Project 1989? FZR250 2KR

My 2KR BDS26 carby's have the round style float's, they're set to 16mm when just touching the pin

 

Do you have a pic of your float's too see what angle the tab's are currently set at?



Just looked at the 2KR service manual and it doesn't have the float height setting's or fuel level's(plus it's in Japanese)
But in section 4, page 6 it show's a pic of the fuel level against the side of the carby

But i did find this on the XJ Rider Yamaha Seca 11 site, they use the same carby's Mikuni BDS26 (later model's use the BDS28)
It list's the float height's as being between 6.2mm to 8.2mm which is way off what my carby's were set at (the one i checked was set at 16mm)
(but i don't know if anyone before me has adjusted them either or even if they've been run at that ?)
http://www.xjrider.com/viewtopic.php?t=7309





Before adjusting (too high)

After adjusting to 7.2mm (mid way between 6.2mm and 8.2mm)

 

Fill the hole with something like Devcon and when set redrill and tap a thread in it. Just dont overtighten the screw.

 

Seca carbs are not downdraft like the FZR's so the float height/level values are not comparable.

 

Yeah, i just posted those pic's to show how the float height's are checked.
Sorry, should have mentioned that above or took my own pic's for you
I didn't look all the way through the 2KR service manual either to find the float height spec's

My BDS26 were set at 16mm, but as ruckusman pointed out the factory spec's are 17.5~19.5mm (so mine were set 1-2mm too high)

 

The angle the BDS26 carby's fuel bowl mounting face need's to be on is around 8-10 degree's,
i found that sitting a roll of 22mm masking tape under the part where the throttle cable end sit's it's about right



Zoomed in on the same






Did you check when you cleaned the carby's that the little mesh filter on the inside of the seat's are clean? (needle/seat)




And that the rubber tip's of the needle's are still soft ?

 

And make sure that the retaining clip on the end of the needle has the 2 little loop's facing toward's the float, not away from it
Sometime's they can foul on the tip of the float's tang and not let it close properly

Also check the pin's alway's come back out the end of the needle's too.
3 of mine were stuck in, so i had to soak them in carby cleaner and blow them out with compressed air quite a few time's before they'd automatically return to the out position

 

That is quite a big drop, 1 tooth off the front sprocket is like adding 3 or 4 teeth to the rear
You will only be able to get about 60km/h out of first gear instead of 75km/h
The chain will need to be shortened to suit as well

How much would you ride it in top gear ?
My FZR sit's on 9000rpm @ 100km/h, having a 14t front sprocket would make the rev's sit on about 11200 rpm

 

Yeah the smaller front sprocket will make the chain really dig into the rubber chain slider at the front of your swinger like Greyimport said.
If you really want lower gearing you could try to find a bigger rear sprocket, that'd solve the issue with the chain slider ^.
You will need a new longer chain if you fit a bigger rear sprocket too, a rear sprocket will cost you around $70 plus the new chain.

Have a look here at the Gearing Commander website
http://www.gearingcommander.com

On the top row below the header, select the bike brand, model and engine size
The 1990 model FZR250 is there, then select km/h and select enter gearing.
It show's the rev's v's speeds through each gear.
In the second selection down you can put an alternative front sprocket by changing the 56t rear sprocket to say a 60 t
Then the section below it calculates the new revs/speed through each gear
Click on the middle one to see what the changes will be


I just put the sprocket sizes 14t F / 56T R into a torque/speed calculator and that gearing will give the bike 21% more torque
It will also lose 21% off your top speed.