Blackbird not reving past 4000 revs..???

troyboy37 · Derestricted Danger Joined: 23 Jan 2008 Karma :

Hi Guys, heres my problem..!!

have a 97 carb bird, the last time I rode her was mid sept, with a little surging as per usual but no problems...

I took her out on Sunday and she stuggled to get a wriggle on... not reving very well.. and struggling to get past 75mph..

Today, I took the tank and air filter housing off..

Checked the plugs (these were fitted in May) the first 3 were normal, but no. 4 was slighly oily..

I balanced the carbs today, with a make do tank and carbs were balanced..

However.....

When I rev'd the bike she only went to 4000 revs then died ... i kept reving her but she wouldnt go past 4000 revs..
When I held the throttle open she went to 4000 revs then dies back to 2000 revs, then went back up to 4000 revs, and back down to 2000.. and so on...

Any ideas guys as I dont know what to do next..???
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Yam FundaAce

temeluchus · World Chat Champion Joined: 01 Oct 2008 Karma :

Did you drain the float bowls?

Hose to the vacuum tap ok?
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Some shite cruiser. Now with guns and FREEDOM!

Scythe · Crazy Courier Joined: 24 Jul 2010 Karma :

My SV did this after a winter lay up, turns out the HT lead had broken down. Check your sparks.
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2009 Yamaha YBR125 -> 2000 SV650S -> 2005 Kawasaki ZX6R 636

Ariel Badger · Super Spammer Joined: 02 Dec 2006 Karma :

You can rule out a lot of problems as it is a four cylinder motor and a simple thing like a single ht lead or a blocked jet would not give such a huge drop in performance. It has to be a common problem to all four pots, is fuel getting to the carbs in a sufficient flow? The ignition will be controlled by a computer of some kind, is it borked, can it be remapped?
How good is your fuel, have you put diesel in it (my mate did)? Is the tank vent clear?
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troyboy37 · Derestricted Danger Joined: 23 Jan 2008 Karma :

No diesel in it.. all the hoses under the tank were connected correctly, What I forgot to say was, that on the morning of the ride I had a flat battery and jump started it with my wifes car (Kia Picanto)..
I wonder if this any issues...??
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Yam FundaAce

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

troyboy37 · Derestricted Danger Joined: 23 Jan 2008 Karma :

it started this morning OK, Gunna charge it and then see if anything improves..
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Yam FundaAce

troyboy37 · Derestricted Danger Joined: 23 Jan 2008 Karma :

So far checked the filter and petcock.. all good..

Battery charged, and all put back together..

Took her for a test ride all seemed good initially.. but then under load when I hit the higher revs it started to sound like it was running on 3 and struggled to keep in the higher revs.

I'm thinking coils or plugs..?? Question

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Yam FundaAce

temeluchus · World Chat Champion Joined: 01 Oct 2008 Karma :

Looks like the HT leads are removable. Pop them off the coils and take the caps off to inspect for rot.
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Some shite cruiser. Now with guns and FREEDOM!

Fizzer Thou · World Chat Champion Joined: 06 Aug 2011 Karma :

If I leave the Exup for any longer than a week without using it then I am pretty sure that condensation forms in the float chamber.It takes some time for it to dissipate once the engine has been run for a while,but I do get similar running problems.

Super unleaded is supposed to lessen the possibility of condensation as some super fuels have less biofuel than ordinary unleaded.
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