MB-5 Honda woes

[motormike]

Chance encounter with a very clean MB-5 today. We rode together for a couple hours, and the poor little bike sucked a crank seal about half-way through the ride. Smoke was abundant, and draining the trans case as it went. Rider and bike made it back without burning a piston, a tense ride for sure. Here's the bike.

[motormike]

*

[tazland001]

Well at least it is an easy engine to work on.

Taz

[z50r-ghost]

OHHHHHHH!!!!
VERY nice condition MB-5!

Damnit i thought it was YOUR MB-5, motormike.... !!

Wow thats clean!

-hope you are doing well, man!

-j

[motormike]

Current owner has had this since '94. came with a parts bike in crap condition, but he saved the engine and a few items. His plan now is to refresh the motor that's in it and add the six-speed from a CR 80 if parts are found before next spring. Before this failure, he has GPS'ed it at 59 mph.

[GKinTN]

GK here, that's my bike! I just joined the site.

It was very cool that Mike followed me back as I limped my MB5 back to the house. We had lost the rest of our riding group so I barely even knew how to get back to town without Mike's help. As Mike mentioned I have owned this bike for a very long time, and this is the closest the bike has ever come to stranding me. Actually I had been questioning the top end and/or main seals on the bike since the summer as it had developed a slight hi end tick to it, though the top end had been done once before at 2500 miles. It also seemed to smoke just a tad more than normal when cold, and I was suspecting that the seals were allowing a little transmission oil into the bottom end while sitting. That said with the "True Grits 50cc Fun Run" to do last month I just didn't have the time to tear my MB5 down. Instead I started sourcing all the parts I needed for the rebuild and figured I'd take it to the "Fun Run" and just run it hard. That said, I did get 1st in my class (of 7 bikes in "my class") and it ran great. Seems though two strokes can sometimes run their best right before they BLOW UP....ha. Then skip forward to yesterday about 28 miles more mileage than at the end of the "Fun Run" and pooof there goes the right side main seal. I probably should have parked it and tried to go get the truck to load it up, but at 28 miles out (and a planned rebuild in the works) I decided to just try and get the bike home. At first it was just smoking alot, but once the transmission oil got a bit lower (Mobil 1 racing oil) it started to pull some air. I bet it burned perhaps a 1/2 quart of the trans oil by the time I got back to the house. At that point I kept the choke on alot for the last 3-4 miles as it started to rev high even without the throttle, hoping the extra choke work would keep it alive. Perhaps with the cool day we had, and all the Mobil 1 racing oil it was pulling it perhaps the bottom end will be ok. Still, I may change the crankshaft out this winter anyway along with the main seals/bearings, top end, and a CR80 6 speed transmission. I have a NOS original cylinder for it too.

Cool site! I may have to get me a scooter too as my only street bike is my MB5.....which is normally quite reliable.

[Spreetard]

Welcome to the forum!

That is one clean mb5! I'm glad to hear it gets regular hard use- I can't stand when fun machines collect dust in "collections." It was made to be used! I'm glad there were no other major problems, sounds like a great excuse to freshen the ol' girl up a bit!

[motormike]

Good to have you aboard, GKinTn. Hope I got the facts straight about your bike.
I'm confident you will find a helpful and informed group here. (Actually, I put Glen in a head-lock until he submitted
and agreed to join the group) Any guesses how long before I sell him a scooter??..............

[Wheelman-111]

Greetings:

Welcome. I have long coveted the MB5 myself, ever since reading about a "New" one in the early-80s in Cycle World. I seem to recall they got a top speed of 55 right out of the crate. Pretty good for 49ccs.
I'm sure you know there was an MB80 in Europe that shared the MB5's frame and perhaps cases and even possibly the crankshaft. Seems like an Upgrade Opportunity to me...

[bradthreee]

I read somewhere that the CR80 is a popular swap that gives you more cc's and a 6 speed gearbox

[motormike]

.....got a phone call from Glen today....seems he is going to Georgia wednesday to inspect/buy an Aero 125.....Okay, I haven't sold him a scooter, but he apparently has very exquisite taste.......

[Bear45-70]

.....got a phone call from Glen today....seems he is going to Georgia wednesday to inspect/buy an Aero 125.....Okay, I haven't sold him a scooter, but he apparently has very exquisite taste.......

[motormike]

I told Glen about your Aero prowess, Bear, and suggested he ask you for pointers with his purchase.

[Bear45-70]

Thank you

[maddog]

manual trans=not a scooter