ESE's works engine tuner

[speedpro]

The other way I have thought of to get weight forward is to use heavy water in the radiator. There's nothing about it in the rules but "Homeland Security" might ask a few questions.

[Frits Overmars]

It was silly to assume Chambers and TeeZee wouldn't have thought about engine position and handling.

It would have been silly of me to assume so. I didn't. People can think about all kind of things but that doesn't mean they will always come up with the right solutions. Judging by the picture I assumed that whoever built the bike had not realized the importance of the weight distribution.

What offended me was the mocking tone. Would have been better to ask then suggest a suitable ratio.

You may have a point there, Bucketracer.

Please don't offend the world renownd GP expert over internet 'tone', remember he is here by choice

No worries, Dave. I can take as good as I can give.

...Bike without rider, 48kg front and 48kg rear for 50/50% weight Bias.

Over here, bikes without riders are not allowed on a racetrack. Yeah, there is that mocking tone again. For decades I have seen useless if not downright misleading quotes of rider-less weights, like 'This bike has a one to one power to weight ratio'. It makes me bristle.

...What is an appropriate weight distribution for a small race bike that doesnt go all that fast?

I would suggest about 60% front, 40% rear, both for fast and not so fast bikes. If I recall correctly, the latest and fastes Aprilia GP-bike, the RSA250, had 62% front.

[husaberg]

I would suggest about 60% front, 40% rear, both for fast and not so fast bikes. If I recall correctly, the latest and fastest Aprilia GP-bike, the RSA250, had 62% front.

Can you access the figures for the RSA and RSW 125's Frits? As i would suggest the HP would be perhaps more comparative?

I would hazard a guess the 125's are a little less front end biased than the 250's?
I had a poke around for the RS125 Honda weight distribution figures but it is not so freely listed.

[bucketracer]

People can think about all kind of things but that doesn't mean they will always come up with the right solutions. Judging by the picture I assumed that whoever built the bike had not realized the importance of the weight distribution.

Yes your right, they did realized its importance and think about it and you can bet TeeZee researched it on the net but they were never confident about what a good weight distribution looked like and tried for what seemed a sensible 50/50.

I would suggest about 60% front, 40% rear, both for fast and not so fast bikes. If I recall correctly, the latest and fastes Aprilia GP-bike, the RSA250, had 62% front.

Well I am blown away by that, we would never have thought 60-62% on the front, thanks for that, its very helpful.

[Frits Overmars]

Can you access the figures for the RSA and RSW 125's Frits? As i would suggest the HP would be perhaps more comparative? I would hazard a guess the 125's are a little less front end biased than the 250's? I had a poke around for the RS125 Honda weight distribution figures but it is not so freely listed.

You are no doubt right about the HP, Husa. But alas, momentarily I am in a country far, far away from home and I have no access to my archives.
What you'd need is the RSW's weight distribution because it has been proven to be better than the RSA's. Lots of GP-riders who were 'lucky' enough to get an RSA at their disposal, had great trouble through lack of front end feedback. In fact, the last rider to become world champion on an RSW125, Hungarian Gábor Talmácsi in 2007, declined the offer of an RSA for the second half of the season for that reason.
The Honda RS125 (the latest version, with link rear suspension), though handling better than its predecessor, handles markedly worse than either an RSW or an RSA, according to GP-riders who made the switch. What I do know, is that this Honda's wheelbase, at 1210 mm, is too long for most kart circuits. I don't know about your racetracks, but I assume (a lot of assuming going on today) that they will be (more or less like) kart tracks.

[F5 Dave]

Many of us race on actual Kart tracks. Some race on full size tracks, or rather the short track option of full size tracks. Our GPs tend to be on longer tracks.

[TZ350]

http://www.motorcycle.com/shoot-outs...out-89190.html

An interesting read.

[F5 Dave]

Is it? Why did they even bother comparing a road bike with a race bike? Against a customer 'onda RS125 would have been better. They sort of mentioned it but had no real time, it would have made so much more sense.

[husaberg]

You are no doubt right about the HP, Husa. But alas, momentarily I am in a country far, far away from home and I have no access to my archives.
What you'd need is the RSW's weight distribution because it has been proven to be better than the RSA's. Lots of GP-riders who were 'lucky' enough to get an RSA at their disposal, had great trouble through lack of front end feedback. In fact, the last rider to become world champion on an RSW125, Hungarian Gábor Talmácsi in 2007, declined the offer of an RSA for the second half of the season for that reason.
The Honda RS125 (the latest version, with link rear suspension), though handling better than its predecessor, handles markedly worse than either an RSW or an RSA, according to GP-riders who made the switch. What I do know, is that this Honda's wheelbase, at 1210 mm, is too long for most kart circuits. I don't know about your racetracks, but I assume (a lot of assuming going on today) that they will be (more or less like) kart tracks.

I was being a little checky asking for both.But as i assumed the only difference in the chassis was the weight distribution (i had read on the Pitlane I think thread about the difference in handling) so i was just wondering what the difference in distribution actually was.
I had also read the Aprilia was preferred (esp to the canterlever Nf4) but as Honda love specs statistics and dimensions i thought i might be able to find it easier.
I had seen as production racer model rsr?125 Aprilia once for sale here.

Not sure on the year 96? or model RSR?but it was about at least 3 times the cost of an equivalent RS125 Honda or like $16000 US. So i would not be hacking one up for a bucket in the near future anyway.
http://raresportbikesforsale.com/199...sr125-gp-rare/

[quallman1234]

Have weighed my RS, it is pretty much 50/50 maybe a tiny bit front heavy, with a full tank.

[richban]

Is it? Why did they even bother comparing a road bike with a race bike? Against a customer 'onda RS125 would have been better. They sort of mentioned it but had no real time, it would have made so much more sense.

Yeah agree. I remember seeing that ages ago and thought what a waist of time. If they were getting the same hp/liter as we do on the FXR the MD would be well over 42. Maybe 43. But hey its only a 250 MX engine. And the RS is a road bike. What the?

[TZ350]

Got it up on the dyno, did the compression test and then warmed it up, and another comp test, 150 psi, engine warm but not hot. Now I will let it cool right off and then re-tighten the head before giving it a proper run.



My reason for giving it a comp test, I wanted a base line, also EngMod gives a compression pressure figure so I wanted to double check that against my ccing work and our other known engines. I thought 9.7cc for 7.2:1 corrected or 13.7:1 geometric was pretty exacting and I was concerned about measuring it accurately.

[TZ350]

Is it? Why did they even bother ...

I thought the HP figures interesting ...

[Ocean1]

The other way I have thought of to get weight forward is to use heavy water in the radiator. There's nothing about it in the rules but "Homeland Security" might ask a few questions.

Homeland Security's predecessors did have a puzzling interest in an early 70’s French Whitbread Round the World entry.

Eventually transpired it was ballasted with uranium.

[wobbly]

Dont want to sound like im slinging shit at you TeeZee but again I dont understand why you would spec a combustion chamber with a huge squish - 0.8mm when 0.65 is fine.
And no squish width, that gives no squish velocity at all at 18.7M/Sec - this is just throwing away alot of power everywhere in the useable band.???.
As the Ex height has a big influence upon the trapped dynamic com, I use the trapped ratio.
For your air cooled 125 on AvGas a ratio of 7.4 will work reliably no matter where the port is.
Here is the output with the Ex at 82*, double the squish velocity, and near on the same pumping pressure prediction.