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Need diagnosis--bandit 1250s

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Tonyg1987
Renault 5 Driver



Joined: 18 Feb 2017
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PostPosted: 08:11 - 01 Aug 2020    Post subject: Need diagnosis--bandit 1250s Reply with quote
Need some help figuring out what's wrong with my bike. I was leaving work late last night, put the key in end attempted to start the bike but it cut out almost immediately. So started it again and this time it fired up but It just isn't running right. The idle rpm was fluctuating almost like the engine wanted to cut back out again. I left it running for a few minutes to see if maybe the engine just needed to warm up but it continued to struggle. I cut the engine and left it for 5 mins and finally I managed to get it running okay as to were I could ride home. Now I have had this problem before, but never has the bike stalled or cut out because of it so obviously the problem is getting worse. The idling in revs has been happening for about six months, it does also happened when riding sometimes. A few times I've been coming up to a set of lights and when I dethrottle and clutch in I can hear the rpm bouncing up and down.... And struggling basically. Usually I know when this was gonna happen by how the bike starts and my previous simple fix had worked for it. Usually I'd cut the engine via kill switch then key. Turn the key back on, but not activate killswitch until about 10 or 15 seconds after the fuel pump does its thing and stops making noise. Sorry for long post but I need some help diagnosing. If it helps I had a brand new starter motor fitted a few months back which works perfectly so I know that has nothing to do with it. Bike gets started 3-4 times a day and this problem happens maybe once every couple of days but does seem more often now. Mileage is at 26.5k not sure if that even helps but maybe something is due a change or service.
Thanks in advance
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droog
Spanner Monkey



Joined: 03 Dec 2019
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PostPosted: 08:55 - 01 Aug 2020    Post subject: Reply with quote
The problem could have a number of causes.

To get the ball rolling;

Valve clearance check on this bike is due every 14500 miles.

When were the valve clearances last checked and were they all within tolerance?
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Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
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PostPosted: 09:24 - 01 Aug 2020    Post subject: Reply with quote
Bad idling and stalling when you stop sounds like an air leak on the intake to me.
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Tonyg1987
Renault 5 Driver



Joined: 18 Feb 2017
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PostPosted: 09:49 - 01 Aug 2020    Post subject: Reply with quote
Droog wrote:
The problem could have a number of causes.

To get the ball rolling;

Valve clearance check on this bike is due every 14500 miles.

When were the valve clearances last checked and were they all within tolerance?
I bought the bike at 14,700 miles.
I've never had it checked. You got a rough estimate for what it would cost in shop?
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Tonyg1987
Renault 5 Driver



Joined: 18 Feb 2017
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PostPosted: 09:51 - 01 Aug 2020    Post subject: Reply with quote
Nobby the Bastard wrote:
Bad idling and stalling when you stop sounds like an air leak on the intake to me.


My dad said it sounded like an airflow problem. I actually thought maybe the fuel pump was on its way out. To my annoyance, it started perfectly this morning when trying to point the fault out to him. Typical.
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 09:56 - 01 Aug 2020    Post subject: Re: Need diagnosis--bandit 1250s Reply with quote
Tonyg1987 wrote:
Turn the key back on, but not activate killswitch until about 10 or 15 seconds after the fuel pump does its thing and stops making noise.


Is it normal for a fuel pump to be running for 15 seconds at startup? I usually expect a couple of clicks.

Perhaps there is an obstruction in the fuel line or a problem with the pump? Maybe a blocked tank breather.

My VFR just had a fuel pump issue, it started stumbling and cutting out as if running out of fuel. Then would start on idle and idle roughly for a short while before cutting out and would stutter then die if throttle was applied.

I've definatively diagnosed this as the fuel pump, mine has an electro-mechanical pump on which a little spring has broken making the points chatter. Easy fix on mine because you can simply replace the points assembly.

