My first Bandit! And the flat spot

[ducatilover]

Air leak or main jet then. Incorrect filter will also do that by causing it to run far to rich.

[maggot]

Air leak or main jet then. Incorrect filter will also do that by causing it to run far to rich.

Wouldn't an air leak be evident due to an uneven idle? Cos mine is all fine. I'm hoping it's as simple as the filter.

[bogan]

Nope, first pop start when warm. With no load, it'll rev cleanly all the way through the range. But when actually riding it won't.

Jetting or slide operation would be my thoughts. How mechanically competent are you? Not too hard a job to check or piss round with, but also not one you want to cock up!

[ducatilover]

Wouldn't an air leak be evident due to an uneven idle? Cos mine is all fine. I'm hoping it's as simple as the filter.

Not necessarily, you're carbs compensate to a point with an air leak, an injected engine hunts at idle with an air leak because of unmetered air vs the o2 sensor signal.
Hopefully a service will clear it up

[bogan]

just a thought, it's not choke sticking or something simple like that?

[maggot]

I'll check the basics again before I head off to work, see if anything new presents itself. If the issue is still happening after the service I'll enlist the help of my old man bike mentor and we'll pull the carbs apart and go through them.
Thanks for all the help so far, really appreciate it.

[maggot]

So got the service done today. Pretty underwhelming! Plugs were apparently not great and were replaced, apparently were looking a bit white previously, so running lean? Usual bits and pieces cleaned, fixed, replaced. The flat spot persists, so will look at pulling the carbs down and checking everything over.
Bit of a grump with the shop, they charged me one hell of a lot, and after all that forget to reconnect the choke. Which I discovered trying to start a very cold bike a very long way from home. So will head back there and kick up a fuss tomorrow. Less than impressed.

So results of the day: bike running lean, new plugs haven't done shit, and a bike shop I'm not interested at paying any more money to work on my bike!

[bogan]

lean is more likely to be an air leak than worn jets etc imo.

[nzspokes]

lean is more likely to be an air leak than worn jets etc imo.

I agree. Carbs would have to have done a lot of work to wear jets. Look over it yourself, get a little spray bottle of water and spray around the carbs while the motor is running. If the motor stumbles youve found the leak. You only need a light spray.

If the flat spot was to be part of the service then they should have sorted it.

[maggot]

Was only a C-service. They wanted to charge me another couple hundred bucks to just have a looksee at the carbs. So I figure it's something that I can do with a more mechanically minded person looking over my shoulder and save myself a tad more cash.
Will try the suggested above.

[ducatilover]

I agree. Carbs would have to have done a lot of work to wear jets.

Some of them had alloy needles, like the early dynojet kits and they can be shagged within 5000km easily

I'd be putting money on an air leak. You need to check the plugs yourself as there is a way to "read them" [sic] to see what's going on.

[maggot]

Some of them had alloy needles, like the early dynojet kits and they can be shagged within 5000km easily

I'd be putting money on an air leak. You need to check the plugs yourself as there is a way to "read them" [sic] to see what's going on.

So would an air leak cause significant problems at only mid and top range? Cos the bottom range is perfectly fine for now.
Sometime next week I'll be bunking down in the garage for a day or two with the old man mentor until this is sorted, he's planning on doing the usual test of running the bike at a certain rev range, killing it and whipping out the plugs to check colour. Hopefully that'll give us some indication of whats going on.

[ducatilover]

So would an air leak cause significant problems at only mid and top range? Cos the bottom range is perfectly fine for now.
Sometime next week I'll be bunking down in the garage for a day or two with the old man mentor until this is sorted, he's planning on doing the usual test of running the bike at a certain rev range, killing it and whipping out the plugs to check colour. Hopefully that'll give us some indication of whats going on.

Plug chop won't work unless the engine's under load. An airleak could stop the slides from fully lifting or be slightly too lean just before they do. I've had these problems before

[maggot]

Plug chop won't work unless the engine's under load. An airleak could stop the slides from fully lifting or be slightly too lean just before they do. I've had these problems before

He's planning to do it under load.
Cheers, I get you now. I'm trying to understand as much of the theoretical as I can so I can deal with these kinda problems if and when they arise again, hence all the silly questions

[ducatilover]

He's planning to do it under load.
Cheers, I get you now. I'm trying to understand as much of the theoretical as I can so I can deal with these kinda problems if and when they arise again, hence all the silly questions

Good stuff then Good luck with it, let us know how you get on.
If you take the diaphragms out of the carbs, use something to hold the slide up a bit when putting them back in, this allows you to seal the diaphragm easier and eliminates the problem with air leaking to/from the top of the slides.