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Aprilia RS257


wazrs257
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the ones i have are really short stroke off my old honda rs 125 mate,they may be ok or a wee bit to short,i could send you one to try

Edited by si.likes.guiness
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the ones i have are really short stroke off my old honda rs 125 mate,they may be ok or a wee bit to short,i could send you one to try

I think the minimum I could get away with is about 120mm. Could you measure the stroke on yours for me? (Sounds a bit wrong!!). I want to try & fit one to the front fairing bracket, across the bike.

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  • 2 weeks later...

Took my RS out for a much longer blast today. I've fitted a 45 degree thermostat and filled it up with a 50-50 mix of anti-freeze. Once warmed up, it ran at a constant 60 degrees so I'm happy with that & the jetting is now pretty much right. :lol:

I still haven't wired up the speedo properly, but it feels like it tops out at about 100 mph, pesky short circuit gearing! It's possible to change all the internal ratios & apparently Rotax 256 (tandem twin) gears fit, so come re-build time I'll be hunting for a set af long circuit ratios. The final drive gearing is currently 16:39, it may be possible to fit a 17t front but the swinging arm will need modifying to avoid fouling. The rear is a one-off, off-set Talon sprocket, I may be able to go down a couple of teeth, but they are expensive to have made.

When I got home a brief check over revealed, 4 out of 6 seat unit bolts missing and the bracket holding the rear shock resevoir to the subframe broken! The good news is, nothing that vibrated loose last time has come loose again! ;)

:lol:

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When I got home a brief check over revealed, 4 out of 6 seat unit bolts missing and the bracket holding the rear shock resevoir to the subframe broken! The good news is, nothing that vibrated loose last time has come loose again! :thumbsup:

:dribble:

Result! Its a case of once you've been over everything once it should stay done up, i'm still re tightening and mending things on my GSXR1216 that vibrate loose/start to fall apart.

Glad its running pretty well now mate

:thumbsup:

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Both of them have 125 exhausts bodged on, no wonder the 1st one only put out 43bhp! Im sure thats the same one that was for sale on e-bay a couple of months ago too. I knew that I wasn't the 1st to do this conversion, but I'm dam sure it's going to be the best! :wub:

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Now the engine's running better, its time to do something about the tank slapping!

Although I understand that this can be a symptom of badly set up suspension, I've decided to fit a steering damper as a 1st step. At least then I can concentrate on feeling what the bikes doing, instead of worrying about which hedge its going to put me through!

Sprint do a steering damper kit for the RS but I couldn't work out where the rear mount would fit, according to their web site "The kit is bolt on and requires no modifications or cutting of the body panels or frame to fit". It turns out this kit uses a 160mm stroke damper, same as currently fitted to my 7/11, so I'll fit that for the time being. I ordered the fitting 'kit' tonight, the guy on the phone said I'd need to drill a hole in the frame to fit the rear mount ("The kit is bolt on and requires no modifications or cutting of the body panels or frame to fit")! :shock: I think I'll drill a hole to do the inital fitting, then get the boss welded to the frame.

The rear shock is a fully adjustable (pre-load, rebound, hi/low speed compression) Wilbers race shock. I got it at the right price from e-bay, but it is set up for someone about a stone lighter than me. Having said that, the sag with me sitting on it is about right. I've e-mailed the importers for advice but got no reply, will have to give them a bell!

The whole rear shock linkage is brand new from Aprilia, but there is some play in it already! I think I'll have to remake the inner bushes a few thou bigger to get rid of all the play.

The forks are a law unto themselves! A full Maxton re-build is preferable purely because I want to use as much of the 'original' bike as possible, but at about £600, very expensive. Fitting a different set of forks is no problem, but most bikes with proper fully adjustable forks weigh about 50% more than my bike, so will need a re-valve anyway.

The head bearings are new & the wheel bearings are fine. Any other suggestions?

;)

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Now the engine's running better, its time to do something about the tank slapping!

Although I understand that this can be a symptom of badly set up suspension, I've decided to fit a steering damper as a 1st step. At least then I can concentrate on feeling what the bikes doing, instead of worrying about which hedge its going to put me through!

