Xr650r difficulty starting on a cold night

[dbc]

On my xr650r I ran a 178 main and a 70 pilot, can't remember the needle.
Because there is no accelerator pump, fine tuning the fuel screw is a little more difficult than a pumper carb.
Out just a tad too much- bog, in just a tad too much- bog.
I found the sweet spot with the 70 pilot right at 7/8 of a turn out.
I did try a 68s pilot, but never got it just right.
With the 68s, try 1~1 1/4 out for starters.
As stated before, make sure the bike's completely warmed up.

While you have the carb off, look down into the intake to see if it's the California "restricted" unit, (the California part tapers down to a slot inside) or the strait thru unit. If it hasn't been changed to the free flowing manifold, now's the time.

 

[bobl]

Something often overlooked is the fuel level. If it's a little low, it can make starting harder. I had a KLX for a while that was difficult to start after sitting for a week. I would turn on the gas, and then shake the bike while holding the front brake. That did two things. One it made sure that the float valve was shaken loose so the carb could fill, and it also sloshed gas fumes into the carb throat. Since it's free, you might try that on a cold start.

Another thing you might try is priming the carb with gas. That will indicate if you are lean, ore rich. If it pops to life after a prime, I would look at fuel level. If it's worse, probably too rich. Easy check, and again, free.

 

[Sharky]

So c&d cycle in San Diego didn’t do a good job on the bike. For some reason they kept the main jet oem and do a 175 pilot. No clue about the needle. I called xrsonly and they told me to switch to a 68s/178 and change needles. So I’m gonna wait for that to come in and pull the carb off and clean everything while I’m at it. I also decided to buy a Mikuni 40mm pumper carb off eBay used for a good deal. I’m gonna rebuild that one while on my off days and switch to that eventually Down the road.

Anyone got any experience with pumper carb jetting and tuning? I read on advrider that people have a difficult time with jetting and tuning it.

Also recognize that recommendations are just places to start. My XRL ran WAAAY better jetted richer than most everyone suggested and still gets 45-50mpg easy.

 

[menG]

I’ll give you suggestion a try thanks dbc I’ll have the jets next week and take everything apart. Thank you.

I move my bike out of the parking garage by foot prior to kick starting it because the hallway is super narrow and there’s always foot traffic there so the gas is moved around prior to starting. Thanks bobl

Hopefully it’s the correct suggestion haha. If not I’m gonna rebuild that tm40 carb and take it to a shop to jet it for me and get through the headaches. What jets were you using sharky?

 

[sportbiker929]

Idle mixture is set too lean

 

[Sharky]

I’ll give you suggestion a try thanks dbc I’ll have the jets next week and take everything apart. Thank you.

I move my bike out of the parking garage by foot prior to kick starting it because the hallway is super narrow and there’s always foot traffic there so the gas is moved around prior to starting. Thanks bobl

Hopefully it’s the correct suggestion haha. If not I’m gonna rebuild that tm40 carb and take it to a shop to jet it for me and get through the headaches. What jets were you using sharky?

I forget what jets i settled on. Its been a few years. Regardless, my experience is on an xrl not a real bike like the R. I never owned an R, but jetting is jetting on those things

 

[menG]

I forget what jets i settled on. Its been a few years. Regardless, my experience is on an xrl not a real bike like the R. I never owned an R, but jetting is jetting on those things

Jetting is a pain man. I went to a shop close by and the guy told me he charges 250-300 to rejet. I rather just do it myself and save 200. Buddy that works on dirt bikes a lot told me to do it myself and rebuild the pumper carb once I get it since it’s not difficult. The L is a dead reliable bike. It just sucks with the emissions where they couldn’t make it better since everything is so strict now adays.

 

[usedtobefast]

Like others have said, it is worth it do do a valve clearance check. Probably a good idea anyway, and if all OK, then you know you have no issues there. And a clean airfilter.

Properly jetted, on a ~60 degree day, the bike should take full choke, no throttle twisting, start up, and start blubering (needing to come off of choke) at about 30-45 seconds after starting. Then you know the pilot jet and air screw and idle are set right. And if you get it working like this, then the cooler temp cold start will work fine.

