I've just fitted my exhaust to my middy build, and run it up.

I'm a little worried about the amount of flame out the back... It looks great, but surely I must be overfuelling or worse?


Video: http://www.digital-car.co.uk/wr4/mk2/video/startexhausts.wmv

Ignore the high idle, hadn't got round to setting that yet. I'm also going to balance the carbs tomorrow to see if that helps.
Engine is a GSXR 1100WP

I'd like to know if people think this is fairly normal and I'm worrying about nothing - or is there a problem here?

PS. Yes I know the left driveshaft is snapped - my mock up shafts didn't take it...

[Edited on 5/4/08 by cloudy]

[Edited on 5/4/08 by cloudy]

vid wont load?

works here, it's a Windows media player file...

James

Does for me.


Wish you would put photos in your archive, it looks awsome

Loads of pics in my build diary:
http://www.locostbuilders.co.uk/viewthread.php?tid=54042&page=33

I had a look, but still a mystery.

I did some work with a westfield with a red top, it ran fine for a couple of minutes before spiting flames out the carbs and exhaust. On that occasion it turned out to be carbon on the head falling off when hot and not enabling the valvles to seat. Once the head was cleaned it all went well.

However no idea with yours, but if no-one comes up with a deffinitive answer!

Cheers

Ian

Cam timing?
Exhaust valve opening while gasses are still burning.
Over fueling as it looks like you flame when the throttle is closed.
Probably one of those things that needs setting up with a rolling road or at least a lamda sensor

It does sound a bit unbalanced in general engine note.
If the carbs are out of balance, you could be getting excess fueling.

excess fuel on overrun would be my guess...

Is that due to the slides not closing fast enough?

James

BTW high idle isn't gonna help with the over run fuelling....

Fixed the idle and balanced it - it's stopped backfiring but it's still hestitant to rev - Won't go past 9k on a 13k redline

3/4 plugs look perfect, but 1/2 are soaking wet and covered in carbon - far too rich. Anything in particular to check on the carbs?

James

PS. If it helps I've been having trouble with the float bowls not sealing - the fuel pump also ticks every 5 ish seconds when it's filled the carbs, I'd assumed that was just a little bit of pressure was lost back to the tank...


[Edited on 6/4/08 by cloudy]

[Edited on 6/4/08 by cloudy]

When you say the float bowls haven't been sealing do you mean against the main carb body, or that the float needles haven't been shutting off the fuel?

I mean the needles, first time I switched on pump it ended up ejecting fuel from the air vents at the top...

James

That won't help, as I've been having this problem. I could switch the pump off and it would actually run better! There was fuel running into the cylinders. Do you know if the floats are set at the right height? Have you had a go at cleaning the needles or looked at buying new needles/seats?

I've just taken the entire set apart and cleaned up - I think i'll run it grav fed and see if it's better...

That was the other thought, what pump are you using? Bike carbs are like webbers, they only like 2-3 psi from the pump.

Using a pump from another carbed bike...

James

That should be ok. As you've suggested though, I'd give gravity fed a bash, as it's a free trial and worth a go. If that does work, then your current pump is just over pressurising the carbs.

Original bike was gravity fed, so maybe just too much for it... I presume you can get hold of adjustable regulators ?

James

Have you got it to rev yet ?

Couple of things, have you got an air box on ? This will make a massive difference to how it runs, most BECS run absolutely sh**e without one ?

Are you getting air leaking into you exhaust manifold ?

It's the same with or without a filter, and I don't believe the exhaust is leaking...

std filter or after market ?

std...

Two problems - leaky float seals and the coil connections were making bad contact during vibration. Tries to wrap round the tacho now