K0 out of a pile

Chrisj796

Member
Today I finished the bottom end, hopefully can get crankcase covers into painter soon an move on to top end.
 

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Chrisj796

Member
I was going to use the blast cabinet with glass beads that I did everything else with to clean the cylinder head. After running it by a few people I am not so sure about it now. I have some mineral spirits I can soak it in.
I was planing on just buying a new top end but after looking at the price difference between OEM an aftermarket I’m guessing the original parts will be worth repairing rather than replacing with cheap aftermarket.
The last few vehicles engine I rebuilt I got hot tanked does anyone have any home remedy’s that have worked well for them?
 

69ST

Well-Known Member
The cylinder head is the odd duck of engine parts, when it comes to cleaning.

Hot tank soaking goes a long way toward loosening, if not removing, most of the dirt & carbon. A thorough soak followed by crushed walnut shell blasting may do what you want, quickly. It won't change the as-cast surfaces of the fins (sandcast texture) or the combustion chamber + valve heads (low gloss, if not oxidized).

It's when you're dealing with heavy carbon/rust in the combustion chamber or heavy oxidation/staining of the sandcast fin surfaces. The combustion chamber can be cleaned using glass bead...paired with low pressure, increased gun distance and working quickly. The ports can be heavily blasted with glass bead and normal gun pressure, working from the outsides of the ports. The valves must be left in place to protect the guides & valve seats (even if the need to be cut).

Aluminum prep, sold through automotive paint suppliers, Eastwood Tool, et al, or oven cleaner containing sodium hydroxide will usually do the job, without profiling the surfaces. A nylon bristle brush is used for the scrubbing, followed by immediate rinsing.

If that doesn't clean the staining from the outside surfaces, then the choices are living with the results...or media blasting. Unlike any other engine part, including the head covers & cases, wet blasting can deliver a result that is reasonably close to original. That sandcast texture is quite compatible with wet media blasting. Dry blasting with glass beads can deliver an okay result...if you work quickly (minimal blast time) and carefully (very low pressure) but it's not as nice, or as close to original, as wet blasting for this item.
 

Chrisj796

Member
The cylinder head is the odd duck of engine parts, when it comes to cleaning.

Hot tank soaking goes a long way toward loosening, if not removing, most of the dirt & carbon. A thorough soak followed by crushed walnut shell blasting may do what you want, quickly. It won't change the as-cast surfaces of the fins (sandcast texture) or the combustion chamber + valve heads (low gloss, if not oxidized).

It's when you're dealing with heavy carbon/rust in the combustion chamber or heavy oxidation/staining of the sandcast fin surfaces. The combustion chamber can be cleaned using glass bead...paired with low pressure, increased gun distance and working quickly. The ports can be heavily blasted with glass bead and normal gun pressure, working from the outsides of the ports. The valves must be left in place to protect the guides & valve seats (even if the need to be cut).

Aluminum prep, sold through automotive paint suppliers, Eastwood Tool, et al, or oven cleaner containing sodium hydroxide will usually do the job, without profiling the surfaces. A nylon bristle brush is used for the scrubbing, followed by immediate rinsing.

If that doesn't clean the staining from the outside surfaces, then the choices are living with the results...or media blasting. Unlike any other engine part, including the head covers & cases, wet blasting can deliver a result that is reasonably close to original. That sandcast texture is quite compatible with wet media blasting. Dry blasting with glass beads can deliver an okay result...if you work quickly (minimal blast time) and carefully (very low pressure) but it's not as nice, or as close to original, as wet blasting for this item.
Thanks I have them sitting a bucket of carb cleaner, will give it a few days see how it’s working.
 

Chrisj796

Member
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Pulled seat apart today an straightened it out then hit it with a buffing wheel. Was this the original seat cover from the K0? I saw a used one with the same pattern on eBay that said it was from a 69-71.
 