If on that ~60 degree day, you don't need any choke to start, you have things too rich.

As for you rejetting vs. paying for it ... do it yourself! I would suggest just working on the pilot jet, air screw, and idle setting at this point. Don't worry about the needle and main jet until you getting the cold start sorted out.

I owned one for ~2 years, and the stock carb is fine, so you should be able to sort it out.

 

[menG]

Like others have said, it is worth it do do a valve clearance check. Probably a good idea anyway, and if all OK, then you know you have no issues there. And a clean airfilter.

Properly jetted, on a ~60 degree day, the bike should take full choke, no throttle twisting, start up, and start blubering (needing to come off of choke) at about 30-45 seconds after starting. Then you know the pilot jet and air screw and idle are set right. And if you get it working like this, then the cooler temp cold start will work fine.

If on that ~60 degree day, you don't need any choke to start, you have things too rich.

As for you rejetting vs. paying for it ... do it yourself! I would suggest just working on the pilot jet, air screw, and idle setting at this point. Don't worry about the needle and main jet until you getting the cold start sorted out.

I owned one for ~2 years, and the stock carb is fine, so you should be able to sort it out.

Greatly appreciate your advice! I just got the needle main and pilot jet in today. I’m gonna pull the carb Monday and redo everything.im going to check the valves Tuesday after I finish with the carb。let’s pray it’s not the valves haha

 

[1962siia]

If you have a full fmf system on the bike it might be worth while contacting them for a jetting recommendation. If its starting easy in mild weather and when warm you aren't too far off I bet.

Good luck!

 

[menG]

If you have a full fmf system on the bike it might be worth while contacting them for a jetting recommendation. If its starting easy in mild weather and when warm you aren't too far off I bet.

Good luck!

Thank you i didn’t know fmf could help I’ll give them a call tomorrow when they’re open.

 

[menG]

I didn’t get a chance to call fmf today because of how many stripped bolts were on the undercover and taking the tank off was just a huge pain with the bolt being so hidden in there with an oversized radiator lol. But I took the carb off and got it all apart. It is running a 175/68 with the clip on the same needle I got at the second from the top. I was advised by xrsonly to use the third position and I cleaned everything out on the inside. There’s some smudge on the tube where the needle sits got that all cleaned. Tomorrow I’m going to pull the plug to see the color if it’s running lean or rich and change it out since I have everything off. Just a question regarding the jetting. With a slow jet and going from 175 to 178 is it going to make a big difference with cold start?

 

[Sharky]

I didn’t get a chance to call fmf today because of how many stripped bolts were on the undercover and taking the tank off was just a huge pain with the bolt being so hidden in there with an oversized radiator lol. But I took the carb off and got it all apart. It is running a 175/68 with the clip on the same needle I got at the second from the top. I was advised by xrsonly to use the third position and I cleaned everything out on the inside. There’s some smudge on the tube where the needle sits got that all cleaned. Tomorrow I’m going to pull the plug to see the color if it’s running lean or rich and change it out since I have everything off. Just a question regarding the jetting. With a slow jet and going from 175 to 178 is it going to make a big difference with cold start?

My thought the 178 is the main and i doubt that will make a difference. I think you need to focus on the small jet and moxture screw initially, then needle height and main for on throttle response-running issues.

 

[menG]

My thought the 178 is the main and i doubt that will make a difference. I think you need to focus on the small jet and moxture screw initially, then needle height and main for on throttle response-running issues.

i don’t think it will make a big difference as well since it’s not a huge step up. But then I don’t know how going from a 68 to 68s with a notch adjusted on the needle would change things.

I learned a great lesson today. To not buy used carbs off eBay to save some money and rebuild it myself. Get a tm40 carb off eBay for 150 that needs a rebuild. Take off the drain plug on the bottom and the needle jet and main falls out. Look at the threads and it’s snapped lol. The guy says it’s in good condition just needs a rebuild. Rip

 

[usedtobefast]

Going from a 175 main jet to a 178 will make zero difference in starting.

Starting will be all about the pilot jet (slow jet), idle, and air screw setting. And clean airfilter, correctly adjusted valves, good gas, good spark plug.

