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Sorry, another jet Q - 1990 XR280R

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Hi all

Apologies for another jetting question but I've searched and not quite found an answer.

I have a 1990 XR250R with a 280 kit on it. I'm about to fit an aftermarket pipe and lose the snorkels if they're still there (only had the bike a couple of weeks).

Carb is stock and I'm at sea level or there abouts.

From what I can gather a 135 Main Jet and 48 pilot would be the go on the post 96 bike but I read that the pre 96ers a different.

This is my first play with XR carbs so any help appreciated. :applause:

Cheers

Andy

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TTT

OK the pipe purchse didn't work out so I'll be de-baffling for now. Assume thhat I'll still need a re-jet. Any ideas?

Thanks

Andy :applause:

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I have had 3 280s, they each had their unique characteristics. Main jet requirements ranged from 138 to 142, pilots 48 to 52, UNI or Twin Air filter, snorkel removed, exhaust opened up. Elevation here is 700-900 ft.

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OK just got myself a Big Gun can and header pipe :thumbsup: so the jetting Q is back on!

Creeky, are these for a pre 95?

Any other advice on jets for a 90 280 with a soon to be pipe?!?

Cheers

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OK just got myself a Big Gun can and header pipe :thumbsup: so the jetting Q is back on!

Creeky, are these for a pre 95?

Any other advice on jets for a 90 280 with a soon to be pipe?!?

Cheers

Sorry, I should have specified. My first 280 was an '87, the others post '96. I jetted the '87 just like the later models.

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My 94 XR277L with a 95 R carb ended up at 138 main, 40 slow, Needle at 2 down from center. And the Fuel screw 1.5 turns out. I have std R headers, aftermarket exhaust, no snorkel and a uni filter. Runs great, idles as low as I want it too and leaves the plug a nice smoke brown. I may play with the jetting some more this summer and see how rich I can go before it runs poorly and then back off. I also want to experiment with different needles.

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So the Big Gun jetting sheet for the full system (yep I have headers as well) says 132 Main and 40 Pilot with stock needle and air screw. Assume this would be for a 250. Does a 280 kit make any difference in jetting?

Cheers

Andy

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Finally fitted the full system yesterday (love it!!) whilst I was in there I dropped the float bowl off the carb and a had a look at the current jets. 135 Main and 45 Pilot. Starts/runs/idles fine, sounds awesome and if it aint broke dont fix it. But those jets seem kinda high (well the 45 especially).

Whats the downside of running too big a jet?

PS the local bike shop said to run 128/40 so now I'm really confused :S

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I decided to look in my carb today too.

I have a 1990 XR250 and the main was a 125. I checked my 86-95 XR250R honda OEM Service Manual and it indeed indicated stock for this range of bike is a 125 main.

I have a Cobra pipe, ground out header welds, de-snorkeled and Uni-Filter so I am going to try out a bigger main. Maybe a 128....maybe a 130.

I do agree that the main jet most recommend is 148, that must be post 96 cause that seems a LOT bigger.

Any thoughts?

Mike

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