Planet Minis

yadihonda · 11-02-2009, 10:15 PM

I recently rec'd a new chinese head for free. I have no idea as to the manufacturer. The intake port opening is between 22mm and 23mm. The problem is that I have a stock 50 carb and manifold (1969 z50k1). The opening on the stock manifold is much smaller.

What problems can I expect if I try to run this wtih the stock carb and manifold? Do I need to update the carb and manifold? Or would I only do that to increase performance, something I'm not too concerned about?

dax · 11-03-2009, 02:07 AM

It will run fine, no broplems. BUT if the combustion chamber is bigger you will have smaller compression ratio and poor performance

mexicanyella · 11-03-2009, 05:53 AM

Also, the Chinese head will be patterned on the newer 12V CDI Honda engines, not the older 6V ones. Combustion chambers were deeper hemispheres on the old ones, with a taller piston dome to match. If you plan to run it on a 6V motor, with its short connecting rod, you'll have to be aware of what piston you're teaming up with it. The Dr. ATV site has a lot of info about what works with what, and a few pistons that allow some combinations of 6V-12V stuff.

Measuring the diameter of the head's combustion chamber will tell you the bore size it was intended for, thus what displacement it was intended for. That ought to help you select a piston.

I rode a hardtail recently with a CT70 engine that had the hardtail's carb, intake and exhaust. That was probably a port mismatch, and it ran pretty good. It was a pretty decent wheelie machine.

yadihonda · 11-03-2009, 07:54 AM

Here is a link to the head that was given to me. These are are sold on Ebay: HONDA Z50 COMPLETED HEAD BRAND NEW READY TO INSTALL:eBay Motors (item 280417215244 end time Nov-29-09 19

39 PST)

I'm at work and can't post measurements. Another thought that I had was regarding an oil pressure plate on the cam gear. I've seen this in later motors. On my stock motors (1969, 1974 and 1975) there isn't a pressure plate. On this new head, the center hole is larger than the stock motor, which is making me suspect this is for a later year model that might require that pressure plate. Is there any way to confirm this by looking at the design of the motor? I'd hate to put it together without that plate if it is required.

T Bolt USA · 11-03-2009, 08:03 AM

Quote:

Originally Posted by yadihonda

I recently rec'd a new chinese head for free. I have no idea as to the manufacturer. The intake port opening is between 22mm and 23mm. The problem is that I have a stock 50 carb and manifold (1969 z50k1). The opening on the stock manifold is much smaller.

What problems can I expect if I try to run this wtih the stock carb and manifold? Do I need to update the carb and manifold? Or would I only do that to increase performance, something I'm not too concerned about?

what engine ?? we have tons of intakes / carbs sitting here

yadihonda · 11-03-2009, 08:26 AM

Sorry about that lack of clarity. The motor is a 1969 z50a k1, all stock.

yadihonda · 11-03-2009, 03:07 PM

I measured the diameter the best I could. Measuring the outside of the bevel = about 48mm. Measuring from inside the bevel = about 40mm. The only markings I can see is a shape that looks like a debossed letter "C" and embossed "B".

The stock z50 piston and cylinder came as a kit with gaskets from DRATV and was meant for 68 thru 81 z50s: Z50A_R 68_TO_81 50CC_CYL_KIT

Do you think this piston is okay for this head based on the measurements above?

