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Birkett SY250R mods question

22 posts in this topic

I have read many references to SY250Rs that were modified by Birketts.  Unfortunately, nowhere have I seen it posted what all these mods were.

Does anyone know what mods were done, and if they could still be viable today or just not cost effective?

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You could give them a call on 01229 716806 

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1 hour ago, mrturtle said:

You could give them a call on 01229 716806 

I will probably send an email, but was curious if anyone may know.  

Sounds as if they took the time and dialed in a few things to make a bike that was deemed very good, even better.

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1 hour ago, leeanthonycook said:

Try this link

 

Found it when I googled the question

hope it helps

Exactly, I had read through many of the Scorpa topics and posts.  That one you linked to really caught my interest.  Was hoping someone might have more details explaining a bit more in detail for tne less obvious changes.

Also read, Birkett removed the studs from the cylinder and used capscrews.  This allowed removing the top end without removing the entire engine apparently.

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Main thing was skimming weight off the flywheel and advancing ignition timing. More power but stalled easier

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6 hours ago, baldilocks said:

Main thing was skimming weight off the flywheel and advancing ignition timing. More power but stalled easier

My reading about the bikes here, seemed to indicate the UK machines came with the heavier flywheel and retarded timing.  Everywhere else in the world supposedly got the lighter flywheel and advanced timing.

The machine I get will be USA version.  So I assume, but can check the timing.  

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Advance the timing, the only thing you will ever need to do

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1 hour ago, faussy said:

Advance the timing, the only thing you will ever need to do

Agree, timing is probably a key to these bikes based on what I read.  

Based on what Benz wrote a while back, seems a few of these mods could be valid still and while may not increase performance per say, could make it more consistent to ride.

I copied the words and info from Benz post a while back.  Others may have additional small changes.  Sadly, Benz may have been enjoying his bike so much, he never added any more info or sorted out how to post photos.

Mods that have been carried out are as follows.............

1) sump guard trimmed on water pump side

2) frame modified so complete rear end,airbox and silencer come off by just removing 4 screws and undo carb rubber

3) thermostate repositioned into water pipe coming from cylinder head

4) beta throttle spring in carb to make throttle lighter

5) larger AJP clutch master cylinder,much lighter than standard

6) carb has been set up by Birkett but as yet i do not know jet sizes

7) reed bloke has been modified,again by Birkett,again i have yet to investigate

Benz

 

I did contact Birketts and await a reply


 

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Birkett told myself back in '08 that for Joe Baker, who was the best uk rider on a scorpa at the time, the timing was advanced a far as the slots would let it. I never quite went that far, about halfway.

I always found the water pump hose extrememly vunerable, doubt trimming the sump would be advisable. Birkett also made a pump housing that had the outlet turn the 90 degrees in alloy rather than the hose, making it less vunerable to rocks

Edited by faussy
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The Beta Rev3 plastic coil protector made a perfect protector for that water pump hose. You had to trim a little plastic of the long "tongue" part, and add a little spacer behind the securing bolt, but it was like it was made for it, and a perfect protector.

Wiseco made a piston that brought it up to 270cc which helped a lot. You had to bore the cylinder and have it re-nikaselled but it was a good mod.

Also a lot of the reed cages had no no reed stoppers installed so the reeds fluttered badly at bigger revs, so adding the curved reed stoppers helped at high revs. They were standard Yamaha stoppers we used to install from memory.

British bikes ha a bigger flywheel weight installed. USA and Australian bikes had the lighter flywheel which helped. Our were also advanced about 4mm from the timing mark, pretty sure UK delivered bikes were set directly on the timing mark.

Ohlins rear shock was the other thing - way better than that standard SACHS

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Thank you both.  Great info.

Still no word back from Birketts.

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I remeber the first round of the wtc i think 09 ish and Sam haslam had secured a scorpa factory ride. They had prepared a bike for him and it was tuned, very tuned, so much so it was virtually unrideable. Be careful what you wish for........

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3 hours ago, nigel dabster said:

I remeber the first round of the wtc i think 09 ish and Sam haslam had secured a scorpa factory ride. They had prepared a bike for him and it was tuned, very tuned, so much so it was virtually unrideable. Be careful what you wish for........

Honestly, more interested in the chassis mods.

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