I wonder if the tank/bodywork was removed when the starter motor was changed and a fuel line has been pinched when it was put back on?
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.
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Tonyg1987
Renault 5 Driver



Joined: 18 Feb 2017
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PostPosted: 10:00 - 01 Aug 2020    Post subject: Re: Need diagnosis--bandit 1250s Reply with quote
stinkwheel wrote:
Tonyg1987 wrote:
Turn the key back on, but not activate killswitch until about 10 or 15 seconds after the fuel pump does its thing and stops making noise.


Is it normal for a fuel pump to be running for 15 seconds at startup? I usually expect a couple of clicks.

Perhaps there is an obstruction in the fuel line or a problem with the pump? Maybe a blocked tank breather.

My VFR just had a fuel pump issue, it started stumbling and cutting out as if running out of fuel. Then would start on idle and idle roughly for a short while before cutting out and would stutter then die if throttle was applied.

I've definatively diagnosed this as the fuel pump, mine has an electro-mechanical pump on which a little spring has broken making the points chatter. Easy fix on mine because you can simply replace the points assembly.

I wonder if the tank/bodywork was removed when the starter motor was changed and a fuel line has been pinched when it was put back on?

Sorry I didn't explain properly... I meant I have to wait 15 seconds after the fuel pump stops making a noise. Fuel pump does its thing for 3 or 4 seconds. But if I start the engine immediately after the noise stops usually the problem occurs. If I wait 15 or 20 seconds it does not happen. Like wise if I turn the engine off and then back on it will work perfectly as normal.

Or that was the case until last night, seems its getting worse
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Kawasaki Jimbo
World Chat Champion



Joined: 09 Oct 2015
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PostPosted: 10:27 - 01 Aug 2020    Post subject: Reply with quote
My R1 did this. Lots of erratic symptoms which turned out to be red herrings. Finally I wired the reg/rec direct to the battery instead of feeding back through the loom as standard, and the problem disappeared. In hindsight I assume there was a weak connection. That could have caused erratic signals/demand from the reg/rec. I'm not sure how you'd safely diagnose that though. I used a connection kit from Eastern Beaver.
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droog
Spanner Monkey



Joined: 03 Dec 2019
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PostPosted: 10:45 - 01 Aug 2020    Post subject: Reply with quote
Tonyg1987 wrote:
Droog wrote:
The problem could have a number of causes.

To get the ball rolling;

Valve clearance check on this bike is due every 14500 miles.

When were the valve clearances last checked and were they all within tolerance?
I bought the bike at 14,700 miles.
I've never had it checked. You got a rough estimate for what it would cost in shop?


I'm not sure as I haven't visited a shop for a long time - sounds like you are due for a check though, particularly if you have no records indicating that they were checked at 14500. If they are checked and are all within tolerance you will know that tight valves are not the cause of your problem.

(You can do the clearance check yourself if you feel reasonably confident with a spanner - get a Haynes/Shop manual, a socket set, some feeler gauges and do the necessary prep before you take anything apart - if not then take it to a decent shop).
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Tdibs
Traffic Copper



Joined: 16 Jan 2015
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PostPosted: 11:12 - 01 Aug 2020    Post subject: Reply with quote
When you say it revs erratically, is it dropping a cylinder? noticeable loss in power and wanting to stall? Or still running on all 4 but just erratic idle?

I'd also start with taking off the tank and having a good check over the fuel/vacuum lines before jumping into a valve check.
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Tonyg1987
Renault 5 Driver



Joined: 18 Feb 2017
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PostPosted: 16:24 - 01 Aug 2020    Post subject: Reply with quote
Tdibs wrote:
When you say it revs erratically, is it dropping a cylinder? noticeable loss in power and wanting to stall? Or still running on all 4 but just erratic idle?

I'd also start with taking off the tank and having a good check over the fuel/vacuum lines before jumping into a valve check.

No actual power loss, and the bike has never cut out while riding. Just a chugging sound similar to when you try and rev a bike while it's cold
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Old Thread Alert!

The last post was made 5 years ago. Instead of replying here, would creating a new thread be more useful?
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