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XS1100UK Forum  |  Technical  |  Advice Needed  |  Topic: 1978 xs1100 wont start and pops thrug carb
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Author Topic: 1978 xs1100 wont start and pops thrug carb  (Read 1832 times)

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jorge lobo

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1978 xs1100 wont start and pops thrug carb
« on: January 03, 2011, 03:28:26 AM »
Hello I have a 1978 xs1100 I did rebuild my carbs with brand new kits, set the timing, but bike wont start and keepsl poping thrug carbs, I did check all the conection and there is no shorts, check the spark and there is  kind of red spark in all 4 but the spurkplugs are getting wet and black, also just replace the TDI box, bike was runing before but rough can any one help me or have any idea wat may be my problem... :frustrated: :frustrated: :huh: :beg: :hitme:
« Last Edit: January 03, 2011, 03:34:46 AM by jorge lobo »

Mick

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #1 on: January 03, 2011, 03:37:10 AM »
Hi Lobo

  Welcome to the forum, you haven't mention which carb kit you used, I've found in the past the main jet needles are to narrow and feck up the mixture, also you haven't mentioned what degree of timing you have set it to, should be set with a strobe light at 5 degrees BTC with engine running at 1500 rpm with vac pipe  disconnected.

  check for airleaks around carb rubbers, cracks are ok its splits you looking for
« Last Edit: January 03, 2011, 03:41:22 AM by Mick »
2H9 standard US import (Shropshire re-reg.1999)
4H3 LG Midnight special
SG frame and Engine (3U9)
LH 4W1 Midnight Special
Stoke On Trent


      MICK

 Don't let me forget tell you the motorcycle run on petrol, like sex is all so beautiful

jorge lobo

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #2 on: January 03, 2011, 04:14:04 AM »
well i did buy a kit recomendet for the bike and i did make sure that all the jets sizes were teh same  2H7 and the timing was set as you describe before the bike was stored for  a few days
carb 132.5
         42.5

FJ111200

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #3 on: January 03, 2011, 10:21:17 AM »
I had this problem once until i followed this procedure. Thanks go to Miti (Jeff).

You'll NEVER get those carbs 100% perfectly set up and that's a very important thing to remember... Striving for perfection when setting up knackered old carbs is one step further down the path of insanity than checking for hairs on the palms of your hands...

You didn't look did you..??? 

Good... 

So... Take a simple paperclip... Straighten it out so you have an even simpler piece of wire...  It's about 1mm thick, but that's not important...  Your paper clip/wire is about to be promoted... It's now a "gauge.."   

Now... Working from the engine side of the carbs, try to slide your gauge between the bottom of #3 carb venturi (the hole through the middle of the carb) and the lowest part of #3 throttle butterfy...

Won't fit..??  Turn the tickover screw clockwise until it will fit...

Too loose..??

Turn the tickover screw anti-clockwise until the gauge just passes through the gap...

A tiny amount of friction is what you're looking for...

You have now "set" #3 carb throttle butterfly to a "baseline" of 1 paperclip...

Congratulations.!!   

Now move the gauge to #4 carb...

Gap WAY too wide..? Turn the balance screw between #3 and #4 carbs anti-clockwise until the guage is the same sliding fit as in #3 carb...

Gap WAY too tight..? Turn the balance screw between #3 and #4 carbs clockwise until the guage is the same sliding fit as in #3 carb...

You have now "balanced" #4 carb to #3 carb... Good eh..?

Now repeat the same process on #2 carb, adjusting the throttle butterfly gap with the screw between #2 and #3 carbs...

Then complete the process by adjusting #1 carb by turning the screw between #1 and #2 carbs...

You should now have 4 carbs, each with a butterfy opening of 1 paperclip....

Try adjusting the tickover screw in/out...

A 4 butterflies should open/close synchronously and by the same amount... Readjust #3 to the 1 paperclip setting and all the others "should" (near as dammit) be 1 paperclip too...


Miti

If you don't support agriculture, quit eating,  yer big bag o' sh!te

jorge lobo

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #4 on: January 03, 2011, 12:59:07 PM »
Thanks for the imput Rick I will try this in the afternoon not sure but hope this solves it let you know what happens

FJ111200

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #5 on: January 03, 2011, 01:02:30 PM »
 :rofl: yeah, i'm Rick with a silent P.  :rofl:

Ah, i see, that's Mick with a silent D.  :rofl:
« Last Edit: January 03, 2011, 01:06:58 PM by FJ111200 »
If you don't support agriculture, quit eating,  yer big bag o' sh!te

Brian

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #6 on: January 03, 2011, 02:11:27 PM »
Hi Jorge,

might be this ????

Pickups, yes I noticed my pickup wires are different colours, they change half way down the pickup tail too, dunno why. If unsure about the colours of the wires you have simply pair them up by doing a cont test, at the TCI they are paired by white or yellow, one set will be white/green....white/red the other set will be yellow/green....yellow/red and fit into the 4 socket on the top row for one pickup and bottom row for the other pickup, if you have them the wrong way round you'll get popping and banging, simply swap them or the coil supply wires grey  orange over.
XS1100 LG & SG, FJ1200

I'm a demon for modifying (erm, posts that is)

शान्तिः शान्तिः शान्तिः

Miti

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #7 on: January 03, 2011, 02:38:05 PM »
Jorge

If it's constantly popping back thru the carbs as it's cranked over, then it's likely that the timing is set 180o out...

If it does nothing as it cranks, then sudddenly pops back, this is unburnt fuel being ignited and could easily be caused by the carbs flooding the engine.

Leave the lower half of the airbox and the air filter off...  See if any fuel is running back into the air filter housing... If it is, your float heights are wrong.