Sprint do a steering damper kit for the RS but I couldn't work out where the rear mount would fit, according to their web site "The kit is bolt on and requires no modifications or cutting of the body panels or frame to fit". It turns out this kit uses a 160mm stroke damper, same as currently fitted to my 7/11, so I'll fit that for the time being. I ordered the fitting 'kit' tonight, the guy on the phone said I'd need to drill a hole in the frame to fit the rear mount ("The kit is bolt on and requires no modifications or cutting of the body panels or frame to fit")! :eusa_whistle: I think I'll drill a hole to do the inital fitting, then get the boss welded to the frame.

The rear shock is a fully adjustable (pre-load, rebound, hi/low speed compression) Wilbers race shock. I got it at the right price from e-bay, but it is set up for someone about a stone lighter than me. Having said that, the sag with me sitting on it is about right. I've e-mailed the importers for advice but got no reply, will have to give them a bell!

The whole rear shock linkage is brand new from Aprilia, but there is some play in it already! I think I'll have to remake the inner bushes a few thou bigger to get rid of all the play.

The forks are a law unto themselves! A full Maxton re-build is preferable purely because I want to use as much of the 'original' bike as possible, but at about £600, very expensive. Fitting a different set of forks is no problem, but most bikes with proper fully adjustable forks weigh about 50% more than my bike, so will need a re-valve anyway.

The head bearings are new & the wheel bearings are fine. Any other suggestions?

:beerchug:

Tyre sizes? swingarm bushes? I guess you've run a spanner over the front and rear ends..

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Tyre sizes? swingarm bushes? I guess you've run a spanner over the front and rear ends..

Everythings torqued up as it should be & the tyres are standard sizes. I can't feel any sideways movement in the swinging arm, there is some up & down but I think thats coming from the linkage. The only way to tell for sure is to clamp a DTI to various parts and actually measure any play.

I can get you some of the radial forks that are for the rs125 I have a set on my bike that might split

Are the radial forks actually any better apart from the trendy radial brake mount? I would like a set of radial forks to have modified by Maxton, but purely because they look more modern (plus the fact that my mudguard mounts have been butchered by some idiot 17 year old!).

:lol:

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Recieved my fitting kit from Sprint today. My GSXR kindly donated its damper, so after lots of uming & aring trying to decide the best place to drill the hole in the frame (internal webbing to avoid!), its now fitted. Going to try it out tomorrow, hopefully it'll calm things down a bit!

4866047505_40ae284776.jpg

4866046965_40133f6a84.jpg

:lol:

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I believe the forks are better, but they still have that rubbish internal design but they are newer so the internals are going to be better condition and one of my suppliers used to race the bikes so they will be in good condition, nothing butchered so perfect for getting maxtion to fit their cartridge kits into.

the only problem is that the the brake system does work with the old style wheel due to that the front brake disc either doesnt come out enough or its out too much, i dont particularly remember but i solved the issue the easy way by buying a new model front wheel but they can go for hundreds and most people sell the wheels in pairs so its difficult to find just one front but they sometimes pop up on ebay, even my friend wont sell them individually. you could alternativley machine some spacers to fit between the disc and wheel but ive not heard of that being done before,

I will send an email to him to check if he has any available.

Edited by Devon
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Adding a spacer between the disc & wheel wouldn't be a problem, I have a lathe at home!

My new steering damper proved its worth today, I wouldn't say its stable now, just that it weaves gently instead of going into a full blown tank slapper! There were a couple of throttle to the stop in top bends, and it felt fine. I'd also dropped the forks through the yokes 10mm to try & get a bit more weight over the front end, & it looks like everythings turned out nice! :eusa_dance:

The main problem now is the gearing, it only drops about 500rpm between gear changes. Looks like Im going to have to modify the swinging arm to allow a 17t front sprocket to be fitted, and look out for a long circuit gearbox.

