another standard carb issue

Hi all
my xr is running rather poor at 3/4-full throttle, it feels like it looses all power and then picks up again like a lot of other members have encountered.

i have tried searching on here and other places but everything i have tried has not cleared it up.
i was lucky enough to get some help from another forum member and we replaced my needle jet which seemed to of worked but it was wet and i wasn't ridding it ham fisted but now the problem seems to of returned(might of also of been the altitude difference).

here is my current setup.
Hrc intake
scorpion straight through exhaust with custom link pipe.
High flow filter(binned the k&n old one)
needle clip in third clip from the top
airbox plugs are removed
68s idle jet(tried a 70s but bike wouldn't start)
175 main jet
16mm float hight
altitude is 300ft

is there something i can try to rectify this  
i also have 178/180 main jets and a 70s idle

thanks in advance for any help  

If a needle-jet has worn (?) then the jet-needle also has - so it follows you replace these as a set. I also hunch your main is on the (too?) large side, you may want to try a smaller one (170, 165 etc).
What fuel consumption do you get compared to another Pig?

Sorry, re-reading yours...

16mm float level?
Too little, the book says 18 but you set it at 19 (to prevent pissing when leaned over on the stand). And, turn the carb towards upside down whilst you blow through a fuelhose to see at what angle the needle closes... as at this angle you must measure the height (without gasket!).

BuRP wrote:If a needle-jet has worn (?) then the jet-needle also has - so it follows you replace these as a set. I also hunch your main is on the (too?) large side, you may want to try a smaller one (170, 165 etc).
What fuel consumption do you get compared to another Pig?

cheers for the replies BuRP
i haven't had chance to measure fuel consumption to another xr yet so i am not 100% sure  
as for the needle jet i have two of them and neither one of them makes any difference that i could tell.

BuRP wrote:16mm float level?
Too little, the book says 18 but you set it at 19 (without gasket!).

one float height adjusted

Yes 16mm its way too low , i used to have mine set at 19 mm if i remember .

As high as possible without spitting fuel out the overflow on the side stand.

ooeddym wrote:As high as possible without spitting fuel out the overflow on the side stand.

well i adjusted it to 19mm and the bike fired up and idled fine,but as soon as i set of i got about two metres and the bike died, tried again and got the same, also if i rev it too much the bike now dies   

You went too far i think , the stock carb can be real pain , no wonder all the cool kids run pumper carbs   

The manual says 16mm. If you didn't have fuel coming out of the overflow when on the stand then I would have left it alone. By increasing the float height you've reduced the amount of fuel in the float bowl before the float valve shuts the fuel off. Sounds like you've increased it too much and now the carb isn't getting the fuel it needs. Mine is set to 16mm and seems fine. It's going to be different for each bike.

I know it's only a rule of thumb but generally 1/4-3/4 throttle is controlled by needle jet
3/4 to wide open is controlled by main jet.


I think Burp is right, you should replace the needle jet and needle as a pair. Experiment with the main jet, and maybe put in a new float valve, it might be sticking. They aren't expensive.

Mad Frosty wrote:You went too far i think ,  the stock carb can be real pain ,  no wonder all the cool kids  run pumper carbs   

HAHA frosty, that is the future plan but for now i need to get this stocker working   

R056rx wrote:The manual says 16mm. If you didn't have fuel coming out of the overflow when on the stand then I would have left it alone. By increasing the float height you've reduced the amount of fuel in the float bowl before the float valve shuts the fuel off. Sounds like you've increased it too much and now the carb isn't getting the fuel it needs. Mine is set to 16mm and seems fine. It's going to be different for each bike.

I know it's only a rule of thumb but generally 1/4-3/4 throttle is controlled by needle jet
3/4 to wide open is controlled by main jet.


I think Burp is right, you should replace the needle jet and needle as a pair. Experiment with the main jet, and maybe put in a new float valve, it might be sticking. They aren't expensive.

hopefully i should have to time to adjust the float height again later so i might try 17mm and see what happens from there.

is it worth me trying the 178 mains in it or is the consensus that i am already running a main jet that's too big?

