MB5 dudes thread take III

So, after 7 pages of replies, I decided to start another one.

So, this first post is more of a showing of information than a question, but I would like to get responses from anyone who has reduced their MB5 wiring harness before.

Also, for any electrical gurus out there, the Yellow and White wires come off of the same coil in mb5 CDI. Will putting them both into the Voltage Regulator really have any affect on the system or the VR? I know that if it is functioning properly I will always just get 12v coming from the regulator, just want to make sure that I am not doing any harm to the CDI/Ignition/Box.

Alright, so based on this Wiring Diagram:

and the "Simplified" wiring diagram:

I have come up with this:


Y - Yellow

W - White

LG - Light Green

R - Red

G - Green

B - Black

L - Blue

From Stator:

Y - lighting

W - lighting

LG/R - Neutral Indicator

G - Universal Ground

B/R - To CDI Box

L/Y To CDI Box

From CDI Box:

G - Universal Ground

B/W - Kill Switch

B/Y - Ignition Coil



Yellow / White into Voltage Reg. -> B/R out to head and taillight

LG/R into indicator light near handlebars (ground for temporary!)


Black/Red into CDI Box, stops there.

Blue/Yellow into CDI Box, stops there.


Black/Yellow from CDI box into high tension coil.

Black/White from CDI box into KIll Switch.

Green from kill switch to ground.

I'll post a full color printable PDF/PNG later today when I have time.

Also, this hasn't been tested yet, but in theory should work.

Re: MB5 dudes thread take III

aaand here it is!

also, here is a link to the print quality pdf version. time to go wire and see if it all works out the way i have it planned. (edited)

Re: MB5 dudes thread take III

Rad. Nice little MB5 hardwiring cheatsheet.

Re: MB5 dudes thread take III

Wiring harness works like a dream, and if you retain the stock wiring blocks you can reuse all those special ends.

Re: MB5 dudes thread take III

This literally could not be more timely. I am sitting here, playing hooky from work, WAITING for the treats Ice Cream Truck to deliver my Trail Tech voltage regulator. I've been blowing headlight bulbs. Not tail, just headlight, figure the VR should fix it but I was wondering how I was gonna tackle the wiring. This should really help a lot!

MB5's are the new Hobbit! Yay!

Re: MB5 dudes thread take III

Figured I would throw a photo up from yesterday before riding.

Re: MB5 dudes thread take III

Since we are posting pics and build details, attached find my MB5, with fresh rubber from treats, the Sava MC7. I recommend anyone else shopping for these tires go one size smaller than I did out back, (I have the 3.5 crammed in there) and get the 3.25 casing or even stick with the 3.0's they will still look huge.

Setup details:

-70cc Kit of some kind (came on bike)

-21 PHBG 101 Main

-Proma Circuit Pipe

-16-43 Gearing (Stock seems to be 13-43)

-4 petal reed block of some kind (looked but didn't pull it out, looks like a Gila block)

The bike seems to wind out at over 60mph, I've GPS'd it at 60.2 recently. 5th can be a chore to get on top of, but when you do, lookout! I can't take any credit for the tuning of the setup, this is how the bike came to me, other than the handlebars and the tires. Whoever put it together actually did a good job. No leaks, idles well, starts first kick, and seems to be going faster than most.. I weigh about 170lbs, btw. Now with a trail tech voltage regulator, hopefully I'll finally stop blowing bulbs and have myself a fun do anything bike.


Re: MB5 dudes thread take III

I haven't really measured or played with MB5 stator but from the drawing it looks like the yellow is just center tap on the windings of the the lighting coil. The white wires is the full windings of the coil so that should be putting out the full power of the lighting setup. Not sure if that would be of any help to anyone. I have the feeling I might be tinkering with a lighting setup on MB5 soon and maybe I would have more useful information to share.


Re: MB5 dudes thread take III

You are like some kind of moped psychic, Naz... FYI I'm already up and getting ready to electrocute myself.

Re: MB5 dudes thread take III

Trail Tech voltage regulator worked the trick. Thanks for all the help guys.

Re: MB5 dudes thread take III

my mb5 won't stop blowing taillight or headlight bulbs, but brakelight works fine. i have a regulator wired up, but i think it's on the yellow wire only...also, you guys running batteries or no? i also heard that if the dash lights are blown out, your other lights will want to blow, too. is this true?

