MB100 development

[koba]

The mainjet will need to be bigger than a std TZR not because of power but because as it is it runs without a filter.

All the talk of main-jet sizing, esp vs horsepower sounds like a load of rot. Do remember all sorts of variables change, such as how hard the jet is being sucked at a given time in a given motor. I'd also take a guess and say the emulsion characteristics are likely to change too.

When I had my MB100 almost standard except for the pipe any bigger than the std main-jet size would be four-stroking with richness. The power had definitely increased and with it the fuel required. It was passing it all through the same size jet.

[husaberg]

All the talk of main-jet sizing, esp vs horsepower sounds like a load of rot. Do remember all sorts of variables change, such as how hard the jet is being sucked at a given time in a given motor. I'd also take a guess and say the emulsion characteristics are likely to change too.

When I had my MB100 almost standard except for the pipe any bigger than the std main-jet size would be four-stroking with richness. The power had definitely increased and with it the fuel required. It was passing it all through the same size jet.

Agreed I believe i gave my H100/tzr250 carb settings about 10 pages ago.
but as a rule it is silly to suggest adding a filter will do anything but richen the fueling.

Just as ripping of a air-filter and air box would not lean out the mixture complicate the mid-range as well.
i was comparing the fueling in relation to the std TZR spec.
but yes engines are all different tuning on the web is nearly impossible.
Carbs are quite forgiving in most respects.
Mine was never a problem with surprisingly near std TZR specs.
Also as you say up to a point carbs will auto enrichen with increased airflow it is in their nature up to a point .


Me harping about the filter is about the fact that Canterbury in the summer is a bit dry and dusty which is not i guess a problem in the Hut

[koba]

Me harping about the filter is about the fact that Canterbury in the summer is a bit dry and dusty which is not i guess a problem in the Hut

Not so much!

[datfreak]

Hi,
I'm new -sorry for the thread revive, there is some very good info here!
If I should start a fresh thread, please let me know.


I've got a 1980 h100a - is this the same engine as the mb100?

I want a fun street bike, probably not to full bucket racer tune.

The bike is STD at the moment, and I was hoping to use a cr85 reed , carby - and a expansion chamber off something that would match (or get one made up)

Is the cr85 reed correct to bolt up? I know it will probably need a spacer and a bit of a die grind , but should be ok as long as the bolts fit.

Any ideas for the expansion pipe? Or porting pics or measurements?

And is there a front disc upgrade, or is it easier to use another front end off another bike?


Thanks guys for joining and asking all these questions.

[koba]

Hi,
I'm new -sorry for the thread revive, there is some very good info here!
If I should start a fresh thread, please let me know.

Probably a good idea, then you can track it more and share some pics etc.

I've got a 1980 h100a - is this the same engine as the mb100?

No, but not far off.
The porting is different in the transfers and the exhaust.
I'm pretty sure the exhaust comes off at a different angle too.
That's the main difference, also some have points and others not.

I want a fun street bike, probably not to full bucket racer tune.

The bike is STD at the moment, and I was hoping to use a cr85 reed , carby - and a expansion chamber off something that would match (or get one made up)

Cool, you could race it anyway.
Not 100% sure about CR85, prob at least close.
Yamahay RD250/350 is a good easy to find starting point for a reed block.

You will alsowant to modify the inlet port to make this worthwhile, carving a port either side is the go.

Is the cr85 reed correct to bolt up? I know it will probably need a spacer and a bit of a die grind , but should be ok as long as the bolts fit.

Will likely need a spacer plate mede up, it can be bolted and devconned but a few welds and filling the rest with devcon is the best (Google Devcon)

Any ideas for the expansion pipe? Or porting pics or measurements?

It really depends on the result you are after, for a roadbike that still has a 4 speed you need to be conservative.
More later.

And is there a front disc upgrade, or is it easier to use another front end off another bike?

Some had front discs, I have an MB100 rolling frame if you are interested...
Front ned off something else is best if getting serious.

