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Help with throttle lag

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Hey guys, I am a proud new owner of an XR650r. I actually traded my R1 for it. I think I took a bit of a hit money wise but who cares. The XR is way more fun. It's super moto'd, uncorked with full fmf Power bomb exhaust. It's quick for sure. I guess I do need some advice though. I have a problem with throttle lag with anything under 60km/h. Most slower speed in all rpms it takes a minute for the go to happen when I turn the throttle. it's quite jumpy, makes it really hard to cruise at slow speed with out the hurky jurky's. It seams to make really good power in the low and mid once it comes on and it starts with no issues. It does seem to have a flat top end. just falls out at about 6500rpm, and every now and then it just turns off as I am deceling with a loud pop. It's got K;n filter, airbox mod and exhaust but not sure what else is in there as far as needles and such. Any help or advice would be appreciated. I know it's got the keihin carb(stock I think)

Another Question I have is I have no mechanical experience, just a brand new socket set(I good one though 🙂. Do you think it is wise to get into the carbs and needles and such. I really have no idea what I am doing, but I have the mechanics manual for the XR650R and I don't think I am that stupid. But I can be at times. what do you guys think?

Thanks eh for the help,

Cheers

Derek

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Hey guys, I am a proud new owner of an XR650r. I actually traded my R1 for it. I think I took a bit of a hit money wise but who cares. The XR is way more fun. It's super moto'd, uncorked with full fmf Power bomb exhaust. It's quick for sure. I guess I do need some advice though. I have a problem with throttle lag with anything under 60km/h. Most slower speed in all rpms it takes a minute for the go to happen when I turn the throttle. it's quite jumpy, makes it really hard to cruise at slow speed with out the hurky jurky's. It seams to make really good power in the low and mid once it comes on and it starts with no issues. It does seem to have a flat top end. just falls out at about 6500rpm, and every now and then it just turns off as I am deceling with a loud pop. It's got K;n filter, airbox mod and exhaust but not sure what else is in there as far as needles and such. Any help or advice would be appreciated. I know it's got the keihin carb(stock I think)

Another Question I have is I have no mechanical experience, just a brand new socket set(I good one though 🙂. Do you think it is wise to get into the carbs and needles and such. I really have no idea what I am doing, but I have the mechanics manual for the XR650R and I don't think I am that stupid. But I can be at times. what do you guys think?

Thanks eh for the help,

Cheers

Derek

Welcome to TT Derek!

First off, it sounds lean. The carb needs to be pulled and checked for what jets are in it now.

What exhaust does it have?

Please read the FAQ at the top of the XR600/650 forum index list. There are a few things in there to help you out.

Rich.

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Hey Thanks for a quick reply. I've looked through the FAQ, definitely some usefull full info info there. It's got an FMF powerbomb exhaust with a sound deadener in the tip. The major problem for me is that when I roll off the throttle and decel it's great but when I roll back on the throttle it lags pretty bad a slow speed. I roll on then about a second the go comes and it's a decent jurk, enough to make slow speed pretty impossible without the clutch. I'll look around here some more. Is there a simply fix to being to lean? Do you think the exhaust sound deadener in the tip would have and effect? I may pull the carb but I don't have a tourque wrench so I am nervouse about doing it!

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Hey Thanks for a quick reply. I've looked through the FAQ, definitely some usefull full info info there. It's got an FMF powerbomb exhaust with a sound deadener in the tip. The major problem for me is that when I roll off the throttle and decel it's great but when I roll back on the throttle it lags pretty bad a slow speed. I roll on then about a second the go comes and it's a decent jurk, enough to make slow speed pretty impossible without the clutch. I'll look around here some more. Is there a simply fix to being to lean? Do you think the exhaust sound deadener in the tip would have and effect? I may pull the carb but I don't have a tourque wrench so I am nervouse about doing it!

The only way to really cure lean conditions is to rejet. Check the jets in the carb for the numbers.

It's an easy job, no torque wrench needed.

Just realize that the carb is a soft metal. Don't over tighten anything.

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yeah I havn't got into the jet's yet, going to wait till tuesday incase I need parts. Just noticed something else. After a good ride today I noticed a lot of black dust from the exhaust on the plastic and the exhaust tip. It also popped a bit when decel from High speed. I know I won't know much but figured maybe it might help asking. It does pull hard though, wheelies in first and second but not it third, even if I bounce on it. Tops out a 160 on my vapor gauge. The only thing that bugs me is the throttle lag issue.

thanks again for the help.

cheers

Derek

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Hello! I have the same problem with my 03' XR650R. Just Bought the bike, and im trying to sort out all the bull that the last guy did. The bike has a Pro circuit T-4 can with some kind of header, not sure which one. Has a uni air filter and i just installed a dynojet jet kit, Dynojet needle third position with a 175 main. Has a 65s slow jet(thinking of changing it to a 68s). And im 1.5 turns out on the idle mixture screw. (Im at sea level by the way) It was doing the same thing before i changed the jetting and is still doing the exact same thing now. Back fires alot on decel which led me to find a exhaust leak. Haven't attacked that yet, but will soon. The exhaust has no end cap in it which im sure makes it run more lean then with one. This problem is really annoying. Hard to go around a corner when the thing wants to jump forward when you role on the throttle. If you get any info on a fix for this little boggle that we both have, please let me know. Ill be sure that ill do same!

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The main that i pulled out of it was much larger than 175 thats in there now. i think a 180, maybe! Thank you for the quick reply! Would a 68 or 68s be enough for the pilot? Do you know the difference between the 68s and 68?

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68 or 68s should work fine. 70 works but makes the cruise mix super rich.

Is this a California model with the smog stuff? If it is and the smog stuff was removed make sure the vacuum nipple, located on the head on the intake port, is sealed off well. When I bought my bike this was just open and caused all kinds of low speed problems. I removed the brass nipple and replaced with with a stainless allen screw.

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Checked the vacum nipple. It was removed. A screw with a washer was in its place. just ordered a 68 pilot. Going to take the exhaust off and fix the leaks. To be continued...

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Bigger pilot and possibly a bigger main would help you.

My 70 pilot runs really good in my bike. It is a 70 not a "70s". It might be because I have a modded airbox side cover:excuseme:

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