Re: MB5 dudes thread take III

If that's true then I need to replace some dash lights too! I am running the battery still, but relocated to inside the tail section.

Re: MB5 dudes thread take III

i have one of these hooked up in place of the battery, but not sure if it actually works because none of my lights work...hah

Re: MB5 dudes thread take III

I am not running a battery in my system. Bike never had one when I picked it up, so I figured I would just leave it that way.

Another question, what type of fork oil are people using?

the Haynes manual says "Fork oil" no weight specified, or ATF.

Re: MB5 dudes thread take III

I would imagine you can run whatever you want in the fork, brand wise, but stick to something like 5wt or 7.5 wt (blend 5 and 10wt together 50/50 to achieve ~7.5wt) for most everyday applications. As for volume, I'm not sure how many cc's our forks call for but it would be good to get that figure from anyone who has it. In lieu of a hard # on oil volume, go with something like 20-30mm from the top of the fork with the legs compressed (if you don't compress the legs when filling you'll massively overfill and blow tons of oil out the top if you lower it back down before sealing. If you do seal it with all that extra oil then you're blowing seals and oil everywhere within the first mile going down the road) and see how that feels. Still bottoms? add a few more cc's until that goes away. Too harsh? Feels over firm or unresponsive? Lower a LITTLE by removing extra oil with a clear syringe and hose. I like motul fork oil and if you buy it at motorcycle shops you'll save $$. Bicycle shops that carry forl oil have small containers marked up like crazy, so stick with moto shops for this kind of thing.

I have a question though guys- what oil are you all running for the transmission? Normal Manual transmission fluid? Motor oil? Gear Oil? Oddly, although apparently I think I can rebuild forks, I don't know dick squiggly about trannys.

Re: MB5 dudes thread take III

The Haynes manual says to use 72.5 - 77.5 cc (or 2.5 - 2.6 US OZ.) in the forks. I was concerned about the weight, I guess sense they don't say, I don't really know the difference in weights.

For the Transmission I am running 30w royal purple. The gearbox takes 0.9 liters for oil changes and 1.0 liters for rebuilds.

Re: MB5 dudes thread take III

Good info there thanks Tom! Time for a crankcase oil change I think.

Regarding the different weights of fork oil- the numbers represent viscosity, or "thickness" of the oil. (ignore fork adjustments or inherent valving characteristics for a moment and focus on the oil itself) 5wt is fairly light and will provide for a smooth, active and fast moving suspension. Some will feel like their forks are "too bouncy" though with 5wt oil esp in forks without sophisticated, or at least effective rebound damping. 10wt is roughly twice as thick and will significantly slow down the compression and rebounding of your fork legs. This will be especially noticeable over high frequency inputs, like washboard bumps in a road, (high frequency impacts = fast, rapid, repeated hits on the fork, often small.) the fork will have more of a tendency to "pack up", or dive and settle- with heavier weight fork oil, but generally provide a very stable feeling ride and less noticeable brake dive etc due to the slower characteristics of the heavier weight oil. Riders who live in hot climates will routinely run 10wt oil however, as in regions like the Southwest, etc the viscosity of the oil goes down significantly as it is usually quite a bit warmer to begin with and naturally all oils weights and behaviors are very vulnerable to temperature and will ride different during different seasons or times of day, and at the beginning of a ride vs well into a ride when things have had a chance to warm up, or early in the freezing ass mornings before the sun gets to doing something about things. You can easily imagine that lighter weight fork oils etc are also popular in colder climates, as thicker oils only get more syrupy and sluggish feeling when you live or ride in cold conditions. Folks who don't know about these differences may be missing an easy opportunity to improve their bike's handling characteristics by simply servicing their suspension and choosing a custom oil weight blend that suits their riding style and climate range. Harder to do with rear shocks, of course- all we can do with most of those is choose an appropriate spring rate for our weights and tune around the front end, with a supporting eye on tire pressure (Yet another factor in suspension tuning) for the best handling package all around..

Re: MB5 dudes thread take III


Thanks for all the great info. This will help when picking out!

Just for posterity sake, I went ahead and drained / filled my forks with 2.5 Synthetic ATF (haynes recommended ATF, this is what I had.) It feels pretty similar to the stock fork fluid: bouncy with a little resistance.

