# '05 BF 650 hare to start when cold and popping through carbs at 1/8-1/4 throttle?



## mrtosh (Oct 22, 2012)

Hello all!

I just sold my'02 Sportsman 700 and picked up a'05 BF 650 SRA. Thing is far quicker than the 700! On to my issues I'm having. When cold it's a bear to start. You have to open the "choke" and give it some throttle. Then when it starts you'll have to babysit the throttle for a good couple minutes before it will idle. If when cold you give it around 1/8 throttle it starts to fall flat and pop then clears up around 1/4 throttle and up. When warm it will fire up no problem and then in neutral if you slowly progress the throttle to around to 3/8-1/4 throttle and hold it, it will pop through the carbs. Anything above that and its good to go. Other than that it has great power and moves out just fine.

Any thoughts on what I should look at first? Carbs or valve lash adjustment?

Thanks in advance fellas! This is a great site!


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## browland (Apr 4, 2009)

mrtosh said:


> Hello all!
> 
> I just sold my'02 Sportsman 700 and picked up a'05 BF 650 SRA. Thing is far quicker than the 700! On to my issues I'm having. When cold it's a bear to start. You have to open the "choke" and give it some throttle. Then when it starts you'll have to babysit the throttle for a good couple minutes before it will idle. If when cold you give it around 1/8 throttle it starts to fall flat and pop then clears up around 1/4 throttle and up. When warm it will fire up no problem and then in neutral if you slowly progress the throttle to around to 3/8-1/4 throttle and hold it, it will pop through the carbs. Anything above that and its good to go. Other than that it has great power and moves out just fine.
> 
> ...


I'd check the plugs and see if they are black to start. Popping thru the carbs is going to be a needle adjustment , add a washer that's .020 and see if that fixes the pop in the carbs, if not add one more up to .040. Hard cold starts is a symptom of tight valves. If you just bought it , you have no idea when they were last adjusted if ever, so I would check that out as well while you are pulling the carbs loose. Fix it all at once and be done


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## mrtosh (Oct 22, 2012)

Thanks for the response! If the plugs are black indicating that it is running rich, wouldn't adding a shim to the needles make it even more rich?


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## eagleeye76 (May 7, 2010)

Mine does the same thing ever since I bought it. Had the valves checked and they are in the middle of the range. It does it more the longer it sits. The more it is below zero it's worse.


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## mrtosh (Oct 22, 2012)

eagleeye76 said:


> Mine does the same thing ever since I bought it. Had the valves checked and they are in the middle of the range. It does it more the longer it sits. The more it is below zero it's worse.


Are you talking about the popping through the carbs or the hard starts?


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## browland (Apr 4, 2009)

mrtosh said:


> Are you talking about the popping through the carbs or the hard starts?


Popping thru the carbs is lean on the needles, or the pilot circuit clogged. raising the needle will enrichen the needle. I say check plugs to see if they are black just to have an idea of how the mixture is , it can be lean on the needles and rich wide open. Valves being too tight effects more than just starting. Think about this, if the valves never fully seat, whats happening to the fuel? some is going out the pipe, some is being forced back up the intake right? same goes with the flame on ignition, your popping in the carbs could be from tight valves. take the lid off and drive it at night , i bet you see a small firework show coming up thru the intake and carbs. Take a look at the plugs, if they are tan or light brown probably just a lean spot in the neeedle. Being a new toy to you, and no longer than it takes, check the valves , either way you are going to be pulling the carbs, while those are out of the way youre only 8 bolts away from accessing all the rockers.


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## mrtosh (Oct 22, 2012)

browland said:


> Popping thru the carbs is lean on the needles, or the pilot circuit clogged. raising the needle will enrichen the needle. I say check plugs to see if they are black just to have an idea of how the mixture is , it can be lean on the needles and rich wide open. Valves being too tight effects more than just starting. Think about this, if the valves never fully seat, whats happening to the fuel? some is going out the pipe, some is being forced back up the intake right? same goes with the flame on ignition, your popping in the carbs could be from tight valves. take the lid off and drive it at night , i bet you see a small firework show coming up thru the intake and carbs. Take a look at the plugs, if they are tan or light brown probably just a lean spot in the neeedle. Being a new toy to you, and no longer than it takes, check the valves , either way you are going to be pulling the carbs, while those are out of the way youre only 8 bolts away from accessing all the rockers.


