Rough Idle with 'povic end can.

Stew · Posted: 09:59 - 04 Sep 2003 Post subject: Rough Idle with 'povic end can.

When I bought my bike last November it came fitted with an akrapovic end can and assumed the bike was set up to suit. I have ridden the bike since then with this can on, however I read a small snippet on the YZF750 which mentioned that "end cans don't work with the EXUP valve". This made me wonder whether fitting the standard can would actually help rideability.
I fitted the standard can (which weighs a tonne in comparison to the 'povic end can) and it did seem to help the bike at low revs but the top end felt kind of 'stifled'. Yesterday I fitted the end can again and when I started the bike up this morning the idle revs seemed to fluctuate more than I have ever noticed before, it also seemed to splutter slightly at low revs although it is fine at anything above 4k rpm.
Has adding the end can made the engine run lean? and perhaps the bike never was jetted to suit the end can. I think I am going to go back to using the standard can for the time being until I can maybe sort out some dyno time to set the bike up to suit the end can, unless there is a simple solution that I can't find.
Can anyone help or suggest anything that might work Question

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TiN · Pocket Tin Joined: 14 Feb 2002 Karma :

Buy a decent bike. Razz

Maybe the engine just needs a little more time to get used to the race can again? It was also pretty cold this morning, so maybe that didn't help.

I reverted back to using a standard can quite a while ago, and it's amazing just how much more comfortable it is on your ears.
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Stew · Posted: 10:09 - 04 Sep 2003 Post subject:

Hmmm, do you think it could be something as simple as that?

And btw, my 'povic isnt actually much louder than standard it just has a better note Razz

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TiN · Pocket Tin Joined: 14 Feb 2002 Karma :

What's the point of having a race can then? Razz

...and I'm sure that it screams a bit louder at higher revs mate. Smile

Another thing - could it be that your bike was setup for the 'povic, so when you put your standard can back on, it made the bike run rich for a while, and fouled up your plugs etc?
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Robby · Dirty Old Man Joined: 16 May 2002 Karma :

One basic thing to remember is that it is very hard for the manufacturers to set the engine up to run perfectly at all revs, so they normally set it a bit rich all over, which you only really feel at the top end. A rich top end feels "wooly".

Race cans make you bike run leaner, but the reason cheaper cans (like Art cans) can get away without rejetting is that the bike is already a little rich and the can balances it out. This is why your used to a crisp top end with the akro.

So by the sound of it your bike is set up for the standard can, and its running lean with the akro at low revs. The standard can probably feels more stifled at the top end because thats where the akro has the advantage, and the baffling in the standard can is making itself known.

Incidentally, with modern bikes the plugs don't need to be tan brown, they are often white with some brown flecks if your bike is set up perfectly - tan indicates slightly rich, but only enough to be healthy. It is better for the environment to run lean. You could try a new set of plugs and see how they look after 200 miles, being a mid nineties bike i'd expect them to be tan coloured.

And i learnt this from UMG, so if i'm wrong blame them.

TiN · Pocket Tin Joined: 14 Feb 2002 Karma :

Nice bit of info there Robby, but I think that Stew is only just experiencing this "problem" after swapping his standard can over for a bit, and then putting the race can back on. His bike has been running the 'povic for a while already.
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Robby · Dirty Old Man Joined: 16 May 2002 Karma :

Is it carbed or FI?

TiN · Pocket Tin Joined: 14 Feb 2002 Karma :

I believe that it's carbed...but I could wrong. It's a mid-90s YZF750...I think Laughing

But even if it was FI, it would still need the fuelling tweaked with a Power Commander type thing.
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Beezkneez · Scooby Slapper Joined: 02 Sep 2003 Karma :

Stew, sounds like you need to lubricate your EXUP valve, by the sounds of it any spluttering below 4k normally relates to a sticky exup valve.

HTH

Bazza
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Stew · Posted: 12:26 - 04 Sep 2003 Post subject:

Cheers for the help guys.
Robby, good info you could be right and maybe I hadn't noticed the 'rough' idle until I had run it for a week on the standard can with a smooth idle. Yeah it is carb fed and perhaps I have had some dodgy fuel and clogged up the needle jet (someone else suggested this to me?).

Beezkneez, yeah I have lubricated my exup in the last 3 weeks. I had a 'small' sqeak coming from the EXUP while I was at bulldog Bash which I found annoying so took the EXUP a quick clean and lube (the wheel was a bit rusted too Confused

but the rest was generally ok). The squeak could be heard every time I released the throttle btw.
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Kickstart · The Oracle Joined: 04 Feb 2002 Karma :