ESE's works engine tuner

[husaberg]

Hold fire: you don't start a LC100 project with your eye's shut (it does require a little bit of preparation to resolve this).
you chose the Honda; it requires less work in the sleeve (offering potentially better heat dissipation) but requires more work in the crank... trade-off's matey.

not worried about the crank work cause my one will still require destroking regardless

Was it really the piston, really??? (only Dave can answer that); and there are truckloads available if one actually go's looking (I just picked up 4 new pistons for $80 total shipped)..

Some of old stock ones at the moment, no more being made if you are talking about rm100 and yz100 or will ever be made the demand is not there.......

including after market Wiseco & woosner for the vintage clan (early 80's RM100/KX100/YZ100 & even TS100 options); not forgetting they make a 48-51mm piston for new CR80/yz80's (for kart racing); and all these big bore options for scooters....google..... Dealing with the pin size requires finding one that fits your engine....

Yes currently Wiesco and woosner make vintage pistons, but for how long the demand get less every year Brent and at what cost
the os 85 to 100cc piston (i have one btw) are 3 times the cost of a similar strike piston and are not available in any more oversizes

Yes, you can still order RG400 pistons (but you could buy 4 wiseco versions above). What's wrong with Dyke rings kart pistons??? or the strike pistons (KT100J)..

The supply of RG400 pistons will dry up very soon...it was a jap export only model made for only a few years ask yourself how long Suzuki will keep making them for.
Dyke rings when was the last time you seen one used in a GP engine 20-30 years ago ask yourself why?
The KT100j has an acre of area on top of the gudgeon. Mike has a pic of one i will add it)it was posted on the thread. Getting it to work in an engine other than a KT100j would be interesting........

I are not sure why your reply carries so much vitriol but regardless why not argue with the maths....
of Dr Jeffery Rowe (Manchester University) and Dr Hans Von der Marwitz (BWM) (whoops i guess that make him German rather than Dutch)
they are the ones that were given the brief to come up with the formula by the FIM and came up with 360cc 2 strokes vs 500cc four strokes..

As for 80cc MX... No way it would make other 2 stroke engines obsolete overnight, makes no sense to me, to do that.
AS i said the origional 4 stroke size was 130 the 140 then 145 then 150 now 158cc the two stroke f4 has never moved the 150's have been great but there is not a long term viable 50-51.5mm piston but there is an option to even up the cc rating to what they should be.
As the four stroke crowd keeps pointing out the two strokes aren't matching the 4 strokes results at the moment...

[F5 Dave]

Hold fire: you don't start a LC100 project with your eye's shut (it does require a little bit of preparation to resolve this).

Plently of Engines that would allow easy transformation to 100cc.
RG150: Bore: 61.00 mm Stroke: 50.60 mm (truck loads of these around).

TS125x/r: Bore: 56.0 Stroke: 50.6 mm
TZR125 / Derbi / Gilera: Bore: 56.4 mm Stroke: 50.60 mm
TZR150 tzm / dtr : Bore: 61.00 mm Stroke: 50.60 mm
Mito: 56 x 50.6 mm

Silly size more crank work required:
RS125 (aprilia): Bore: 54 mm Stroke: 54.4 mm
KR150: 59 x 54.4
NSR125: Bore x Stroke, 54 x 54.5 mm

This is like shooting fish in a barrel.

ok, its like this: RG150, most of these have been snaffeled up but streetstock racers. I've had people from Auckland ringing me in the hope I'll know of one tucked away that hasn't got knackered cases (surprisingly common).

Everything else listed: erm, c'mon - never sold in NZ, so you're looking at ebay in the hope you won't get hung out & still have to pay a crazy shipping price.

Whereas there are still a several models (TS100, TF100, GP100, MB100, H100, A100 etc) that could spring a new lease of life with a cheap KT piston. 107cc would be all that was required & leave a few O/Ss.

