Replacing a cylinder head
Discussion
CBF500 73k miles.
Due to the absolute ballache of snapped studs, snapped cobalt drill bits, wandering drills and generally losing the will to live I've decided it's going to be easier to remove the cylinder head and replace it with a good secondhand one (Bottom end is solid with no knocks.) than fixing the absolute clusterf
k of what I've got. I am confident enough in doing the work but was wondering how far I should go? The engine never felt as though lacked power but was down to 160psi (on both cylinders) from a factory spec of circa 200. Is this likely to be a valve, piston ring or the starter not being able to meet the rpm? Just thinking that if i'm going this far is it wise to replace them or would it also need a rebore?
I'll add that this bike was bought with the purpose of learning about this kind of stuff so I'd rather not just chuck another engine in (they start at £200 ish and all require welding of either snapped studs or and mounting points).
Due to the absolute ballache of snapped studs, snapped cobalt drill bits, wandering drills and generally losing the will to live I've decided it's going to be easier to remove the cylinder head and replace it with a good secondhand one (Bottom end is solid with no knocks.) than fixing the absolute clusterf
k of what I've got. I am confident enough in doing the work but was wondering how far I should go? The engine never felt as though lacked power but was down to 160psi (on both cylinders) from a factory spec of circa 200. Is this likely to be a valve, piston ring or the starter not being able to meet the rpm? Just thinking that if i'm going this far is it wise to replace them or would it also need a rebore? I'll add that this bike was bought with the purpose of learning about this kind of stuff so I'd rather not just chuck another engine in (they start at £200 ish and all require welding of either snapped studs or and mounting points).
In the same situation, I'd pull the barrels. You can't really assess any bottom end play, or ring/bore wear with the barrels still fitted. I'd probably (depending on price) fit a set of rings after deglazing the bores. If the motor was sound to begin with, I doubt there would be any need to go further.
Biker9090 said:
CBF500 73k miles.
Due to the absolute ballache of snapped studs, snapped cobalt drill bits, wandering drills and generally losing the will to live I've decided it's going to be easier to remove the cylinder head and replace it with a good secondhand one (Bottom end is solid with no knocks.) than fixing the absolute clusterfk of what I've got. I am confident enough in doing the work but was wondering how far I should go? The engine never felt as though lacked power but was down to 160psi (on both cylinders) from a factory spec of circa 200. Is this likely to be a valve, piston ring or the starter not being able to meet the rpm? Just thinking that if i'm going this far is it wise to replace them or would it also need a rebore?
I'll add that this bike was bought with the purpose of learning about this kind of stuff so I'd rather not just chuck another engine in (they start at £200 ish and all require welding of either snapped studs or and mounting points).
Not much point guessing.Due to the absolute ballache of snapped studs, snapped cobalt drill bits, wandering drills and generally losing the will to live I've decided it's going to be easier to remove the cylinder head and replace it with a good secondhand one (Bottom end is solid with no knocks.) than fixing the absolute clusterf
k of what I've got. I am confident enough in doing the work but was wondering how far I should go? The engine never felt as though lacked power but was down to 160psi (on both cylinders) from a factory spec of circa 200. Is this likely to be a valve, piston ring or the starter not being able to meet the rpm? Just thinking that if i'm going this far is it wise to replace them or would it also need a rebore? I'll add that this bike was bought with the purpose of learning about this kind of stuff so I'd rather not just chuck another engine in (they start at £200 ish and all require welding of either snapped studs or and mounting points).
Once the head is off you can look at bore wear etc.
I would take it apart and then decide whether to replace the head or the whole motor.
Depends what's available used of course.
I've never put much faith in exact compression numbers, I'd be reassured that both are the same and maybe measure bores and rings?
Yeah, a secondhand engine is the last option at the moment.
All of them available are either expensive or require extensive welding work to repair cracked/snapped studs and mounting points vs considerably less for a good cylinder head with cams and caps. I have a friend who can remove the studs on a seperated head for no cost.