Intake Port Question for z50-img_1722.jpg

Intake Port Question for z50-img_1723.jpg

Intake Port Question for z50-img_1725.jpg

yadihonda · 11-03-2009, 03:41 PM

The depth of the chamber matches an old stock head. The diameter of the chamber seems to match as well, with exception to that bevel. There isn't any bevel on the old stock head. Is that bevel going to increase the combustion area, decrease the compression, and create a performance problem?

mexicanyella · 11-03-2009, 04:53 PM

I think what you have there might be a head for a new-style 70 (47mm bore, not 39). What about throwing a 47mm cylinder on it since you're into the top end anyway, and a compatible piston from Dr.ATV? Z-70 madness.

yadihonda · 11-03-2009, 04:57 PM

I'd consider doing just that if I could confirm what you are saying. How can I confirm these dimensions and what you are saying?

mexicanyella · 11-03-2009, 08:10 PM

It occurred to me after writing that that I don't have a new-type 70 head here. I have a China E22 head from a 110 clone, but it's got a bevel outer diameter of around 52mm, so it won't be a good visual comparison. I do have a couple old-style short-rod 6V 70 heads. I'll go dig them out and measure them later tonight and let you know the diameter, combustion chamber depth etc. Might be tomorrow before I have that info though. Maybe in the meantime dirtbkr188 or someone will confirm what combustion chamber shape you've got. Once you know that, the performance section of Dr. ATV's site has pretty clear explanations on what pistons work with what combinations.

dirtbkr188 · 11-03-2009, 08:37 PM

I do have an XR70 head here that I can measure, along with a few other ones.
yadi, can you take a few more pictures of the head you have, from a few different angles, and include pics of the sides where the cam covers go ? It'll give everyone a better idea of what type head it is.

schofell84 · 11-03-2009, 09:02 PM

can you port the stock manifold to match?

yadihonda · 11-03-2009, 09:09 PM

More pictures.. The last picture is obviously the head gasket that came wit the cylinder/piston kit from DRATV. The metal ring around the bore is 39mm but because the chamfer/bevel is larger, the metal ring does not meet completely flush to the head. I would think that would be a problem....

Intake Port Question for z50-img_1726.jpg

Intake Port Question for z50-img_1727.jpg

Intake Port Question for z50-img_1728.jpg

Intake Port Question for z50-img_1729.jpg

yadihonda · 11-03-2009, 09:13 PM

Schoffell84 - I think my problems could be more serious than the manifold and port match - if my head won't match my piston and cylinder. I'm in a learning mode right now....there are simply too many options out there and I may have found two of them, albeit incompatible. I waiting for the experts with experience to help me.

mexicanyella · 11-03-2009, 11:29 PM

I measured the combustion chamber on a late 70s ATC 70 head, which would have the short connecting rod, 6V points ignition and what Dr. ATV calls "old 70 dome" head and piston. It also has the squish band/bevel around the chamber, but the angle of the bevel is steeper (more perpendicular to the head gasket surface, less perpendicular to the direction of piston travel).

The steeper bevel makes for a narrower bevel measurement in terms of its i.d., which I made to be 44.5-45mm. The outside of the bevel is 47ish, like yours. I was using some crude tools but the chamber depth I measured was about 13mm from the head gasket surface (no gasket in place).

I also measured a stock head off a '74 Z50A. No bevel. Just a dome, same 13mm depth but smaller diameter to match the 39mm bore.

If I'm right that you've got a "new 70 dome" head there, I think you could run this piston:

47MM_PISTON_KIT (OLD_50_DOME) OR (NEW_70_DOME) (SHORT_ROD) (SHORT_CYLINDER) (100020)

in a 47mm (72cc) cylinder on your current bottom end, with either your new 70 dome head OR a stock head off a 6V short-rod 50cc motor. Depending on what port sizes you wanted to use, etc.

A PM member called mtubbs had one of those pistons he was willing to sell recently; if the general agreement is that you DO now have a "new 70 dome" and you choose to go the 70 route, you might send him a PM and see if he's still got it.

yadihonda · 11-04-2009, 07:40 AM

Thanks for working on this with me Mex.

I have an email, with pictures, into DRATV. Hopefully he can identify the head and make the recommendation for the next step. Luckily, I have another z50 motor that needs a top end as well. If I can salvage the head on that one, then my 39mm cylinder and piston can be used on that...should my mystery head be a 47mm (70 head).

