#6

[husaberg]

I've been looking for a good big end bearing for Gary's bike. Whilst at the kart shop I checked out a KT100 rod kit. Turns out the big end bearing is 26X20X13.8, EXACTLY the same as a MB100. Moral dilemna for a bit. They are a bit different to look at and I could spot one even if it was all assembled onto the crank/rod. Further research has come up with a same size bearing with a description that makes it similar design to the KT part. Moral dilemna over. It does mean if you wanted to build a cheater engine which handled 16,000rpm that the parts are available from your local kart shop.
Just in case anyone thinks I honestly thought for more than a second about using an illegal bearing, anyone is welcome to have a look inside my engine, or Gary's but you'd have to ask him about pulling his one apart.

I thought you had a larger Big end than std say 22mm or so. I will understand if its a Secret mind you

[speedpro]

Correct, 22mm big end in my bike.

I'm not going to Te Puke. Looking at the budget, keeping the wife happy(ish), and still not right after Tokoroa. Still got a neck that makes crunchy sounds when I move it and ribs that still aren't attached to vertabrae properly.

Gary's bike is being repaired at a leisurely pace and will be some time before it's going again. That said the crank is at the kart shop to be disassembled and checked over. If needed we'll get some new bits and reassemble it properly.

[speedpro]

The word on the crank is that the motor stopped just in time. The big end cage had a break. There's something up with the pin as well and it needs to be replaced. Sensible thing to do is throw a rod kit at it.

[speedpro]

All the bits for Gary's bike are with the kart shop and being reassembled or bored so it's only a matter of time until it's back together.

Call me slow but I've only just had a brilliant idea. A KT100 piston fits in an MB100 engine really nicely, but with a stock crankshaft the engine capacity ends up over 105cc so you end up being restricted to a 24mm carb and aircooling. Rather than spend money on a new crankpin to reduce the stroke and get the capacity down, why not use a Team ESE plenum chamber and a modified 24mm carb. It solves so many problems. Using a straight rubber carb mount a straight velocity stack can be mounted on the reed block being fed from the plenum. This will give the perfect inlet tract for the engine being fed from the plenum for practically no restriction, less than a carb anyway. The carb can then be placed wherever it will fit on the bike and plenum. This could be a good way of getting round the problem of fitting carbs on MB engines fitted to other frames like RS's etc. The air cooling might be a bit of a handicap but with the big copper fins like ESE use it won't be all that bad. Air cooling may be a bit of a problem at something like a GP at Taupo but recently it hasn't been an issue and probably won't be this weekend either. Careful design should avoid the problem with the fuel/oil pooling in the bottom of the plenum. An engine with this configuration should be good for 30hp if it's built right and not cost much at all beyond the cost of the usual rebuild and some porting.

[husaberg]

All the bits for Gary's bike are with the kart shop and being reassembled or bored so it's only a matter of time until it's back together.

Call me slow but I've only just had a brilliant idea. A KT100 piston fits in an MB100 engine really nicely, but with a stock crankshaft the engine capacity ends up over 105cc so you end up being restricted to a 24mm carb and aircooling. Rather than spend money on a new crankpin to reduce the stroke and get the capacity down, why not use a Team ESE plenum chamber and a modified 24mm carb. It solves so many problems. Using a straight rubber carb mount a straight velocity stack can be mounted on the reed block being fed from the plenum. This will give the perfect inlet tract for the engine being fed from the plenum for practically no restriction, less than a carb anyway. The carb can then be placed wherever it will fit on the bike and plenum. This could be a good way of getting round the problem of fitting carbs on MB engines fitted to other frames like RS's etc. The air cooling might be a bit of a handicap but with the big copper fins like ESE use it won't be all that bad. Air cooling may be a bit of a problem at something like a GP at Taupo but recently it hasn't been an issue and probably won't be this weekend either. Careful design should avoid the problem with the fuel/oil pooling in the bottom of the plenum. An engine with this configuration should be good for 30hp if it's built right and not cost much at all beyond the cost of the usual rebuild and some porting.