Thanks guys for joining and asking all these questions.

[husaberg]

The Air cooled CR80 reed is the same bolt pattern as the MB/H100 and will fit with a bit of work on the inlet opening.

the MB100 is a better starting point for a bucket as it has better finning and more transfer duration (kobs may have mentioned this.)
the RD250 inlet will fit pretty good after redrilling 2 holes and a bit of work with a chainsaw file to the two others and offer a decent inlet with a TZR250 carb (Dave has one or 2 for sale i believe.)http://www.trademe.co.nz/motors/moto...-642773065.htm
The H100 choke will fit the TZR carb too if he only has the chokeless one left.....

IF you get an aircooled cr80 cylinder you can use this as a template for the inlet

OH he has an ignition as well.
http://www.trademe.co.nz/motors/moto...-642773826.htm

Or ask Mike re the cylinder he might be able to hook you up with a Brand new ready to race set up.

Ex pipe dimensions here is a simple calculator.
http://www.underdogsracing.com/fospipe.html

or here is the Bell based one.
http://www.bucketracing.co.nz/pipe.php

But get the gearbox 6 speed MB5 and match the porting to suit your track and your ability and match the pipe to suit.

find a honda front end with a 2'5x17 say CRB250 NC19 rim and brake fork set up and ya half way there.
Long term it might be easier to start with a complete chassis.

[datfreak]

thanks Koba and Husaberg for this info.

My bike is the 5 speed w cdi.(ignition opens a whole other line of questions - will Jaycars programmable ignition kit run off the cdi pulse signal - are there real gains to be had etc --these qs can wait i guess)

I was just about to order the cr85 parts from ebay then read these posts -- anyone know if the cr80 air cooled reed is the same boltup as the later water models? The later ones are very plentyful on ebay, including aftermarket performance upgrades.

Those pipe calc programs are brillant! I have a spare header pipe in gc, which will help in measurements before I start butchering.

Koba - waht do you mean by "carving a port either side" in regards to the inlet? Cutting ports at the same height to the original inlet but further around the bore ?

[F5 Dave]

Much as I'd like to sell some bits (I gave some Nigerians my bank details last week but once they'd had a look they left me a deposit) anyhoo, first I'd check your states laws for noise and moded bikes.

Also do a budget of what this will cost, including a million welding jobs . .to end up with a pretty woeful flexi 100 as a road bike. Best add everything in that list and ask yourself if that wouldn't be better sunk into an RGV.

the inlet is one narrow port. A smaller one added either side is safer than a dirty big hole.

[husaberg]

Much as I'd like to sell some bits (I gave some Nigerians my bank details last week but once they'd had a look they left me a deposit) anyhoo, first I'd check your states laws for noise and moded bikes.

Also do a budget of what this will cost, including a million welding jobs . .to end up with a pretty woeful flexi 100 as a road bike. Best add everything in that list and ask yourself if that wouldn't be better sunk into an RGV.

the inlet is one narrow port. A smaller one added either side is safer than a dirty big hole.

Shit Dave you actually read is post properly. i obviously didn't.

there is a thread on a US site for MB5's that covers road mods.
Not sure re the later reed, but just ask for the measurement.from memory the later ones have no bridge in the reed

I was real interested when i seen Mikes triple window inlet, as when mine was done i just replicated the large single port of the air cooled CR80.
I never had an issue with the rings but i seriously doubt mine had 30 hp like mikes. Maybe i wasn't greedy enough.
I should get Hilley to post some pics of my old cylinder........
To fit the reed a fair bit of material is removed.Plus cut outs for the reed screws
probably would have a port map somewhere but it was done all to bell other than the carb size and was real flat torque and not very peaky at all.