If it does turn out to be a 70 head, then wouldn't I be going out on the slippery slope of a different carb (or jets) and manifold? The current carb is the original from a 1969 z50ak1.

mexicanyella · 11-04-2009, 08:14 AM

Maybe, but I took a spin on a friend's K1 (I think) hardtail over the summer, which he'd picked up with a three-speed CT70 motor swapped into it. It still had the original old-style hardtail carb, intake manifold and air filter on it, and the original hardtail stock exhaust, but all this bolted to a CT70 motor with CT70 head. So there was some port mismatch going on, and as far as my friend could tell the stock carb still had the stock jetting.

Other than the clutch being adjusted too tight, making for some jerky shifts, the thing was a blast to ride. Didn't seem underjetted to me. It seemed wheelie-prone to me. I didn't get a chance to wind it out and see where it ran out of breath, but it sure had more torque than my 50cc hardtail. I remember coming almost to a stop in second gear, gassing the throttle and the front wheel coming off the ground a bit--instant forward motion--whereas my 50 would sort of lug along for a bit until the rpms came up enough for the clutch to lock in, if I did the same thing on it.

Even if you try this and it doesn't work, or you elect not to limit a stock 70 with a 50 carb and exhaust, I don't think jetting a 70 will be a slippery slope. You could always start with a carb intended for a 70 so you'd be in the ballpark to begin with, or if you elect to go aftermarket, just make sure there's a range of jets available for it before you buy. Enough people here have tried enough combinations that you should be able to get recommendations of what jets to start with for just about any combination.

My point is, I think you're on as slippery of a slope as you're going to get on already, and dealing with it. You could always try the stock setup (say things like "yeah, well, I'm running my 'engine break-in setup' right now) while you consider other intake options.

dirtbkr188 · 11-04-2009, 02:50 PM

I took some measurements of an XR70 head and also an E22 head from an Xtreme SuperStock88 engine. The Xtreme engine was a 47mm bore and 49.5 stroke using a 69mm tall cylinder. Here are the results:

XR70

Bevel OD - 47.40mm
Bevel ID - 41.45mm
Depth - 14.40mm
Intake valve - 23mm
Exhaust valve - 20mm

E22

Bevel OD - 46.86mm
Bevel Id - 40.36mm
Depth - 13.40mm
Intake valve - 23mm
Exhaust valve - 20mm

I'm expecting a TB race head within the next day or two, I can measure that one also, if you'd like.

yadihonda · 11-05-2009, 08:37 PM

FYI - I sent an inquiry to DRATV, where I bought the cyl and piston kit (for stock z50). This was the reply:

it looks like a not so good 70cc head ??

measure the od of the face of the intake valve if it is around 23mm then it is a 70cc head or maybe even a 90 or 110 head.

anyway if it has a 23mm intake valve it may not work with a 39mm bore ?

I measured it the best I could and the intake seems to be bigger than 23mm...take it with a grain of salt because its not easy to measure...I made markings on paper and measured the marks. Also, the intake looks the same size as my old stock z50 head. I'm not sure if I understand DRATV's email.

Should I just toss this brand new head? Also, how difficult would it be to rehab an old head that came from a non-running motor? Its 40 years old and has a lot of carbon on it. I don't have a spring compressor or tools to grind or resurface seats.....

11-02-2009, 10:15 PM	#1 (permalink)
yadihonda 1st Gear Member Join Date: Jun 2009 Location: Eastern PA Posts: 102 My Mood:	Intake Port Question for z50 I recently rec'd a new chinese head for free. I have no idea as to the manufacturer. The intake port opening is between 22mm and 23mm. The problem is that I have a stock 50 carb and manifold (1969 z50k1). The opening on the stock manifold is much smaller. What problems can I expect if I try to run this wtih the stock carb and manifold? Do I need to update the carb and manifold? Or would I only do that to increase performance, something I'm not too concerned about?