All of them available are either expensive or require extensive welding work to repair cracked/snapped studs and mounting points vs considerably less for a good cylinder head with cams and caps. I have a friend who can remove the studs on a seperated head for no cost.
Biker9090 said:
Yeah, a secondhand engine is the last option at the moment.
All of them available are either expensive or require extensive welding work to repair cracked/snapped studs and mounting points vs considerably less for a good cylinder head with cams and caps. I have a friend who can remove the studs on a seperated head for no cost.
I'd be reluctant to spend actual money buying an engine that's already got obvious problems.All of them available are either expensive or require extensive welding work to repair cracked/snapped studs and mounting points vs considerably less for a good cylinder head with cams and caps. I have a friend who can remove the studs on a seperated head for no cost.
If the head is what's giving you trouble, then replacing just that makes a lot of sense.
Are you absolutely sure about compatibility?
The worst outcome is probably putting money, time and emotion into the head, then finding the old one won't come off without wrecking the block, it doesn't fit or some other show stopper.
Obviously you will have the cost of a headgasket.
Are these chain drive cams?
What other parts might be wanted?
Will the engine come out? Will you do any painting, renew lots of fasteners, odds and ends?
Mission creep soon adds cost, and at the end of it, there will still be other parts of the bike which are high mileage.
If you ever sell the bike, it's still high mileage and amateur engine work rarely adds value IMHO.
So, it might be good to know what the long game is?
If you expect a lot more years and miles out of it, maybe it's worth spending more. (time as well as $$$)
But I also think in terms of how long will it be off the road?
If my bike's engine died, buying something newer and breaking the old one would be an option.
Or buy an extra bike and fix the old one in 'slow time'.
In the end you have to do what suits you, not what people like me tell you is the sensible choice.
Biker9090 said:
CBF500 73k miles.
Due to the absolute ballache of snapped studs, snapped cobalt drill bits, wandering drills and generally losing the will to live I've decided it's going to be easier to remove than fixing the absolute clusterfk of what I've got.
Sorry but I couldn't help but laugh, I have felt this pain and empty feeling many times on what should be a simple job Due to the absolute ballache of snapped studs, snapped cobalt drill bits, wandering drills and generally losing the will to live I've decided it's going to be easier to remove than fixing the absolute clusterf
k of what I've got. 
OutInTheShed said:
I'd be reluctant to spend actual money buying an engine that's already got obvious problems.
If the head is what's giving you trouble, then replacing just that makes a lot of sense.
Are you absolutely sure about compatibility?
The worst outcome is probably putting money, time and emotion into the head, then finding the old one won't come off without wrecking the block, it doesn't fit or some other show stopper.
Obviously you will have the cost of a headgasket.
Are these chain drive cams?
What other parts might be wanted?
Will the engine come out? Will you do any painting, renew lots of fasteners, odds and ends?
Mission creep soon adds cost, and at the end of it, there will still be other parts of the bike which are high mileage.
If you ever sell the bike, it's still high mileage and amateur engine work rarely adds value IMHO.
So, it might be good to know what the long game is?
If you expect a lot more years and miles out of it, maybe it's worth spending more. (time as well as $$$)
But I also think in terms of how long will it be off the road?
If my bike's engine died, buying something newer and breaking the old one would be an option.
Or buy an extra bike and fix the old one in 'slow time'.
In the end you have to do what suits you, not what people like me tell you is the sensible choice.
Yeah, certain on compatibility. They're also identical to the old cb models barring the ports for the PAIR system. I'll need a head and cam gasket plus bolts. Bike was bought to learn this kind of thing on before attempting valve clearance etc on my VFR. Intend to run it into the ground. Used mainly as a winter hack.If the head is what's giving you trouble, then replacing just that makes a lot of sense.
Are you absolutely sure about compatibility?
The worst outcome is probably putting money, time and emotion into the head, then finding the old one won't come off without wrecking the block, it doesn't fit or some other show stopper.
Obviously you will have the cost of a headgasket.