My buddy down in town recommended 20wt fork oil and has some for me to try, so come friday thats what I'll do.

Another note:

Anyone with the following pipes want to make some measurements?

Homoet for 50cc

Homoet for 70cc

Techno Performace

Proma GP for MB5

I can measure out the Proma GP for MBX50.

Re: MB5 dudes thread take III

Josh Besecker /

just got my homoet 70cc yesterday. what measurements you need?

I also just got my 8 petal reeds and mounting adapter ... these holes are definitely going to need to be opened up... not the end of the world, but for $120 you would hope the hand filing would be nonexistent...

OOOHH and I'm planning on reusing my original cylinder studs, reed block studs, and exhaust studs.... anyone know of any foreseeable problems with doing that? (edited)

Re: MB5 dudes thread take III

Tom 20 wt oil will be like having maple syrup in there Homie, unless you live in phoenix or something... You could potentially blend it with lighter oil like that 2.5 you have around and get something closer to 15wt or thereabouts... I'd be cautious about going 20wt though unless you have something specific in mind with what you're trying to get out of it handling wise... Of course if your fork has no dampening in it, the heavier weight could add stability to a bouncy setup..

Re: MB5 dudes thread take III

Josh we need to get together and play MB's soon!

Re: MB5 dudes thread take III

All the measurements:

Header length,

Cone length(s) and diameters on each side,

dwell length (if any),

and stinger length.

If we could compile this information we could more accurately assign pipes for builds, also opens up the door to homemade pipes.

Steve -- I really, really, love the feel and handling of my CRF50 forks, they respond quickly, have no sluggish bounce, don't compress when I am coming to a stop, but take road bumps well. -- That's the handling I want.

Also, I need new rear suspension, I have it, just haven't bolted it on yet.

Re: MB5 dudes thread take III

@Josh- please get those Reeds in there (snap a couple pics first!) and report back on how things go.

@Tom- I'd love to see that fork on the bike, have you got pics up anywhere? I didn't think the CRF50 forks would be long enough or stiff enough, but you sound like you're really happy with them.

Re: MB5 dudes thread take III

Shoot Tom those are the CRF forks above in that pic? They look identical to the MB forks!

Re: MB5 dudes thread take III


Sorry, kind of a confusing post. CRF50 forks are on my rigid freespirit. I'll go ahead and meassure my spare set though and see if they'll mount up to an mb5 and how much of a difference it will be.

Re: MB5 dudes thread take III

Josh Besecker /

Did some dremmeling of the reed block mounting holes tonight... Nothing crazy, but a bit of material was removed. That and I think my CDI is ok... spark plug has good blue spark when I kick it over... But she still isn't starting... I took the carb apart and cleaned it out real well, and she still wouldn't fire over... there's a good amount of sediment in my fuel filter, and I bet the tank's shot... I also found this site HERE It's not the most informative, but it was cool to see his homemade seat... I should get to taking the measurements tomorrow... I'll just wrap a string around the cones and measure the string lengths.... Tomorrow will be another day trying to figure out what's up with her...

Re: MB5 dudes thread take III

Josh Besecker /

...or later tonight will!! I couldn't stop thinking about the bike...So I tore back into the carb again... I don't know how it didn't fall out the first time, but the needle clip was bent wide, and had allowed the needle to slide... or not slide...Sure as shit, a little gas in her and I got her back to life... The roommates parents are staying with us from Germany for the next week, or I wouldn't have gave a shit and really fired her up... but now I can sleep soundly.... After some debater I think I'm going to wait to put all the goodies on her til after she's all inspected and registered... Thats the first thing to do on Monday... If all goes well later today... Now just to get the baretta back and blasting, but that's for another thread~~~ :-)

Re: MB5 dudes thread take III

josh email me your # dude. Maybe I'll stop by today and see how it's coming along. I may head down to the old Bent Bike myself, on the hunt for a front Brake M/C plunger assembly so I can get my front end back together, but I might just be lazy and hang out. Either way, holler at ya boy.

Re: MB5 dudes thread take III

Josh Besecker /

Just scored this beauty... And it's just as well, my current tank is hosed... Now I just need to find tank decals... But at least she's running~

Re: MB5 dudes thread take III

good find!

i am going to have to POR15 my tank in a hot minute or else let it goto ruination, just been having too much fun riding it to want to take it off the streets for 3 days. hah.

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