11-03-2009, 02:07 AM	#2 (permalink)
dax 1st Gear Member Join Date: Jun 2006 Posts: 156	Re: Intake Port Question for z50 It will run fine, no broplems. BUT if the combustion chamber is bigger you will have smaller compression ratio and poor performance

11-03-2009, 05:53 AM	#3 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 972	Re: Intake Port Question for z50 Also, the Chinese head will be patterned on the newer 12V CDI Honda engines, not the older 6V ones. Combustion chambers were deeper hemispheres on the old ones, with a taller piston dome to match. If you plan to run it on a 6V motor, with its short connecting rod, you'll have to be aware of what piston you're teaming up with it. The Dr. ATV site has a lot of info about what works with what, and a few pistons that allow some combinations of 6V-12V stuff. Measuring the diameter of the head's combustion chamber will tell you the bore size it was intended for, thus what displacement it was intended for. That ought to help you select a piston. I rode a hardtail recently with a CT70 engine that had the hardtail's carb, intake and exhaust. That was probably a port mismatch, and it ran pretty good. It was a pretty decent wheelie machine.

11-03-2009, 07:54 AM	#4 (permalink)
yadihonda 1st Gear Member Join Date: Jun 2009 Location: Eastern PA Posts: 102 My Mood:	Re: Intake Port Question for z50 Here is a link to the head that was given to me. These are are sold on Ebay: HONDA Z50 COMPLETED HEAD BRAND NEW READY TO INSTALL:eBay Motors (item 280417215244 end time Nov-29-09 1939 PST) I'm at work and can't post measurements. Another thought that I had was regarding an oil pressure plate on the cam gear. I've seen this in later motors. On my stock motors (1969, 1974 and 1975) there isn't a pressure plate. On this new head, the center hole is larger than the stock motor, which is making me suspect this is for a later year model that might require that pressure plate. Is there any way to confirm this by looking at the design of the motor? I'd hate to put it together without that plate if it is required.

11-03-2009, 08:26 AM	#6 (permalink)
yadihonda 1st Gear Member Join Date: Jun 2009 Location: Eastern PA Posts: 102 My Mood:	Re: Intake Port Question for z50 Sorry about that lack of clarity. The motor is a 1969 z50a k1, all stock.

11-03-2009, 03:07 PM	#7 (permalink)
yadihonda 1st Gear Member Join Date: Jun 2009 Location: Eastern PA Posts: 102 My Mood:	Re: Intake Port Question for z50 I measured the diameter the best I could. Measuring the outside of the bevel = about 48mm. Measuring from inside the bevel = about 40mm. The only markings I can see is a shape that looks like a debossed letter "C" and embossed "B". The stock z50 piston and cylinder came as a kit with gaskets from DRATV and was meant for 68 thru 81 z50s: Z50A_R 68_TO_81 50CC_CYL_KIT Do you think this piston is okay for this head based on the measurements above?

11-03-2009, 03:41 PM	#8 (permalink)
yadihonda 1st Gear Member Join Date: Jun 2009 Location: Eastern PA Posts: 102 My Mood:	Re: Intake Port Question for z50 The depth of the chamber matches an old stock head. The diameter of the chamber seems to match as well, with exception to that bevel. There isn't any bevel on the old stock head. Is that bevel going to increase the combustion area, decrease the compression, and create a performance problem?

11-03-2009, 04:53 PM	#9 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 972	Re: Intake Port Question for z50 I think what you have there might be a head for a new-style 70 (47mm bore, not 39). What about throwing a 47mm cylinder on it since you're into the top end anyway, and a compatible piston from Dr.ATV? Z-70 madness.

11-03-2009, 04:57 PM	#10 (permalink)
yadihonda 1st Gear Member Join Date: Jun 2009 Location: Eastern PA Posts: 102 My Mood:	Re: Intake Port Question for z50 I'd consider doing just that if I could confirm what you are saying. How can I confirm these dimensions and what you are saying?

