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#1 butcher650

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Posted 02 July 2020 - 02:57 pm

Howdy Folks.
Since my bike is now legal and road worthy, I've been using the 1st tank of fuel just locally on shortish runs to a) Test the bike, b) bed the new brakes in and c) get my eye and confidence back in. I have however noticed (and this is the only thing, so I'm really happy and has exceeded my expectations), that its not quite as forthcoming on acceleration past 4.5 rpms, or if I dump the thottle and go for it. When doing this, it also sounds slightly different to how it did before. Don't get me wrong, its not far off, but enough to notice the hesitation. Sounds sort of like the exhaust could be leaking, so I'll re-seal the joint underneath as a first port of call, but to the more savvy out there, could this be a carb problem? They did sync up nice, and stationary reving, there is no lumps or hesitation at all. Smooth rev all the way up and down, even when cold.

#2 dapleb

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Posted 02 July 2020 - 03:24 pm

What aboot yer carb to hairbox wubbers?
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#3 butcher650

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Posted 02 July 2020 - 03:35 pm

What aboot yer carb to hairbox wubbers?

I did the silicon mod quite some time ago, and when I re-fitted them, they seemed ok. I shall doubly check em. Manifold to carb rubbers are new-uns.

#4 MipeTDM

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Posted 02 July 2020 - 04:52 pm

I experienced something quite similar a while back (hesitation) above 5000 RPM, at full throttle. One of the rubber carb membranes ruptured.

You can easily check this by taking the airbox off, start the engine and play with the throttle. Both slides should move up and down simultaneously. If they don't, one of the membranes has likely an issue (leak). In my bike one of them did not move up at all, although both slides went up easily on a finger's push.

I replaced them with some new ones from AliExpress and all is fine since!



#5 butcher650

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Posted 02 July 2020 - 05:34 pm

Ah - Thanks a lot Mipe. I will have the tank off and have a good look. I've recently done a carb strip down, and they were ok when I re-fitted them, but its not to say something has gone wrong since. Cheers!

#6 drewpy

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Posted 03 July 2020 - 06:56 am

Ah - Thanks a lot Mipe. I will have the tank off and have a good look. I've recently done a carb strip down, and they were ok when I re-fitted them, but its not to say something has gone wrong since. Cheers!

check the diaphragms didn't move when bolting the top down, mine had shrunk slightly unseating them


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#7 butcher650

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Posted 03 July 2020 - 07:46 am

I'll investigate. Does one need to re-sync carbs if I do end up replacing the diaphragms?

#8 butcher650

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Posted 03 July 2020 - 12:19 pm

Just taken it for another lunch time blat, and its defo hesitating - Did a bit more overtaking, and certainly not taking off like it used to. Even at lower revs. Idle is lovely, as is stationary reving. Carbs off again and diaphragm inspection. Am I right in thinking new-uns are jeffing expensive, or did I dream that?

#9 Rallyist

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Posted 03 July 2020 - 02:30 pm

Can you give it a bit of choke when it starts hesitating?


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#10 drewpy

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Posted 03 July 2020 - 03:04 pm

NRP carbs do them


"As I Lay Rubber down to street, I pray for traction I can keep. But if I skid and begin to slide, please dear god protect my ride"

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#11 butcher650

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Posted 03 July 2020 - 03:43 pm

Can you give it a bit of choke when it starts hesitating?


I'll try next time I give it a ride.

NRP carbs do them


Cheers!

#12 MipeTDM

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Posted 03 July 2020 - 05:30 pm

Just taken it for another lunch time blat, and its defo hesitating - Did a bit more overtaking, and certainly not taking off like it used to. Even at lower revs. Idle is lovely, as is stationary reving. Carbs off again and diaphragm inspection. Am I right in thinking new-uns are jeffing expensive, or did I dream that?

Nope, I ordered mine from AliExpress (you need 2 pcs):

https://www.aliexpre...2493135002.html

If you have time to wait for them. I have two bikes, so I was not to bothered and wanted to try them. Have been running them in the bike for more than a year, now.

 

I'll investigate. Does one need to re-sync carbs if I do end up replacing the diaphragms?

No, that wasn't needed in my bike. Unless you synched with a big air leak or something like that: you would notice that by rough idling after fitting them.



#13 butcher650

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Posted 14 September 2020 - 10:03 am

So, I'm back again after a few weeks of ridiculous business, and finally had the chance to whip the tank off and do some Columbo: 

 

RHS carb slider is not moving at all, whereas the left is: 

 

 

 

I'm assuming, and 90% sure there is a leak in the RH carb diaphragm. So, I shall order replacements and do both. Here be-ith my questions for you lovely lot (again): 

 

1 - Can I get away with replacing the diaphragms without taking the carbs completely off and disconnecting the throttle cables? I ask this because a), they were a PAIN to reconnect, and my back at 6ft 6" after doing so, didn't thank me. 

 

2 - Is replacement the only way to go? - I guess it is. 

 

The RH slider does move easily with a finger push. 



#14 Bjørge

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Posted 14 September 2020 - 12:45 pm

So, I'm back again after a few weeks of ridiculous business, and finally had the chance to whip the tank off and do some Columbo: 

 

RHS carb slider is not moving at all, whereas the left is: 

 

 

 

I'm assuming, and 90% sure there is a leak in the RH carb diaphragm. So, I shall order replacements and do both. Here be-ith my questions for you lovely lot (again): 

 

1 - Can I get away with replacing the diaphragms without taking the carbs completely off and disconnecting the throttle cables? I ask this because a), they were a PAIN to reconnect, and my back at 6ft 6" after doing so, didn't thank me. 

 

2 - Is replacement the only way to go? - I guess it is. 

 

The RH slider does move easily with a finger push. 

 

1) Yes, I did so a few weeks ago. A bit cramped, but I managed to. If you want more room, remove the carbs from the inlets w/o taking the throttle cable off....


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#15 Studley Ramrod

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Posted 14 September 2020 - 01:33 pm

Be very wary of the tiny lickle o rings that locate next to the diaphragms, esp. if you're not removing the carbs.  The angle of the carbs makes it easy for the o rings to fall out and you'll be lucky to find it if one does drop out of the recess.


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#16 dablik

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Posted 14 September 2020 - 03:59 pm

As above, rest them on top a little without undoing the throttle linkage, put rags or summit to catch the little oring..


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#17 butcher650

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Posted 14 September 2020 - 05:36 pm

Super - thanks chaps!

Does one need to make sure bowls are emtpy before doing this?

#18 MipeTDM

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Posted 14 September 2020 - 05:54 pm

1. Indeed, removed the carbs from the manifold rubbers, and left the throttle cables attached. Tilted the carbs so the black covers are pretty much on top. Opened them one at a time.

2. Yes.

 

I did not worry about the carb bowls, I cannot recall any leakage either (or maybe it did not impress me ;) ). You're not putting them completely upside down. You could put a rag below the carbs to be sure or course.



#19 butcher650

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Posted 14 September 2020 - 08:34 pm

Super super duper. 

 

Thanks so much guys, you all is the beees kneees. 




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