Topic: 1986 Honda MB-5 Project

[ColinMc]

Well, I know this thread is useless without pics, but I have one of the bike before I brought it back from Holland with me. I'm tearing it back apart again and going nuts. I miss my Derbi GPR50R and this is gonna fill that void lol.



I'll take pics of it's current state tonight along with all the other stuff I have to get pics of for the forum lol. It's my "in between" project. The thing I work on when i'm waiting on parts for the CB750K6 project heh.

I have a Malossi 70cc big bore kit and head. Jolly Moto pipe...still have to get a good carb and reeds. I have a chrome aluminum dutch hand made swingarm, Honda MBX wheels...and a few other goodies.

[scunny]

nice wee bikes, good for bucket racing

[ColinMc]

Actually the plan is just for a fun back roads bike, i'm going to modified the crap out of it, but the bottom end is gonna get upgraded too. Ditching the oil pump and running premix...all that good stuff. The plan is a fun street legal bike that won't ever go near a highway but still rips it up under 60mph lol.

[Gregorymoto]

Funny man, my dad had one he took to the track when he was racing and used it to get around the pits. I was a kid and  I soooo wanted it.
Good luck

[bryanj]

WHOA there, not sure if premix is a good idea as those little swines had mega trouble with the mains in standard form and there were many bulletins from Honda about how to rebuild bottom ends and several special tools, one of which was a generator casing with what looked like an electric kettle element attached to heat the casing and remove bearing "Preload"

[ColinMc]

I had a different one in holland that I ran premix after the oil pump went with no problems...I won't be using the stock carb. The stock carb is what causes the issue with running premix since most people don't use a larger main to compensate for less fuel and less oil than would normally be injected. I'm going to be running a Keihin Flatslide racing carb I have left over from a Derbi GPR I used to own so it's a non issue.

Main point being, nothing on this bike is gonna be stock, it's going to be a complete motor build up to both compensate for the crapload more power, and the lack of an injection system.

Here's the frame after being blasted and primered for now since i'll be welding on some rearset brackets and other fun stuff:


The fancy shmancy Dutch hand made chrome reinforced swingarm:


Oh and my spare 2k mile donor motor that will be the candidate for mucho mods:


I have a bunch more goodies including all the hop up parts but I just took quick pics of this stuff...

[ColinMc]

Ok here's a question for my friends across the pond...I have wheels from a 1986 Honda MBX125 i'm going to be using on this bike. They are aluminum wheels, no where is it marked "tubed" or "tubeless". I mounted a set of new Pirelli Sport demons and they hold air fine with no tubes...but i'm worried things could go bad quickly. If anyone could find out whether the MBX125 had tubed tires from the factory or not please let me know. I got the wheels from the UK and they had tubes in the tires that came on them, but they were tires that were made to use tubes...

So all in all I either need to know if a 1986 honda mbx125 needs tubes, or if there is an easy way to tell what wheels can take what kind of tires?

Here's a pic of the back wheel so you can see the style...and that it's holding the pirelli sport demon with full pressure no problem....

[bert96]

 I thought they only made the MB5 between 1980 and '82?


 I had a '82.

[ColinMc]

In Europe they made it for much longer and I brought this one back with me from Holland. They also made an MBX50, an MT50, MB80, MBX80, and an MBX125.

[bryanj]

A lot of that was for the UK market where you can ride a "moped" at 16 and a moped now is less than 50cc and not capable of exceeding 30 mph, whilst a 17 year old (and older) who is a "learner" is restricted to a 125cc max which has a restricted power to weight ratio of something i cant remember, usually done by restricting the exhaust, strangling the carb and sometimes timing mods

[ColinMc]

Yeah when I lived in Holland 50cc and under was for 16-18 and you couldn't drive a car until 18. Also at 18 you could take a test to bump up to 125's and then 250's...I could be slightly mistaken about that.

My Malaguti Phantom F12 50lc I had was limited to 50KMH I think it was but of course the first thing you do is take the restrictors out. The MB8 and MBX50 as well as their dirt bike variants were also available in Holland, not sure about the MBX125 though.

[bert96]

Check this site,

http://www.mb5.co.uk/index.html

[ColinMc]

Thanks, I e-mailed him and a few people from some Dutch sites I still had bookmarked from High School lol. For now just trying to figure out the tube or no tube in the tires mystery lol. My dutch is still pretty good so being able to get info from those sites is great.