11-03-2009, 08:10 PM	#11 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 972	Re: Intake Port Question for z50 It occurred to me after writing that that I don't have a new-type 70 head here. I have a China E22 head from a 110 clone, but it's got a bevel outer diameter of around 52mm, so it won't be a good visual comparison. I do have a couple old-style short-rod 6V 70 heads. I'll go dig them out and measure them later tonight and let you know the diameter, combustion chamber depth etc. Might be tomorrow before I have that info though. Maybe in the meantime dirtbkr188 or someone will confirm what combustion chamber shape you've got. Once you know that, the performance section of Dr. ATV's site has pretty clear explanations on what pistons work with what combinations.

11-03-2009, 08:37 PM	#12 (permalink)
dirtbkr188 3rd Gear Member Join Date: May 2004 Location: New Jersey Posts: 2,970	Re: Intake Port Question for z50 I do have an XR70 head here that I can measure, along with a few other ones. yadi, can you take a few more pictures of the head you have, from a few different angles, and include pics of the sides where the cam covers go ? It'll give everyone a better idea of what type head it is.

11-03-2009, 09:02 PM	#13 (permalink)
schofell84 2nd Gear Member Join Date: Feb 2007 Location: Ogdensburg Posts: 277	Re: Intake Port Question for z50 can you port the stock manifold to match?

11-03-2009, 09:09 PM	#14 (permalink)
yadihonda 1st Gear Member Join Date: Jun 2009 Location: Eastern PA Posts: 102 My Mood:	Re: Intake Port Question for z50 More pictures.. The last picture is obviously the head gasket that came wit the cylinder/piston kit from DRATV. The metal ring around the bore is 39mm but because the chamfer/bevel is larger, the metal ring does not meet completely flush to the head. I would think that would be a problem....

11-03-2009, 09:13 PM	#15 (permalink)
yadihonda 1st Gear Member Join Date: Jun 2009 Location: Eastern PA Posts: 102 My Mood:	Re: Intake Port Question for z50 Schoffell84 - I think my problems could be more serious than the manifold and port match - if my head won't match my piston and cylinder. I'm in a learning mode right now....there are simply too many options out there and I may have found two of them, albeit incompatible. I waiting for the experts with experience to help me.

11-03-2009, 11:29 PM	#16 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 972	Re: Intake Port Question for z50 I measured the combustion chamber on a late 70s ATC 70 head, which would have the short connecting rod, 6V points ignition and what Dr. ATV calls "old 70 dome" head and piston. It also has the squish band/bevel around the chamber, but the angle of the bevel is steeper (more perpendicular to the head gasket surface, less perpendicular to the direction of piston travel). The steeper bevel makes for a narrower bevel measurement in terms of its i.d., which I made to be 44.5-45mm. The outside of the bevel is 47ish, like yours. I was using some crude tools but the chamber depth I measured was about 13mm from the head gasket surface (no gasket in place). I also measured a stock head off a '74 Z50A. No bevel. Just a dome, same 13mm depth but smaller diameter to match the 39mm bore. If I'm right that you've got a "new 70 dome" head there, I think you could run this piston: 47MM_PISTON_KIT (OLD_50_DOME) OR (NEW_70_DOME) (SHORT_ROD) (SHORT_CYLINDER) (100020) in a 47mm (72cc) cylinder on your current bottom end, with either your new 70 dome head OR a stock head off a 6V short-rod 50cc motor. Depending on what port sizes you wanted to use, etc. A PM member called mtubbs had one of those pistons he was willing to sell recently; if the general agreement is that you DO now have a "new 70 dome" and you choose to go the 70 route, you might send him a PM and see if he's still got it.

