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The 2-Stroke Garage => Turning Wrenches => Topic started by: justthisguy on July 08, 2019, 11:41:12 AM

Title: Recommended jetting for RD250A y-boot Uni air filter?
Post by: justthisguy on July 08, 2019, 11:41:12 AM
The boots from my stock airbox slipped off my carbs, and it's been a PITA to get them back on--they'll just barely cover the intakes, and slip off with a light nudge. Figured I'll just the cut the knot and replace the airbox entirely with the Economy Y-boot filter kit with the Uni filter (https://www.economycycle.com/shop/yamaha-rz-350/fuel-and-airintake-yamaha-rz-350/air-filters/economy-y-boot-filter-kit-for-yamaha-rd250350400-r5-ds7-rz350/), but I'm guessing the carbs will need to be upjetted? Wondering what range I should be playing with.

Specs: 1973 RD250, completely stock, sea level. This bike is a daily rider and I'm not trying to wring every bit of performance out of it, so I don't mind if it's running a touch richer than optimal. Thanks all!
Title: Re: Recommended jetting for RD250A y-boot Uni air filter?
Post by: quocle603 on July 08, 2019, 06:52:04 PM
What is the jet spec for a stock RD250A?
Title: Re: Recommended jetting for RD250A y-boot Uni air filter?
Post by: m in sc on July 08, 2019, 09:13:32 PM
just use the y boot on the stock box..? then no need to rejet :twocents:
Title: Re: Recommended jetting for RD250A y-boot Uni air filter?
Post by: quocle603 on July 08, 2019, 10:02:17 PM
Try revive your yboot with alcohol and wintergreen solution. A lot of people have had good results with it
Title: Re: Recommended jetting for RD250A y-boot Uni air filter?
Post by: pdxjim on July 09, 2019, 01:10:58 AM
Quote from: m in sc on July 08, 2019, 09:13:32 PM
just use the y boot on the stock box..? then no need to rejet :twocents:

Look at the brain on this ^ guy!  :whoop:

... and for basic around town riding with stock pipes, the airbox offers the best performance.
Title: Re: Recommended jetting for RD250A y-boot Uni air filter?
Post by: 2t Fan on July 09, 2019, 02:55:46 AM
From my experience I feel that EC Y boot mechanism need a support clamping to the chassis. Or over a period from swinging the foam filter can crack and separate from the housing
Title: Re: Recommended jetting for RD250A y-boot Uni air filter?
Post by: justthisguy on July 09, 2019, 12:55:18 PM
Thank ye.

I put in the order last night, figuring I can use y'alls advice on trying to revive the old boot, fitting the boot from EC, or just throwing my hands in the air and using the y-boot kit in whole if I just can't get the boots to stay on regardless.

For the record, John @ EC recommended main jets at 150-160 and moving the needle clip to 4. Didn't mention anything about pilot jets, but I went ahead and ordered a pair of 30s just in case; it's been a while since I cracked open the carbs, but they were either 25 or 27.5 IIRC.

Per 2t Fan's note, I'll take a look when at fabbing up chassis support for it after it comes in, maybe finally put my 3D printer to use for something other than the super nerdy stuff I use it for.
Title: Re: Recommended jetting for RD250A y-boot Uni air filter?
Post by: m in sc on July 09, 2019, 12:58:35 PM
just fit the boot from economy, its the same boot, just not all shrunken and hard.

:twocents:
Title: Re: Recommended jetting for RD250A y-boot Uni air filter?
Post by: quocle603 on July 09, 2019, 01:38:17 PM
Those are similar jet setting I currently have.