Holy Exhaust

[Moo.]

Probably smited from heaven more like.. My question is, could holes in my exhaust lower my mpg by a noticable amount? My bikes consumption is rather guzzling, even for a Cb250n notorious for 50mpg.. it usually achieves 35 Apart from a worn out engine, and me changing all the gaskets (which i shall do when money comes around) I recently plugged up all the holes in the exhaust to see if it will go up i shall probably re-balance the carbs aswell For reference it had 2 pinholes in various placed, and 2 more about the size of a bic pen where it rotted through praised be for gun-gum

Cheers, Malc
____________________
A2 Passed 18/6/10

[DrDonnyBrago]

[woodyfjr]

Any extra holes in the exhaust can make things worse, as for 35mpg I would check the choke system isnt stick slightly on.
Also adjust the tappets as they are very easy on a CB250n then balance the carbs.
____________________
If you don't pay your exorcist you can get repossessed.

If you have to rev it! Don't Buy it!

[StevRS]

Bear in mind some of the holes (the drain holes on the cans for instance) are meant to be there!

First thing I'd do is balance the carbs. A good pointer if they're way out is lumpy low-range or running hot. If you're lucky you might find the exhaust isn't causing you so much bother after all.
____________________
MV Agusta Brutale 800 RR, Unfinished 1978 XS250

[Scotsman37]

Have you checked to see if the fuel mixture is correct as the revs maybe sitting to high and so burning more fuel than need be?

Have you checked the downpipe end where it connects to the engine is airtight just in case you're losing compression there also?

[Moo.]

I though it was quite a big drop in mpg for the size of the holes, so i'll check out other problems. I have previously balanced it before, so a carb tune, when i bought it, it was waaaay out.

These certainly werent holes meant to be there, both were rusty and non-circular. I'll fiddle with the fuel mix, as it bogs till about 1/4 throttle then picks up and is fine.

Anyone used Redex before? I used it a couple of times and it seemed to bring the mpg down even more
____________________
A2 Passed 18/6/10

[woodyfjr]

The air screw only does the first 25% of revs nothing else.
____________________
If you don't pay your exorcist you can get repossessed.

If you have to rev it! Don't Buy it!

[Scotsman37]

[woodyfjr]

True, however the loss of 15mpg wont be from the air screw I think its the valves and or air filter.
____________________
If you don't pay your exorcist you can get repossessed.

If you have to rev it! Don't Buy it!

[Moo.]

Air filter was brand spanking new and the valves have been done recently, just rebalanced it was quite a bit off, so got them both spot on But i'll take another look at the valves cos its getting tappy Hopefully should get a bit more miles for my money But cheers guys
____________________
A2 Passed 18/6/10