69ST

Well-Known Member
Looks like an original seat pan, with the early stages of metal failure. See those puckered sections of the side rails? That's the Achilles Heel of these. You really should straighten, then bead blast, the metal...see what you're starting with. Finding one of these early pans without any cracking is uncommon. Any breaks, no matter how small, will doom your seat restoration to early failure. The metal is thin, structural strength comes from the shape of the pan and it must be intact. Otherwise, the pan will have the structural rigidity of rubber; the rear section will soon collapse onto the TL bracket. The good news is that it is possible to weld the breaks, add an angle brace to each side and prevent a repeat performance...while retaining all of the original stamping detail. Not much in the way of material resources are needed to do this and do it right.

FYI, Honda added angle reinforcements to the seat pans beginning with the K2 model. They also went to a synthetic foam, with a much longer lifespan. Unfortunately, the K0 & K1 seat foam each have a shape unique to their specific model. K0 reproduction molded foam is available from a few different vendors. Best to source the new foam & cover from the same vendor.
 

Chrisj796

Member
Looks like an original seat pan, with the early stages of metal failure. See those puckered sections of the side rails? That's the Achilles Heel of these. You really should straighten, then bead blast, the metal...see what you're starting with. Finding one of these early pans without any cracking is uncommon. Any breaks, no matter how small, will doom your seat restoration to early failure. The metal is thin, structural strength comes from the shape of the pan and it must be intact. Otherwise, the pan will have the structural rigidity of rubber; the rear section will soon collapse onto the TL bracket. The good news is that it is possible to weld the breaks, add an angle brace to each side and prevent a repeat performance...while retaining all of the original stamping detail. Not much in the way of material resources are needed to do this and do it right.

FYI, Honda added angle reinforcements to the seat pans beginning with the K2 model. They also went to a synthetic foam, with a much longer lifespan. Unfortunately, the K0 & K1 seat foam each have a shape unique to their specific model. K0 reproduction molded foam is available from a few different vendors. Best to source the new foam & cover from the same vendor.

it does have a small crack on both cut outs for shocks, looks like they stamped one of the tabs right on the lip which make it weak. does anyone have a photo of a nice one? I will have a welder take a wire feed to it an knock the humps out of the rear of it.
 

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Chrisj796

Member
Lapped valves today, everything is looking good. Welder got finished with my seat pan and I am drop off parts next week for paint. Also does anyone know of you can paint the cylinder head or just leave it raw aluminum, I got my clean but it doesn’t look as uniform as some I have seen on the internet. I am curious if they are painted or using some sort of resurfacing on them?
 

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Chrisj796

Member
Got top end back on, cylinder head isn’t as nice as I would have liked but It will work for now.
 

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OLD CT

Well-Known Member
Neverdull works great Chris at the stage you are at with the cleaning, try it... It looks REAL GOOD, if there isn't built up grease which obviously yours does not have. 16T is not a good choice for 72ccs or even 88ccs.
 

Chrisj796

Member
Neverdull works great Chris, try it... It looks REAL GOOD, if there isn't built up grease which obviously yours does not have. 16T is not a good choice for 72ccs or even 88ccs.
Ok I have tried a few different things on it an just can’t seem to cut the oxidation between fins without damaging the surface. Why is the 16 tooth not good?
 

OLD CT

Well-Known Member
The higher you can get the top gear to rev out, in your case ''3rd'' the faster you ultimately go.
10 thousand rpms in 4th on my 124cc H is darn near 70 mph. If I go too tall, it will not rev out to 10k and you lose mph.
 
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Chrisj796

Member
Hey everyone, I was tinkering with engine today spinning it around by hand listening to valves and noticed I cannot spin it backwards. Will go about one turn then locks up, I cannot spin sprocket either. Spin it forward an it works great an sprocket spins freely. Is this normal or is something not assembled right in transmission?
 

Philct70

New Member
Any update on your problem Chris? I don't think that sounds right. I will check mine when I can. I also found this awesome copy for the seat on eBay UK 124200958143 price is good, perfect fit and quality
 
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