Honda 250 Superdream - Engine Rebuild Questions
Discussion
Hey everyone,
I recently bought this item as part of an evening project, my intention is to rebuild it
http://www.ebay.co.uk/itm/330851692833?ssPageName=...
Now as the link shows, the outside is pretty nasty looking. All dirty and tired looking aesthetically.
What would be the best way to tidy this up? I was thinking of sanding it down, cleaning it and then having it painted/powder coated in black (not sure if the black would affect the air cooling since it absorbs heat more?) Is this an inadvisable route?
Also I plan on refurbing the carb myself, Would there be any problems with having it chrome plated? Also if I rebuild the carb, is there any way that when I fire the engine up for the first time after the rebuild that the mixture will be too lean/rich and consequently burn out the valves?
I am a novice but I have bought this engine to learn!
Many thanks,
Matt
I recently bought this item as part of an evening project, my intention is to rebuild it
http://www.ebay.co.uk/itm/330851692833?ssPageName=...
Now as the link shows, the outside is pretty nasty looking. All dirty and tired looking aesthetically.
What would be the best way to tidy this up? I was thinking of sanding it down, cleaning it and then having it painted/powder coated in black (not sure if the black would affect the air cooling since it absorbs heat more?) Is this an inadvisable route?
Also I plan on refurbing the carb myself, Would there be any problems with having it chrome plated? Also if I rebuild the carb, is there any way that when I fire the engine up for the first time after the rebuild that the mixture will be too lean/rich and consequently burn out the valves?
I am a novice but I have bought this engine to learn!
Many thanks,
Matt
I think you would be better starting with understanding what you need the engine for. There is no point spending time and money 'Learning' on an engine that is not right for the final project.
You would also be better starting with a known runner. Your lack of knowledge could again waste time on something that was' unbeknown to you, beyond economic repair.
You will not be able to powder coat as the process is very hot which will damage seals etc in the engine. Chrome on the carb will be very expensive. Google DIY blasting with baking soda which will do a nice job of cleaning ali parts. Plenty of bike engines are painted black.
Steve
You would also be better starting with a known runner. Your lack of knowledge could again waste time on something that was' unbeknown to you, beyond economic repair.
You will not be able to powder coat as the process is very hot which will damage seals etc in the engine. Chrome on the carb will be very expensive. Google DIY blasting with baking soda which will do a nice job of cleaning ali parts. Plenty of bike engines are painted black.
Steve
Id without question plug all the holes up and get it Aqua blasted , well that's what i do to my bikes engine and cases.
That engine of your would look to good to use , and its a good one to do just make some plates to cover the exhaust with some sealer same for the inlet and go from there .....
They come up just as they left the factory , basically a blast cabinet with water heated to 40-60 degrees with a media added like shot blasting but with added water at 60 psi.
At the eng rinse with water and put it on a revolving table in front of a Andrews heater for 20 min.
Pit your not near Npton you could plug the holes and id do it for a few Guinness ;D
That engine of your would look to good to use , and its a good one to do just make some plates to cover the exhaust with some sealer same for the inlet and go from there .....
They come up just as they left the factory , basically a blast cabinet with water heated to 40-60 degrees with a media added like shot blasting but with added water at 60 psi.
At the eng rinse with water and put it on a revolving table in front of a Andrews heater for 20 min.
Pit your not near Npton you could plug the holes and id do it for a few Guinness ;D
Edited by packman10_4 on Friday 11th January 07:55
You can take the carb apart and clean it, and as long as you don't adjust the jetting it'll be fine. Not sure how the carb on those works but they're not normally too hard to take apart, and old ones will benefit from a good cleaning. You shouldn't need to take out the butterfly, just strip it down so that you can get to the fuel/air passageways and blow them through with carb cleaner + an air line (or footpump ). Clean out the main bore with carb cleaner to get rid of the gunge, and make sure everything moves freely. A good mini project in itself. Keep everything scrupulously clean when you put it back together.
). Clean out the main bore with carb cleaner to get rid of the gunge, and make sure everything moves freely. A good mini project in itself. Keep everything scrupulously clean when you put it back together. Before you start tarting it up....
