Xr650r difficulty starting on a cold night

[menG]

Hello veterans! I picked up an xrr a month back and got really familiar with the kickstart and everything on the bike. Whenever I get off work late at night, I try to start the bike with the choke on after kicking the engine through a couple times to clear it. The bike does not like to start with the choke on. But if I play with the idle screw and turn the choke on it still doesn’t turn on. Might spudder for a split second before dying. Then if I turn off the choke and turn the idle screw up it will start but bogs for a second or two then dies. If I apply light throttle to hold up rpms it warms up a bit then it will idle. The bike on a hot day or when the engine is hot will start on one kick.

I’m not great with carbureted bikes. I had a 696 monster a while back and with choke fully on it never had an issue even under 40 degrees starting. But this bike with it being kick start and all really works up a sweat for me after work lol.

The shop I got it from just rebuilt the engine. I’m just wondering if the carbs jetted properly or tuned properly. Is it running rich that’s causing this issue?

Thanks in advance for chiming in!

 

[Free_Bird]

Check easy stuff like air filter. Ride out at tank full of gas with some carb cleaner in it. Check Carb vacuum lines for bad connections.
Vacuum line leak causes very rough engine.

My experience with Carbs is their very temperamental when starting.
Just the right amount of choke depending on a start attempt.

Cold engine full choke and moderated off as the engine warms up.
First attempt Cold start is full choke.
Second attempt Cold start is full choke.
Third,fourth and fifth attempt Cold start quarter to half choke.

Hot engine without choke but a little throttle helps start.

Over use of the choke can flood foul the Start. The Sparkplug becomes wet with gasoline and doesn't spark. The solution is to wait for the gas to evaporate. Waiting ten minutes before trying to start the engine with little or no choke.

A FYI and not required, but if the bike is being a pain this is most sure thing.

A technique used on very cold engines and ones started up after a long time. Spray Starter Fluid directly in the carbs. removing air filters to get to the carb is okay once in while. For more frequent use of starter fluid modding done to just get a small tube to spray in the carbs without removing parts. On the XR650r mod might be a small hole drilled(1/8") on the Airbox or rubber boots near the carb. It needs to allow a small diameter rigid tube that sprays the starter fluid into or very close to the carbs. The engine will Start quickly and it still needs adjusting throttle or choke to warm up.

What is going to fix it ? A start would once the engine is warmed up set the idle to spec. Only change choke or throttle to get it started.

Because of emission standards there may be covers over idle A/F mixture screws. Check with XR650r riders about this mod. It amounts to a small metal disk held by adhesive that covers Idle Mixture Screws. Using a drill to pierce a hole in the middle of the disk to pry the disk out. Careful there is a screw head on other side of that disk. The disk is very thin and is soft aluminum.
Next have to note the amount of turns changes from factory set. Some use a reference number of turns from screw stop. Be careful the mixture screw has a arrow like end that can easily break the soft aluminum stop in the carb. Only light tightening to notice it has met the stop.
Hopefully one just does counterclockwise adjustment from the factory setting. A half turn counterclockwise will make a difference. A full turn counterclockwise for more troublesome starters.

Note this mod only changes idle characteristics. For better overall performance it is a re-jetting mod.

 

[ScottRNelson]

Another source of help on this issue is on ThumperTalk in the XR subforum. You'll definitely find people familiar with that particular bike there.

I've found that it often takes a while to find out exactly what a particular bike wants when you start it. I've had my 2001 XR650L for 11 years now and I know exactly what it needs in all conditions. Last summer I acquired a 1997 XR650L and it doesn't behave exactly the same. Takes a bit more to start it after it has sat for a few days. I'll probably have that one figured out by the time I sell it next spring.

I know this doesn't help you, but the number one reason I bought the L rather than the R is that I have too much experience with kick start bikes that didn't want to start under various conditions and just got tired of it.

And when all else fails, you can always squirt a few seconds worth of starter fluid into the intake. I've done that too many times.

 

[menG]

Thanks for the input guys. I’ve posted on thumpertalkk last night still waiting for more responses. I searched on barf and apparently a lot of users has had an xrr before haha.

Kick starting the bike isn’t really the issue. It’s just the bike is uncorked, has some nice bits on there. Fresh engine rebuild and just doesn’t like to start in the cold. Choke does nothing is the thing that really gets me a little upset.

After acquiring the bike I have went over all the wiring and changed a headlight that isn’t crap at night.