[datfreak]

---snip -- i just replicated the large single port of the air cooled CR80.
I never had an issue with the rings but i seriously doubt mine had 30 hp like mikes... I should get Hilley to post some pics of my old cylinder........
... probably would have a port map somewhere but it was done all to bell other than the carb size and was real flat torque and not very peaky at all.

that is a very good idea copying the cr80 port design - if you have any pics that would be very helpful. When you say flat curve, is that flat enough to use as a road bike? I expect it to be a little difficult to get off the line, but ok once rolling.

I dont want to have a 30hp 100cc road bike (i kinda do but being realistic here) - if I could get 18-20 without it being crazy peaky, i'd be happy. Noise wise, it should not be too bad if I can find a good muffler.

[husaberg]

that is a very good idea copying the cr80 port design - if you have any pics that would be very helpful. When you say flat curve, is that flat enough to use as a road bike? I expect it to be a little difficult to get off the line, but ok once rolling.

I dont want to have a 30hp 100cc road bike (i kinda do but being realistic here) - if I could get 18-20 without it being crazy peaky, i'd be happy. Noise wise, it should not be too bad if I can find a good muffler.

Earlier in the thread i posted a link to the 125cc kit made for the MB8,
everything i have read leads me to believe it would fit the MB100. as it seems it is a debored MB100 rather than a big bore 50,
Personally I would start from there.http://www.50cc.eu/en/product.asp?P=...ocilindro-57mm


I have a port map for the cr80 but no idea where?
The only thing was the CR80 had a bridged EX.

well try this for inspiration
http://www.thumpertalk.com/topic/771...-hybrid/page-2

[speedpro]

Re-cut the combustion chamber, lots of compression, use the standard reed block but with a single CF petal and remove the centre bridge, use an adaptor plate and fit a RD350 carb mount to the reed, 28mm Keihin carb, add an extra piston port each side of the existing port, some sort of decent pipe, and you should be looking at close to 20rwhp without touching the ports. To help the powerband you will be better off with another ignition. The old H100 is a bit "less" than a MB100 but not much. My son has the loan of a H100 powered bucket at the moment and it is a honey. Probably a bit less than 20hp but would be sweet on the road.

[koba]

Ditching the head gasket is a good start or no $, just use Master gasket in place.
Seriously.

Not as good as recuting as speedpro says.
Maybe pay to check the squish.
If that doesn't make sense read a good book or seven on 2 stroke tuning.
Start with A. Graham Bell's book, "Two-Stroke Performance Tuning".

[SwePatrick]

Earlier in the thread i posted a link to the 125cc kit made for the MB8,
everything i have read leads me to believe it would fit the MB100. as it seems it is a debored MB100 rather than a big bore 50,
Personally I would start from there.http://www.50cc.eu/en/product.asp?P=...ocilindro-57mm


I have a port map for the cr80 but no idea where?
The only thing was the CR80 had a bridged EX.

well try this for inspiration
http://www.thumpertalk.com/topic/771...-hybrid/page-2

Yes you are correct.
MB8 is 49,5mm stroke and 45bore.
The cylinder fits 100 engine,, actually it´s made for the 100cc engine.
And the mb8 guys are lucky as it is a direct bolt on.
Almost all things are interchangable with CR80 up til -82 also.
Put an CR80 crank in an MB5 engine, weld a bit on blockscaskets and mill out room for the ports and skirt on cylinder, race hard!!
Bore it to 52mm with polini piston and you might tune it real hard, a friend has around 25hp+ at the rear wheel in his 'dragbike'.(probably 27-28hp actually)
and, 5gear gearbox from MB5 is a nifty little piece, can take all the power from mine 132cc project with ease.
I´ve got in the ballpark of 35hp+ at the rear wheel as we speak, if one could guess.
The 6 speed gearbox went boom almost immidietly
You can also fit clutch from lifan and songshen engines, to get a cheap uprated clutch.
I got an 6disc from YX engine with uprated CR85 clutchsprings.

Nice little engines theese hondas

[F5 Dave]

MT50 trailbike version had a 5 speed. Our MB50 (or MB5) had the 6. People use them here with 30hp rear wheel.