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Refresher Course Needed

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Okay guys - I'm usually pretty good with the jetting portion of bikes, but this kida got me stumped. Probably due to not messing with jetting for a while.

2005 TTR 125L

air box mod

replaced stock end cap with open "EBay" cap

pilot = 17.5

main = 112.5

needle bottom clip setting

mix screw 2 out

So she bogs at the crack of the throttle, but then clears right after. I've tried screwing out the mix screw with little or no change. I've changed out the pilot with a 20, and it seems to run horribly at idle (even after adjusting the mix) but seems to bog a bit less (not much) at the crack of the throttle.

I have not messed with the needle, but didn't think this was the issue since a needle only comes on at 1/4 and up to 1/2 throttle. Really seems to be the pilot, but I don't want to go bigger than a 20 pilot. Any thoughts on what way to go? Could it be I should be going LEANER instead of richer? Seems to bog, so my first reaction was it is too lean.

Thanks!

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So she bogs at the crack of the throttle,

Thanks!

Does it bog when you open the throttle fast or does it do it when you open the throttle slowly too?? Does it bog under load or just in neutral? Answer these questions before we can begin to diagnose you jetting issue. Also take a look at the TT-R 125 sticky and the "Jetting 101" section at the top of the TT-R forum

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Yup... read it and made a print out bible of it.

As for the bog... it can happen running downhill, so no stress on the motor. (runs fine in neutral) Seems to do this at a crack of the throttle which leads me to the pilot jet. Gets worse on fast roll on but still does it as I slightly crack it.

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The stock pipe with the "e-bay" tip doesn't flow as well as say a powercore 4 or a pro circuit T-4 and I think those jetting specs may have been established around the assumption of an aftermarket pipe. Go down in the pilot and it should be fine.

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For a stock motor with the basic BBR filter and airbox mods, the ticket is a Keihin 24mm carb off a Honda 200x. It's night and day difference. Probably around 1 hp improvement. And on a 7.3hp bike, that's a lot. It jets in seconds and runs perfect and revs to the moon. You need a few mods to complete it, but it's well worth it. Although you need a decent pipe to get the full benefit out it.

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Please enlighten us on the "few mods to complete it" statement.

fergy

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JSanfilippo

So you think I'm running rich? I'll give it a go. I went back to the 17.5 from the 20, but I'll try the stocker just for testing.

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Sounds like the jetting is close with the 17.5 pilot. Have you tried moving the clip down one on the needle (richer) or up one (leaner)?

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Consider the needle, byggd has the right idea. Does this bike have an accelerator pump? sounds to me like it could be an issue in this area. My wifes TTR 250 had a similar problem it was the accelerator pump diaphram. If it has an AP make sure it is working and timed correctly.

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there is no accelorator pump on the carb, the carbs are very tempermental, i have an '03 with a home made version of the exhaust tip & the air box mods & it's rejetted & it is very responsive, pull the choke does it get any better? if so you need to go richer, try to turn the screw out some more to see if it gets better

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Needle was set at bottom clip (richest setting) I'll try the 17.5 with the needle set at the middle and then top.

No pumper on these carbs. Pulling the choke wants ti kill it so maybe it's a richness issue... strange as I remember this particular "feeling" as being the opposite problem. (too lean)

Well, anything is worth a try. My 2004 TE Husky pumper was nortorious for this as well. Ended up being a "drill out" adjustment on that one.

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Needle was set at bottom clip (richest setting) I'll try the 17.5 with the needle set at the middle and then top.

No pumper on these carbs. Pulling the choke wants ti kill it so maybe it's a richness issue... strange as I remember this particular "feeling" as being the opposite problem. (too lean)

Well, anything is worth a try. My 2004 TE Husky pumper was nortorious for this as well. Ended up being a "drill out" adjustment on that one.

It can be hard to distinguish between a bog and a cut out. Bog is when you dont have enough air and the engine "gurgles" never stops running just seems like it has no power.

A lean situation would lead to a lot of back popping on decel and when WOT you would have the engine cutting out then coming back to life it wont feel like a los of power it would feel like the engine is sputtering turning on and off rapidly.

It deffinatly sounds like a rich problem on the pilot.

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Thanks for all the info, riders. I gotta say the the TTR section of this forum kicks butt.

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Update... previous owner had dropped the clip on the needle to the bottom setting and I thought this was right on. (richer) Decided to experiment and put it back to the middle. RIGHT ON... bog is nearly gone. Some fine tuning on the mix and I should be right there.

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