Low rpm hesitation

[GS TRV]

I was in town earlier and left the bike for a couple of hours. When I came back I started it without the choke although I would normally give it a whirl.

Anyway I noticed immediately on the way home that there is a hesitation at low rpm around 2-2.5 k.

It feels like - dodgy fuel,a failed spake plug, throttle cable incorrectly seated ( although I've experienced that and it's not as bad as that).

It seems to also tickover less smoothly and vibrates even more than usual.

It's not a major issue and only seems to effect low revs but its still annoying.

Bike has 44k on it and was going fine up until today. I'm not sure if starting it without the choke would make anything to do with it. Maybe hall sensor??

Any help much appreciated.

Trev

 

[davegs]

I was in town earlier and left the bike for a couple of hours. When I came back I started it without the choke although I would normally give it a whirl.

Anyway I noticed immediately on the way home that there is a hesitation at low rpm around 2-2.5 k.

It feels like - dodgy fuel,a failed spake plug, throttle cable incorrectly seated ( although I've experienced that and it's not as bad as that).

It seems to also tickover less smoothly and vibrates even more than usual.

It's not a major issue and only seems to effect low revs but its still annoying.

Bike has 44k on it and was going fine up until today. I'm not sure if starting it without the choke would make anything to do with it. Maybe hall sensor??

Any help much appreciated.

Trev

If it's 2003 could be a coil?, choke makes no difference, not a choke anyway just speeds up tick over.

 

[skywalker]

Spray left inlet manifold with brake cleaner or equivelent and listen to the tickover speed -it'll either drop or increase depending on what u use. Result its leaking and requires replacing not resealing with gobbo. Most common fault thats not spotted -especially on this site !!

 

[Marlou]

Spray left inlet manifold with brake cleaner or equivelent and listen to the tickover speed -it'll either drop or increase depending on what u use. Result its leaking and requires replacing not resealing with gobbo. Most common fault thats not spotted -especially on this site !!

But not always the case!!!!

Mine was the throttle balancing was out…

 

[Ian J Hartley]

If the bikes a twin spark, My monies on a faulty stick coil.

Just replaced both of mine as one was duff. Gave exactly the same symptoms rough idle lumpy engine and hesitation in the lower rev range.

Do a search for the test procedure, pretty simple really. Start the bike and pull each of the lower secondary plugs off, one at a time.

If the bike stops, which ever secondary you pulled off, the stick coil on that side is stuffed.

Carefully as you are dealing with High tension electrics, so make sure the leads are dry and you don't touch the inside of the plug leads. It hurts. Also keep the time you have the plugs disconnected with the engine running to a minimum to prevent damage to the secondary coil.

 

[JohnnyBoxer]

Spray left inlet manifold with brake cleaner or equivelent and listen to the tickover speed -it'll either drop or increase depending on what u use. Result its leaking and requires replacing not resealing with gobbo. Most common fault thats not spotted -especially on this site !!

You spotted this on mine, even before the physical symptoms appeared

Top spannerman

 

[GS TRV]

Spray left inlet manifold with brake cleaner or equivelent and listen to the tickover speed -it'll either drop or increase depending on what u use. Result its leaking and requires replacing not resealing with gobbo. Most common fault thats not spotted -especially on this site !!

Where do I spray then???

Thanks

 

[GS TRV]

Where do I spray then???

Thanks

Would wd40 do the same job??

 

[JohnnyBoxer]

Where do I spray then???

Thanks

Left hand throttle body where it connects into the pot, short rubber inlet

Brake cleaner is best I think as it has a higher solvent level & isn't as dense a solution & doesn't contain oil like WD

 

[skywalker]

Would wd40 do the same job??

No as JB says its too dense plus it can attack rubber. Brake cleaner or electrical contact spray is best. Since it tends to draw extra air through the bit that leaks this causes the fuel/air mixture to be even weaker than it should be as its on the forward side of the throttle position sensor. Bear in mind that a different throttle openings the throttle sensor is telling the ECU where its at so the ECU calculates the amount of fuel for that given setting.Adding more air (leaking manifold) will cause the symptoms your describing. Its a quick and simple test that's often over looked when setting up throttle balance. For some reason on 850/1100/1150 is always the left one. 1200 its the right one

 

[GS TRV]

Well either way I will have to take it to my mechanic. You guys def know your stuff - thanks for all your help.

Just one more Q- is it likely to cut out the bike completely or can I ride with for the next few days? Don't want to get caught out on the weekly commute.

Trev

 

[skywalker]

Why ?? Its a piece of piss to test. Get the engine warm and then test. If you need to replace- remove injector (leave fuel line connected and undo 2 bolts and gently ease injector out of throttle body)
Slacken rear clip where air tube goes into airbox (leave other end attached to throttle body)
Slacken clip on inlet manifold and slide whole assembly back.
2 bolts hold the manifold to the head. remove manifold and scotchbrite the gasket surface.
Apply a VERY THIN SMEAR of gasket goo and reassemble -what could be easier

 

[skywalker]

Is the bike twin spark (usually says 2 spark on the plug cover) or single ?
If its twin spark another problem area is the main stick coils under the cover.
Get the plastic coil puller from your toolkit and with the bike running gently pull the coil away from the plug approx 5 -10 mm. U should here a "cracking"noise as the spark jumps across to the plug. Don't worry u won't get a shock.
Unlikely for this setup to suddenly cut out -just be carefull

Single spark - symptoms tend to show up when its warm.
In all circumstances you should be carefull as you know there's a fault when riding slowly

 

[monkeyboy]

This sounds a bit like what my bike does and has been doing for the last couple of years. I'll be interested to see what you find. My bike just hesitates/surges/feels wrong at constant throttle 2.5-3k. All other riding is fine. I've changed everything, and I mean everything. TPS, injectors, temp sensors, coil, plugs, HT leads, complete wiring loom, ECU, timing chains, everything. Still does it. I think it's haunted

 

[GS TRV]

It's a twin spark.

Off to Brian at Mototech for the rescue tomorrow - he's a total guru so will keep you all posted.

Sorry but its way over my head to dismantle the thing

 

[(RIP) DitchWater]

This sounds a bit like what my bike does and has been doing for the last couple of years. I'll be interested to see what you find. My bike just hesitates/surges/feels wrong at constant throttle 2.5-3k. All other riding is fine. I've changed everything, and I mean everything. TPS, injectors, temp sensors, coil, plugs, HT leads, complete wiring loom, ECU, timing chains, everything. Still does it. I think it's haunted

I know the feeling.

I may start a new thread about a rough running problem when my bike is warm but need to try a couple of things first.

 

[monkeyboy]

I know the feeling.

I may start a new thread about a rough running problem when my bike is warm but need to try a couple of things first.

Does one of those things involve a priest?

I'll watch with interest. I'm going to buy a good cable oilier and mimic the deepwater horizon oil spill to see if that helps next.

 

[GS TRV]

Took it to Mototech and coils were removed. Rusted and in pretty bad nick so looks like that's the prob.

 

[GS TRV]

New coils fitted and bike is flying again. Yay