[F5 Dave]

. .
While F5dave (or others) is bound to post "Flogged out MX bikes" the reality is most engines now used by two stroke bucket racers start there life as flogged out anyway (its a lottery).
...

yup damn right I will. Street bikes are lower spec'd & last & last. MX bikes are raced & then sold & then used as trailbikes, sold & then thrashed till they die in a million bits. The only way you'll get one is a running bike. Less & less 80s about. May as well run 85s, who could tell the diff? Then may as well buy a latter model one. Cost of racing goes up.


Ah heck I'm feeling complacent, maybe it would be easier, I'd love to race one.

[husaberg]

Whereas there are still a several models (TS100, TF100, GP100, MB100, H100, A100 etc) that could spring a new lease of life with a cheap KT piston. 107cc would be all that was required & leave a few O/Ss.

its not that often we agree, still don't totally. I feel the cc i feel need to go to about 112cc.
Why to allow for al these other bikes you quoted that are 50.6mm stroke rather than the MB100 49.5mm hense a few more cc
if 1mm oversize which is not over the top in my opinion so that makes 53mm
53mm bore x50.6mm stroke =111.63
it is still well within the formula below.

[wobbly]

Several observations from the pics.
It is detonating - or more likely pre igniting.
Look at the middle of the piston crown, there are speckles all around this area, only one thing does this.
The crown has a white sheen to it, its too lean at some point in the fuel curve.
It should be light coffee brown, everywhere, for optimised AvGas
There is a dark area over the Ex port, this implies the engine has crap scavenging and has alot of short circuiting, or the stinger is too small.
The A transfer rearward radial angle may be too steep, allowing direct looping into the EX when at BDC - the stinger size is a little harder to optimise, being a very high specific output air cooled
and very little anecdotal evidence to point you in the right direction.
Having no marking under the crown, doesnt mean it isnt over heating, in this case it isnt being overheated for long enough, and you are probably very close to optimum ignition timing,where as
over advanced would colour up the underside alot quicker.
The spark plug - why are you running a 9 in a Super Hot air cooled engine that is always going to be running up against the fins thermal ability to reject heat fast enough.
A KT100 making 18 Hp with more finning than you have will tolerate a 9 plug - just.
That is the reason there is no distinct burn line on the porcelain - as ALL of the porcelain is running too hot for an oil zone to form, and give you a reading.
I would be fitting a 10.5 - this is what the 28 Hp, 22,000 rpm 100cc air cooled kart engines HAVE to run or they seize instantly.The end of the earth electrode is blasted clean - that is heat induced deto, or as I said at the beginning, maybe this is causing pre - ignition.

[Bert]

Maybe this should have been restarted in the thread started by Skunk last year..

I are not sure why your reply carries so much vitriol but regardless why not argue with the maths....

As for 80cc MX... No way it would make other 2 stroke engines obsolete overnight, makes no sense to me, to do that.
As the four stroke crowd keeps pointing out the two strokes aren't matching the 4 strokes results at the moment...

Not meant to be; just presenting another side of the argument (being one that has ran out of oversizes on a TF in the past; and has done a 125/100 conversion).
Maths: Not to be an ass but what are the constraints / brief / specs and formula behind the resulting figures; to enable the formula to be scaled down to F4 (opps: read the article now; but still no real answers).

Yes you have a point about supply and demand, but I guess it depends on how long you want the rules to be valid for.
80's, with the right formula I don't believe they will make other engines obsolete any more than lifting the CC size for 100's for those with 125's.

This is like shooting fish in a barrel.
Everything else listed: erm, c'mon - never sold in NZ, so you're looking at ebay in the hope you won't get hung out & still have to pay a crazy shipping price.

Whereas there are still a several models (TS100, TF100, GP100, MB100, H100, A100 etc) that could spring a new lease of life with a cheap KT piston. 107cc would be all that was required & leave a few O/Ss.

Dead fish; but I have seen most of them sold (likely one off imports) over the past few years on trademe. but yes your point is valid (and we have discussed this previously).