What do you know about the engine? When was it last run? Was it running OK at that point? How long has it been standing, and under what conditions (i.e. could water have got into it)?
Are you prepared to do a full stripdown (if required)? If you do end up pulling it apart, you're lucky in that as it's a Honda you'll almost certainly still be able to get all the bits you need (you'll just be paying for most of David Silver's next holiday).
I'm not trying to put you off, but I do have experience of doing up old bikes, and it's best that you go in with your eyes open.
As for your specific questions:
I'd get the engine blasted (as said above) then spray the rough cast items (crankcases, etc.) with clear lacquer or silver engine paint. Make sure you get the heat resistant stuff as air cooled engines get very hot, and some paints/lacquers will go yellowish after a while. All the smooth items (generator cover, clutch cover, etc.) can be polished (to a mirror finish if you're so inclined).
The carbs will probably come up quite well (inside & out) with something like Wynn's Fuel Injection Intake & Carb Cleaner. If you can't get them clean enough yourself, the best bet would be to get them ultrasonically cleaned. I wouldn't bother chroming them. Be very careful when removing the various jets, emulsion tubes, floats, etc. as they get damaged easily. You'll need some overhaul kits (new gaskets & O-rings) when you re-assemble them. Try to get the float heights set as accurately as you can on the bench, as it's easier than fiddling with them when they're in situ.
Oh, and Good Luck!
What do you know about the engine? When was it last run? Was it running OK at that point? How long has it been standing, and under what conditions (i.e. could water have got into it)?
Are you prepared to do a full stripdown (if required)? If you do end up pulling it apart, you're lucky in that as it's a Honda you'll almost certainly still be able to get all the bits you need (you'll just be paying for most of David Silver's next holiday
). I'm not trying to put you off, but I do have experience of doing up old bikes, and it's best that you go in with your eyes open.
As for your specific questions:
I'd get the engine blasted (as said above) then spray the rough cast items (crankcases, etc.) with clear lacquer or silver engine paint. Make sure you get the heat resistant stuff as air cooled engines get very hot, and some paints/lacquers will go yellowish after a while. All the smooth items (generator cover, clutch cover, etc.) can be polished (to a mirror finish if you're so inclined).
The carbs will probably come up quite well (inside & out) with something like Wynn's Fuel Injection Intake & Carb Cleaner. If you can't get them clean enough yourself, the best bet would be to get them ultrasonically cleaned. I wouldn't bother chroming them. Be very careful when removing the various jets, emulsion tubes, floats, etc. as they get damaged easily. You'll need some overhaul kits (new gaskets & O-rings) when you re-assemble them. Try to get the float heights set as accurately as you can on the bench, as it's easier than fiddling with them when they're in situ.
Oh, and Good Luck!
The Black Flash said:
You can take the carb apart and clean it, and as long as you don't adjust the jetting it'll be fine. Not sure how the carb on those works but they're not normally too hard to take apart, and old ones will benefit from a good cleaning. You shouldn't need to take out the butterfly, just strip it down so that you can get to the fuel/air passageways and blow them through with carb cleaner + an air line (or footpump ). Clean out the main bore with carb cleaner to get rid of the gunge, and make sure everything moves freely. A good mini project in itself. Keep everything scrupulously clean when you put it back together.
< This, bike CV carbs of this era are a piece of piss to overhaul, arm yourself with new gaskets & O'Rings & airline an a can of carb cleaner or cellulose thinners for those probably Keihin beauties and your away ). Clean out the main bore with carb cleaner to get rid of the gunge, and make sure everything moves freely. A good mini project in itself. Keep everything scrupulously clean when you put it back together. 
as I remember correctly that motor had cam-chain,camshaft and rocker arm wear woes this affected both the SD 250 & 400 variants of this motor 
not sure how bad a problem that was as I was never a fan of that kind of bike 
Edited by Sardonicus on Friday 11th January 21:17
Thanks for the replies all
Just to answer some questions, the reason I bought the engine was to learn a bit more about engines and general engineering principles, and maybe eventually use the engine in some sort of simple buggy. I know it's an expensive way of learning but it was either this or an XBOX to occupy me in the evenings.