Did you buy new jets? Many times going from an old "been clogged and been cleaned" pilot jet to a new pilot jet does wonders. Just because you can see daylight through the holes in a jet does not mean it is the correct size.

Meaning, a new 68 pilot has zero gunk anywhere, an 8 year old used 68 pilot probably flows less gas due to some residual gunk on it.

Have you found a good jetting chart or info?

For valve adjustment, here is a decent video:

https://www.youtube.com/watch?v=tZECP_trzgc

 

[Tom G]

i don’t think it will make a big difference as well since it’s not a huge step up. But then I don’t know how going from a 68 to 68s with a notch adjusted on the needle would change things.

I learned a great lesson today. To not buy used carbs off eBay to save some money and rebuild it myself. Get a tm40 carb off eBay for 150 that needs a rebuild. Take off the drain plug on the bottom and the needle jet and main falls out. Look at the threads and it’s snapped lol. The guy says it’s in good condition just needs a rebuild. Rip

Ask him to take it back since he sold it in "good" condition. Ebay will help you get your money back. Did that a few times when the seller tried to offload his trash on eBay and misrepresented it in the description.

 

[augustiron]

I recall it is important to have a 68S and not just a 68, they are different as the S has emulsion holes that are needed.

Quick search...
https://thumpertalk.com/forums/topic/365779-68s-vs-a-68-slow-jet-for-a-xr650r/

 

[ScottRNelson]

Did you buy new jets? Many times going from an old "been clogged and been cleaned" pilot jet to a new pilot jet does wonders. Just because you can see daylight through the holes in a jet does not mean it is the correct size.

Meaning, a new 68 pilot has zero gunk anywhere, an 8 year old used 68 pilot probably flows less gas due to some residual gunk on it.

After purchasing my XR650L eleven years ago, I put new jets in it, even though they were the same sizes as what was already in there. It ran better when I did that.

Jets aren't that expensive that you can't just put in what you know will be good. Jets ordered from https://jetsrus.com/ are all under seven bucks for my bike and I only need two of them total.

 

[OaklandF4i]

I recall it is important to have a 68S and not just a 68, they are different as the S has emulsion holes that are needed.

Quick search...
https://thumpertalk.com/forums/topic/365779-68s-vs-a-68-slow-jet-for-a-xr650r/

Wow... I've always wondered about the "s" on some jets and heard a lot of conflicting explanations. Finally, the real info and great linked thread to read. Fantastic info!

According to that thread, the 68s is slightly richer than the regular 68 due to the emulsion holes. The ''s" jets are Honda specific part numbers 99105-MBN-0680 for the 68s and 99105-MBN-0700 for 70s.

Sounds like DBC got it right with the regular non "s" 70 pilot which would fit right between the 68s and 70s on the scale.

This thread delivers.

 

[menG]

Going from a 175 main jet to a 178 will make zero difference in starting.

Starting will be all about the pilot jet (slow jet), idle, and air screw setting. And clean airfilter, correctly adjusted valves, good gas, good spark plug.

Did you buy new jets? Many times going from an old "been clogged and been cleaned" pilot jet to a new pilot jet does wonders. Just because you can see daylight through the holes in a jet does not mean it is the correct size.

Meaning, a new 68 pilot has zero gunk anywhere, an 8 year old used 68 pilot probably flows less gas due to some residual gunk on it.

Have you found a good jetting chart or info?

For valve adjustment, here is a decent video:

https://www.youtube.com/watch?v=tZECP_trzgc

Thanks for info! I called xrsonly and hey suggested running a 68s and 178 needle 3rd position right in the middle. The previous setup was 68 175 and 2nd from top. I checked the jets they were all clean. The shop said they just went through the whole carb in the rebuild but I could never trust anyone’s words and rather go through it myself. The carbs on the bike right now but I still have to go to the hardware store and get a spark plug socket and an extension to get the tank back on then bolt the radiator and guards back on. But I’m going to try to start it once I get the tank back on and see if it made a difference. They had a good site for jetting but recently went on there and it’s been taken down for some time do you have the chart handy by any chance?