely. Used to be a time where they were a dime a dozen. Now you'll be lucky if you can get a 3BN head I swear.
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@Calum The way I see it, whatever I'm removing now is needed and more to be corrected. Its already looking better.
@Pablo13 Well, whatever you do, it's likely to affect the fueling.
So to avoid the engine failing again, make sure you ensure it's jetted appropriately. If it's overfueling, you'll bore wash the engine and risk scuffing the bores. If it's underfueling, it'll detonate and seize again.
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@Calum The way I see it, whatever I'm removing now is needed and more to be corrected. Its already looking better.
@Pablo13 Looks like they filed the top of the head and not touched the actual dome part. Personally if you've paid someone to do a job and that's the result of their handywork, I'd ask for a refund. As with everything in life, quality does not come cheap and if you pay peanuts, you will only ever get monkeys!!!
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I'll be keeping a close eye on things, regular compression tests and plug chops to see whats going on.
I think I've done what I wanted with the head for now. I'd say I've given it more of a polish than anything
Its far far from perfect, but also a lot better than what it was :smiling_face_with_open_mouth:
one of the marks is still fingernail deep, but I'm reluctant to go much further without taking it somewhere knowledgeable with two stroke machining. I'm happy enough to fit and find out for now :winking_face:
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I'll be keeping a close eye on things, regular compression tests and plug chops to see whats going on.
I think I've done what I wanted with the head for now. I'd say I've given it more of a polish than anything
Its far far from perfect, but also a lot better than what it was :smiling_face_with_open_mouth:
one of the marks is still fingernail deep, but I'm reluctant to go much further without taking it somewhere knowledgeable with two stroke machining. I'm happy enough to fit and find out for now :winking_face:
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I'll be keeping a close eye on things, regular compression tests and plug chops to see whats going on.
I think I've done what I wanted with the head for now. I'd say I've given it more of a polish than anything
Its far far from perfect, but also a lot better than what it was :smiling_face_with_open_mouth:
one of the marks is still fingernail deep, but I'm reluctant to go much further without taking it somewhere knowledgeable with two stroke machining. I'm happy enough to fit and find out for now :winking_face:
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@Pablo13 That's a million times better, let's hope you haven't modified the squish.
With a bit of luck, the carbon build up ought to fill in the gaps lol
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@Calum heads really aren’t expensive I see them all the time for 30 pound but that said I’d be more than happy to run that head
@declan Cheap as chips mate.
£140 he wants for that 3MB.
Used to be able to get them for £30, but not anymore. You can only get restrictive 3BN heads these days. Which need money spent on them to bring the power back up. Which he could just do to his current damaged head.
These look unrestrictive, but I don't know if they fit.
If you find a 3MB for £30 in usable condition, buy it. Would be myt advice.
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Its back together and running. Not ridden yet, but let it get to temp and adjusted idle. Took about twenty kicks to start first, but now its starting first kick. Took a compression reading before I started the engine with the exhaust off
Pretty busy tomorrow, but If I get a moment Ill take it for a spin and see what is what
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That's odd. Why did it take so long to start?
You made sure the oil pump does not have any air in it and is operating correctly?
@Calum I'd adjusted the throttle too much so when I fired it idled around 7k I think was the reason. Took it out for 15 gentle miles yesterday and all seemed well, and took to work this morning, so far so good. Just trying to be gentle and keep the revs relatively low for the meanwhile and get some miles under her belt.
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My big bore Athena made 14 bar compression.
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Little update. After running it in a little and opening it up a bit, I wasn't particularly impressed. It felt worse than before up top. So I did mess with the squish too much I think. Luckily managed to get another 3mb head in a more normal condition for £25 and have just fitted it and compression tested it and its up, so hopefully tomorrow's ride will be an improvement.
Now I have the old head here may as well look into getting it sorted properly at some stage and swapping back later down the line.