As far as I know, the engine was running when it was removed from the bike. Additionally, the last owner said it had been stored indoors for the time he had it. When it was all assembled, I could turn everything over by hand, everything felt OK.
I've started taking it apart and I've found a few interesting surprises. Firstly, the flat face part of the valves seem to have a tiny bit of corrosion on them. Secondly, there seems to be a bit of dirt on the pistons which is a tad worrying, but there isn't anything drastic. I'm wondering if the motor was stored in a garage and exposed to damp air.
At present, I am stuck on the engine/cylinder block (the head is removed). It's so, so, so stuck. My guess is that it hasn't ever been removed!
Interesting to hear the comments RE: The cam chain. I have owned many chain driven cars before and they have typically been fine for well over 100k miles. In fact, I drove a 535i 1989 BMW with 234,000 miles on it and the chain had never been replaced, there was no rattling at all. I would rather not replace it if I can avoid it.
Oh something else: Someone has been in the cylinder head before. There is a scribe mark on the end of the camshaft which is handy, and some red paint on the chain. No idea what was done though!
If anyone can help with advice on how to remove the ruddy cylinder block I would be very grateful.
Best wishes,
Matt
Just to answer some questions, the reason I bought the engine was to learn a bit more about engines and general engineering principles, and maybe eventually use the engine in some sort of simple buggy. I know it's an expensive way of learning but it was either this or an XBOX to occupy me in the evenings.
As far as I know, the engine was running when it was removed from the bike. Additionally, the last owner said it had been stored indoors for the time he had it. When it was all assembled, I could turn everything over by hand, everything felt OK.
I've started taking it apart and I've found a few interesting surprises. Firstly, the flat face part of the valves seem to have a tiny bit of corrosion on them. Secondly, there seems to be a bit of dirt on the pistons which is a tad worrying, but there isn't anything drastic. I'm wondering if the motor was stored in a garage and exposed to damp air.
At present, I am stuck on the engine/cylinder block (the head is removed). It's so, so, so stuck. My guess is that it hasn't ever been removed!
Interesting to hear the comments RE: The cam chain. I have owned many chain driven cars before and they have typically been fine for well over 100k miles. In fact, I drove a 535i 1989 BMW with 234,000 miles on it and the chain had never been replaced, there was no rattling at all. I would rather not replace it if I can avoid it.
Oh something else: Someone has been in the cylinder head before. There is a scribe mark on the end of the camshaft which is handy, and some red paint on the chain. No idea what was done though!
If anyone can help with advice on how to remove the ruddy cylinder block I would be very grateful.
Best wishes,
Matt
Bike camchains are very different to car camchains, in that quite a few bikes (especially certain Honda models) developed very bad reputations for failures in that area, though mostly due to the tensioner mechanisms rather than the actual chain. I suspect that's the reason for someone having been in there before. While it's in bits you should at least replace the tensioner.
I wouldn't worry too much about a bit of corrosion on the valves & piston tops - it'll almost certainly clean up OK.
As for the barrels being stuck, I assume you've tried tapping it all round with a mallet & using a large screwdriver (or similar) to try to prise it off (assuming that it has pry points - most do). Be careful not to put any pressure on the cooling fins on the barrel; they break easily. It may sound silly, but are you sure that ALL the bolts are out? The last time I had one stuck it did eventually shift, but it took quite a lot of force.
I wouldn't worry too much about a bit of corrosion on the valves & piston tops - it'll almost certainly clean up OK.
As for the barrels being stuck, I assume you've tried tapping it all round with a mallet & using a large screwdriver (or similar) to try to prise it off (assuming that it has pry points - most do). Be careful not to put any pressure on the cooling fins on the barrel; they break easily. It may sound silly, but are you sure that ALL the bolts are out? The last time I had one stuck it did eventually shift, but it took quite a lot of force.
Edited by S7Paul on Saturday 12th January 17:07
S7Paul said:
Bike camchains are very different to car camchains, in that quite a few bikes (especially certain Honda models) have developed very bad reputations for failures in that area, though mostly due to the tensioner mechanisms rather than the actual chain. I suspect that's the reason for someone having been in there before. While it's in bits you should at least replace the tensioner.
I wouldn't worry too much about a bit of corrosion on the valves & piston tops - it'll almost certainly clean up OK.
