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1Back to top Go down   Hesitation and/or surge Empty Hesitation and/or surge on Thu Apr 25, 2013 11:38 pm

t1slc

t1slc
active member
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I just bought a 1991 k100rs. The bike is having some hesitation (or surging) issue. It seems to happen in all gears. It's as if the engine is loosing a bit of power, then kicks back in. The duration of the hesitation then surge varies from feeling like being buffeted by the wind, to more like hitting the brakes, or running out of gas.
I just replaced the spark plugs, which seemed to help a bit. The old plugs did not have the ferrules on the end, and I don't think they were the right kind. The threaded exposed end appeared corroded and the inside of the cable connector also looked like there was a bit of corrosion and 'gunk'. I have not replaced the cables. I will post photos of the old plugs.
There also sounds like there is a puttering sound that you can hear at idle. Potentially an air leak or vacuum leak? I can post a video with sound later too.
I'm new to motorcycles so I'm not sure what is normal as far as sounds, but I'm pretty sure the hesitation is not normal.

    

2Back to top Go down   Hesitation and/or surge Empty Re: Hesitation and/or surge on Fri Apr 26, 2013 12:02 am

RicK G

RicK G
VIP
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The correct plugs are NGK DR7EA or equivilant Bosch but I recommend the NGK
Probably pay to get plug leads as well I use EME leads which are from NGK http://www.ebay.com/itm/BMW-K75-K100-K1100-K1200-Ign-Spark-Plug-Wires-Copper-Core-SILICONE-Jacket-/251263624189?hash=item3a807aa3fd&item=251263624189&pt=Motorcycles_Parts_Accessories&vxp=mtr
The puttering could be a leaking exhaust gasget or a cracked exhaust pipe, if the exhaust is cracked then it can be TIG welded and if you do that also weld a steel strap to the outer side of the pipes about 40mm from the head this will or should prevent it cracking again.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

3Back to top Go down   Hesitation and/or surge Empty Re: Hesitation and/or surge on Fri Apr 26, 2013 12:19 am

t1slc

t1slc
active member
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Thanks Rick. Do the NGK leads also have the resistor built in similar to the OEM?
Here a picture of the old spark plug (a NGK D8EA) Hesitation and/or surge Img_6610
The new plugs are NGK DR7EA (with the screw on ferrule or bobbin or terminal.) I thought I read somewhere that the "R" in the spark plug type indicates that it has built in resistence. Is this true for the NGK?

Any other thoughts about what might be causing the hesitation, even with new plugs? Would cleaning the fuel injectors help? The fuel lines look like they could be replaced, but would that be a poential cause? Do you have good sources for fuel lines? I have noticed a pretty strong fuel vapor smell from the bike, but the fuel lines don't seem to be leaking.

I will check out the exhaust gasket and pipe, thanks for your thoughts!

-Just looked at the specs on the cables...they do have built in resistence.



Last edited by t1slc on Fri Apr 26, 2013 12:21 am; edited 1 time in total (Reason for editing : found my own answer to my cable question)

    

4Back to top Go down   Hesitation and/or surge Empty Re: Hesitation and/or surge on Fri Apr 26, 2013 1:01 am

RicK G

RicK G
VIP
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The D8EA is wrong all round the K100 has D7EA with a restive lead where the 16v have a resistive plug, that is what the R in the plug type is for. The K1100 and K100 16v have a different end on the lead at the coil than the 8v engines so if you get them from EME specify that is what you need.
There are some fuel lines that will fuel to permeat through without actually leaking. You need the lines that are for submersion in fuel which is the same as in the tank I know NAPA has the correct lines but I don't know part numbers etc. Being an Aussie we often have different standards and so have different numbers.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

5Back to top Go down   Hesitation and/or surge Empty more information on Fri Apr 26, 2013 1:29 am

ibjman

ibjman
Life time member
Life time member
more information about the surge would be helpful, providing you still have it after the plugs & leads are correct.
I for one can not tell if you are experiencing just a gentle slow down, starve for fuel or are having total intermittent loss of complete ignition which would be a lot more "stacotto like" in nature.
As you study & read more through the forum, you'll find many problems asked & addressed over & over & you'll get a feel for what is more/less likely.
Probably want to read this: http://www.verrill.com/moto/newkbike.shtml
first.

    

6Back to top Go down   Hesitation and/or surge Empty Re: Hesitation and/or surge on Fri Apr 26, 2013 4:30 am

92KK 84WW Olaf

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I had an issue with the external fuel lines and ordered new ones from BMW. They actually gave me a 1m length of the correct line and it was very reasonable. Just cut to length. But its a good idea to make them longer so you can raise the rear of the tank without removing them, means you can access electrics more easily, also coolant top up and earth connections under the petrol tank, and all with less risk of spilt fuel, fuel vapour and dirt getting in fuel lines.

Those fuel lines should really be replaced after no more than 10 years. They do let vapour escape when they fail. At 80mph you would be well fried if it ignited by the time you get to stop. It is really a safety issue as much as anything else. My new fuel line had the manufacture date stamped on it, as did the old ones which were seriously old!!

As far as I can see we seem to use the NGK D8EA plugs here for the 8 valve K100. I have been using them for 3 years with no problems. The difference between 7 and 8 is temperature only, but I take mine out occasionally to check and they are always the right colour. However I have not found anywhere that the D8EA is recommended, seems to be D7EA. I did try to change them but could not get the Bosch ones so decided to leave it alone.

Sounds a little like fuel starvation, also check fuel filter [inside petrol tank] and the in tank fuel lines. A failure in the supply side means you will lose fuel pressure as the fuel would simply leak from the supply pipe back inside the petrol tank. This might show in a visual inspection. A leak in the supply pipe outside the tank would most likely [but not always, as I know] be visible.

92KK


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 105,200 miles
1983 K100RS 0011171 Fricka 606 29,495 miles Damn K Pox Its a Bat outta Hell Now 36,188  miles
    

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