I just got a killer deal on a 1982 Honda MB5, got it running today although it still needs some carb work. It also came with two spare motors, a 1980 CR80 and a spare MB5 motor. From my understanding you can use the top end on the MB5 motor, does anyone have any experience with this?
Honda MB5/CR80 Hybrid
Started by
mitsudriver274
, Jan 19 2010 11:53 PM
42 replies to this topic
Posted 27 January 2010 - 12:43 AM
Well i'm still going on with the build, picked up a few items, full 1980 cr80 gasket kit, mb5 main bearings and seals, and a Wiseco .080 over piston.
Does anyone know how much free play the rod should have on the crank? It has about 1mm play sideways, but it does not feel tight around the crank and wobbles about 1mm. Is the crank toast?
If I wanted to make some more power, what setup should I run, the stock carb is 26mm so I feel it is plenty big, would a modern cr80 pipe work?
Does anyone know how much free play the rod should have on the crank? It has about 1mm play sideways, but it does not feel tight around the crank and wobbles about 1mm. Is the crank toast?
If I wanted to make some more power, what setup should I run, the stock carb is 26mm so I feel it is plenty big, would a modern cr80 pipe work?
Posted 27 January 2010 - 01:53 AM
isn't the mb5 a 2 stroke 50cc? I've ridden a few of those in the past, and if my mind serves me right, they did make a 80cc version of it called the mb8, and a offroad version called the MT5\MT8.
Posted 27 January 2010 - 10:02 AM
mitsudriver274 said:
Well i'm still going on with the build, picked up a few items, full 1980 cr80 gasket kit, mb5 main bearings and seals, and a Wiseco .080 over piston.
Does anyone know how much free play the rod should have on the crank? It has about 1mm play sideways, but it does not feel tight around the crank and wobbles about 1mm. Is the crank toast?
If I wanted to make some more power, what setup should I run, the stock carb is 26mm so I feel it is plenty big, would a modern cr80 pipe work?
Does anyone know how much free play the rod should have on the crank? It has about 1mm play sideways, but it does not feel tight around the crank and wobbles about 1mm. Is the crank toast?
If I wanted to make some more power, what setup should I run, the stock carb is 26mm so I feel it is plenty big, would a modern cr80 pipe work?
Any up and down play on the bottom end of the connecting rod means that the bottom end bearings are hosed and need replaced. If you put a new top end on that rod and put it back together, you are going to be running time bomb.
Posted 27 January 2010 - 10:08 PM
Misudriver hay ive got one that runs great but needs a tank you can get for a deal 82 mb5 black ,red my kids ride it alot needs new home soon
Posted 28 January 2010 - 11:45 AM
The MB5 was only sold for one year in the states 1982 I remember beating on the poor thing it saw more time in the dirt than street! Much more popular in UK / Europe it was classified as a scooter but not in the states it was considered a motorcycle due to the size of the wheels.
The state of washington has some law that if it has over 15 or 16" wheels and goes faster then 35 mph it is a motorcycle and requires an endorsement to ride it legally.
I used to get told the opposite that one wasn't needed when I used to have this 2001 Aprillia RS 50. The common mistake was cause it was 50 cc's it wasn't required which is wrong.
http://www.mb5.co.uk/ This site might have some useful info just remember the US model wasn't as restricted I think the fastest I ever got it to go was 50 mph and that was stock setup.
The state of washington has some law that if it has over 15 or 16" wheels and goes faster then 35 mph it is a motorcycle and requires an endorsement to ride it legally.
I used to get told the opposite that one wasn't needed when I used to have this 2001 Aprillia RS 50. The common mistake was cause it was 50 cc's it wasn't required which is wrong.
http://www.mb5.co.uk/ This site might have some useful info just remember the US model wasn't as restricted I think the fastest I ever got it to go was 50 mph and that was stock setup.
Posted 28 January 2010 - 01:09 PM
Yes the mb5 came in one year 1982, it is a 50cc motorcycle, I don't know how but I got mine registered as a scooter. I've decided to just take the crank out and take it to a tech.
Posted 28 January 2010 - 11:17 PM
you can get loads of hop-up parts for those engines. they still sell 60 and 70cc bigbore kits here in norway, you can get carbon reeds for them too.
if you wanna go all out you could get a MT8 engine, that engine is identical to the 50cc on and will bolt directly to your frame, and then get a Parmakit 125cc big-bore kit, a 34mm carb, a cr125 reedcage and CR125 exhaust, that should make it rip pretty good.
if you wanna go all out you could get a MT8 engine, that engine is identical to the 50cc on and will bolt directly to your frame, and then get a Parmakit 125cc big-bore kit, a 34mm carb, a cr125 reedcage and CR125 exhaust, that should make it rip pretty good.
Posted 28 January 2010 - 11:21 PM
here is a video of a modded MT-5 with a MT-8 engine with a 125cc kit on it, the quality is bad but you get the idea of how it goes, notice the 2nd gear powerwheelies:)
Posted 29 January 2010 - 01:19 PM
That looks like it would be fun but I'd be scared about the bottom end not being up to standards and having problems with main bearings or what it does to the clutch n tranny.