I can't figure the constant slagging of the standard carb. My XR has standard carb. and runs like a dream, float level 16mm, no pissing missing farting or any other crap, hauls ass even with the idiotic 15/41 gearing and stock exhaust   

beaver350 wrote:I can't figure the constant slagging of the standard carb. My XR has standard carb. and runs like a dream, float level 16mm, no pissing missing farting or any other crap, hauls ass even with the idiotic 15/41 gearing and stock exhaust   

mine did until 3/4 throttle or pinned throttle and now it wont even run haha.
mine does leak on the side stand if the roads not flat so hopefully 17mm might just help that slightly without starving the engine   

beaver350 wrote:I can't figure the constant slagging of the standard carb. My XR has standard carb. and runs like a dream, float level 16mm, no pissing missing farting or any other crap, hauls ass even with the idiotic 15/41 gearing and stock exhaust   

Some work just fine , some ( like mine ) just refuse to behave . There  is a reason why so many XR owners have changed the OEM carb for TM40 , edelbrock or FCR41 ,  trust me i would rather spend the money  differently if the stocker worked properly . If yours still work fine that is great   , i am more than happy with the TM40 , it was the end of all issues .  

Mad Frosty wrote:

beaver350 wrote:I can't figure the constant slagging of the standard carb. My XR has standard carb. and runs like a dream, float level 16mm, no pissing missing farting or any other crap, hauls ass even with the idiotic 15/41 gearing and stock exhaust   

Some work just fine , some ( like mine ) just refuse to behave . There  is a reason why so many XR owners have changed the OEM carb for TM40 , edelbrock or FCR41 ,  trust me i would rather spend the money  differently if the stocker worked properly . If yours still work fine that is great   , i am more than happy with the TM40 , it was the end of all issues .  

Swap my clutch for the TM40 frosty haha   

hi guys, so my float height is now 17mm and i have swapped my mains to 178 and it seems to fly now although i haven't pinned the throttle yet because of the following problems.
I hadn't touched the idle jet or mixture screw and i had a nightmare trying to fire it up were as it would fire up with no choke after 2-3 kicks from cold or first kick from warm.
Earlier on it wouldn't fire up at all and the odd time i did get it to fire up it just died straight away so i have had a play around with the mixture screw and idle and i can now get it to idle even though its popping a lot and when i ride the bike it runs fine until i start to slow down and then the bike dies  

any idea's how many turns out on the idle screw i should be? or any other advice would be great.

thanks

kirky wrote:

Mad Frosty wrote:

beaver350 wrote:I can't figure the constant slagging of the standard carb. My XR has standard carb. and runs like a dream, float level 16mm, no pissing missing farting or any other crap, hauls ass even with the idiotic 15/41 gearing and stock exhaust   

Some work just fine , some ( like mine ) just refuse to behave . There  is a reason why so many XR owners have changed the OEM carb for TM40 , edelbrock or FCR41 ,  trust me i would rather spend the money  differently if the stocker worked properly . If yours still work fine that is great   , i am more than happy with the TM40 , it was the end of all issues .  

Swap my clutch for the TM40 frosty  haha   

Hydraulic clutch For the stocker carb , i take it   

kirky wrote:hi guys, so my float height is now 17mm and i have swapped my mains to 178 and it seems to fly now although i haven't pinned the throttle yet because of the following problems.
I hadn't  touched the idle jet or mixture screw and i had a nightmare trying to fire it up were as it would fire up with no choke after 2-3 kicks from cold or first kick from warm.
Earlier on it wouldn't fire up at all and the odd time i did get it to fire up it just died straight away so i have had a play around with the mixture screw and idle and i can now get it to idle even though its popping a lot and when i ride the bike it runs fine until i start to slow down and then the bike dies  

any idea's how many turns out on the idle screw i should be? or any other advice would be great.

thanks

I might be wrong but i think its the pilot jet , used to have the exact same problem with the old carb .

well a bit more news, tried the needle now in 2nd,3rd,4th needle clips and it just wont run right.
2nd clip position the bike was hesitating and stuttering a lot.
3rd clip position was the same but with erratic idle
4th clip position the bikes struggling to idle and wont run at 30mph on a steady throttle, the bike keep surging.

i was hoping to be getting muddy this weekend but its not looking likely at the minute   

Could it be something as simple as the throttle stop screw being way out? I don't think that there is any easy way to set this without the engine running and being warmed up. If you know it's going to die on idle then keep blipping the throttle to stop it stalling and at the same time adjust the throttle stop screw to get the idle high enough.

If it's not that simple then I'd be starting from absolute basics. Make sure the carb is totally clean, then clean it again, and then finally clean it again. (I used boiling lemon juice and water and got brilliant results - I did an earlier post on this)
Replace the float valve cos this can wear out and not sit properly. If it's worn then it'll cause all sorts of strange symptoms. It's not expensive so it's well worth replacing.

Set the jets to a standard setting. B53e needle on the 3rd clip down from the top, 175 main, 65s or 68s pilot jet. This is very helpful...http://www.xr650r.co.uk/service/jetting/jetting.shtml

Make sure the air filter is clean, not over oiled, and has a good seal in the airbox.