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11-04-2009, 07:40 AM	#17 (permalink)
yadihonda 1st Gear Member Join Date: Jun 2009 Location: Eastern PA Posts: 102 My Mood:	Re: Intake Port Question for z50 Thanks for working on this with me Mex. I have an email, with pictures, into DRATV. Hopefully he can identify the head and make the recommendation for the next step. Luckily, I have another z50 motor that needs a top end as well. If I can salvage the head on that one, then my 39mm cylinder and piston can be used on that...should my mystery head be a 47mm (70 head). If it does turn out to be a 70 head, then wouldn't I be going out on the slippery slope of a different carb (or jets) and manifold? The current carb is the original from a 1969 z50ak1.

11-04-2009, 08:14 AM	#18 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 972	Re: Intake Port Question for z50 Maybe, but I took a spin on a friend's K1 (I think) hardtail over the summer, which he'd picked up with a three-speed CT70 motor swapped into it. It still had the original old-style hardtail carb, intake manifold and air filter on it, and the original hardtail stock exhaust, but all this bolted to a CT70 motor with CT70 head. So there was some port mismatch going on, and as far as my friend could tell the stock carb still had the stock jetting. Other than the clutch being adjusted too tight, making for some jerky shifts, the thing was a blast to ride. Didn't seem underjetted to me. It seemed wheelie-prone to me. I didn't get a chance to wind it out and see where it ran out of breath, but it sure had more torque than my 50cc hardtail. I remember coming almost to a stop in second gear, gassing the throttle and the front wheel coming off the ground a bit--instant forward motion--whereas my 50 would sort of lug along for a bit until the rpms came up enough for the clutch to lock in, if I did the same thing on it. Even if you try this and it doesn't work, or you elect not to limit a stock 70 with a 50 carb and exhaust, I don't think jetting a 70 will be a slippery slope. You could always start with a carb intended for a 70 so you'd be in the ballpark to begin with, or if you elect to go aftermarket, just make sure there's a range of jets available for it before you buy. Enough people here have tried enough combinations that you should be able to get recommendations of what jets to start with for just about any combination. My point is, I think you're on as slippery of a slope as you're going to get on already, and dealing with it. You could always try the stock setup (say things like "yeah, well, I'm running my 'engine break-in setup' right now) while you consider other intake options. Last edited by mexicanyella; 11-04-2009 at 08:18 AM.

11-04-2009, 02:50 PM	#19 (permalink)
dirtbkr188 3rd Gear Member Join Date: May 2004 Location: New Jersey Posts: 2,970	Re: Intake Port Question for z50 I took some measurements of an XR70 head and also an E22 head from an Xtreme SuperStock88 engine. The Xtreme engine was a 47mm bore and 49.5 stroke using a 69mm tall cylinder. Here are the results: XR70 Bevel OD - 47.40mm Bevel ID - 41.45mm Depth - 14.40mm Intake valve - 23mm Exhaust valve - 20mm E22 Bevel OD - 46.86mm Bevel Id - 40.36mm Depth - 13.40mm Intake valve - 23mm Exhaust valve - 20mm I'm expecting a TB race head within the next day or two, I can measure that one also, if you'd like.

11-05-2009, 08:37 PM	#20 (permalink)
yadihonda 1st Gear Member Join Date: Jun 2009 Location: Eastern PA Posts: 102 My Mood:	Re: Intake Port Question for z50 FYI - I sent an inquiry to DRATV, where I bought the cyl and piston kit (for stock z50). This was the reply: it looks like a not so good 70cc head ?? measure the od of the face of the intake valve if it is around 23mm then it is a 70cc head or maybe even a 90 or 110 head. anyway if it has a 23mm intake valve it may not work with a 39mm bore ? I measured it the best I could and the intake seems to be bigger than 23mm...take it with a grain of salt because its not easy to measure...I made markings on paper and measured the marks. Also, the intake looks the same size as my old stock z50 head. I'm not sure if I understand DRATV's email. Should I just toss this brand new head? Also, how difficult would it be to rehab an old head that came from a non-running motor? Its 40 years old and has a lot of carbon on it. I don't have a spring compressor or tools to grind or resurface seats.....