ESE's works engine tuner

[mr bucketracer]

I made a watercooled TF with a Ziffle head and a straight exhaust port. It was shit...

all these go prity good

[TZ350]

Attachment 320700 they breed

Classic Bucket engines, maybe we could have a pre 82 Bucket class based on crankcase and cylinder being pre 82.

[Yow Ling]

Classic Bucket engines, maybe we could have a pre 82 Bucket class based on crankcase and cylinder being pre 82.

Just pre FXR wouldd get most of them

[jonny quest]

Anyone have any experience with the Aprilia RS125 Rotax 123 engine? I'm in the USA, where they're rare. I test rode one that's completely de restricted. Now, I haven't torn into it... just quick test ride to see if I would like it for a personal commuter bike.

It's dog ass slow on bottom end, is this common? Fairly zippy on top end for what it is. For me to be happy riding this, I'll need to drastically fix this.

So, are they really that bad power wise down low? Does anyone have any pipe specs, cylinder specs?

[TZ350]

Anyone have any experience with the Aprilia RS125 Rotax 123 engine?

Fairly rare down here too and being a water cooled 125 they don't fit into our class rules for Buckets, so sorry don't know much about them. But maybe someone else may have ridden one.

[wobbly]

Several companies do aftermarket big bore cylinder kits for the 123.
The ports are not that clever, but with some detail grinding,the kitted bike is fast everywhere.
From memory it made +8 Hp at the bottom of the powerband.

[jonny quest]

Good to know. Thanks Wobbly. I was probably going to do a big bore and stroker out the stock parts. Just kind of wanted an idea of what others have found.

Everything is typically geared more towards upper peak power when talking performance. I don't even really care about that much in this case.

No one talks much about pipe measurement, to find out unknown dimensions. Here's a quick run down of what I used to do.

On a stamped pipe, 90 deg from seam I would mark stamping every 1/2". Measure each diameter there, and write down numbers. You would start to see a pattern in each progressive number. When you could see this pattern change, go back and mark the gross taper changes 1/8" and measure. You can then determine each section, header, diffuser and so on. Mark the pipe out in it's header, diffuser diameters, then take a cloth tape measure, measure inside and outside of these separate sections, and divide by 2 for length.

Anyone else have a better way?

[ief]

Guess it will depend on the pipe but given the fact most designs are 1,2 or maybe 3 step diffusers and at most 2 step baffles..

I just look for the changes in dia and check with a caliper and measure with a piece of wire the circumference, that + length gives the angle, subtract material thickness x 2. Sometimes they aren't round so I take the average.

Will allways be off a bit but close enough unless top tuned... but then a stamped exhaust wouldn't be used so...

[JanBros]

I'm making a DIY dyno in "bucket" tradition (meaning on a tight budget as in no money involved, only scrap ). if anyone has done this or has some idea's - do's or don'ts - or whatever, I've opened a topic about it here :

http://www.kiwibiker.co.nz/forums/sh...post1130959381

[lodgernz]

Good to know. Thanks Wobbly. I was probably going to do a big bore and stroker out the stock parts. Just kind of wanted an idea of what others have found.

Everything is typically geared more towards upper peak power when talking performance. I don't even really care about that much in this case.

No one talks much about pipe measurement, to find out unknown dimensions. Here's a quick run down of what I used to do.

On a stamped pipe, 90 deg from seam I would mark stamping every 1/2". Measure each diameter there, and write down numbers. You would start to see a pattern in each progressive number. When you could see this pattern change, go back and mark the gross taper changes 1/8" and measure. You can then determine each section, header, diffuser and so on. Mark the pipe out in it's header, diffuser diameters, then take a cloth tape measure, measure inside and outside of these separate sections, and divide by 2 for length.

Anyone else have a better way?

Same, but put the dimensions into Excel and draw a line graph from the length and diameter data. The transition points become very obvious and reasonably precise.
I actually made a third column in Excel with the same diameter values *-1 and drew a double line graph. Looks like a pipe...

[dark art]

Had a 2003 Rs 125 with a Arrow pipe and never liked the engine. Too peaky for road use, too slow for track use.
The exhaust valve opens on the low end until ~4000 rpm (from memory), probably to ease the starter motor life. It opens around 7500 and the arrow pipe is too short for the engine spec, it only hits around 8500, so the engine have 1000 rpm dead spot.

There are some mods to the CDI and exhaust valve controller to make it better but is never a smooth engine without some serious tweaking. Made a new pipe for it and the low end improved quite a lot, almost rideable on the roads...

If was today I would kept the bike and spend some time tune it. Could be made quite fast and rideable, even with the stock cylinder.

[jonny quest]

Good info. So the bike I rode was performing as designed. I seriously can't believe people like these things. It was awful. I expected a tame smooth power out of a stocker with not much hit, and fairly mellow top end.

Even though I've never riden a early 60's 125 single full on race bike... I bet they performed exactly like this motor.

[breezy]

Anyone have any experience with the Aprilia RS125 Rotax 123 engine? I'm in the USA, where they're rare. I test rode one that's completely de restricted. Now, I haven't torn into it... just quick test ride to see if I would like it for a personal commuter bike.

It's dog ass slow on bottom end, is this common? Fairly zippy on top end for what it is. For me to be happy riding this, I'll need to drastically fix this.

So, are they really that bad power wise down low? Does anyone have any pipe specs, cylinder specs?

i repaired one for a friends son, who seized it, couple of years back. i rode it round for a while afterwards , i found it ok for a 125. i raced one last year pretty much standard, arrows exhaust, power valve held open, ecu de-restricted. once on the pipe i found it a joy to ride, as long as you screamed the nuts off it where ever possible.

[cotswold]

Good info. So the bike I rode was performing as designed. I seriously can't believe people like these things. It was awful. I expected a tame smooth power out of a stocker with not much hit, and fairly mellow top end.

Even though I've never riden a early 60's 125 single full on race bike... I bet they performed exactly like this motor.

I liked mine, pootled through traffic sweet as then if you wanted to go play it went real well, best handling small road bike I have ever had, bit of a sod to start if you left it for a week or so between uses though ( Gianelli pipe )

[2T Institute]

Anyone have any experience with the Aprilia RS125 Rotax 123 engine? I'm in the USA, where they're rare. I test rode one that's completely de restricted. Now, I haven't torn into it... just quick test ride to see if I would like it for a personal commuter bike.

It's dog ass slow on bottom end, is this common? Fairly zippy on top end for what it is. For me to be happy riding this, I'll need to drastically fix this.

So, are they really that bad power wise down low? Does anyone have any pipe specs, cylinder specs?

I have built many many 122/123 engines big bore, stroker, long rod, stroked and big bored. Best of all was the plain 125cc engine. If it has no bottom end it is only de restricted not tuned with a VHSB 34mm Dellorto(PJME speced carb are only good for UK conditions) the 28mm PHBE with a TPS can be tuned very well too. Big gains are with the ignition and the power valve is sensitive to opening point especialy on constant throttle. TYGA pipe works the best as does a Honda RS 125 pipe. VHM heads have a habit of cracking. Standard squish is 1.2mm and that has to be fixed. To make it go fast suspension is the key, it's way to heavy for a race bike but as a commuter/scratcher it's unreal especialy if you have a quickshift. Water temp runs way to high and easy fix is to swap to the Rotax MAX thermostat.