Honda MB5/CR80 Hybrid

[Sw1ft]

I know they weren't a direct fit. I found an old tutorial on the site but the pictures were missing. I just translated it with Google translate, but its understandable

Hi, has received some inquiries about how to put showa forks on mt5, so I thought I could make a tutorial.

The first thing to consider about the showa is if you want to have sm wheels or if you want to create a bracket to the drum for the 21 "front wheel. But it is too large and will easily look stupid.

The first thing to notice is that the showa control crown is 1mm wider mt5 a steering crown. Bearing cups in the frame is 24mm Showa while steering the crown is 25 The easiest way to do it is to use the Dremel, but since this is such an important work, because it is easy to be slack if you do it this way.

Therefore, you should find the way to the hardware store where you can buy staples for grinding the drill that is just 25mm wide!

So is it just to "hone" the stock plates of the frame and put the board through the crown!

(Note: if you have Furia Showa el. you have to "hone" it creates bowls that sit on the original mt5 also to use them on show control crown)

Put a good dose of grease in the lower bearing plate and place in the balls, then snap it together,

Then do exactly the same in the upper bearing and put the bowl on top of stock.

Almost done! But now you need a spacer to sit between the frame and control the crown, I used the crown mt5 lock from the presentation that I drill up. Remember that it is important to have enough spacers here so there will not be slack!

[mitsudriver274]

Finally decided to make some progress on the bike, found a machine shop in town that will do the machining on the mb5 head.

I'm at the stage at which I should start figuring out what carburetor to run, anyone have any advice? The bike will be a street bike, so I want it to have some low end grunt.

I was thinking of running between a 20-28mm carb.

[mitsudriver274]

I believe I have finally decided on what pipe and carb to run. Unless someone has any better ideas.

Homoet 70cc Pipe

Mikuni 26mm VM round slide

or go oem?

04 cr85r carb

[mitsudriver274]

I have moved forward with the project.

The biggest hurdle was machining the cylinder head to match the cr80r bore.

From the 1982 cr80r motor I am using the bottom end and cylinder.

From the MB5 I am using the cylinder head and left side cover.

Once the motor was mocked up, I set her in the frame and kept measuring. Two days later I figured out where my cylinder head mount needed to be. In order to get the left side cover to match up perfectly, the cylinder head mount would need to be cut off the frame and moved slightly forward. I fudged everything a little and used a boring mill to locate a new hole as close as possible to the old one. I will have a little bit of a gap between the frame and left side cover but its something i'm ok with.

Bolted up the motor and started to locate my sprocket. my original idea was to fabricate a rear cradle that would wrap from the back motor mount to the front lower. I decided to split cradle into two mounts for a simpler design that would require much less CAD work.

The upper motor mount. Consists of 3/4" mild steel rod bored out to 7/16th, I had these tabs water jet cut out of 3/16 4130 steel. I assembled the whole rear end of the bike (swingarm, wheel, sprocket chain) and made sure everything lined up correctly, tacked the mount together, broke it down and welded her up.

If anyone would like the .dxf file for the parts I can email them to you.

Very simple:

The motor is pretty locked in at this point, I measured some more and have come up with a lower mount that bolts up to the left center stand bracket and ties into the front motor mount. This will give me 3 solid points of attachment, and for the amount of power I am making this should be very sturdy.

I sent out the .dxf file today so hopefully this week I will get the part back and finish up the lower motor mount.

I figured out what carb and pipe I will be running decided to go for a more streetable setup:

24mm oko flatslide carb

Tecno Pipe <== This pipe will not work with the cr80r motor without modification. The exhaust port on the mb5 points to the left and the cr80r points to the right, does anyone know if the mb8/mt8 pipes are the same?

Edited July 11, 2011 by mitsudriver274

[Sw1ft]

Took some pictures of my Mt8 if that might help

[mitsudriver274]

Made some forward progress last week.

The motor is complete, all I have left is to bolt up the right cover and she's ready to be sprayed with flat black.

The pipe was modified by cutting the exhaust flange off. I then added a 40 degree bend from a piece of 1/18 U bend my boss had laying around the shop.

I still have to modify the right rear shock mount for the shock to clear the chain.

She is slowly coming together.

Edited July 30, 2011 by mitsudriver274

[canammx1]

Made some forward progress last week.

The motor is complete, all I have left is to bolt up the right cover and she's ready to be sprayed with flat black.

The pipe was modified by cutting the exhaust flange off. I then added a 40 degree bend from a piece of 1/18 U bend my boss had laying around the shop.

I still have to modify the right rear shock mount for the left shock to clear the chain.

She is slowly coming together.

Looking awesome, I like the paint as is, but the flat black will look stealthy.

[mitsudriver274]

Unfortunately the tank does have a pretty good dent in her, I don't know if I will be able to fix that tank. I will take it to a local radiator shop to get cleaned and coated for $60 so it doesn't give me any problems. Over the winter I will figure out what to do for the tank.

The oko 24mm flatslide barely fits, I have about a 1/4 gap between the throttle linkage mount and the frame.

Is it necessary to run a carb perfectly vertical or can I slant it to one side for some clearance if I need to later, I believe that would cause the float bowl to work improperly.

