Lets talk Air-Cooled Yamaha two-stroke Singles....RSX?

[Teflon-Mike]

OK, well, my 'enduro' frame and bits came back from the powder-coaters today; so placing an order for parts to get it built back up. From dimensions; odered seals I am told to fit an RSX100.... we dont know if the forks are from a DT80, or an earlier DT125, or WHAT really, so it's merely co-incidence they should be same size as the RSX... and more co-incident that I have, in my trawlings trying to find compaitible parts, been pondering Yamaha 'interchangeability'. Points for instance; my bike ough NOT have them, but it has; and the ones ordered, by description seem to be common to almost everything Yamaha built in the 1970's from the FSIE to the XS650.

Anyway; RSX motor; was trying to call up micro-fish & parts numbers to check crank & crank-case numbers, without much luck; becouse in my trawlings, came accross specs that suggest that RSX100 shares same stroke as the DT125.....

I thought that the RSX engine was based on the earlier YB100, with a more inclined almost horizontal cylinder; and essentially a bored out FSIE engine.... BUT.... I also thought that the RSX100 was a 'square' bore and stroke, opened out to over square 125; and that the DT125 engine was 'Square' and bored to over-square 175... but specs I'm pulling up, suggest that the stroke is the same on the RSX100, RSX125, DT125 and DT175....

So..... now wondering; was the RSX engine based on teh air-cooled DT? Would explain its more upright cylinder.... and if so, what commonality is there between DT100; & RSX100, DT125 & RSX125 and the DT175.....

Air-cooled DT125 offered 15bhp, compared to the 11, the 'standard' RSX125 offered.... so did 'full power' air colled DT barels go on them? and if so, what about the 175's?
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[Blau Zedong]

It's not an RSX, it's an RXS. Engine is a reedvalve jobby which shares certain aspects of it's layout with the DT175MX and the RD125LC but I don't think there is any parts interchangeability as such. The earlier RS 100 and 125 are similar to the twinshock DT 100 and 125 engines, although not identical.
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18:54:48 Rob Fzs: jews don't give away stuff for free

18:54:59 Rob Fzs: unless its their clothes/ hair/ golden teeth

[N cee thirty]

The RXS has the same stroke as the dt175,but the crankcases need boring out a few mm for the barrel to fit properly.

The con-rod on the RXS uses the same size big end pin as the DT, but the little end is 14mm on the RXS and 16mm on the DT so the rod will need swapping to fit the DT piston.
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[Blau Zedong]

No way does a DT175 barrell fit an RXS bottom end. The stud spacing is totally different and it has a seperate 6 stud mount for the cylinder head.
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18:54:48 Rob Fzs: jews don't give away stuff for free

18:54:59 Rob Fzs: unless its their clothes/ hair/ golden teeth

[UnspeedySam]

[N cee thirty]

i'm not saying its easy,but its not impossible either if you have the time and money
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[Blau Zedong]

It's possible to make an RXS a 125 by mixing and matching OEM parts but I can't remember which off hand. I'd just tune the stock engine personally, it can be made vicious as fuck by porting, optimising the squish and using a 31K YPVS carb.
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18:54:48 Rob Fzs: jews don't give away stuff for free

18:54:59 Rob Fzs: unless its their clothes/ hair/ golden teeth

[N cee thirty]

what pipe would you say is best ? if you know

there's a micron on ebay atm,but most are for show
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[UnspeedySam]

[Blau Zedong]

[Teflon-Mike]

https://i178.photobucket.com/albums/w269/teflons-torque/030_035_Yamaha_DT/imag2255.jpg

Cleaning up the 175 lump for painting; and having poke and prod, as you do, looking at the rings through the exhaust port and 'stuff'... pondering, as you do... and wondering if I could come up with a cunning use for the 125 bottom end in the back of the rangie....

And was thinking along the lines of an air-cooled commuter with a vengence.... wondering if any one had ever stuck 175 top end on RSX engine....

So further thoughts..... any-one ever power-valved an air cooled engine?

I was pondering TZR barel with the jacket milled off and plate stack finning.... or am I being daft?
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[27cows]

To my knowledge, the other barrel that will slot straight on is the (overseas only) RX/RXS115 item. I've seen one on the road. Whole motors or bits of them turn up from time to time. But apparently there's virtually no performance gain using the 115 top end, as you might expect really.

The RXS100 is an updated version of the RS125 motor - various bits can be swapped between the two, mostly gearbox & clutch components.

Best pipe is the standard one. The spannies for the RXS are all shite, unless you enjoy riding everywhere at about 17,000rpm
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The RXS100: vehicle of choice for Chuck Norris