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850 T3 Off Idle lag / carb sputter when hot

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Falcone
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    Posted: 17 Oct 2019 at 17:10
I’ve synced with mercury vacuum sync But I have not cracked open the carbs yet since purchasing a few months ago from PO. She’s cold blooded but runs strong when warm. When she gets hot, she has a bit of a hard time breathing. I’m not sure if jetting is off or what. She has a hard time pulling off into first from stop. I have to really lean and give gas to get it firing or she kind of stammers. Sometimes there’s even a sound of a breathy sputter that has a hiss to it. It will also sometimes happen at higher RPMs in 3rd. 

I’m assuming something is up in the carbs. I plan on taking them off this weekend and going through them. Just wondering if anyone’s had this issue and found something else to be wrong. Seems to just really struggle when hot. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AAC76T3 Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 04:30
bump? help?Cry
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 07:49
Did you take the carbs off to check?

First check that the "choke" plunger is seating properly at the bottom and that the seal there is still good. If not then you get far too much fuel through. If cable operated make sure there is slack in the cable.
Brian.

Better 5 minutes late in this world than years early in the next.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GuzziPaul Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 08:30
Plug colour? Thats what I have been judging my carbs by (as well as a vacuum gauge and feel).

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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 10:11
If that was my bike I'd start by stripping the carbs to make sure that all was clean and that the jetting and settings were standard,including float hight.
Check also that the heat insulating gaskets are in good condition (two per side)where the inlet tract is bolted to the head. Beneath the Allen screw heads that hold the inlet tract there should be fiber heat insulating washers as well as steel washers. Are they present?
Could be that the carb's are getting too warm and effecting the mixture.
And as Brian says, check that the "choke" pistons are sealing properly.

Edited by Dave P. - 23 Oct 2019 at 11:44
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 13:15
Another thought occurs to me.Have you checked the valve clearances since you bought the bike? They could be too tight which would cause problems when the bike is up to temperature.
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 17:21
What Dave & Brian said

Quote since purchasing a few months ago from PO

This may be the crux of the problem, petrol had dried out in the float chambers and left nasty deposits. Was bike running OK before purchase? Sometimes you inherit "issues" which may be why PO sold it in the first place

Ouch


"Chicken nuggets don't dance on a Tuesday."
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