I don't really disagree about new life into old air cooled 100cc engines where re-sleeving becomes far too expensive; its just the LC 100's in relation to the 125's

But deep down; I'd just love to race a 80/85cc against a 150cc fours; I could image it could appeal more to the XYZ gens...

once again sorry TZ; I'll stop now.

[kel]

Several observations from the pics.

Great post Wob!

A big thanks and a Merry Christmas to Frits, Wob and all the other contributors that make this thread such an informative and rewarding read.

[TZ350]

Thanks Wob

Several observations from the pics.
It is detonating - or more likely pre igniting.

Look at the middle of the piston crown, there are speckles all around this area, only one thing does this.
The crown has a white sheen to it, its too lean at some point in the fuel curve.

It should be light coffee brown, everywhere, for optimized AvGas.

There is a dark area over the Ex port, this implies the engine has crap scavenging and has alot of short circuiting, or the stinger is too small.

The A transfer rearward radial angle may be too steep, allowing direct looping into the EX when at BDC - the stinger size is a little harder to optimise, being a very high specific output air cooled and very little anecdotal evidence to point you in the right direction.

Having no marking under the crown, doesn't mean it isn't over heating, in this case it isn't being overheated for long enough, and you are probably very close to optimum ignition timing, where as over advanced would color up the underside a lot quicker.

The spark plug - why are you running a 9 in a Super Hot air cooled engine that is always going to be running up against the fins thermal ability to reject heat fast enough. A KT100 making 18 Hp with more fining than you have will tolerate a 9 plug - just.

A hot air cooled engine that is always going to be running up against the fins thermal ability to reject heat fast enough ... That is the reason there is no distinct burn line on the porcelain - as ALL of the porcelain is running too hot for an oil zone to form, and give you a reading.

For 10,5's I will have to do a 3/4" reach conversion.

I would be fitting a 10.5 - this is what the 28 Hp, 22,000 rpm 100cc air cooled kart engines HAVE to run or they seize instantly.The end of the earth electrode is blasted clean - that is heat induced deto, or as I said at the beginning, maybe this is causing pre - ignition.

... and I thought the 9's were going to be to cold but Ok as luck would have it, I have one or two 10's (good old Ebay), so B10's it is.

[Haufen]

Attachment 275028 Attachment 275029 Attachment 275030

Ok Popped the bonnet on the Beast to find out why it nipped up at Tokoroa

Attachment 275027 Attachment 275031 Attachment 275032

Light four corner seizure, but why???? ....

Is that a crack in your cases above the inlet port? Lower right picture, right side.

[F5 Dave]

. . .
Having no marking under the crown, doesnt mean it isnt over heating, in this case it isnt being overheated for long enough, and you are probably very . . . .

also I guess having that hole drilled in the piston might clean up that area.

[TZ350]

Is that a crack in your cases above the inlet port? Lower right picture, right side.

Hi Haufen, I can't see in the picture where you mean, but will have a very good look at the cylinder when I get back to the workshop.

[TZ350]

I reckon we still had it too lean.

Looks like you are right ..... 150main next????

[TZ350]

I have a few RGV250 cylinders stacked away.

Rule 24.2 3 F4 2 stroke max capacity for rebored engines 104cc
F4 4 stroke max capacity for rebored engines 158.09cc (note this was initially 130.5cc the 145cc then 150cc previously)

So to be fair, it should be 158.09 cc four strokes vs 113.82 cc 2 strokes of unlimited carb size.

To be really fair to old farts like me, it should be 125cc (actually 137cc to allow for max oversize re bores) LC and unlimited carb.

OK I would settle for 125+cc water cooled but still 24mm carb restricted.

I mean come on now, I ask you, how much hp could someone make with a restrictive 24mm's, it couldn't be much.

..... 125+cc LC and 24mm max, now that would be fair ... true .....

[cotswold]

I have a few RGV250 cylinders stacked away.



To be really fair to old farts like me, it should be 125cc (actually 137cc to allow for max oversize re bores) LC and unlimited carb.

..... now that would be fair ... true .....

Cagiva mito

[TZ350]

Cagiva mito

I think I have a cylinder somewhere.