[Ecosse]

I'm watching this one.

[bert96]

Thanks, I e-mailed him and a few people from some Dutch sites I still had bookmarked from High School lol. For now just trying to figure out the tube or no tube in the tires mystery lol. My dutch is still pretty good so being able to get info from those sites is great.

I'm not sure but,just by the look of these wheels, i think they are tubeless.

[rachet]

I'm watching this one.

+1

[ColinMc]

Lol, well i'm gonna do mockup tonight to see where the new footpeg brackets can go. I have a spare set from a FZ750 i'm gonna see if I can make work. I'll see if I can get some pics...and some other measurements for other stuff. Trying to make headway on a few things at once with a tight work schedule and classes doesn't work out so well.

I have new straight rate springs coming from Sonic Springs, new rear shocks coming from 50cc.nl that are longer than stock, and some other goodies. I have an original seat in great shape I could use...or an extra junk seat I might modify to look cooler lol.

[333]

Story-  I'm at the Vintage Japanese Motorcycle Show at The White Rose M/C club in Hanover PA about 5-6 years ago.  2 of our group were very competitive and both had MB5s.  We were on the road, going to breakfast in a nearby town when they both took the lead of the pack.  One of them was in a full "Rollie Free"(except not striped down), and when he passed me, he reached down with his left hand and shifted!

[ColinMc]

Lol, yeah wind is your enemy on a small two stroke. All 6'2" of me would go into full tuck mode on my Derbi GPR no matter how uncomfortable and id' get an extra 5mph on a looooong straightaway...

Anyways, so the e-mails I've gotten back from people are mixed. No one seems to remember if the MBX came with tubes in the tires from the factory. Most people that have new tires put on the shop puts tubes in anyways, then the next shop sees the tubes and puts tubes in again...but i'm stumped, there HAS to be some way to tell these are gonna be safe without tubes short of me driving down the road and seeing what happens. The tires mount fine and the beads popped into place, and they are still holding air fine. Bah...i might just go with tubes anyways just in case, but it'd be nice to not have them and know for sure it's ok lol.

[bryanj]

Try finding a parts list and see if it lists tubes

[ColinMc]

Good call, just e-mailed David Silver Spares

[ColinMc]

Well according to David Silver Spares, they need tubes  that means the tires are coming back off and tubes are going back in...blah!

[DarkRider]

Better to be safe then to be sorry with things like tires..

[rbmgf7]

lol, i just saw one of these in a campus lot today. said right there, Honda MB-5. looked real good except looks like someone dropped it on the muffler.

i'm starting to love the diversity of bikes I'm seeing on campus this year. I've already seen a CB500 and CB350. There's a nice older Suzuki one lunger, twin, and Kawa KZ CSR1000 that've floated around the past couple years.

[ColinMc]

Better to be safe then to be sorry with things like tires..

Yup, just a pain because I got the tires all mounted and everything lol. Oh well, for first set backs this is minor compared to some other projects i've had. I have everything mocked up in the basement, next week i'm going to make some brackets to weld on to mount some FZ750 rearsets, they should fit and won't look too weird on there. Next step after that is the motor buildup, I think I have everything I need before I get started but i'm going to inventory the couple totes of stuff I have full that are labeled MB-5. Ever since my first car project where I didn't do a good job labeling or storing things I learned my lesson, plastic totes, ziploc bags, a sharpie marker, and a digital camera are you best friend for EVERYTHING!

[333]

If the tires are mounted and holding air, why put tubes in?  Yes, the bikes of the era that this forum is devoted have to make compromises on tires by using tubeless tires with tubes, but when I first started in the M/C business back in the day, there was a case of a tubeless tire and rim, and the owner put a tube in.  It pushed the tire off the bead at speed.

So I would ask why, and refer to my first sentence.

[ColinMc]

Well what i'm worried about, is that the tires do mount and hold air, but i'm not sure these rims are designed for anything at speed like that...isn't there a chance things could go bad once things are moving, especially at higher speeds say in a corner? The original Honda MB5 rims can have normal tires mounted without tubes and they'll hold air, but they most certainly are for tubed tires so I would never risk it.

