Author Topic: Aprilia TZRS 125 hybrid...  (Read 2776 times)

Martin77

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Aprilia TZRS 125 hybrid...
« on: September 29, 2014, 11:34:39 AM »
thought I'd post a pic or two up of a little project we've been working on over the last few months, which is slowly getting closer to being finished. It's always the last bits that take the longest isn't it?

It's an Aprilia RS50, bought as a wreck for 200, fitted with a TZR 4HW engine, intended as a sporty little bike for my partner Alison. I would go into all the issues and problems and jobs, but I dont think I have enough time to go into them all in one post :o

The engine has a foam pod filter, re-cut O ring head (lower compression than standard..not on purpose, I just did it a bit much by accident), 4DL cdi (because the 4HW one was dead and the 4DL one came up at a reasonable price), 350 YPVS servo and control box with dip switches to control opening points and one of my 2MA spec pipes to finish it off. No porting mods or tuning at all... it took a long time to get to grips with the jetting, because I couldn't believe just how big a main jet it wanted, up from the standard 210 to a 440. It runs well though, very useable and smooth, and dynoed at 26hp (would be over 28 on a dynojet).

Next job is trying to improve the handling/suspension a little,  most of the fiddling is me being pedantic...but the important thing is Alison likes it and it gives her something interesting to learn on.

ybk

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Re: Aprilia TZRS 125 hybrid...
« Reply #1 on: September 29, 2014, 11:46:01 AM »
That's really cool, reminds me of a cagiva planet.. The motor doesn't look out of place, like it was made for it. The tank is quite colorful  ;D

Martin77

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Re: Aprilia TZRS 125 hybrid...
« Reply #2 on: September 29, 2014, 05:39:52 PM »
It looks ok considering where the various bits came from.. the tank was a real pain, the paint wouldn't stick to the plastic and kept bubbling up in blisters everywhere, so we thought we'd cover it with comic book cut outs. Seems to be working so far, still the logos and other bits to finish yet though.


casal-fan

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Re: Aprilia TZRS 125 hybrid...
« Reply #3 on: September 29, 2014, 07:35:37 PM »
 ;D Craking ;D
Your girlfriend must be a very cool lady if she likes it so much... does she have a sister? O0


Martin77

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Re: Aprilia TZRS 125 hybrid...
« Reply #4 on: September 29, 2014, 07:49:52 PM »
Sadly not.... apparently she accidently pulled a wheelie on her RXS today!

Louis

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Re: Aprilia TZRS 125 hybrid...
« Reply #5 on: September 29, 2014, 10:27:04 PM »
Looking good Martin,

Still trying to get my girlfriend on a twostroke ::), seems you are so many steps ahead ;D

Do you use the original RS50 radiator for the 125?
King off all twostrokes ''TZR250 3MA''

Martin77

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Re: Aprilia TZRS 125 hybrid...
« Reply #6 on: September 29, 2014, 11:25:30 PM »
So far yeah, the standard RS rad, I guess it might be a bit small for a trackday, but seems to be doing the job ok on the road..

Not all women like the smell of two strokes. I'm a lucky fella :)

Russ B

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Re: Aprilia TZRS 125 hybrid...
« Reply #7 on: September 30, 2014, 12:01:57 PM »
I remember seeing it on the 125 forum......very clever mix & match of parts & certainly different  :) I did like it better with the purple tank though  ;)


That's really cool, reminds me of a cagiva planet.. The motor doesn't look out of place, like it was made for it. The tank is quite colorful  ;D

Cagiva Planet...maybe if you squint..lol........I bought a Planet & done it up for the missus to use......although...I have been using it as its fun & comfortable.....lol... >:D





I have bought another one for me though just to keep the peace... ;D



It doesn't look much like this now though. Its in bits at the moment but won't be far from completion soon I hope  O0



2 wheels....2 strokes.......
Bikes I own
TZR250 3MA
3 x Cagiva Mito's
2 x Cagiva Planet's

Martin77

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Re: Aprilia TZRS 125 hybrid...
« Reply #8 on: September 30, 2014, 06:14:35 PM »
The Planet's are tres cool... that's the sort of look we were aiming for, but prehaps a bit smaller, and also something a little different from a factory bike. The purple tank was nice, but because we'd removed the outer cover, we had to spray the tank itself, which did not like having paint on it. It bubbled up everywhere and looked like it has severe acne... so the solution we came up with was to decoupage it instead, so even if it does get a bit lumpy it's less obvious. Still needs some work with logos etc.

Martin77

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Re: Aprilia TZRS 125 hybrid...
« Reply #9 on: March 18, 2017, 10:58:32 PM »
So, 18 months later I figured I'll put an update to this little project.. it's come along a lot.

