1150 -sudden "let go"

[Chris G]

Hi all,

2001 1150, running fine, [little bit of 3k surge] but,,,,,, EVERY time I slow down and the revs get to around 1800 rpm [either throttle closed or otherwise] the bike feels like it suddenly lets go - just feels like it has jumped into neutral. The bike revs up and down okay with no load ie in neutral. could it be hall sensors????

other thing is it does it in all gears so prolly not the tranmission

bloody annoying as for me 1800 rpm and third gear is corner speed - which can be interesting


help

 

[Colban]

Hall sensors are dear to replace.
Have you tried balancing the throttle bodies after checking valve clearances and end float?.
How old are the plugs?.Maybe new pair required?.

 

[Chris G]

Hall sensors are dear to replace.
Have you tried balancing the throttle bodies after checking valve clearances and end float?.
How old are the plugs?.Maybe new pair required?.

Hi,

the valves were done recently, and the plugs are new, the balance has been done a couple of times to try and sort this- but no avail

 

[iletts]

by letting go I assume you mean dying/stalling?

air leak on inlet(s)? check TB seals/rubber tubes ok and clamps tight

 

[Spout]

by letting go I assume you mean dying/stalling?

I'm reading it as the opposite. Slowing down, relying on engine braking, gets to 1800 revs and the bike "carries on" and doesn't slow further?
In which case it'll be one of the sensors giving out incorrect info and overriding the injectors/throttle position.

Don't know which it'll be Chris, but I bet your nearest diagnostics machine will

 

[Chris G]

I'm reading it as the opposite. Slowing down, relying on engine braking, gets to 1800 revs and the bike "carries on" and doesn't slow further?
In which case it'll be one of the sensors giving out incorrect info and overriding the injectors/throttle position.

Don't know which it'll be Chris, but I bet your nearest diagnostics machine will

cheers Paul et al,

it is acshually:-
Slowing down, relying on engine braking, gets to 1800 revs and the bike "carries on" and then instantly recovers- it is just this one rev point.



the diagnostic machine I have tried it on [called Mrs Chris G] says the fault "could possibly" be repaired by the application of a black n yellow 800gs around march next year


However, I may need a fix to get me through the wet months

 

[Colban]

Does sound like a trip to your local friendly dealer for a plug in sensor check.
Could be O2 sensor,air temp sensor,hall sensor.

 

[(RIP) MOTÖRHEAD]

Hall sensors are dear to replace.
Have you tried balancing the throttle bodies after checking valve clearances and end float?.
How old are the plugs?.Maybe new pair required?.
Does sound like a trip to your local friendly dealer for a plug in sensor check.
Could be O2 sensor,air temp sensor,hall sensor

You just keep naming all the parts on the bike & I'm sure he'll get there in the end.

 

[littleredrooster]

It's unlikely that you have a fault as such. I have described this before, but for your edification will repeat it here:

This is a feature of the fuel injection system. It is called 'fuel over-run cut-off' and, as its name suggests, it cuts the fuel supply (on the over-run) altogether at engine speeds above 2500rpm (IIRC). As the engine slows down past 2500rpm, it starts the fuel supply up once again and this is the slight 'surge' that you feel. The easy way is not to let the engine drop this low in the rev range (it gets a bit rough there, anyway?) but change to a lower gear before then.
The feeling can be 'masked' to some extent by fiddling with the TPS - setting it to the lower of the recommended voltage lessens the surge effect, but also (IMO) detracts from the driveability of the engine.

 

[(RIP) Kaister]

cheers Paul et al,

it is acshually:-
Slowing down, relying on engine braking, gets to 1800 revs and the bike "carries on" and then instantly recovers- it is just this one rev point.



the diagnostic machine I have tried it on [called Mrs Chris G] says the fault "could possibly" be repaired by the application of a black n yellow 800gs around march next year


However, I may need a fix to get me through the wet months

sounds very much like incorrect fuelling just off idle.

either wrong mixture via brass screws or sticky throttle cables

i'd say balance your idle with a manometer using cable and brass screws together

- and check your butterfly actuators as a long shot

 

[littleredrooster]

sounds very much like incorrect fuelling just off idle.....

No, I think it's correct fuelling, he just doesn't describe it very well. See my post above.

 

[Chris G]

It's unlikely that you have a fault as such. I have described this before, but for your edification will repeat it here:

This is a feature of the fuel injection system. It is called 'fuel over-run cut-off' and, as its name suggests, it cuts the fuel supply (on the over-run) altogether at engine speeds above 2500rpm (IIRC). As the engine slows down past 2500rpm, it starts the fuel supply up once again and this is the slight 'surge' that you feel. The easy way is not to let the engine drop this low in the rev range (it gets a bit rough there, anyway?) but change to a lower gear before then.
The feeling can be 'masked' to some extent by fiddling with the TPS - setting it to the lower of the recommended voltage lessens the surge effect, but also (IMO) detracts from the driveability of the engine.

Little red,,,,,,,,

the surge is not slight as you say- it is enough to send you over the other side of the road when cornering, my bike has always been very smooth at the bottom end, and tbh spends a lot of the last 60k running in the lower revs- just cos it is smooth and it has the torque.

it is a definite step change in running- hence the problem- I am to strip and check all the seals on the inlets this weekend as well as a balance-n-tps twiddle as well as tank vent hose check etc,


Phil,

when you say
- and check your butterfly actuators as a long shot
do you just mean the throttle bodies or summat else??


cheers for the suppport so far chaps

 

[(RIP) Kaister]

flip the cables off the quadrants that rotate the butterflys and check they shut smoothly.

i'd be pretty certain its a combination of LRR's diagnosis and mine - idle fuelling and mixture related.

whats changed recently ? - have you had it serviced ?
could even be a sticky throttle rubber grip on the end weight.

 

[Comfy Old Boots]

Hall sensors are dear to replace.
Have you tried balancing the throttle bodies after checking valve clearances and end float?.
How old are the plugs?.Maybe new pair required?.

daft old things the oilhead. they feck'n go loike the clappers though yeah?

 

[littleredrooster]

Little red,,,,,,,,

the surge is not slight as you say- it is enough to send you over the other side of the road when cornering......

In which case your TPS setting is miles out. It needs to be about 0.36V - 0.38V to (almost) eliminate this. You can go up to 0.40V, but this magnifies the surge that you are experiencing.