Very valid points! Do the carbs need to be removed to set the valve lash? I was under the impression you didn't have to pull the carbs for that. Thanks again for the input/advice as well!


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## browland (Apr 4, 2009)

mrtosh said:


> Very valid points! Do the carbs need to be removed to set the valve lash? I was under the impression you didn't have to pull the carbs for that. Thanks again for the input/advice as well!


I guess you dont "have to " pull the carbs, but if you are going to be messing with the needles you are going to have to pull them from the boots anyways. Pull the left side fender or engine cover, pull the airbox, the battery and battery box, carbs can be removed from the boots and displaced enough to remove the slides, and the inspection covers for valve adjustment.


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## mrtosh (Oct 22, 2012)

Excellent! Was hoping I didn't have to pull the whole front clip! Thanks again!


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## browland (Apr 4, 2009)

mrtosh said:


> Excellent! Was hoping I didn't have to pull the whole front clip! Thanks again!


anytime


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## 650Brute (Dec 18, 2008)

All excellent advice, that said, I've done all this... I think a hard cold start & carb popping is nature of the carb'd beast.

Mine does it (mods in sig) and we have tried it all, I learned to accept it as the ol' Brute flat gets it done.


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## browland (Apr 4, 2009)

I finally got my big bike perfect I think. No choke , no backfiring , no popping in the pipe , at all , ever . Lol dead stop high range will stand straight up with no bogg or hesitation. I'm finally happy with it and can't imagine it being any better . The only adjustments I make is with temperature change having to adjust fuel screws . Nothing more . Now if I can get my daughters brute to run the same ima be ecstatic ! 




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## mrtosh (Oct 22, 2012)

Just finished up doing the valves. Man that front intake set was a pain in the *****! It does start a lot better. Pops right over. It does still pop a bit at 1/8 throttle or so. Not as bad as before but still there. Looks like I'm gonna tear apart the carbs and clean everything. 
,
Can anybody tell me what size the Pilot and Main jets are stock? May just order new Keihin jets. Any tips or things I should be careful with when removing the carbs? Also do I have to drain the coolant like the manual states? Will I have to re-sync the carbs when done? Also should I go ahead and washer the needle out now or wait to see if cleaning the carbs does the trick?

Thanks in advance fellas!

---------- Post added at 07:08 PM ---------- Previous post was at 07:06 PM ----------

Also the plugs didn't look too bad. They were a little wet but not black or lean.


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## browland (Apr 4, 2009)

mrtosh said:


> Just finished up doing the valves. Man that front intake set was a pain in the *****! It does start a lot better. Pops right over. It does still pop a bit at 1/8 throttle or so. Not as bad as before but still there. Looks like I'm gonna tear apart the carbs and clean everything.
> ,
> Can anybody tell me what size the Pilot and Main jets are stock? May just order new Keihin jets. Any tips or things I should be careful with when removing the carbs? Also do I have to drain the coolant like the manual states? Will I have to re-sync the carbs when done? Also should I go ahead and washer the needle out now or wait to see if cleaning the carbs does the trick?
> 
> ...


The valves you mentioned being a pain to set ... Are you talking about the ones on the front cylinder that face the steering stem or bumper? Those are exhaust . Hope you set them all to the correct clearance or your intakes will be loose and the exhaust will be tight . 




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## mrtosh (Oct 22, 2012)

browland said:


> The valves you mentioned being a pain to set ... Are you talking about the ones on the front cylinder that face the steering stem or bumper? Those are exhaust . Hope you set them all to the correct clearance or your intakes will be loose and the exhaust will be tight .
> 
> 
> 
> ...