I found that the carb rebuild kits I used gave VERY different float height requirements.. I expected the new needle valves to seal better, but they seem to need more effort to seal them and my float heights are MUCH lower than before the kits were fitted...(they're set with carbs upside down).

HTH

Miti
Jeff Mitchell
XS1100S (5K7 Red Sport Project) - (B Reg)
XS1100S (5k7 Trike Project) - (Y Reg)
XS1100LG (4H3 - MNS Restoration Project) - 1980 (RIP Brian)
Hesketh V1000 (Pre-Prod Engine)

Tom

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #8 on: January 03, 2011, 07:57:24 PM »
Leave the lower half of the airbox and the air filter off...  See if any fuel is running back into the air filter housing... If it is, your float heights are wrong.

WHOA!!!! :shock: :shock:

This is Ok with the engine off, but then the vac taps are shut so I'm assuming you're gonna do it with the engine running/truning over,  NOOOOOOOO!!!!!!!!!!!

If your ignition timing is 180o out and it spits back there is a really serious chance of setting fire to the bike with catastrophic results. One lesser known reason for air filters is as a flame arrestor against spit back.


Go on, ask me how I know :muppet:
It makes you look a twat but question everything!!


Tom, belligerent old tosser!!
Dazed and confused

jorge lobo

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #9 on: January 03, 2011, 10:51:28 PM »

Ok guys I did check the sparkplugs,wires and they are in the right place , set the timing magnets to 0.7 spark looks much better I did follow the paper clip advice and that is done to.
BUT IT DOESN'T START I'M ABOUT TO RESING any other ideas I don't think is the CDI box
Oh... What do you mean having the ignition 180 of
The sprkplugs still to wet what is the best way to regulate the floaters

jorge lobo

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #10 on: January 03, 2011, 11:39:04 PM »
Yes I did but I also make sure that they are in the right place  :cold: :frustrated:

Mick

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #11 on: January 04, 2011, 12:10:32 AM »
left coil to grey wire right coil to orange wire, unless your pick up ATU (mechanic advance unit or Automatic timing unit) has been re-assemble 180 degree out (the wrong way round) hope that helps, if so change the coil wire round, grey wire right coil orange wire left coil  :grin:

2H9 standard US import (Shropshire re-reg.1999)
4H3 LG Midnight special
SG frame and Engine (3U9)
LH 4W1 Midnight Special
Stoke On Trent


      MICK

 Don't let me forget tell you the motorcycle run on petrol, like sex is all so beautiful

Miti

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    • Mitiweb
Re: 1978 xs1100 wont start and pops thrug carb
« Reply #12 on: January 04, 2011, 12:45:54 PM »
Leave the lower half of the airbox and the air filter off...  See if any fuel is running back into the air filter housing... If it is, your float heights are wrong.

WHOA!!!! :shock: :shock:


Chickenshit..!!! :grin: :rofl: :rofl: :rofl:

This is a right of passage and anyone who hasn't set their air filter on fire whilst fettling carbs or being over-enthusiastic with the easy start is clearly homosexual..!!

(I nearly said gay, but I reserve the right to use English words for what they actually mean).

Miti
Jeff Mitchell
XS1100S (5K7 Red Sport Project) - (B Reg)
XS1100S (5k7 Trike Project) - (Y Reg)
XS1100LG (4H3 - MNS Restoration Project) - 1980 (RIP Brian)
Hesketh V1000 (Pre-Prod Engine)

spanner1954

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #13 on: January 04, 2011, 05:40:05 PM »
 :bowing: :bowing:  love it miti , well im not a homosexual as ive set a good few on fire, last one was a bsa shooting star with a fibre glass golstar tank on  :frustrated: :frustrated:   had to rip it off and throw it up the garden  :rofl: :rofl: it fecked it up but it was full so i saved the bike  :rofl: :rofl: :rofl:    :hitme:  .
xs 1100s 5k7 streetfighter trike , old hippy biker n triker .
sheffield south yorkshire.

Miti

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Re: 1978 xs1100 wont start and pops thrug carb
« Reply #14 on: January 04, 2011, 06:50:33 PM »
Last one I did was a Z750/4 R1 which had been "rewired" by a local bike shop... The twits had rewired the whole thing in the same colour wire... The battery box was full of choccie-block connector strips and the battery was left sitting on the swing-arm.. UP AGAINST THE CHAIN...!!!

The poor owner had been totally fleeced, the bike still didn't run and he was getting desperate...  I fitted a GT750P harness and switchgear for him and made up a few spurious wiring parts, so we could at least get the battery back in it's box...  There was a Boyer ignition fitted but the wiring had been butchered... After splicing it into the new wiring, I was cranking the engine to try to get her to fire... She spluttered a few times and backfired and I thought I was nearly there.... So... I sprayed half a can of easy-start into the air filter inlet and tried again....

My big mistake was that I was standing at the left of the bike, leaning over it to reach the starter and twistgrip... The bike backfired and ignited the airbox full of easy-start... It blew the cap off the filter-box, which shot upwards, riding a column of blue flame...!!  It passed by my right ear and took away half my beard and my right eyebrow and eyelashes...

Talk about a cure for constipation..!!! Ain't nobody gonna try turd-burgling with that kind of cross-town traffic..!!

I thang yow..!!

Miti
Jeff Mitchell
XS1100S (5K7 Red Sport Project) - (B Reg)
XS1100S (5k7 Trike Project) - (Y Reg)
XS1100LG (4H3 - MNS Restoration Project) - 1980 (RIP Brian)
Hesketh V1000 (Pre-Prod Engine)

XS1100UK Forum  |  Technical  |  Advice Needed  |  Topic: 1978 xs1100 wont start and pops thrug carb
 

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