Author Topic: RD250 Reeds  (Read 4624 times)

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Offline Twojays66

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RD250 Reeds
« on: September 30, 2015, 06:03:07 PM »
I want to get some reeds for our RD250's carbs (28mm Mikuni). Can anyone recommend where to get them from. I want standard ones. Happy if they are carbon, but don't need Boyesen ones do I? Standard motor and carbs with Gibson pipes.

I read on the South Coast Classic Racing Team website about an rd250 that was using standard carbon reeds. Is that anyone on here?

Offline betty foRD

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Re: RD250 Reeds
« Reply #1 on: October 01, 2015, 06:00:18 PM »
You've posted in the racing section so is it safe to assume this is for a ported engine for track use?
First stop would be to ask the engine builder/tuner as he will have had something complimentary in mind when he configured the carb,port,pipe mix.
But given that might be you...then depending on application and budget I would go as follows.

1. Stock steel reeds and blocks from a 250LC, low cost plug n play but with higher resonant frequency than std. AC reeds so can carry a few more revs.
2.  Carbon reeds as per your post, I think this refers to using a 3 petal element form a later MX yam and chopping off the third petal to make a 2 petal affair for the RD. can't remember the engine off top of my head but you'll find it if you search around.

After that it gets a bit more technical...but i don't think that's required if you have stock carbs and gibsons.

Rev 'em till they rattle

Offline 5port

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Re: RD250 Reeds
« Reply #2 on: October 01, 2015, 07:41:09 PM »
Try searching for the tuning info by Ed Erlenbach, Dale Alexander etc... There is certainly some benefits to be had in the reed/inlet.  You can get quite a bit of extra reed cage (petal) area with modifications.  The refered racers certainly know what they are on about, and alot of it does not cost!     
5port

Offline gibba1008

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Re: RD250 Reeds
« Reply #3 on: October 03, 2015, 06:46:37 PM »
You've posted in the racing section so is it safe to assume this is for a ported engine for track use?
First stop would be to ask the engine builder/tuner as he will have had something complimentary in mind when he configured the carb,port,pipe mix.
But given that might be you...then depending on application and budget I would go as follows.

1. Stock steel reeds and blocks from a 250LC, low cost plug n play but with higher resonant frequency than std. AC reeds so can carry a few more revs.
2.  Carbon reeds as per your post, I think this refers to using a 3 petal element form a later MX yam and chopping off the third petal to make a 2 petal affair for the RD. can't remember the engine off top of my head but you'll find it if you search around.

After that it gets a bit more technical...but i don't think that's required if you have stock carbs and gibsons.

Yz 125 reeds, I have the part number somewhere around :-\

Offline andy_g

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Re: RD250 Reeds
« Reply #4 on: October 29, 2015, 08:36:08 AM »
Malossi sell carbon fibre sheet for reeds. Just make your own. You only need a pair of sharp scissors!
Make sure you cut the reeds as a pair i the same direction as the flex is different depending on which way you have the woven fabric.

http://www.ve-uk.com/general-and-universal-parts/malossi-reeds/0/malossi/

Have several sets being used, on mine and a mates bike.

Offline Levy1982

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RD250 Reeds
« Reply #5 on: October 29, 2015, 09:19:11 AM »
Polini also do carbon sheets for reeds, choose the right thickness to suit your needs ;)

Offline andy_g

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Re: RD250 Reeds
« Reply #6 on: October 29, 2015, 05:09:12 PM »
Any of those thickness reeds should be fine, should you find you get a flat spot then just be aware you may have found the natural frequency of the reed. Just cut another stiffer set, ie cut a different angle from the sheet.

Offline betty foRD

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Re: RD250 Reeds
« Reply #7 on: October 29, 2015, 08:36:04 PM »
I would strongly advise against suck it and see tinkering with home made reeds unless you are a compulsive tinkerer...it's up there with blending your own 2t with vegetable (cooking) oil to save money.
Its really not a one size fits all when it comes to the actual composite material. Even the thickness variation only changes one parameter. Different reed blocks have diferent apeture aspect ratios and petal angles. Each require a diferent warp and weft ratio.
Composite reeds soften as they warm up so AC engines can have a profound effect on reed stiffness as they heat up.
Any of the branded composite reeds will work better than stock steel type but you need to keep your eye on them. Standard steel reeds are generally fit and forget.

If you are going racing then before you start changing reed type you need to change the reed block itself.





Rev 'em till they rattle

Offline betty foRD

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Re: RD250 Reeds
« Reply #8 on: October 29, 2015, 11:11:16 PM »
Only advising the majority against making their own reeds and yes the preferred plug and play upgrade is simply to buy a branded reed and fit.

Rev 'em till they rattle

Offline 5port

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Re: RD250 Reeds
« Reply #9 on: February 14, 2016, 06:52:55 PM »
Worth noting that Ed has got 70bhp from engines breathing through modified standard RD cages.  Also, the "TDR" reeds he refers to are "Tony Doukas Racing reeds", NOT (Yamaha) TDR reeds!  ;)
5port

Offline kawazonkey

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Re: RD250 Reeds
« Reply #10 on: February 17, 2016, 11:52:19 PM »
Are Harpowa still about? I had a set of reeds from them in my old 250LC.

Offline 5port

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Re: RD250 Reeds
« Reply #11 on: February 22, 2016, 10:07:57 AM »
Have read from someone who had a fibre reed break up,.. still fcuked the piston/cylinder.  :'(  Whatever reed you run, it needs the cage and stops to suit its characteristics. Not too difficult in a normal road engine but, top information in racing.  ??? 
5port