 

[ST Guy]

By uncorked, I assume you mean an aftermarket pipe/muffler.

Has the bike been rejetted? Sometimes adjustments need to be made after opening up the exhaust. Generally speaking, bikes come from the factory on the lean side. Lean it out more by opening up the exhaust and you can end up with cold starting issues.

 

[ScottRNelson]

By uncorked, I assume you mean an aftermarket pipe/muffler.

Has the bike been rejetted? Sometimes adjustments need to be made after opening up the exhaust. Generally speaking, bikes come from the factory on the lean side. Lean it out more by opening up the exhaust and you can end up with cold starting issues.

I don't see how a pipe will effect idle speed in any way. In other words, the speeds the engine runs when trying to start the thing.

Intake changes could affect it a little bit, though.

 

[OaklandF4i]

A cold engine generally needs a slightly richer fuel mixture to start, same with ambient air temps. The fact that you have to adjust the idle up and give it very slight throttle to get it running when cold only confirms that it wants a bit more fuel when the air temperature drops and engine is cold.

There are a few possibilities.

Its possible the choke isn't operating correctly. What carb do you have in the bike? Have you pulled it to check the chokes operation? Always good to eliminate the obvious. :thumbup

Do you require any choke to start the engine cold in warmer ambient temperatures?

What pilot jet do you have in the carb (vs stock) and have you adjusted your fuel screw correctly (plenty of online Faqs or instructions to do so.) How many turns out is your fuel screw?

Have you tried to use only 1/4 or 1/2 choke after work when the ambient temp is colder? It's possible that full choke is too much fuel.

Its also possible that either the pilot and or fuel screw setting is too lean.

Assuming the motor, head, carb and everything else is good.. cold starting a large thumper is about proper tune, finding the right settings, and technique.

 

[menG]

Hey guys thanks for you inputs on resolving the cold start issue on my bike. I enriched the mixture in the carb by turning it all the way to the right until it dies then gave it a turn and a half back. The bike feels like it was running more lean than rich to correct myself. So I cold started it after it rained in so cal and it seems to work better with the choke on now. I need to rejet it. I don’t the the shop I got the bike from rejetted the carb since the engine rebuild.

I pulled out the drain plug on the shifter side today while doing an oil change and found some metal shavings on the magnetic drain plug. Now I’m at a road block. The engine was just rebuilt 1000 miles ago. Should there be some metal shavings on the magnetic drain plug? I’m just curious now since it is a rebuilt engine. If anyone Have any past experiences that would be great!

 

[Maddevill]

If that oil was in the bike since the rebuild you may be ok. Drain it and refill it and ride it for a bit. Pull the drain plug back out and if you see no metal you're good to go. If you see more metal you have problems. New motors often shed bits of metal while breaking in.

Mad

 

[menG]

If that oil was in the bike since the rebuild you may be ok. Drain it and refill it and ride it for a bit. Pull the drain plug back out and if you see no metal you're good to go. If you see more metal you have problems. New motors often shed bits of metal while breaking in.

Mad

Thanks for heads up! I’ll keep an eye out next week when I tilt it over to check. It’s raining over here in la I won’t be riding until it clears up.

 

[Sharky]

A cold engine generally needs a slightly richer fuel mixture to start, same with ambient air temps. The fact that you have to adjust the idle up and give it very slight throttle to get it running when cold only confirms that it wants a bit more fuel when the air temperature drops and engine is cold.

There are a few possibilities.

Its possible the choke isn't operating correctly. What carb do you have in the bike? Have you pulled it to check the chokes operation? Always good to eliminate the obvious. :thumbup

Do you require any choke to start the engine cold in warmer ambient temperatures?

What pilot jet do you have in the carb (vs stock) and have you adjusted your fuel screw correctly (plenty of online Faqs or instructions to do so.) How many turns out is your fuel screw?

Have you tried to use only 1/4 or 1/2 choke after work when the ambient temp is colder? It's possible that full choke is too much fuel.

Its also possible that either the pilot and or fuel screw setting is too lean.

Assuming the motor, head, carb and everything else is good.. cold starting a large thumper is about proper tune, finding the right settings, and technique.

A quick reading of the OP post, makes me think this bike is already jetted pretty rich and the choke it too much for it to start.