Thanks for the reply I wouldn't worry too much about a bit of corrosion on the valves & piston tops - it'll almost certainly clean up OK.
Before buying any new bits I plan on taking the whole thing apart and assessing whether there is anything serious enough to prevent it being economically viable to get running again.
Kind regards,
Matt
Right, the cylinder block is off. I decided the best way to do it was walk away, have some tea whilst reading PH, and then reattempt.
Only issue is that in the process of lifting it off the pistons and removing the tensioner rail I put a couple of very light scratches on the mating face of the block. I hope this doesn't effect the sealing when I place a new gasket on the surfaces.
Best regards,
Matt
Only issue is that in the process of lifting it off the pistons and removing the tensioner rail I put a couple of very light scratches on the mating face of the block. I hope this doesn't effect the sealing when I place a new gasket on the surfaces.
Best regards,
Matt
BeirutTaxi said:
Right, the cylinder block is off. I decided the best way to do it was walk away, have some tea whilst reading PH, and then reattempt.
Only issue is that in the process of lifting it off the pistons and removing the tensioner rail I put a couple of very light scratches on the mating face of the block. I hope this doesn't effect the sealing when I place a new gasket on the surfaces.
Best regards,
Matt
Unless the scratches run across oilways or to the edge of the bores you'll be OK. Just lightly rub them down flush (i.e. just take the high points off).Only issue is that in the process of lifting it off the pistons and removing the tensioner rail I put a couple of very light scratches on the mating face of the block. I hope this doesn't effect the sealing when I place a new gasket on the surfaces.
Best regards,
Matt
S7Paul said:
Hard to tell without seeing/feeling it. If you can clearly feel it with your fingernail you may need a rebore. Do you know if the pistons are standard size or do they have any numbers on the top indicating that they're oversize (i.e. that it's already been re-bored at some point)?
I can feel it with my fingernail - I suspect a rebore is in order! Is it the liners/sleeves that are re-bored or does the whole block have to be altered?Through looking around, I've found that there are +0.250mm, +0.500mm and +1.00 oversize. Additionally, there are +2.00mm oversize pistons for sale from a pattern parts website, however Honda only ever sold up to +1.00mm oversize pistons.
Quite what the effects of +2.00mm would be I'm not sure of, and will seek some expert advice on!
Best regards,
Matt
I've never had a Superdream motor in bits but I assume it's got steel liners in the aluminium barrels. Take the barrels and the new pistons to a machine shop that specialises in such things. I'd go for the minimum overbore size you need to get rid of the scratch. that way you still have some rebore allowance left. If you go for the maximum oversize pistons now, and the engine has another problem in that area in future, you'll need new liners or (most likely) barrels. Get the cylinders measured first to give you an idea of whether you need +0.50, or whether +0.25 will do.
Incidentally, where on the South Coast are you?
Incidentally, where on the South Coast are you?
S7Paul said:
I've never had a Superdream motor in bits but I assume it's got steel liners in the aluminium barrels. Take the barrels and the new pistons to a machine shop that specialises in such things. I'd go for the minimum overbore size you need to get rid of the scratch. that way you still have some rebore allowance left. If you go for the maximum oversize pistons now, and the engine has another problem in that area in future, you'll need new liners or (most likely) barrels. Get the cylinders measured first to give you an idea of whether you need +0.50, or whether +0.25 will do.
Incidentally, where on the South Coast are you?
Thank you for the help Paul, it's much appreciated Incidentally, where on the South Coast are you?
I am near Southampton & Winchester at the moment.
Best regards,
Matt
BeirutTaxi said:
Thank you for the help Paul, it's much appreciated
I am near Southampton & Winchester at the moment.
Best regards,
Matt
No problem. The reason I asked where you were is that if you were nearer Portsmouth I'd suggest using Banda Engineering for any machining work. However I don't doubt there are people nearer to you that can do the job.I am near Southampton & Winchester at the moment.
Best regards,
Matt
If you need parts, the best places I found (other than eBay) are David Silver Spares and CMS in the Netherlands http://www.cmsnl.com/
OP, if you do decide to get any engine machining work done go to owlesbury crankshaft's. http://www.ocservice.co.uk
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