If you talk to Grumph he has done a 54mm(cr125 piston i think) for Kevin Orr ,(Yes everyone says they don't do that big i know but it appears they do) he might even part with the cylinder as Kevin i think preferred the 100cc one then you could also put the pin 180 degrees out and........... either that or the Athena one for the MB8 goes to 57mm and CR125 pistons can be used again................

[Grumph]

Nah, Kev's parked the Hondog up as a piece of historic memorabilia now. The big motor was somewhat more torquey but was only put together as a proof of concept trial and never developed. Spending most of the year in Oz will do that.
It was pretty historic at last Greymouth anyway - front slick 13 years old, rear, 14....tyres, they're all in the mind.....
Academic anyway as he did most of his passing in the gutter.
Went out well though - first 2 stroke home each time.

I suspect he's hoping I'll come up with something trick for him - or he'll buy something off trademe and it'll turn up here to be prepped.

[husaberg]

Nah, Kev's parked the Hondog up as a piece of historic memorabilia now. The big motor was somewhat more torquey but was only put together as a proof of concept trial and never developed. Spending most of the year in Oz will do that.
It was pretty historic at last Greymouth anyway - front slick 13 years old, rear, 14....tyres, they're all in the mind.....
Academic anyway as he did most of his passing in the gutter.
Went out well though - first 2 stroke home each time.

I suspect he's hoping I'll come up with something trick for him - or he'll buy something off trademe and it'll turn up here to be prepped.

Was i right on the bore and the source of pistons? I did think you were having an Mb100 clearing sale though?

[Grumph]

Shit, it was more than four years ago now I built that motor...I think it was a wiseco CR125 piston.

Dave was the beneficiary of the parts clearout

[F5 Dave]

I think he told me it was 54.5 CR oversize, but shit it was more than 4 months ago.

[Skunk]

Call me slow but I've only just had a brilliant idea. A KT100 piston fits in an MB100 engine really nicely, but with a stock crankshaft the engine capacity ends up over 105cc so you end up being restricted to a 24mm carb and aircooling.

You are slow but with a quick bike...
Why not increase the 100cc overbore limit to 106cc from 104cc and stop all the expense and stuffing about. Might see a few more 2 smokes at the track instead of FXRs.

[speedpro]

You are slow but with a quick bike...
Why not increase the 100cc overbore limit to 106cc from 104cc and stop all the expense and stuffing about. Might see a few more 2 smokes at the track instead of FXRs.

That's the whole point of my post, going oversize saves a barrel and is cheaper when using KT100 pistons and with a plenum you aren't disadvantaged by having to use a 24mm carb. Building a plenum isn't a whole lot of stuffing about either.
Plus from what Rob says you get some pretty impressive fireworks when it pops back in the plenum with flames coming out all around the place.

[F5 Dave]

isn't confirmed that a 24 won't still be a restriction with a plenum or that it won't hurt throttle response. Or is it?


106.2 would help TS100, TF100, GP100, MB100, H100, A100 & possibly others.

Have to change
F4 2 stroke engines over 106.2cc are restricted to carburation equivalent to a single 24mm carburettor - else it won't help much.

[F5 Dave]

. . .
Plus from what Rob says you get some pretty impressive fireworks when it pops back in the plenum with flames coming out all around the place.

Doesn't any of that sound a tiny bit dangerous?

[richban]

Doesn't any of that sound a tiny bit dangerous?

why not develop a plenum on the other side of the carb like everyone else. Out there I know.

[Yow Ling]

isn't confirmed that a 24 won't still be a restriction with a plenum or that it won't hurt throttle response. Or is it?


106.2 would help TS100, TF100, GP100, MB100, H100, A100 & possibly others.

Have to change
F4 2 stroke engines over 106.2cc are restricted to carburation equivalent to a single 24mm carburettor - else it won't help much.

To keep the change fair , maybe some compassion could be shown to the diesel brigade by allowing then 160 cc , then everyone benifits .