Are these chain drive cams?
What other parts might be wanted?
Will the engine come out? Will you do any painting, renew lots of fasteners, odds and ends?
Mission creep soon adds cost, and at the end of it, there will still be other parts of the bike which are high mileage.
If you ever sell the bike, it's still high mileage and amateur engine work rarely adds value IMHO.
So, it might be good to know what the long game is?
If you expect a lot more years and miles out of it, maybe it's worth spending more. (time as well as $$$)
But I also think in terms of how long will it be off the road?
If my bike's engine died, buying something newer and breaking the old one would be an option.
Or buy an extra bike and fix the old one in 'slow time'.
In the end you have to do what suits you, not what people like me tell you is the sensible choice.
Assuming you haven’t actually buggered the head, have you considered sending it to an engineering company? They can repair all sorts of horrible damage, snapped bolts etc and usually charge very little for their services.
They are getting few and far between as car and bike engines are rarely rebuilt but there are plenty specialising in truck or agricultural engines and they’ll often take on other work.
They are getting few and far between as car and bike engines are rarely rebuilt but there are plenty specialising in truck or agricultural engines and they’ll often take on other work.
Newarch said:
Assuming you haven’t actually buggered the head, have you considered sending it to an engineering company? They can repair all sorts of horrible damage, snapped bolts etc and usually charge very little for their services.
They are getting few and far between as car and bike engines are rarely rebuilt but there are plenty specialising in truck or agricultural engines and they’ll often take on other work.
I guess it is a vague possibility. The damage is really where the drill has slipped in one and snapped off in another. I'm not entirely sure how well the threads could be closed up? They are getting few and far between as car and bike engines are rarely rebuilt but there are plenty specialising in truck or agricultural engines and they’ll often take on other work.
Biker9090 said:
Newarch said:
Assuming you haven’t actually buggered the head, have you considered sending it to an engineering company? They can repair all sorts of horrible damage, snapped bolts etc and usually charge very little for their services.
They are getting few and far between as car and bike engines are rarely rebuilt but there are plenty specialising in truck or agricultural engines and they’ll often take on other work.
I guess it is a vague possibility. The damage is really where the drill has slipped in one and snapped off in another. I'm not entirely sure how well the threads could be closed up? They are getting few and far between as car and bike engines are rarely rebuilt but there are plenty specialising in truck or agricultural engines and they’ll often take on other work.
Why where you removing the head in the first place?
Biker9090 said:
Newarch said:
Assuming you haven’t actually buggered the head, have you considered sending it to an engineering company? They can repair all sorts of horrible damage, snapped bolts etc and usually charge very little for their services.
They are getting few and far between as car and bike engines are rarely rebuilt but there are plenty specialising in truck or agricultural engines and they’ll often take on other work.
I guess it is a vague possibility. The damage is really where the drill has slipped in one and snapped off in another. I'm not entirely sure how well the threads could be closed up? They are getting few and far between as car and bike engines are rarely rebuilt but there are plenty specialising in truck or agricultural engines and they’ll often take on other work.
I think they can drill the hole out oversize then fit an insert to bring it back to the correct size. I’ve never sent my local firm anything they couldn’t handle, apart from cracking obviously.
Newarch said:
Assuming you haven’t actually buggered the head, have you considered sending it to an engineering company? They can repair all sorts of horrible damage, snapped bolts etc and usually charge very little for their services.
They are getting few and far between as car and bike engines are rarely rebuilt but there are plenty specialising in truck or agricultural engines and they’ll often take on other work.
I agree with this suggestion. You should never underestimate what a good engineering company can do. I recently had a stainless steel exhaust elbow stud shear on a marine engine. I took the heat exchanger to the local head specialist (advertising slogan "You won't get a better head job in Adelaide"), who removed the seized length of stud with a perfect thread left behind. Almost miraculous! They are getting few and far between as car and bike engines are rarely rebuilt but there are plenty specialising in truck or agricultural engines and they’ll often take on other work.
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