Correct. I set the exhaust valves(lower most forward set to. 008) and the intake valves(on the top nearest the carbs to. 006. I can see the confusion in my post though. Meant to say the front cylinder intake set sucked to do lol.


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## browland (Apr 4, 2009)

No need to drain the coolant to pull the carbs. Be careful when you pull the bowls off that you don't hit the floats , the tabs bend easy and you will have to reset float height. Be careful with the slides , there is a tiny brass jet in the outer lip of each, if you can see light thru it don't even remove it . The main jets should be 155 front and 155 rear if it hasn't been tampered with by someone else. 38 pilots. Pay attention when removing the pilot screws. Should be the screw, spring , washer and o ring. o ring sometimes likes to stay behind. If you go sticking something in there to remove it be careful not to pry against threads and try not to cut or break the o ring , when you reinstall make sure the washer is above the o ring , against the spring . If you clean the passages , use compressed air to blow thru each one after you soak them. When you reinstall the slides make sure the outer lip is recessed in the body before you put the caps on or you will have a leak or possibly pinch the diaphragm and put a hole in it, do not touch the adjustment screw used for synch unless you have a manometer or carb synch tool . It's a screw on top of the linkage on the rear carb. There are two springs , one over the other. If you don't mess with it , typically you won't have to synch. If you want to add a shim to the needle I would start with .020-.025 under each needle . That should get you going . Don't put it all back together and try to test drive with the air box off or the lid off. It's a pain in the rear to put it all back together to test only to have to try again but it's a must . The jets can be boiled in lemon juice and it will clean them really well if they are clogged. Hope this helps you get it done 




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## mrtosh (Oct 22, 2012)

Excellent advice! Thanks Browland! Question on the pilot jet size, I remember reading somewhere that they are .40. Is that true or is it. 38? Are there different sizes for different years?

---------- Post added at 08:33 PM ---------- Previous post was at 08:31 PM ----------

Also do the bowls need to be drained before removal?


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## browland (Apr 4, 2009)

If its a brute force 650i it will have 38's




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## mrtosh (Oct 22, 2012)

Alright. Sounds good! Thanks again!


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## browland (Apr 4, 2009)

40 pilots are in the sra models , what all is done to your bike ? 




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## mrtosh (Oct 22, 2012)

Its bone stock right now. May do a Dynatek cdi and a HMF slip on. But for now I want to get this popping issue straightened out. So go with the 40's for the pilot jets and 155 for the front and rear mains?


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## browland (Apr 4, 2009)

If its stock completely , I would add a shim under each needle and see if the condition improves. Pilots are fine . No need to change. 




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## browland (Apr 4, 2009)

Man honestly if that bike still has its cherry you should see where the pilot screws are set at 




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## browland (Apr 4, 2009)

You can flip the carbs , remove the plugs covering the pilot screws , make a mark with a sharpie or marker on the body, straight inline with the screw head. Turn the screws clockwise until they LIGHTLY seat, counting the number of turns it requires to seat. If its less than 3 turns you may possibly fix the issue with the pilot screws. Do that and report back or text me , 3373023193




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## eagleeye76 (May 7, 2010)

mrtosh said:


> Are you talking about the popping through the carbs or the hard starts?


Yes on both


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## eagleeye76 (May 7, 2010)

I thought the jets in the rear were always bigger for cooling? Is that wrong?


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## browland (Apr 4, 2009)

eagleeye76 said:


> I thought the jets in the rear were always bigger for cooling? Is that wrong?


It's not for cooling with the engine being liquid cooled . The front will run cooler only when moving . From what I see tuning these things is the length and diameter of the exhaust make the difference in jetting and a/f ratio. 




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## mrtosh (Oct 22, 2012)

Update : Under the greatly appreciated guidance of Browland. I was able to adjust the valves and clean the carbs. My fuel inlet tube for the front Carb was leaking so I'm waiting on that fitting to come in. I also shimmed the needles and set the pilot screws out 2 turns. I'll post after I get the fitting and throw the carbs back on.


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## Takeum (Sep 18, 2012)

Mine had 40 piot in front and 38 in the rear carb.... Go figure,,,


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