:thumbsup:

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Talk about 2 steps forward & 3 steps back! I've just been out in the garage tinkering with my bike & whilst re-fitting the exhaust I noticed that one of the front engine mounts has cracked! :thumbsup: They're made from 8mm thick HE30 plate, the kart ones that I got when I bought the engine were only 6mm. ;)

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  • 3 weeks later...

Have spent the last couple of weeks making new engine mounting plates. These are the same as the last set, except that the spacers are now made from 25mm diameter HE30 instead of 20mm, and they are now welded to the mounting plates to increase strength.

I've also treated her to a gearbox of fresh Silkolene light gear oil and a general 'fettle' (including a new K8 needle). Whilst changing the gearbox oil, I removed the clutch cover & checked the diameter of the clutch drum. There are two different clutches fitted to the Rotax 257, 116mm & 132mm diameter, Mine's fitted with the bigger 132mm version.

Total distance today was 38.6 miles (got my speedo set up too!), and it used 3.5kg of fuel. Taking fuel as 6lbs per gallon, this gives a very frugal 30mpg, amazing! On the down side top speed is only 103mph, gets there fkin quick mind! The biggest culprits are 5th & 6th gears, still very closely spaced despite the highest final drive I can fit. With better internal ratios I think it should top out at around 120ish, without loosing out too much on acceleration.

The only real victim of vibration today was the Scitsu temp gauge, the needle fell off! Hopefully I can get a new one under warranty. :shock:

Quite pleased with the days proceedings, despite the rain!

:rolleyes:

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Can you mount the engine in rubber bushes to stop vibration from killing your bike?

I have considered this. To do it properly though, I would have to bore out the mounts on the crank cases & press bushes in, unfortunatley there isn't enough room around the mounts. Its generally just a case of having a quick check over the bike & nipping up anything thats come loose (or locktighting). With gearing sorted out it should be better, it wouldn't spend quite so much time buried in the red!

:eusa_whistle:

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I have considered this. To do it properly though, I would have to bore out the mounts on the crank cases & press bushes in, unfortunatley there isn't enough room around the mounts. Its generally just a case of having a quick check over the bike & nipping up anything thats come loose (or locktighting). With gearing sorted out it should be better, it wouldn't spend quite so much time buried in the red!

:)

Fair enough. It's a cool little bike. :D

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I've improved the rubber mounting of the temp gauge today, so hopefully the new one should last a bit longer! I expected teething problems when I built the bike, and am getting them! Cant wait till I get them all ironed out so I can sort the cosmetics.

its a very cool project and i cant wait to see it in the flesh.so to speek :thumbsup:

Thanks! Coming to a gravel trap near you sometime early next year! :eusa_dance:

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  • 2 months later...

Thanks to one of the pistonheads links above from Stuntmonkee, I am now the proud owner of a spare motor. Its a tuned kart engine that the guy originally fitted to an RS125, but replaced with an un-tuned standard engine after it started 'rattling'. I paid less for it than I was going to pay for just a top end that needed welding/re-plating, I'm well pleased! :beerchug:

I picked it up today, so stripped the top end to have a quick look. Its suffered a mild siezure thats trapped the ring in its groove, the plating is also damaged. It looks like a 'chunk' of plating has flaked off, which is a pity because you still see the honing marks, so it can't have been run much since its last re-plate. The crank feels ok, so I'll probably re-build the bottom end with some higher gear ratios & new mains, and use the top end off the engine thats currently in my bike.

:icon_salut:

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  • 1 month later...

No real progress as yet. Unless you call dropping it while putting it on a paddock stand while pissed and breaking the number plate progress! :eusa_think: Still waiting for a 256 gearbox with the right ratios to turn up. Hope to find one soon, as I want to do a TD on it this year & with a top speed of 103mph I'll get murdered even in the slow group! :thumbsup:

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Waz does the 256 cluster slip onto the 257 clutch and output shafts(256 is a dry clutch)?

I was told by the guy that built my pipe, and from a couple of other sources that they are interchangable. Being a tandem twin, I'd imagine that the shafts/gearbox would be a similar width, so it may be possible to use the 256 shafts with the 257 wet clutch. Will let you know as soon as I've got one sorted. :icon_blackeye:

Edited by wazrs257
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