Does anybody know if the honda h100a tank will fit on the mb5 frame? I know the motor is a direct swapClicky

The frame looks very similar

[frdbtr]

Any auto body shop can pull that dent for you easily.

[mitsudriver274]

I have a few years of experience with bodywork.

The only way I think I could pull that dent is with a slide hammer and a custom attachment, or with a stud gun.

Unfortunately at the time I do not have access to any of those tools.

I feel that the cost of someone else pulling the dent + materials to prep the tank for paint+ and getting the tank painted (+$62 for the decals) would cost almost as much as a decent tank. I will have to crunch some numbers.

I def like the look of the 1982 H100A tank much better though.

Looking closer at the pictures the swingarm mount, looks identical. The rear shocks mount in a different location (that the mb5 frame looks like it has the provision for) If the motor directly swaps in to the mb5 frame then I know the back half of the bike is the same, but from the motormount forward they may have extended the frame.

So I found some specs...

Mb5 / 1981 Honda H100

Overall Length = 74in / 74in (1885mm = 74.21)

Overall Width = 25.8in / 30.7in

Overall Height = 45.7in / 40.94in

Seat Height = 29.5in / 29.9in

Wheel Base = 48.2 / 48.2

If the wheelbase on both bikes is identical, the motor swaps in from the h100a into the mb5, is it safe to assume they are the same frame?

Not the best picture, but I do love the lines of the tank.

Edited August 1, 2011 by mitsudriver274

[pixelmonkey380]

the tank will work on the mb5 frame; however you will need a few more parts to complete the swap including the seat pan and a few brackets + washers.

the mb5 tank runs the length of the seat, where the H100 ends before the seat.

hope it helps!

chris<pixelmonkey>?

[huckersteve]

Amazing project you have going here and I'm sure we can all learn a lot from what you're figuring out for us all! Bike is looking great and I will look forward to seeing the finished product!

PS- I am very close to acquiring my own MB5 here in a matter of days. I'll try to remember to get back on here and post when I've gotten it. Good luck and don't stop!

[mitsudriver274]

Moved forward today

Pipe is finished, picked up an isolation mount for my exhaust bracket. Modified the swingarm and picked up all the hardware to mount the shocks. Did my second mock up with the finished parts with good results.

I don't know if this is kosher and wanted your guys opinion. Instead of mounting the clip ons below the top triple clamp, I slid the forks up 1.25" and mounted the clip ons on top of the triple clamp.

I will post pictures tomorrow

Time to break her down for paint, doin it rat rod style.

[huckersteve]

I think you're gonna rub tire on the underside of the bottom crown with the forks that low in the triple clamps, but hey- give it a roll up the block and see what happens!

Also, awesome news- we just picked up our own MB5 today! I'll post pics here soon, but not in your thread. Carry on!

[huckersteve]

OK it's been a month, BUMPING for new info. Also, I'm including a couple links to threads about the MB5 on my favorite moped forum, mopedarmy.com and some info about my bike in particular.

First Link:

http://www.mopedarmy.com/forums/read.php?7,2797082

Older thread:

http://www.mopedarmy.com/forums/read.php?7,2055717,page=1

Setup details:

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

-21 PHBG 104 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. This past weekend I installed a Trail Tech voltage regulator to solve some bulb blowing issues, and am in the midst of rebuilding the front brake assembly.

Good news: I have a line right now on a complete CR80 (1983) that if I'm able to acquire it will be the donor for it's six speed gearbox and clutch at the very least. Other mods possible with a complete CR80 donor bike might include swingarm swap, and/or front end swap. If I can't use the fork without turning the MB into a chopper, I'm going to try to move the disc brake over if nothing else. I'll update here for sure if I'm able to get the CR80 in my garage! (Fingers crossed!!)

[mitsudriver274]

Well she runs, Not well though still trying to figure out the bugs.

I'm using the mb5 stator, it barely fits in the cr80r case but it clears. My problem seems to be timing related.

I had a good side shot but my computer isn't cooperating. I'll try to get one up soon.

[huckersteve]

Mitsu Dude, where in WA are you? I'm in Skyway, South Seattle area.. Would love to ride MB's together when yours is sorted!

[mitsudriver274]

I'm in Bellingham

Can anyone tell me what a two stroke acts like when the timing is off? And is there anyway to use a stobe light to check the timing?

[james1300]

I too have an MB5! I'm also from Washington! SE Washington, the TriCities.

I bought mine as a 'rescue'. The farm boy I bought it from was going to use it as a farm bike.

It ran. But needs alot of work. Im looking for a head light and chrome head light bezel.

I'm really looking for a manual as well!

[huckersteve]

James take some time and dig around on Moped Army. There's a wiki page there with info including links to a PDF version of the MB5 service manual.

@Mitsu- how goes the tuning? I just received my 14t front ring and new chain. Michelin Gazelles coming tomorrow, so by the weekend I'll have a pretty different riding bike I hope. I also finished my front brake repairs, so that's all good, but still working on my headlight.

I am stll trying to line up a CR80 donor bike for my re-imagining plans. I'm thinking part Supermotard, part Adventure bike.. MB5's are the best, BTW!