Starting with the suspension, I got a Fastace shock that was the right length and allowed preload and rebound adjustment, but the spring was a bit hard and it had too much compression damping. A new spring wasn't too expensive which helped soften the rear and I also had a go at stripping the shim stack and losing a few shims to soften the hit over bumps. Seemed to work pretty well. I guess a small bike is never going to be too plush on the bumpy lanes though.

Up front I've fitted a Race Tech emulator (well, a chinese copy of one) which needed an adaptor and different spring on the valve, but that works pretty well to be honest. The forks only damp on one side which speeds up changes if nothing else!

Aswell as the suspension, putting on a Michelin front, and Sava rear without inner tubes made a nice improvement to feel and cornering response. It is now handling pretty good, quite sharp and crisp. A bit frisky sometimes, but I like that, makes it feel more exciting!

Last winter it went on a diet. Originally it weighed 107kg without fuel, and I was aiming for 100kg. So, a new rear subframe using a Honda RS125 seat was made, small oil tank in the seat hump and Lithium battery and teeny rear light set up. The front end lost as much as possible from the steered mass, so it has twin lights from a Derbi GPR, and digital vapor dash with a modded TZR125 tacho. Losing all the weight from the forks made a huge improvement to the handling.

It now has an alloy front engine stay and bottom frame cross member which lost another kg.

I tried to strip it as far as possible while retaining the ease of use needed for a roadbike, so I'm really pleased that it's now down to 94kg without fuel, some 13kg less! With only 26ish hp on tap, that makes quite a difference to how the bike feels and accelerates.

A new pipe was made to be a little revvier and give better overrev. It only gained about 0.5hp, but the wider powerband and better revs made it racier to ride. The extra revs meant I could drop a tooth off the front sprocket without losing top speed, but gaining extra thrust for accelerating. Getting the jetting right started to get beyond the realms of normal jets, richer and richer it went, until I gave up buying them and just drilled them instead. 2.2mm felt good and gave good plug colour. 2.2mm is about size 600! 

It also has a zeeltronic cdi.. it was meant for the TDR but I stuck it on the RS instead..

And recently I splashed some cash on a lightly used 170cc Athena top end for it. Most people reported a good increase  in bottom end grunt but no real gain at peak hp. It turns out this is mainly due to the cylinder casting being the same as their 125cc cylinder, so it has 125cc sized ports. I opened them up to 170cc sized ports by widening the exhaust 5mm, and lifting the transfers about 1mm. The pipe stinger was made larger to suit too.

Initially the 170 kit felt awful, until I double checked the pv setting and found the spool must have a different end for DT's, as even with the pulley lined up, it was about 3mm closed. Once that was reset, it flew... I'm very impressed.. the bottom end makes cruising more relaxed, and the extra top end means it'll now hoist a wheelie in 2nd. Sadly the local dyno was sold off, so I've no idea how much power it's making, but I'd guess low 30's. How well the Athena top end will last, or if the fuel tap can flow enough (now up to 2.3mm main jet), or if the stock 50 rad can cope... we'll see..

So it's lost 13kg and gained maybe 5hp everywhere... I really like it!

Martin77

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Re: Aprilia TZRS 125 hybrid...
« Reply #10 on: March 18, 2017, 11:09:00 PM »



Martin77

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Re: Aprilia TZRS 125 hybrid...
« Reply #11 on: March 18, 2017, 11:15:30 PM »
The Athena cylinder post porting;





Dyno comparing the new spec pipe to the old one, still on the 1255 cylinder here;


James P

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Re: Aprilia TZRS 125 hybrid...
« Reply #12 on: March 19, 2017, 02:50:18 PM »
...I gave up buying them and just drilled them instead. 2.2mm felt good and gave good plug colour. 2.2mm is about size 600!

That is a big main jet Martin! Has it got the standard TM28SS carb? If so, does it still have the power jet fitted/working?? Are you running it on methanol??? ;D

Regards,
James

Martin77

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Re: Aprilia TZRS 125 hybrid...
« Reply #13 on: March 19, 2017, 03:59:34 PM »
Yup, stock 28mm carb with pod filter. I can only assume the signal is very weak so it doesn't suck very hard. 2.2mm is actually about 650 jet size. I'm going to try a 2.4mm jet with the 170 top end.. that's 770! Powerjet is clear, though not sure it does a lot with pod filters.

James P

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Re: Aprilia TZRS 125 hybrid...
« Reply #14 on: March 22, 2017, 09:24:51 AM »
Yup, stock 28mm carb with pod filter. I can only assume the signal is very weak so it doesn't suck very hard. 2.2mm is actually about 650 jet size. I'm going to try a 2.4mm jet with the 170 top end.. that's 770! Powerjet is clear, though not sure it does a lot with pod filters.
Hmmm, interesting. Is it worth trying some type of extension tube/trumpet between the carb and the filter (if you have space) to see if the vacuum can be improved?

Regards,
James