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Surging When Running


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#1 ManonEdge

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Posted 11 November 2018 - 06:04 pm

Hi all,

Have just swapped carbs out as said in earlier post.

Bike starts fine, ticks over ok & accelerates ok. But when trying to hold a constant speed I get surging. Is fine once over 70 however.

Any pointers would be appreciated

Cheers

#2 Studley Ramrod

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Posted 11 November 2018 - 06:27 pm

Sounds like lean surging, try turning the pilot screws out in half turn increments.  Assuming you have correct free play on the throttle and the fuel levels are correct ?

 

Handy guide to tuning CV carbs here http://www.factorypr...pm_engines.html


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#3 ManonEdge

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Posted 11 November 2018 - 07:03 pm

Studley, thanks very much I’ll give that a go

#4 fixitsan

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Posted 11 November 2018 - 09:10 pm

Sounds like lean surging, try turning the pilot screws out in half turn increments.  Assuming you have correct free play on the throttle and the fuel levels are correct ?

 

Handy guide to tuning CV carbs here http://www.factorypr...pm_engines.html

 

 

Is there a retaining clip on the needle, one which you can change the height of.....or are they captive sprung needles ? I can't remember


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#5 Studley Ramrod

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Posted 12 November 2018 - 09:42 am

Yes there is.


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#6 fixitsan

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Posted 12 November 2018 - 12:58 pm

Could be worth raising the needle if the pilot jet adjustment won't help.

 

 

A simple diagnostic is to ride into the surging problem revs and pull the choke out  alittle.... if the situation improves with a bit of choke then it was originally too lean, and vice versa


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#7 Studley Ramrod

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Posted 12 November 2018 - 01:45 pm

And, for pilot screw settings you could try the blip throttle test as covered in the Factorypro CV tuning guide.


Mk2a 2000 in Silver. Top end Refurb @ 41100 miles, Scottoiler, Renthal Road High Bars, Up & Back Bar Risers, Bellypan, DL650 Handguards, Capt. Picard Bar Ends, House of Henty SS Wheel spacers, New Seat Cover Fitted. 58 MPG !!  Now owned by chrisbee !   Studley's mk2a Bloggerydoodaah !  Photos of my first MK1  Photos of my MK2a  TPLQHCSRSFC No. 1 Fan


#8 ManonEdge

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Posted 02 December 2018 - 11:25 am

Still no joy in resolving this weirded surging issue.

Re stripped & re cleaned the carbs,

Swapped over all the internal components from the original carbs, which despite the damage to the left diaphragm cover, always ran quite smoothly.

Set the mixture screws the same as the original carbs.

Even changed out the cables as I noticed the push cable was starting to fray.

Balanced the carbs.

Bike starts easily & ticks over nicely at 1250 rpm.
Pull away is smooth & strong & will accelerate easily when riding.

But still this very slight surging when trying to cruise at any steady speed. Really annoying.

I did try check the float levels as described in the Haynes , tbh this seems a bit of a hit and miss procedure and not accurate. This is what prompted me to swap out the internal components from the original carbs as they always seemed ok.

Only thing I have noticed is the choke, although I can see it is working ok is not having a massive effect on revs when I pull it. Only rises slightly on the Rev counter.

Going to try see if the fuel pump is delivering properly although it looked ok when I stripped it.
The only other thing I haven’t touched is the throttle position sensor, which I believe can be tricky but I do have the option of fitting the original onto the replacement carbs.

The carb rubbers were replaced so I’m sure the carbs are seating ok.

It appears impossible to me to make adjustments to the mixture screws while the carbs are fitted.

Any ideas, tips or suggestions greatly received before I have to admit defeat and get looked at by a garage.

Btw, the reason I started in on this is when riding on the motorway in some horrendous weather the engine cut on me when I came off at the junction. Although it restarted it did it again at the next junction. Got going again after a bit & got me home ok. I put it down to wet electrics. Only did the carbs as when looking at other bits noticed the bodge / damage to them.
I have dried everything out & cleaned & checked the plugs.

If you got to the end of this ramble cheers

#9 dablik

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Posted 02 December 2018 - 11:40 am

Had the same issue on mine, mk1, and seems the HT leads caused my surging as after replacing them the problem dissapeared never to come back, i only replaced as i had spare to hand, but wrapping them can do the same job, not sure yours is the same issue but worth looking at.


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#10 Andy25

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Posted 02 December 2018 - 12:59 pm

As Dablik says HT Leads wrap / replace
Your cutting out issue in wet weather and surging are both symptoms of Issues with the HT Leads ( Had problems with mine this week on mk 2 )
Only about £20 for a coil / Lead or £5 for self amalgamating Tape
Got to be worth trying first

Just a head's up if you do get new coil / Lead don't leave it too long or
it will rub against the Fan then start the same problem all over again
Learned that yesterday

#11 dablik

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Posted 02 December 2018 - 03:02 pm

Check plug caps as well and see the right side particularly is not rusty on the bottom end where the screw holds the resistor and spring in, my thermostat had also been leaking and that was the result which no doubt contributed to my problem, replaced both caps and resealed the thermostat.


Bigred mk1 R1 Calipers- Braided lines- Givi wing rack-Crash bungs- Hi vis bullets-PR2's- and a hoot to ride.

Quad 900 Silver Laser duo tech pipes-Scott oiler-Engine crash bars- Radiator mounted see me ring LED's-Datatool system 3 alarm -Centre stand- Extender fender-Renthal bars-Handle bar risers-Mirror extenders-BMW GS Handgaurds-Acumen uprated horn & Nautilus-Stainless steel Radiator guard-Givi wing rack-OEM screen-Yammy touring screen-MRA Vario-MRA Double bubble cut down for fast as fk riding-Tiger screen-Tank protector-Stomp grip panels-Optimate lead   Gone to Heaven  :sorry: 

 

1991 MK1 in need of some TLC watch this space   :) Sorted and on the Road Mick  :P  :P it's the bike that Jack built  ;) Gone to Heaven  :wub: 

 


#12 ManonEdge

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Posted 02 December 2018 - 09:14 pm

Brilliant, cheers chaps,

Had thought about changing the coils leads when I saw today that their not too pricey.

Will get them ordered and fit next weekend.

Will report back when done

#13 ManonEdge

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Posted 27 January 2019 - 08:31 pm

Bought & fitted new coils & leads but didn’t do the trick.

So carbs off again, stripped but this time give a right good clean in a ultra sonic bath. Re built & fitted.

Toyed with splitting them but opted instead of making a little tool that allowed me to get at the inside choke & shut off valve.

Did find the inner choke had a little wear & damage on the thin tip end but not sure as to what effect this would have on running.

Anyway, fired her up last night and difference was noticeable.adjusted tick over to a little under 1500.

Had her out on a test run today, sweet as a nut. No surging at all, pulled well and felt great.

Chuffed to have sorted it.

Thanks to all who gave tips and advice

#14 TKH

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Posted 27 January 2019 - 10:09 pm

Really pleased you sorted it. Did you tape up the new leads with self amalgamating tape?




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