Make sure that there are no air leaks from the rubber carb boots. I'm told a good way of checking is to use butane gas blown around the boots whilst the engine is running. If it's leaking then the revs will increase.

 This is lifted from the FAQ section of www.xr650r.co.uk, how to adjust pilot screw...

Make sure your engine is fully warmed up and set the pilot screw to 1.5 turns out. Then with the 68s installed, turn the pilot screw clockwise until the idle slows. Then turn the pilot screw counterclockwise until the idle slows again. Make a mental note of how many turns you made in between the low idle points. Then turn the pilot screw half way between the low idle points to finish the adjustment. If you turn the adjuster counterclockwise and the idle doesn't drop down, then you need a larger pilot jet. If you turn the pilot screw clockwise and the idle doesn't drop down, then you need a smaller pilot jet. After adjusting your pilot circuit, re-adjust your idle speed if necessary.

Just one last thing.... I've read more than once of new BRP owners getting the choke wrong. Seems daft but I guess it's easy to do. All the way forward and up is on, all the way back and down is off.  

R056rx wrote:Could it be something as simple as the throttle stop screw being way out? I don't think that there is any easy way to set this without the engine running and being warmed up. If you know it's going to die on idle then keep blipping the throttle to stop it stalling and at the same time adjust the throttle stop screw to get the idle high enough.

If it's not that simple then I'd be starting from absolute basics. Make sure the carb is totally clean, then clean it again, and then finally clean it again. (I used boiling lemon juice and water and got brilliant results - I did an earlier post on this)
Replace the float valve cos this can wear out and not sit properly. If it's worn then it'll cause all sorts of strange symptoms. It's not expensive so it's well worth replacing.

Set the jets to a standard setting. B53e needle on the 3rd clip down from the top, 175 main, 65s or 68s pilot jet. This is very helpful...http://www.xr650r.co.uk/service/jetting/jetting.shtml

Make sure the air filter is clean, not over oiled, and has a good seal in the airbox.

Make sure that there are no air leaks from the rubber carb boots. I'm told a good way of checking is to use butane gas blown around the boots whilst the engine is running. If it's leaking then the revs will increase.

 This is lifted from the FAQ section of www.xr650r.co.uk, how to adjust pilot screw...

Make sure your engine is fully warmed up and set the pilot screw to 1.5 turns out. Then with the 68s installed, turn the pilot screw clockwise until the idle slows. Then turn the pilot screw counterclockwise until the idle slows again. Make a mental note of how many turns you made in between the low idle points. Then turn the pilot screw half way between the low idle points to finish the adjustment. If you turn the adjuster counterclockwise and the idle doesn't drop down, then you need a larger pilot jet. If you turn the pilot screw clockwise and the idle doesn't drop down, then you need a smaller pilot jet. After adjusting your pilot circuit, re-adjust your idle speed if necessary.

cheers R056rx, thats the guide i have been using to try and set it correctly   
do you know were the best place would be to order a new float valve? i did find it for £20 online but they wanted £30 to deliver it  
i might have to try the 178mains with the 70s idle tomorrow and i will follow this guide as if it was the bible.
and whilst i have to carb off(again) i will give it another good clean out   

I've just had a look at my receipts and it was actually a bit more expensive than I remembered. £27.50.
That was from my local Honda dealer.
I've since found a great source for OEM parts, and they are local to me so very convenient. They do post out, but I don't know how much they charge....    http://www.johnoldfield.co.uk

I also use this site to find the part number and get an idea of the price, but they do charge a fortune to deliver!!...   
http://www.lingshondaparts.com/honda_motorcycle_parts_block_selection_M30.php?mod_01=7723

33 pounds greedy feckers   

R056rx wrote:I've just had a look at my receipts and it was actually a bit more expensive than I remembered. £27.50.
That was from my local Honda dealer.
I've since found a great source for OEM parts, and they are local to me so very convenient. They do post out, but I don't know how much they charge....    http://www.johnoldfield.co.uk

I also use this site to find the part number and get an idea of the price, but they do charge a fortune to deliver!!...   
http://www.lingshondaparts.com/honda_motorcycle_parts_block_selection_M30.php?mod_01=7723

sorry for the late reply but my response didn't post for some reason earlier  and thanks for the info R056rx

yeah i did find if for £20 but they also wanted £30 to deliver it   haha

i normally use www.fowlersparts.co.uk for part numbers as they let you know if the part has been replaced by another one and i also use doblo's honda, i get a nice 20% discount of them but not for xr parts unfortunately