Gents,

Rookie here....Can I assume the exhaust valves are the flat flap laying just inside the exhaust port. Can I clean them in that position? They look quite clean..not much build up at all...I would prefer to not remove them....any tips? Thanks in advance.

Michael
_________________
'93 MC21 250sp Repsol "Doohan"

Michael,

You can sort of clean them in place, but your not going to really be able to get the carbon build up that ends up all over them.

Your best bet is to take them out and scrap/scrub/polish them out of the cylinders.
_________________
Charles Gallant

Thanks Charles for the quick response as always......I am afraid I am a little over my head (maybe not) on the removal....is there a step by step anywhere?
_________________
'93 MC21 250sp Repsol "Doohan"

It's not rocket science to be honest.

Look up the RC Valve page in the Online Parts Manual for a schematic of them.

Remove the expansion chambers and turn the crank so the piston is at TDC to stop the flaps from dropping into the cylinder!

Unscrew the RC pulley retaining nut (left hand thread) and pop the pulley off. You can leave the cables connected to the pulley.

Unbolt the RC Valve backplate and then extract the RC shaft. Easiest done with the correct Honda tool unless the valves are cleaned regularly (as they should be!).

With the backplate off there is nothing to hold the shaft in but carbon! There's an E-clip behind the oil seal which usually deforms as the shaft is extracted, but can be straightened. Removing the shaft normally damages the oil seal so it should be replaced when cleaning the assembly.

Again, if the valves are cleaned regularly it all comes apart very quickly and easily, without damaging the oil seal or E-clip.

In the best tradition of Haynes... "refitting is the reverse of removal"!
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

And if it won't come out, the completely un-endorsed-by-NSR-world method, is to refit a washer and the nut, then use the claws of a hammer to extract the valve.

Worked for me, but I'm the gentle sort...

Here's mine before and after:


_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Thanks Dave/Andy...that should do it. I can now see most of that nasty carbon builds up where you can't see it. I will give it a go......by the way that exhaust valve is not the highest tech looking piece on a NSR motor!
_________________
'93 MC21 250sp Repsol "Doohan"

Maybe not, but it's pretty effective.

The RS250 is a far better design, and I've often wondered why when Honda made the change from hex barrels to the later round ones they never incorporated the RS type of valve. Mind you, when an full-on F3 can make almost the same power as the RS250, I guess Honda needed to ensure the production bike wasn't quite what the GP bike was!
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!

Andy, In the event of the oil seal being damaged during RC valve extraction, where can replacement seals be sourced? I had a look on Tyga's website but couldn't see them on there.
(PS - Great forum)
_________________
Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

Any Honda dealer in the UK, no problem... part# 91201-PA9-004 for all models.

If they ask what it is, just say an oil seal!
_________________
Andy.
NSR-WORLD.COM

Please keep all responses to Forum posts on the Forum so that others may benefit.

Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.

Check us out on Facebook! Please "like" our page!