Posted 29 January 2010 - 02:03 PM
After looking at the frame of the bike and the 1980 cr80r motor, I feel it would be easier to fabricate a rear bracket then to add material under the cylinder head. So far I don't see why everyone claims you cannot fit the cr80 motor in.
As far as boring out these old heads, do these motors have a nickel plating? And how far out can you bore these motors out, wiseco offers a piston kit that goes .080 over (2mm).
The stock cr80r motor runs a 26mm carb, is that a good size to stick with or what can I run for some more power, but I do not want to over carb the thing.
Being limited on pipes I believe I will be running this one: http://www.treatland...-proma-pipe.htm
As far as boring out these old heads, do these motors have a nickel plating? And how far out can you bore these motors out, wiseco offers a piston kit that goes .080 over (2mm).
The stock cr80r motor runs a 26mm carb, is that a good size to stick with or what can I run for some more power, but I do not want to over carb the thing.
Being limited on pipes I believe I will be running this one: http://www.treatland...-proma-pipe.htm
Posted 29 January 2010 - 04:10 PM
they are steel cylinders, you can get far with a bore and portjob.
Posted 01 February 2010 - 03:40 PM
I tried emailing my supplier but I ended up with a .080 over piston (wiseco).
http://cgi.ebay.com/...sQ5fAccessories
Leaving me with a bore of 51.5mm and a disp of 86cc.
The stock carb is 26mm, can I run something a little bigger, around 28mm? That is what the cr85r expert is running
Will the newer exhaust systems from the cr85's fit this exhaust flange?
http://cgi.ebay.com/...sQ5fAccessories
Leaving me with a bore of 51.5mm and a disp of 86cc.
The stock carb is 26mm, can I run something a little bigger, around 28mm? That is what the cr85r expert is running
Will the newer exhaust systems from the cr85's fit this exhaust flange?
Posted 29 March 2010 - 08:07 PM
mitsudriver274 said:
After looking at the frame of the bike and the 1980 cr80r motor, I feel it would be easier to fabricate a rear bracket then to add material under the cylinder head. So far I don't see why everyone claims you cannot fit the cr80 motor in.
As far as boring out these old heads, do these motors have a nickel plating? And how far out can you bore these motors out, wiseco offers a piston kit that goes .080 over (2mm).
The stock cr80r motor runs a 26mm carb, is that a good size to stick with or what can I run for some more power, but I do not want to over carb the thing.
Being limited on pipes I believe I will be running this one: http://www.treatland...-proma-pipe.htm
As far as boring out these old heads, do these motors have a nickel plating? And how far out can you bore these motors out, wiseco offers a piston kit that goes .080 over (2mm).
The stock cr80r motor runs a 26mm carb, is that a good size to stick with or what can I run for some more power, but I do not want to over carb the thing.
Being limited on pipes I believe I will be running this one: http://www.treatland...-proma-pipe.htm
I'm building a MB5/CR80 also. I'm using the MB5 engine and adding the CR80 crank, cylinder, trans, clutch. I've gotten the cases ready and am building a new crank tommorrow. Are you still working on yours?
Posted 04 September 2010 - 12:56 PM
Any updates? I love the old Mt and Mb's
I have a Mt5 with a 125 big bore Mt8 engine
I have a Mt5 with a 125 big bore Mt8 engine
Posted 16 September 2010 - 05:39 PM
I have not abandoned this project, it just has been slow moving due to funds.
Progress So far:
- Bike is stripped down to the frame, I have everything disassembled.
- Cr80 motor is near complete, case halves are put together, replaced all the bearings/seals/gaskets. Right case cover has a crack in it so I need to fix that and get a pulley remover to grab the cdi off the mb5 motor. My biggest hurdle right now is finding someone that will machine the mb5 head (reshape the combustion chamber, enlarge and taper the cylinder head bolt holes)
Progress So far:
- Bike is stripped down to the frame, I have everything disassembled.
- Cr80 motor is near complete, case halves are put together, replaced all the bearings/seals/gaskets. Right case cover has a crack in it so I need to fix that and get a pulley remover to grab the cdi off the mb5 motor. My biggest hurdle right now is finding someone that will machine the mb5 head (reshape the combustion chamber, enlarge and taper the cylinder head bolt holes)
Posted 16 February 2011 - 10:01 PM
*BUMP* for an update, as I'm about to hopefully score an MB5 and I'm thinking that the CR80/MB5 Hybrid is a must for my intended build...
Progress? Other MB5 guys lurking on this forum?
Progress? Other MB5 guys lurking on this forum?
Posted 17 February 2011 - 08:58 AM
Yeah bout time for an update.
Here's a picture of my Mt5/8
I want to give this thing an update one day. New swing arm,disc brakes and new suspension. If i find some cheap parts.
Guy on a Norwegian moped forum made this
Here's a picture of my Mt5/8
I want to give this thing an update one day. New swing arm,disc brakes and new suspension. If i find some cheap parts.
Guy on a Norwegian moped forum made this
Posted 19 February 2011 - 02:18 PM
Do you know what suspension is on that mt8? I would like to upgrade my front forks to something newer, but i'm not sure what will fit. What do I need to measure on my bike?
