MB100 development

[Hilleye]

Bastard, she started to warm it up, sounded ok at the time, little death rattley on shut down, but same as yesterday. Started again and died waiting to go on the track. Then wouldn't start and stay running for more than a few seconds, even on the roller, clunking and backfiring just got progressively worse.

Pulled it out this evening, haven't split the case yet, but can feel about 1 - 2 mm of lateral play in the crank. I'm assuming that this means the main bearings and hence crank seals have gone.

Small end and big end feel fine and were covered in 2T mix so pretty sure they were being well lubed. No play in either bearing. No signs of seizure on the piston. Nothing in the barrel either. Will post photos of everything tomorrow to give you all a good look at the whole package. Your advice will be appreciated from that point onwards.

Real bitch was I was lending it to a mate so he could experience and potentially get into bucket racing, needless to say he's been put off two strokes by the experience, but hopefully not buckets all together. And I myself have come to the conclusion that you need to pack an engine for each race, just to be safe.

[TZ350]

Real bitch was I was lending it to a mate so could he experience and potentially get into bucket racing, needless to say he's been put off two strokes by the experience, but hopefully not buckets all together. And I myself have come to the conclusion that you need to pack an engine for each race, just to be safe.

Pity your mate missed out, but once you have properly overhalled that MB engine and got it sorted it should be very reliable, they are well proven engines.

[Hilleye]

...but once you have properly overhalled that MB engine and got it sorted it should be very reliable, they are well proven engines.

Is that like one of those Tui adds?

[husaberg]

Pity your mate missed out, but once you have properly overhalled that MB engine and got it sorted it should be very reliable, they are well proven engines.

Id go along with that. decent bearing and a quality port job and proper jetting and they last well.

I would be interested to see if the stator has touched the magnets as I had a mag side bearing go once but upon inspection it was from a bloody wheel bearing or similar it definitely wasn't a C3 bearing.

[Kickaha]

Is that like one of those Tui adds?

No it isn't

I've seen those engines easily do a season (or more) without being touched

[TZ350]

Is that like one of those Tui adds?

Nope .... but expecting an engine that has had a thrashing for how long? then left neglected to last again without some attention may have been a bit much.

It might be Buckets but its real Racing, for racing, you need a race ready engine, you can't expect to cut corners and last.

If you overhaul it with good parts like slotted rod, silver bigend brg, decent C3-4 brgs (for side clearance) new oil seals and a re-bore with a decent piston. Read everything you can about how the ports should be finished and if you still have the big heavy original flywheel ignition loose it. Good ignitions are much cheaper now and if you don't want to mess with a programmable get a straight line MX ignition, something from Ebay like the stator Speedpro is using would be the go. CC the head to get the correct (or at least known) compression ratio and set the ignition and main jet up on a dyno if you can. Modifying the clutch pack like Speedpros wouldn’t be a bad idea either. There has been a heap of good info posted on your thread.

And there have been a lot of very good MB100's built, they are a proven engine.

Get the details right and you will have yourself a really reliable and fast bike.

Please post photos and comment about your progress as you go, its great to watch someone elses race project progress.

[dangerous]

Hilleye... how come the bike was on the back of the ute yesterday? Think earler in the thread the squared off ex port was mentioned, just found some pics including this one, looks like it has just had a hone (still got a spear piston for the current over size if ya want it) still some what out of shape but I never had issues with it.

[Hilleye]

Hilleye... how come the bike was on the back of the ute yesterday? Think earler in the thread the squared off ex port was mentioned, just found some pics including this one, looks like it has just had a hone (still got a spear piston for the current over size if ya want it) still some what out of shape but I never had issues with it.

I think bike has run a main bearing.

That picture is what the port still looks like now.

Would definitely be keen on the piston if possible. Heading into town this morning and could pick up at same time.

[Buckets4Me]

Would definitely be keen on the piston if possible. Heading into town this morning and could pick up at same time.

my engine gp125 witch tz built 6 years ago is still making 18-19 h/p and has only had 1 piston changed in that time

2 strokes when rebuilt well will out last the 4 stroke brethren

and cost less to rebuild when you bend a valve snap a cam chain or just forget to check the oil

[dangerous]

my engine gp125 witch tz built 6 years ago is still making 18-19 h/p and has only had 1 piston changed in that time

2 strokes when rebuilt well will out last the 4 stroke brethren

and cost less to rebuild when you bend a valve snap a cam chain or just forget to check the oil

Interesting... cos after 2 hard out meetings the bike was going the best it had, but I thought a freshen up with new piston and hone would be in order... it didnt run aswell again... morel, dont fuck with if alls going well... but then my luck next meet and it woulda blowen.

I think bike has run a main bearing.

That picture is what the port still looks like now.

Would definitely be keen on the piston if possible. Heading into town this morning and could pick up at same time.

crap... never went near the bottom end and god knows how long since it was done.
Yeah thats how it was after being re ported to round off the squaring and a hone with the new piston as above.
Will look for the other pisto and ring when I get the chance (as per pm) oddly enough just back in from Burnham, so could have droped it off LOL.

[Hilleye]

Ok, have split the crankcase here are the results. I'll work my way down the engine.

Head.

[Hilleye]

Barrel.

Inlet port.


Exhaust port.

[Hilleye]

Reeds and inlet manifold.


Piston.

[Hilleye]

Crankcase, gearbox and clutch.


The attached thumbnail is a picture of a random bolt that fell out of the crankcase when split. If anyone could enlighten me as to its purpose I'd be much obliged. For the life of me I can't find anything that even remotely fits and wonder if it's just been floating around in the oil.

[dangerous]

Ok, have split the crankcase here are the results. I'll work my way down the engine.

All looks ok so far, the orange discolouring is copper spray I used to use, head looks a bit wet and one side looks like deternation marks or does it just need a wipe clean?
Intakes rugh as guts aye, allways was but it is how it came to me ohh and its a RG250 reed block.
Barrel looking ok tho pic 3 seems a bit odd but Im asuming its what ever you are sitting the barrel on for the photo... not a gouge in it aye?

The attached thumbnail is a picture of a random bolt that fell out of the crankcase when split. If anyone could enlighten me as to its purpose I'd be much obliged. For the life of me I can't find anything that even remotely fits and wonder if it's just been floating around in the oil.

AHHHHH... thats were that farking thing went, I knew it wouldent a gone far actually its a handy item Honda put in the bottom end to prop the reed block up with when taking photos, ya dont get that with a BMW aye...

So... no damage or issues found then, I asume it was this head of a nut that got cought court up in the box?