 

[augustiron]

As a former XR650R owner, i feel your pain.
I never got the hang of starting mine with the stock carb, then engine mods like the high compression 680 kit, stage 3 cam, etc made it even harder.
I finally put an Edelbrock Quicksilver carb on it and got it dialed and it ran better, and started easier hot and cold.

They are quirky beasts to figure out.

 

[menG]

Well. Still didn’t fix the cold start issue. Choke still don’t do jack. Makes me feel like the bike doesn’t want to start cold late in the night. Seems like it’s not jetted correctly and I don’t know if the previous owner jetted it. This bike is getting me frustrated.

As a former XR650R owner, i feel your pain.
I never got the hang of starting mine with the stock carb, then engine mods like the high compression 680 kit, stage 3 cam, etc made it even harder.
I finally put an Edelbrock Quicksilver carb on it and got it dialed and it ran better, and started easier hot and cold.

They are quirky beasts to figure out.

Yeah. It’s making me want to pull my hair out lol. I haven’t seen any edelbrock carbs but I’ve heard some great things about the lectron carbs. Suppose to be better for cold starts and better mpg. Self adjustment and all the good stuff. Anyone got experience with their gen 2 carbs? The only thing is the 900$ price tag for the kit with tax.

 

[menG]

A quick reading of the OP post, makes me think this bike is already jetted pretty rich and the choke it too much for it to start.

That’s what I thought it was jetted too rich and the choke doesn’t work because of that. But then I played with the carb adjuster and it seems like it was running lean. I turned it a bit to get it more rich but the choke still does nothing lol. Oh well I’ll figure it out eventually. Just have to play with it on my next offday.

 

[Sharky]

That’s what I thought it was jetted too rich and the choke doesn’t work because of that. But then I played with the carb adjuster and it seems like it was running lean. I turned it a bit to get it more rich but the choke still does nothing lol. Oh well I’ll figure it out eventually. Just have to play with it on my next offday.

I would figure out what the stock jets should and and check what you got. With upgrades it will need aome jetting, but you wont know where to start until you figure out whats in there.

Also, maybe check the valve clearances?

 

[OaklandF4i]

OP -

No matter what carb you have, it will require tuning. Some are easier than others, but it will still take some tuning. Large changes in temperature, weather, or altitude will also take some tuning. So before you consider "upgrading" the carb, keep that in mind. I can say from first hand experience the stock oem carb on the XR650R can be made to work properly. I am not saying other carbs arent good, just that the oem can work as designed.

One of the reasons I asked some of the questions I did in my previous post is to get an idea and clues to your current jetting.

In the middle of day when its warmest outside and with a cold engine that has been sitting, does it require any choke to start? If so how much. 1/4, 1/2, full. If it requires full choke when its warm outside, your pilot or fuel screw setting might be too lean at night when its 30 degrees colder.

How many turns out your fuel screw is will also be a clue to your pilot jet. If its all the way out, your pilot may be too small and the bike is lean even with full choke. If its only out 3/4 a turn, it may be on the richer side and you may need a smaller pilot and the the bike is too rich with full choke at night.

No one can help until you can share these with us. :thumbup

This is how I adjust a fuel screw on a 4t thumper. Bike needs to be fully warmed up to adjust the fuel screw, like ridden for 10-15 minutes. A few minutes idling is rarely enough. I don't like to adjust to a stumble and back off, I like to adjust to the highest idle and back off.

After the bike is fully warmed up, lower the idle with the idle adjustment screw until its barely running... lowest idle possible.

Turn the fuel screw in until the idles drops and or dies. If it doesn't when turning in, your pilot is too large and the bike too rich.

Next start turning your fuel screw out slowly until the idle increases. Continue turning out until the idle reaches it highest point (not until it stumbles as that is generally too rich.) Then back in 1/4 turn. Make a note of how many turns out from slightly seated it is.

If its more than three turns, you pilot might be too small, ie lean. Less than 3/4 turn, too large ie rich.

You can't do this properly with a high idle screw setting. To properly do this, its needs be barely running... you may even need to blip the throttle occasionally. Adjust the idle screw back to your preferred setting after adjusting the fuel screw.

The choke mechanism is pretty simple. In most carbs its merely a butterfly constricting air thereby enrichening the mixture (a few have a separate circuit controlled by a needle valve.) Easy to check its functionality when you pull the carb to verify what jets you have in the bike.

Why you have the carb out, may as well clean the jets. Soak overnight and put guitar string or something similar through the pilot to ensure its clear and clean if there is any question.

