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The TTR250 FAQ web pages -> TTR250 -> Repairs and maintenance -> Jetting help
Post Info TOPIC: Jetting help
TTRfan


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Jetting help
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truslack wrote:

Running a 52.5 pilot jet, and a 140 main, it misfires at midrange, and cuts out momentarily when changing from high to low throttle openings.

You can't be far out then! My friend had problems with his engine when he fitted an FMF as it made the mixture VERY lean and he burnt out his spark plug and was lucky no other real damage was done.

Any improvement if you give it a bit of choke? If so your mixture is probably lean.

If that makes it worse, does taking the airbox cover off make it run any better? If so, that means probably an over-rich mixture.

As has been said elsewhere, the only way we are ever going to get our jetting near 100% is to set the carb up on a dyno but that is unrealistic for most owners.

The best we can do is to run some simple tests to check whether the TTR is running rich or lean and adjust from there perhaps moving the needle a clip or two first and, if problems persist and jets are known to be clean, changing the main jet.

Brian



-- Edited by TTRfan on Tuesday 26th of June 2012 01:20:13 PM

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truslack


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Hey, I'm struggling to jet my 1995 250 Raid.

 

It has an FMF powercore 4 exhaust, and has had the top of the snorkel cut off. Can anyone advise on a good pair of jets for this setup?



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TTRfan


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truslack wrote:

Hey, I'm struggling to jet my 1995 250 Raid.

 It has an FMF powercore 4 exhaust, and has had the top of the snorkel cut off. Can anyone advise on a good pair of jets for this setup?

What main and pilot jets are you running at the moment?

Also, what problems are you experiencing?

Brian



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truslack


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Running a 52.5 pilot jet, and a 140 main, it misfires at midrange, and cuts out momentarily when changing from high to low throttle openings.



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Current: Suzuki RG 125 Gamma, Armstrong MT500, MZ ETZ300, Triumph Tiger 885i, Kawasaki GTR1000, Kawasaki GPZ750, CZ175 Trial, Yamaha TTR250 Raid
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truslack


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I've swapped between choke, airbox off, different airfilters etc, negligible difference whatever I do! It's really quite puzzling. I'm going to have to take the plug out again and see what it looks like.

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TTRfan


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Does it run better with the original exhaust on?



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TTRfan


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Just had a look at my parts catalogue.

4 different part numbers are given for carbs for the white TTRs!

I haven't checked whether the part numbers listed are still current.

Main jets:

Model 4GY1 up to frame number 008400 - 142

4GY1 (from 008401), 4RR1, 4RR2 - 147

4GY3 (Raid), 4GY5 (Raid), 4WA1 (Raid) - 145

Nozzles:

4GY1 and 4GY3 use 4GY-14341-00

4GY5, 4RR1, 4RR2 AND 4WA1 use 4RR-13341-00

Only one version of the petrol baffle is shown - 4GY-14153-00

Pilot jets:

4GY1, 4GY3 use 43F-14342-24

4GY5, 4RR1, 4RR2, 4WA1 use 43F-14342-25

All the other carb parts are common for all the models.

Brian



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truslack


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Having found the RAID standard main jet is 145, I am ordering a 147.5 and a 150 to try, hopefully this will sort it.

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