So in the end, do I go with what they originally used? I know tubeless tires were available in 1986...so why would Honda use tubes in the tires if they didn't need them? So i wouldn't be worried about the tube pushing the tires off the rims, or Honda wouldn't have used them in the first place...

I'm not trying to be argumentative, just genuinely curious...

[bryanj]

Reason 4 not using tubless then was cost as they were a fair bit dearer and the MB5 was a budget bike for youngsters

[333]

It might say somewhere on the rim if it is tubeless or not.  The point of my last post was that it seems to me( and that experience related to me) was saying was that having tubeless tire and rim, and using a tube will increase the chance of the tire being pushed off the rim.

[ColinMc]

Ahhhh ok! I get your meaning now lol. Well i'm gonna go with no tubes for now anyways...I got in touch with a friend in Holland that races MB-5's, and he uses MBX wheels with no tubes on the track all the time with no issues.

Oh and I went nuts today...bought a complete Derbi GPR/Senda motor to put in. Using an 80cc MHR kit on that sucker and a nice pipe...reliable liquid cooled power and 6 speeds here I come! The Senda version has a kick start, so I can use the stock MB5 wiring and everything! Not sure how well the motor will fit without much mods...but it's an easy frame to modify. So we'll see lol. Either way..waiting until I get that before going further with the rearsets and whatnot. For now sorting out the suspension and brakes so support speeds Honda never planned for this little guy.

[Ecosse]

What are your plans for suspension improvements? I know nothing about these things.

When I see your username I thin Colin McRae (RIP)... I still can't believe he's gone.





Or is he? It's you isn't it? It's OK, your secret's safe with me.    

[ColinMc]

I'm going to use a nice set of dual shocks in the rear...not going crazy with money, but new ones from 50cc.nl for now that are 30mm longer than stock. The front end is going to be MBX125 forks, with Sonic Springs internals, MBX front disc and braking system. Not a lot out there for this bike...i'm contemplating adapting a Derbi GPR front end to fit this bike...USD forks, nice braking system...but using the MBX wheels might be troublesome...


Oh and my name is Colin McCarthy...hence the user name, although I do love rally racing, not to mention the Colin McRae rally games for PC. I know, I can't believe he's gone either...amazing driver.

[bryanj]

Colin, check out ebay item 230294356118.

He has several set up and workshop original Honda "blue Book" instructions including MBX 50;MTX 50; MTX125 etc

[SHANWHAN]

I have a swiss mb5 rubbish as standard restricted worse than a british on and 4 speed so only capable of 25mph BUT look at the benifits for a special

mbx80 wheels as standard
down tubes for extra big engine support

heres some easy mods to help you acheive 70 mph+
h100a engine fits straight in {h100s is a #$%* to fit stay away} and use an mb8 exhaust youll get one of these exhausts from europe model never sold in uk
carb use mb8 if you keep engine standard or mbx 125 if tuning and you need the inlet for either to if your gonna mega port use a mbx inlet with a KR1S sideslide carb

serious styling modding try nsr80 parts

ill post some pics of mine once its been sprayed

[pknopp]

 I just picked up a project 1982 MB5 and found this thread. Any further progress here?

[ColinMc]

Thread reborn! Lol, back to work on this along with my CB750. Still trying to get some MBX125 wheel parts and whatnot to make the swap complete. Got a set of forks for an MBX125 anyways...it's coming along. Just a matter of getting parts together. Already did some frame reinforcement and whatnot...so it's coming along anyways...this, my XS500 with a TS400 motor project, and my CB750 project are finally all kinda making progress at once. I'll get pics involved soon. For now i've been trying to sell of parts I don't need from all these projects.

[Ecosse]

Thread reborn!

[ColinMc]

Well should get the MBX125 forks any day now. Got the senda motor and put the MHR80 kit on it, blocked off the oil pump...all that good stuff. But I also put the 70cc Malossi kit on my stock MB5 motor...still on the fence about what motor to use. The H100 conversion is tempting but too much of a pain getting parts...this bike is bad enough as it is lol.

I need the MBX forks so I can get her in rolling chassis to mockup the motor/exhaust/footpegs...before I do any welding of brackets and stuff. A tank/seat decision is going to be made too...I might not go with stock at this point. We'll see how things go though. I have 3 spare tanks one of which is a disaster that I could cut up and see what I come up with. An extra gallon of capacity would be nice.