If the carb is functioning and tuned correctly and its still not starting when cold, then its time to look at other items like an air leak, valves, or even technique. Good luck:thumbup

 

[augustiron]

One big difference between the stock and the Edelbrock for example, the edelbrock is a pumper carb, stock is not.

I forget the number, but it was like 2 or 3 twists of the throttle to prime it when cold, then kick, got it fired on the first kick ice cold.

The pumper made the difference in starting, and performance.

Nut as mentioned, make sure the valves are in spec, and there are no other issues.

 

[menG]

OP -

No matter what carb you have, it will require tuning. Some are easier than others, but it will still take some tuning. Large changes in temperature, weather, or altitude will also take some tuning. So before you consider "upgrading" the carb, keep that in mind. I can say from first hand experience the stock oem carb on the XR650R can be made to work properly. I am not saying other carbs arent good, just that the oem can work as designed.

One of the reasons I asked some of the questions I did in my previous post is to get an idea and clues to your current jetting.

In the middle of day when its warmest outside and with a cold engine that has been sitting, does it require any choke to start? If so how much. 1/4, 1/2, full. If it requires full choke when its warm outside, your pilot or fuel screw setting might be too lean at night when its 30 degrees colder.

How many turns out your fuel screw is will also be a clue to your pilot jet. If its all the way out, your pilot may be too small and the bike is lean even with full choke. If its only out 3/4 a turn, it may be on the richer side and you may need a smaller pilot and the the bike is too rich with full choke at night.

No one can help until you can share these with us. :thumbup

This is how I adjust a fuel screw on a 4t thumper. Bike needs to be fully warmed up to adjust the fuel screw, like ridden for 10-15 minutes. A few minutes idling is rarely enough. I don't like to adjust to a stumble and back off, I like to adjust to the highest idle and back off.

After the bike is fully warmed up, lower the idle with the idle adjustment screw until its barely running... lowest idle possible.

Turn the fuel screw in until the idles drops and or dies. If it doesn't when turning in, your pilot is too large and the bike too rich.

Next start turning your fuel screw out slowly until the idle increases. Continue turning out until the idle reaches it highest point (not until it stumbles as that is generally too rich.) Then back in 1/4 turn. Make a note of how many turns out from slightly seated it is.

If its more than three turns, you pilot might be too small, ie lean. Less than 3/4 turn, too large ie rich.

You can't do this properly with a high idle screw setting. To properly do this, its needs be barely running... you may even need to blip the throttle occasionally. Adjust the idle screw back to your preferred setting after adjusting the fuel screw.

The choke mechanism is pretty simple. In most carbs its merely a butterfly constricting air thereby enrichening the mixture (a few have a separate circuit controlled by a needle valve.) Easy to check its functionality when you pull the carb to verify what jets you have in the bike.

Why you have the carb out, may as well clean the jets. Soak overnight and put guitar string or something similar through the pilot to ensure its clear and clean if there is any question.

If the carb is functioning and tuned correctly and its still not starting when cold, then its time to look at other items like an air leak, valves, or even technique. Good luck:thumbup

Thank you for the helpful info and sorry for not providing more info about the bike.

It’s 1300 miles on a rebuild. The bike has full fmf pipes and that’s about it. I didn’t open up the side panel or drill any holes. I adjusted the pilot jet all the way out And the bike on a day like today requires barely any choke. I started it 10 minutes ago, I turned the idle screw up choke 1/4 way and took about 5 kicks. Started up but bogs and then dies right away. If the engine is warm one kick does the job. The bike struggles to stay at idle on a cold start. If I do full choke the bike will not start. I tried it all at 1/4,1/2,3/4 and full and it rarely helps. The best thing is turning the idle screw up and giving it a little throttle. Then turn back down on the idle screw after warm.

A month back when the weather was warmer around noonish, it takes one to two kicks with no choke, but I had to turn the idle screw up. That was before I adjusted the carb.

So I’m guessing it’s probably running too lean, ill have to get a jet kit and retune it. And again thanks for all the helpful info you provided.

 

[menG]

I would figure out what the stock jets should and and check what you got. With upgrades it will need aome jetting, but you wont know where to start until you figure out whats in there.

Also, maybe check the valve clearances?

I don’t think it’s valves as of right now it’s probably the jetting. I’m gonna get a kit online. Thanks for the help

 

[menG]

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.