Idle Speed and Fuel level

[MikeH]

When the tank is full my bike ticks over at about 1200 rpm with the engine warmed up. But as it approaches the reserve the tickover starts to get lower an lower until it gets so bad at say 10 miles from switching over to the reserve it will die completely when I pull up.

I'm also wondering about the fuel consumption, I'm having to fill up every 100 miles which equates to just under 35mpg, this on a bike which only pushes out 50BHP on a good day it seems a bit low when my mates 600 will do at least 40 without being too careful.

Any tips to sort the idle and other than riding like a nun how do I improve the consumption ? does it just need a good tune up ?

Mike
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Busa Junkie

[stinkwheel]

Well, sounds like there is something not right. Unless you are banging it all the way up to the redline in every gear you should be getting much better fuel consumption.

The tickover thing sounds bloody weird. I wonder if the tank breather is partially obstructed? That or an obstruction in the fuel line/tap somewhere? As if there is some obstruction which is being overcome by the head of fuel pressure in the tank. Vacuum tap malfunction/leaking vacuum? Does the bike 'search' at tickover (surge up and down the revs rather than sit steady)?

Try running it with the tap on 'pri', try running it with the fuel cap open. Check the vacuum hose is attached. Check the fuel tap. Check the float height with the carbs in place (you have that manual right?).

Maybe worth running some redex through it?

Can't help wondering, given the bike has been heavily messed with at some point (it was your one that has the upside down gearbox in yeah?) if someone has bee 'at it'.

Going through everything listed under a major service wont do any harm and might bring something to light.

Odd.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[MikeH]

[stinkwheel]

Well that narrows it down a hell of a lot. It is either a problem with the vacuum line between the inlet manifold and the fuel tap or a problem with the fuel tap itself. The tap is dismantleable, there is an o-ring in there somewhere that could have gone bye-bye.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[MikeH]

Yep, just been reading about the tap and the gauzes etc...

Also I've got a couple of vacuum gauges in the garage so I'll stick them on and see how the carb balance is looking, I'll also take a looksee at the plugs just incase she's a running bit rich.

What sort of mileage are you getting out of a tank on yours ?
My riding is pretty mixed commuting stuff, 20 miles each way, mainly main road so 60-70mph the odd blatt to get past a truck etc and then about 3 mile slow traffic/filtering.

Mike
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Busa Junkie

[stinkwheel]

I was getting 90-100 miles out of a tank (to reserve) the other weekend giving it big-beans down the motorway (cruising between 90 and 105).

So say 12.5 litres to reserve. That is say 95 miles from 2.75 gallons.

Which is 35mpg. That is thrashing the nads off it though.

When I was riding it slowly along some A roads due to poor visability I filled up in Selkirk and rode to Edinburgh then filled up again (42 miles). It took 4 litres which is 48mpg.

Thinking about it, that is crap compared to my GPZ. Maybe I need to do some servicing myself. Mind you, mine is running rich as hell at the moment with the new exhaust on, pops and bangs like a rally car on the overrun.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[MikeH]

I would expect it to be worse than a road bike being sat upright, it will knock some of the MPG off with all the extra drag, but I was expecting mid 40's. To be honest at 35mpg I'd be as well chopping it out for a 600 sports bike at least I'd get value for money

Wish I had some spare cash 'cause it's in the local bike shop saturday for a new rear tyre, I could have got them to sort it and save me the hassle, but then knowing dealers they'd probably have some monkey f'kg about with it for a couple of hours and it'd come out worse than it went in

As for cruising at 90 to 105 mine will only just manage a ton unless I get it on a motorway, eat beans the night before and lie down on the tank
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Busa Junkie

[stinkwheel]